View source for Tetraethyllead

{{Short description|Organolead compound}}
{{Use dmy dates|date=August 2020}}

{{Chembox
| Watchedfields = changed
| verifiedrevid = 470603872
| Name = 
| ImageFile = Tetraethyllead-Skeletal-SVG.svg
| ImageFile_Ref = {{Chemboximage|correct|??}}
| ImageSize = 200
| ImageAlt = Skeletal formula
| ImageFile1 = Tetraethyllead-3D-balls.png
| ImageSize1 = 180
| ImageAlt1 = Ball-and-stick model
| PIN = Tetraethylplumbane
| SystematicName = <!-- Tetraethylplumbane (substitutive) OR Tetraethyllead (additive) -->
| OtherNames = Lead tetraethyl<br />
Tetraethyl lead<br />
Tetra-ethyl lead
| Section1 = {{Chembox Identifiers
| Abbreviations = TEL
| CASNo = 78-00-2
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 6511
| ChemSpiderID = 6265
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| EINECS = 201-075-4
| UNNumber = 1649
| MeSHName = Tetraethyl+lead
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 30182
| RTECS = TP4550000
| Beilstein = 3903146
| Gmelin = 68951
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 13426ZWT6A
| SMILES = CC[Pb](CC)(CC)CC
| StdInChI = 1S/4C2H5.Pb/c4*1-2;/h4*1H2,2H3;
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = MRMOZBOQVYRSEM-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
}}
| Section2 = {{Chembox Properties
| C = 8
| H = 20
| Pb = 1
| Appearance = Colorless liquid
| Odor = pleasant, sweet<ref name=PGCH />
| Density = 1.653 g cm<sup>−3</sup>
| MeltingPtC = −136
| BoilingPtC = 84 to 85
| BoilingPt_notes = 15&nbsp;mmHg
| RefractIndex = 1.5198
| Solubility = 200 [[parts per billion]] (ppb) (20&nbsp;°C)<ref name=PGCH />
| VaporPressure = 0.2 [[mmHg]] (20&nbsp;°C)<ref name=PGCH />
}}
| Section3 = {{Chembox Structure
| MolShape = Tetrahedral
| Dipole = 0 D}}
| Section4 = {{Chembox Hazards
| MainHazards = Flammable, extremely toxic
| GHSPictograms = {{GHS skull and crossbones}} {{GHS health hazard}} {{GHS environment}}
| HPhrases = {{H-phrases|300+310+330|360|373|410}}
| PPhrases = {{P-phrases|201|202|260|262|264|270|271|273|280|281|284|301+310|302+350|304+340|308+313|310|314|320|321|322|330|361|363|391|403+233|405|501}}
| NFPA-H = 4
| NFPA-F = 2
| NFPA-R = 3
| FlashPtC = 73
| IDLH = 40 mg/m<sup>3</sup> (as Pb)<ref name=PGCH>{{PGCH|0601}}</ref>
| LC50 = 850 mg/m<sup>3</sup> (rat, 1 hr)<ref name=IDLH>{{IDLH|78002|Tetraethyl lead}}</ref>
| LD50 = 35 mg/kg (rat, oral)<br />17 mg/kg (rat, oral)<br />12.3 mg/kg (rat, oral)<ref name=IDLH />
| REL = TWA 0.075 mg/m<sup>3</sup> [skin]<ref name=PGCH />
| PEL = TWA 0.075 mg/m<sup>3</sup> [skin]<ref name=PGCH />
| ExploLimits = 1.8%–?<ref name=PGCH />
| LCLo = 650 mg/m<sup>3</sup> (mouse, 7 hr)<ref name=IDLH />
| LDLo = 30 mg/kg (rabbit, oral)<br />24 mg/kg (rat, oral)<ref name=IDLH />
}}
| Section5 = 
| Section6 = 
| Section8 = {{Chembox Related
| OtherCompounds ={{unbulleted list|[[Tetramethyllead]]|[[Tetraethylmethane]]|[[Tetraethylsilane]]|[[Tetraethylgermanium]]|[[Tetraethyltin]]}}
}}
}}

'''Tetraethyllead''' (commonly styled '''tetraethyl lead'''), abbreviated '''TEL''', is an [[organolead compound]] with the formula [[lead|Pb]]([[ethyl group|C<sub>2</sub>H<sub>5</sub>]])<sub>4</sub>. It was widely used as a [[fuel]] additive for much of the 20th century, first being mixed with [[gasoline]] beginning in the 1920s. This "leaded gasoline" had an increased [[octane rating]] that allowed [[Compression ratio|engine compression]] to be raised substantially and in turn increased vehicle performance and fuel economy.<ref name=BMJ1928>{{cite journal|journal=British Medical Journal|volume=1|issue=3504|pages=366–7|date=3 March 1928|pmid=20773729|pmc=2455205|doi=10.1136/bmj.1.3504.366|title=Tetra-Ethyl Lead as an Addition to Petrol}}</ref><ref>{{citation|title=After Lead?|work=[[Popular Science]]|page=94|edition=October 1987|url=https://books.google.com/books?id=oAAAAAAAMBAJ&pg=PA94|publisher=Bonnier Corporation|date=October 1987|access-date=23 August 2020|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713180334/https://books.google.com/books?id=oAAAAAAAMBAJ&pg=PA94#v=onepage&q&f=false|url-status=live}}</ref> TEL was first [[chemical synthesis|synthesized]] by German chemist [[Carl Jacob Löwig]] in 1853. American chemical engineer [[Thomas Midgley Jr.]], who was working for the U.S. corporation [[General Motors]], was the first to discover its effectiveness as an [[Antiknock agent|knock inhibitor]] on December 9, 1921, after spending six years attempting to find an [[antiknock agent|additive]] that was both highly effective and inexpensive.<ref>{{Cite journal |last=Nriagu |first=Jerome O. |date=1990-03-01 |title=The rise and fall of leaded gasoline |url=https://www.sciencedirect.com/science/article/abs/pii/004896979090318O |journal=Science of the Total Environment |volume=92 |pages=13–28 |doi=10.1016/0048-9697(90)90318-O |bibcode=1990ScTEn..92...13N |issn=0048-9697|url-access=subscription }}</ref>

Of the some 33,000 substances in total screened, [[lead]] was found to be the most effective antiknock agent,<ref>{{Cite journal |last=Nriagu |first=Jerome O. |date=1990-03-01 |title=The rise and fall of leaded gasoline |url=https://www.sciencedirect.com/science/article/abs/pii/004896979090318O |journal=Science of the Total Environment |volume=92 |pages=13–28 |doi=10.1016/0048-9697(90)90318-O |bibcode=1990ScTEn..92...13N |issn=0048-9697|url-access=subscription }}</ref><ref>{{Cite journal |last=Seyferth |first=Dietmar |date=2003-12-01 |title=The Rise and Fall of Tetraethyllead. 2. |url=https://pubs.acs.org/doi/10.1021/om030621b |journal=Organometallics |volume=22 |issue=25 |page=5157 |doi=10.1021/om030621b |issn=0276-7333|url-access=subscription }}</ref> in that it necessitated the smallest concentrations necessary; a treatment of 1 part TEL to 1300 parts gasoline by weight is sufficient to suppress detonation.<ref>{{Cite journal |last=Seyferth |first=Dietmar |date=2003-12-01 |title=The Rise and Fall of Tetraethyllead. 2. |url=https://pubs.acs.org/doi/10.1021/om030621b |journal=Organometallics |volume=22 |issue=25 |page=5163 |doi=10.1021/om030621b |issn=0276-7333 |quote="After the Ethyl concentrate has been mixed with gasoline (1 part of tetraethyllead to 1300 of gasoline) Midgley said there is no health hazard, provided that it is not misused; nor, he claimed, was there any evidence that the exhaust of a motor using leaded gasoline as fuel was dangerous."|url-access=subscription }}</ref> The four ethyl groups in the compound served to dissolve the active lead atom within the fuel.<ref name=":2">{{Cite journal |last=Seyferth |first=Dietmar |date=2003-12-01 |title=The Rise and Fall of Tetraethyllead. 2. |url=https://pubs.acs.org/doi/10.1021/om030621b |journal=Organometallics |volume=22 |issue=25 |pages=5154–5178 |doi=10.1021/om030621b |issn=0276-7333 |quote="For the purpose of this essay it will suffice to say that, in order to be effective, tetraethyllead must undergo thermal decomposition in the automobile engine to give ultimately ethyl radicals and gaseous lead atoms. The latter, in the presence of air, are oxidized to lead monoxide. This, either in gaseous form or as a fog of fine particles, is believed to inactivate intermediates of the hydrocarbon oxidation, perhaps alkyl hydro-peroxides, thus inhibiting the chain-branching reactions that would result in detonation (i.e., knock). Thus,tetraethyllead is a gasoline-soluble and volatile source of lead atoms at the operating temperature of the engine. It is not the intact molecule which is the effective antiknock agent; it is merely a lead carrier."|url-access=subscription }}</ref> When injected into the combustion chamber, tetraethyllead decomposed upon heating into ethyl [[Radical (chemistry)|radicals]], lead, and lead oxide. The [[Lead(II) oxide|lead oxide]] scavenges radicals and therefore inhibits a flame from developing until full compression has been achieved, allowing the optimal timing of [[Ignition timing|ignition]], as well as the lowering of fuel consumption.<ref name=":2" /> Throughout the sixty year period from 1926 to 1985, an estimated 20 trillion liters of leaded gasoline at an average lead concentration of 0.4 g/L were produced and sold in the United States alone, or an equivalent of 8 million tons of inorganic lead,<ref>{{Cite journal |last=Nriagu |first=Jerome O. |date=1990-03-01 |title=The rise and fall of leaded gasoline |url=https://www.sciencedirect.com/science/article/abs/pii/004896979090318O |journal=Science of the Total Environment |volume=92 |pages=13–28 |doi=10.1016/0048-9697(90)90318-O |bibcode=1990ScTEn..92...13N |issn=0048-9697|url-access=subscription }}</ref> three quarters of which would have been emitted in the form of [[Lead(II) chloride|lead chloride]] and [[Lead(II) bromide|lead bromide]]. Estimating a similar amount of lead to have come from other countries' emissions, a total of more than 15 million tonnes of lead may have been released into the [[Atmosphere of Earth|atmosphere]].<ref>{{Cite journal |last1=Hewitt |first1=C Nicholas |last2=Rashed |first2=M B |date=1988 |title=Organic lead compounds in vehicle exhaust |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/aoc.590020202 |journal=Applied Organometallic Chemistry |language=en |volume=2 |issue=2 |pages=95–100 |doi=10.1002/aoc.590020202 |issn=1099-0739 |quote="Of the alkyllead additive in fuel about. 75% is emitted from the exhaust as a complex mixture of inorganic lead salts with the majority of the remainder being deposited in the engine and exhaust system."|url-access=subscription }}</ref>

In the mid-20th century, scientists discovered that TEL caused [[lead poisoning]] and was highly [[Neurotoxicity|neurotoxic]] to the human brain, especially in children.<ref name="AMA_study=">{{Cite news |url=https://today.duke.edu/2017/03/lead-exposure-childhood-linked-lower-iq-lower-status |title=LEAD EXPOSURE IN CHILDHOOD LINKED TO LOWER IQ, LOWER STATUS: Leaded gasoline creates a natural experiment in long-term study |publisher=Duke University |date=28 March 2017 |access-date=11 March 2022 |archive-date=13 July 2024 |archive-url=https://web.archive.org/web/20240713180335/https://today.duke.edu/2017/03/lead-exposure-childhood-linked-lower-iq-lower-status |url-status=live}}</ref> The [[United States]] and many other countries began phasing out the use of TEL in automotive fuel in the 1970s. With [[United States Environmental Protection Agency|EPA]] guidance and oversight, the United States achieved the total elimination of sales of leaded gasoline for on-road vehicles on January 1, 1996.<ref>Newell R. G.; Rogers. K. The market-based lead-phasedown. Resources for the Future (Discussion paper) 2003, 3-37.</ref> By the early 2000s, most countries had banned the use of TEL in gasoline. In July 2021, the sale of leaded gasoline for cars was completely phased out worldwide following the termination of production by [[Algeria]], prompting the [[United Nations Environment Programme|United Nations Environment Program]] (UNEP) to declare an "official end" of its use in cars on August 30, 2021.<ref name="cbc-Aug2021">{{cite web |title=It's official: You can't buy leaded gasoline for cars anywhere on Earth |url=https://www.cbc.ca/news/science/un-leaded-gasoline-1.6158216 |website=cbc.ca |publisher=CBC News |access-date=30 August 2021 |date=30 August 2021 |archive-date=30 August 2021 |archive-url=https://web.archive.org/web/20210830160136/https://www.cbc.ca/news/science/un-leaded-gasoline-1.6158216 |url-status=live }}</ref> In 2011, researchers retroactively estimated the annual impact of tetraethyl lead worldwide to be 1.1 million excess deaths, 322 million lost IQ points, 60+ million crimes, and 4% of worldwide [[Gross domestic product|GDP]] (around 2.4 trillion United States dollars per year).<ref>{{Cite journal |last1=Tsai |first1=Peter L. |last2=Hatfield |first2=Thomas H. |date=2011 |title=Global Benefits From the Phaseout of Leaded Fuel |journal=Journal of Environmental Health |volume=74 |issue=5 |pages=8–15 |jstor=26329321 |issn=0022-0892}}</ref>

{{TOC limit|3}}

== Synthesis and properties ==
TEL is produced on an industrial scale by reacting [[chloroethane]] (ethyl chloride) with a [[sodium]]–[[lead]] [[alloy]].<ref name="Seyferth">{{cite journal |last= Seyferth |first=D. |title= The Rise and Fall of Tetraethyllead. 2 |journal= [[Organometallics]] |year= 2003 |volume= 22 |pages= 5154–5178 |doi= 10.1021/om030621b |issue= 25|doi-access=  }}</ref><ref name="Jewkes">{{cite book |last1=Jewkes |first1=John |last2=Sawers |first2=David |last3=Richard |first3=Richard |title=The sources of invention |date=1969 |publisher=W. W. Norton |location=New York |isbn=978-0-393-00502-8 |pages=[https://archive.org/details/sourcesofinventi0000jewk_x4v4/page/235 235]–237 |edition=2nd |url=https://archive.org/details/sourcesofinventi0000jewk_x4v4 |url-access=registration |access-date=11 July 2018}}</ref>

{{block indent|4 NaPb + 4 CH{{sub|3}}CH{{sub|2}}Cl → Pb(CH{{sub|3}}CH{{sub|2}}){{sub|4}} + 4 NaCl + 3 Pb}}

The product is recovered by steam distillation, leaving a sludge of lead and [[sodium chloride]].<ref>{{cite book |last1=Davis |first1=William E. |title=Emission Study of Industrial Sources of Lead Air Pollutants, 1970 |date=1973 |location=United States |publisher=Environmental Protection Agency |page=57 |url=https://books.google.com/books?id=gA05nZLq6q4C |language=en |access-date=22 March 2023 |archive-date=7 June 2023 |archive-url=https://web.archive.org/web/20230607225235/https://books.google.com/books?id=gA05nZLq6q4C |url-status=live }}</ref> TEL is a [[Viscosity|viscous]] colorless [[liquid]] with a sweet odor.<ref>{{cite book |last1=Dara |first1=S.S. |last2=Shete |first2=S.D. |title=S. Chand's Applied Chemistry Volume 2 (For 2nd Semester of Mumbai University) |publisher=S. Chand Publishing |isbn=978-81-219-3495-4 |page=93 |url=https://books.google.com/books?id=CDJlDwAAQBAJ |language=en |access-date=22 March 2023 |archive-date=7 June 2023 |archive-url=https://web.archive.org/web/20230607225236/https://books.google.com/books?id=CDJlDwAAQBAJ |url-status=live }}</ref> Because TEL is charge neutral and contains an exterior of alkyl groups, it is highly [[Lipophilicity|lipophilic]] and soluble in petrol (gasoline). This property, which allows it to dissolve so evenly and effectively in motor fuel, also allowed easy absorption by body fats and lipids and diffusion through the blood–brain barrier (BBB). The lead (II) ions (Pb<sup>2+</sup>) would accumulate within the limbic forebrain, frontal cortex, and [[hippocampus]].<ref name="Cadet & Bolla">{{cite journal |last1=Cadet |first1=J. L. |last2=Bolla |first2=K. I. |title=Environmental Toxins and Disorders of the Nervous System |journal=Neurology and Clinical Neuroscience |year=2007 |pages=1477–1488 |doi=10.1016/B978-0-323-03354-1.50115-2 |isbn=978-0-323-03354-1}}</ref> Practically speaking, TEL is a "central nervous system toxin which produces an acute toxic psychosis."<ref>{{Cite journal |last=Gidlow |first=D. A. |date=2015-07-01 |title=Lead toxicity |url=https://academic.oup.com/occmed/article-abstract/65/5/348/1425465 |journal=Occupational Medicine |volume=65 |issue=5 |pages=348–356 |doi=10.1093/occmed/kqv018 |pmid=26187801 |issn=0962-7480|url-access=subscription }}</ref>

There is no cure for direct poisoning by TEL. Inorganic lead compounds, such as those present in [[Exhaust gas|engine exhausts]], could be removed from the system through the administration of [[Chelation|chelating agents]], which bind to the inorganic lead and flush them out of the body. However, highly lipid-soluble TEL cannot be removed this way, and treatments are of a supportive nature.<ref>{{Cite journal |last=Gidlow |first=D. A. |date=2015-07-01 |title=Lead toxicity |url=https://academic.oup.com/occmed/article-abstract/65/5/348/1425465 |journal=Occupational Medicine |volume=65 |issue=5 |pages=348–356 |doi=10.1093/occmed/kqv018 |pmid=26187801 |issn=0962-7480 |quote="... Unlike inorganic lead and its compounds, where chelating agents may be used in the case of poisoning, there is no specific antidote for organic lead poisoning—treatment consists of supportive treatment and adequate sedation."|url-access=subscription }}</ref>

Despite decades of research, no reactions were found to improve upon this process; it is rather difficult, involves reactive metallic sodium, and converts only 25% of the lead to TEL. A related compound, [[tetramethyllead]], was commercially produced by a different electrolytic reaction. However, tetramethyllead was even more difficult to make, and it did not find use beyond niche applications.<ref name="Seyferth" /> A highly efficient pathway utilizing ethyl chloride with a slight excess of [[lithium]] was developed, with a TEL yield over lead of over 90%. However, by then the fuel additive had started to fall out of favor and into disrepute, and the process was never put into practice.<ref name=":3">{{cite journal |last1=Seyferth |first1=Dietmar |title=The Rise and Fall of Tetraethyllead. 2 |journal=Organometallics |date=December 2003 |volume=22 |issue=25 |page=5174 |doi=10.1021/om030621b |url=https://pubs.acs.org/doi/pdf/10.1021/om030621b |language=en |issn=0276-7333 |access-date=31 August 2021 |archive-date=6 November 2021 |archive-url=https://web.archive.org/web/20211106205506/https://pubs.acs.org/doi/pdf/10.1021/om030621b |url-status=live |url-access=subscription }}</ref>

== Reactions ==
A noteworthy feature of TEL is the weakness of its four C–Pb bonds. At the temperatures found in [[internal combustion engine]]s, TEL decomposes completely into lead as well as combustible, short-lived ethyl [[Radical (chemistry)|radicals]]. Lead and lead oxide scavenge [[Radical (chemistry)|radical intermediates]] in [[combustion]] reactions. Engine knock is caused by a [[cool flame]], an oscillating low-temperature combustion reaction that occurs before the proper, hot ignition. Lead quenches the pyrolyzed radicals and thus kills the radical chain reaction that would sustain a cool flame, preventing it from disturbing the smooth ignition of the hot flame front. Lead itself is the reactive antiknock agent, and the ethyl groups serve as a gasoline-soluble carrier.<ref name="Seyferth" />

When TEL burns, it produces not only carbon dioxide and water, but also lead and lead(II) oxide:<ref name=kloprogge826/>
<chem>Pb(C2H5)4 + 13 O2 -> 8 CO2 + 10 H2O + Pb</chem>
<chem>Pb(C2H5)4 + 27 O2 -> 16 CO2 + 20 H2O + 2 PbO</chem>

Pb and PbO would quickly over-accumulate and foul an engine. For this reason, [[1,2-dichloroethane]] and [[1,2-dibromoethane]] were also added to gasoline as lead scavengers—these agents form volatile [[lead(II) chloride]] and [[lead(II) bromide]], respectively, which flush the lead from the engine and into the air:<ref name=kloprogge826>{{cite book |last1=Kloprogge |first1=J. Theo |last2=Ponce |first2=Concepcion P. |last3=Loomis |first3=Tom |title=The Periodic Table: Nature's Building Blocks: An Introduction to the Naturally Occurring Elements, Their Origins and Their Uses |date=18 November 2020 |publisher=Elsevier |isbn=978-0-12-821538-8 |page=826 |url=https://books.google.com/books?id=hGa8DwAAQBAJ |language=en |access-date=22 March 2023 |archive-date=13 July 2024 |archive-url=https://web.archive.org/web/20240713180335/https://books.google.com/books?id=hGa8DwAAQBAJ |url-status=live }}</ref>

<chem>Pb(C2H5)4 + C2H4X2 + 16 O2 -> 10 CO2 + 12 H2O + PbX2</chem>

== In motor fuel ==
TEL was extensively used as a [[gasoline additive]] beginning in the 1920s,<ref name=Kovarik2005 /> wherein it served as an effective [[antiknock agent]] and reduced exhaust [[Poppet valve|valve]] and [[valve seat]] wear. Concerns were raised in reputable journals of likely health outcomes of fine particles of lead in the atmosphere as early as 1924.<ref name="Seyferth1">{{cite journal |last1=Seyferth |first1=Dietmar |title=The Rise and Fall of Tetraethyllead. 1. Discovery and Slow Development in European Universities, 1853−1920 |journal=Organometallics |date=June 2003 |volume=22 |issue=12 |pages=2346–2357 |doi=10.1021/om030245v |doi-access= }}</ref><ref name="Seyferthb">{{cite journal |last1=Seyferth |first1=Dietmar |title=The Rise and Fall of Tetraethyllead. 2. |journal=Organometallics |date=December 2003 |volume=22 |issue=25 |pages=5154–5178 |doi=10.1021/om030621b |url=http://www.hvonstorch.de/klima/pdf/blei/seyferth_2003.pdf |access-date=7 October 2018 |archive-date=8 October 2018 |archive-url=https://web.archive.org/web/20181008022721/http://www.hvonstorch.de/klima/pdf/blei/seyferth_2003.pdf |url-status=live }}</ref><ref>{{cite news |url=http://nla.gov.au/nla.news-article36628530 |title=A New Automobile Fuel |newspaper=[[The Advertiser (Adelaide)]] |location=South Australia |date=16 January 1924 |access-date=25 April 2017 |page=15 |via=National Library of Australia |archive-date=13 July 2024 |archive-url=https://web.archive.org/web/20240713180337/https://trove.nla.gov.au/newspaper/article/36628530 |url-status=live }}</ref>

=== Valve wear preventive ===
Tetraethyllead helps cool intake valves and is an excellent buffer against microwelds forming between exhaust valves and their [[Valve seat|seats]].<ref>{{cite web|url=http://www.imperialclub.com/Repair/Lit/Master/291/page13.htm|title=1972 Imperial & Chrysler Engine Performance Facts & Fixes Service Book (Session 291)|website=Online Imperial Club|access-date=31 July 2011|archive-date=27 September 2011|archive-url=https://web.archive.org/web/20110927095854/http://www.imperialclub.com/Repair/Lit/Master/291/page13.htm}}</ref> Once these valves reopen, the microwelds pull apart and abrade the valves and seats, leading to valve recession. When TEL began to be phased out, the automotive industry began specifying hardened valve seats and upgraded materials which allow for high wear resistance without requiring lead.<ref>{{cite web|url=http://www.imperialclub.com/Repair/Lit/Master/302/page04.htm|title=1973 Imperial and Chrysler Clean Air System Reference Service Repair Book from the Master Technician's Service Conference (Session 302)|website=Online Imperial Club|access-date=31 July 2011|archive-date=27 September 2011|archive-url=https://web.archive.org/web/20110927095859/http://www.imperialclub.com/Repair/Lit/Master/302/page04.htm}}</ref>

=== Antiknock agent ===
A gasoline-fueled reciprocating engine requires fuel of sufficient [[octane rating]] to prevent uncontrolled combustion (pre-ignition and [[engine knock|detonation]]).<ref name="Seyferth" /> Antiknock agents allow the use of higher [[compression ratio]]s for greater [[fuel efficiency|efficiency]]<ref name="SAEtrans-hce1959">{{cite tech report |last1=Caris |first1=D. F. |last2=Nelson |first2=E. E. |year=1959 |title=A New Look at High Compression Engines |number=590015 |doi=10.4271/590015 |publisher=Society of Automotive Engineers }}</ref> and peak [[power (physics)|power]].<ref>{{cite journal|last1=Loeb|first1=A. P.|title=Birth of the Kettering Doctrine: Fordism, Sloanism and Tetraethyl Lead|journal=Business and Economic History|date=Fall 1995|volume=24|issue=2|url=http://www.thebhc.org/sites/default/files/beh/BEHprint/v024n1/p0072-p0087.pdf|archive-url=https://web.archive.org/web/20151027191244/http://www.thebhc.org/sites/default/files/beh/BEHprint/v024n1/p0072-p0087.pdf|archive-date=2015-10-27|url-status = live}}</ref> Adding varying amounts of additives to gasoline allowed easy, inexpensive control of octane ratings. TEL offered the business advantage of being commercially profitable because its use for this purpose could be patented.<ref name=Kovarik2005 /> Aviation fuels with TEL used in WWII reached octane ratings of 150 to enable turbocharged and supercharged engines such as the [[Rolls-Royce Merlin]] and [[Rolls-Royce Griffon|Griffon]] to reach high horsepower ratings at altitude.<ref>{{cite book|title = I Kept No Diary|author = F. R. Banks|date = 1978|publisher = Airlife Publishing, Ltd.|isbn = 978-0-9504543-9-9}}</ref> In military aviation, TEL manipulation allowed a range of different fuels to be tailored for particular flight conditions.{{citation needed|date=September 2021}}

In 1935 a license to produce TEL was given to [[IG Farben]], enabling the newly formed German {{lang|de|[[Luftwaffe]]}} to use high-octane gasoline for high altitude flight. A company, Ethyl GmbH, was formed that produced TEL at two sites in Germany with a government contract from 10 June 1936.<ref>[[Rainer Karlsch]], Raymond G. Stokes. ''"Faktor Öl". Die Mineralölwirtschaft in Deutschland 1859–1974.'' C. H. Beck, München, 2003, {{ISBN|3-406-50276-8}}, p. 187.</ref>

In 1938 the United Kingdom [[Air Ministry]] contracted with [[Imperial Chemical Industries|ICI]] for the construction and operation of a TEL plant. A site was chosen at Holford Moss, near Plumley in Cheshire. Construction started in April 1939 and TEL was being produced by September 1940.<ref name="Plumley TEL Works">{{cite web |title=Northwich |url=https://www.octelamlwch.co.uk/northwich/ |website=Octel Bromine Works |access-date=9 January 2022 |archive-date=11 January 2022 |archive-url=https://web.archive.org/web/20220111091720/https://www.octelamlwch.co.uk/northwich/ |url-status=live }}</ref>

=== "Ethyl Fluid" ===
[[File:EthylCorporationSign.jpg|thumb|upright|280px|Sign on an antique gasoline pump advertising tetraethyllead by the [[Ethyl Corporation]]]]
For mixing with raw gasoline, TEL was most commonly supplied in the form of "Ethyl Fluid", consisting of TEL blended with 1,2-dichloroethane and 1,2-dibromoethane, which prevent lead from building up in the engine. Ethyl Fluid also contained a reddish dye to distinguish treated from untreated gasoline and discourage the use of leaded gasoline for other purposes such as cleaning.<ref name="redrum">{{cite journal |url=https://pubs.acs.org/doi/10.1021/om030621b |title=The Rise and Fall of Tetraethyllead |year=2003 |doi=10.1021/om030621b |last1=Seyferth |first1=Dietmar |journal=Organometallics |volume=22 |issue=25 |pages=5154–5178 |access-date=14 February 2023 |archive-date=16 March 2023 |archive-url=https://web.archive.org/web/20230316072417/https://pubs.acs.org/doi/10.1021/om030621b |url-status=live |url-access=subscription }}</ref>

In the 1920s, before safety procedures were strengthened, 17 workers for the [[Ethyl Corporation]], [[DuPont (1802–2017)|DuPont]], and [[Standard Oil]] died from the effects of exposure to lead.<ref name="Kovarik2005" /> The grim news was not well received by US legislators and a brief ban was put into place. However, it was lifted on recommendation of the United States [[Surgeon General of the United States|Surgeon General]] and a panel of scientists in 1929, after extensive [[Lobbying in the United States|lobbying]] efforts by the aforementioned companies.<ref name=Kovarik2005 /> It would be another half century until a similar effort was made to rein in the additive, spearheaded by the EPA in the 1980s. This time, concerns for health and the environment were aided by the increasing use of [[catalytic converter]]s, which cannot tolerate TEL.<ref name=":3" />

Ethyl Fluid's formulation consisted of:<ref name="Seyferth" />
* 61.45% tetraethyllead
* 18.80% [[1,2-dichloroethane]]
* 17.85% [[1,2-dibromoethane]]
* 1.90% inerts, preservatives, and dyes

It was found that dichloroethane and dibromoethane act in a synergistic manner, in that approximately equal quantities of both provide the best scavenging ability, thus preventing engines from fouling up due to deposits of inorganic lead within the pistons and exhausts.<ref name="Seyferth" />

=== Phaseout and ban ===
In most industrialized countries, a phaseout of TEL from road vehicle fuels was completed by the early 2000s because of concerns over air and soil lead levels and the [[Bioaccumulation|accumulative]] neurotoxicity [[Lead poisoning|of lead]]. In the European Union, tetraethyllead has been classified as a [[Substance of Very High Concern]] and placed on the Candidate List for Authorization under [[Registration, Evaluation, Authorisation and Restriction of Chemicals|Registration, Evaluation, Authorization and Restriction of Chemicals]] (REACH).<ref>{{Cite web |url=https://echa.europa.eu/documents/10162/0b417b76-b533-42a1-9bd2-519f1dc1990d |title=Inclusion of Substances of Very High Concern in the Candidate List – Decision of the European Chemicals Agency ED/169/2012 |access-date=28 August 2017 |archive-date=28 August 2017 |archive-url=https://web.archive.org/web/20170828225609/https://echa.europa.eu/documents/10162/0b417b76-b533-42a1-9bd2-519f1dc1990d |url-status=live }}</ref> Potential use of TEL would need to be authorized through the [[REACH authorisation procedure|REACH authorization procedure]]. While not a complete ban, it introduces significant obligations such as a mandatory analysis of alternatives and socioeconomic analysis.{{citation needed|date=September 2021}}

The use of [[catalytic converter]]s, mandated in the United States for 1975 and later model-year cars to meet tighter emissions regulations, started a gradual phase-out of leaded gasoline in the U.S.<ref name=Kitman /> The need for TEL was lessened by several advances in automotive engineering and petroleum chemistry. Safer methods for making higher-octane blending stocks such as [[reformate]] and [[iso-octane]] reduced the need to rely on TEL, as did other antiknock additives of varying toxicity including metallic compounds such as [[methylcyclopentadienyl manganese tricarbonyl]] (MMT) as well as [[oxygenate]]s including [[Methyl tert-butyl ether|methyl ''tert''-butyl ether]] (MTBE), [[tert-Amyl methyl ether|''tert''-amyl methyl ether]] (TAME), and [[Ethyl tert-butyl ether|ethyl ''tert''-butyl ether]] (ETBE).{{citation needed|date=September 2021}}

The first country to completely ban leaded gasoline was [[Japan]] in 1986.<ref>{{cite web |last1=Hofverberg |first1=Elin |title=The History of the Elimination of Leaded Gasoline |work=In Custodia Legis: Law Librarians of Congress |url=https://blogs.loc.gov/law/2022/04/the-history-of-the-elimination-of-leaded-gasoline/ |access-date=4 January 2023 |date=14 April 2022 |archive-date=13 July 2024 |archive-url=https://web.archive.org/web/20240713180336/https://blogs.loc.gov/law/2022/04/the-history-of-the-elimination-of-leaded-gasoline/ |url-status=live }}</ref>

Since January 1993, all gasoline powered cars sold in the [[European Union]] and the [[United Kingdom]] have been required to use unleaded fuel. This was to comply with the [[European emission standards|Euro 1 emission standards]] which mandated that all new cars to be fitted with a [[catalytic converter]].<ref>{{cite web |title=Euro emissions standards |url=https://www.theaa.com/driving-advice/fuels-environment/euro-emissions-standards |publisher=[[The AA]] |access-date=31 December 2022 |archive-date=31 December 2022 |archive-url=https://web.archive.org/web/20221231192512/https://www.theaa.com/driving-advice/fuels-environment/euro-emissions-standards |url-status=live }}</ref> Unleaded fuel was first introduced in the United Kingdom in June 1986.<ref>{{cite news |title=Throwback Thursday 1989: the switchover to unleaded petrol |url=https://www.autocar.co.uk/car-news/throwback-thursday-1989-switchover-unleaded-petrol |access-date=31 December 2022 |work=Autocar |language=en |archive-date=31 December 2022 |archive-url=https://web.archive.org/web/20221231202830/https://www.autocar.co.uk/car-news/throwback-thursday-1989-switchover-unleaded-petrol |url-status=live }}</ref>

Leaded gasoline was removed from the forecourts in the United Kingdom on January 1, 2000, and a Lead Replacement Petrol was introduced although this was largely withdrawn by 2003 due to dwindling sales.<ref>{{cite news |first=Andrew |last=Clark |title=Petrol for older cars about to disappear |url=https://www.theguardian.com/uk/2002/aug/15/oil.business |work=The Guardian |date=15 August 2002 |language=en |access-date=1 January 2023 |archive-date=29 December 2016 |archive-url=https://web.archive.org/web/20161229112618/https://www.theguardian.com/uk/2002/aug/15/oil.business |url-status=live }}</ref><ref>{{cite web |title=Guide to lead replacement petrol (LRP) |publisher=The AA |url=https://www.theaa.com/driving-advice/fuels-environment/lrp |access-date=1 January 2023 |archive-date=1 January 2023 |archive-url=https://web.archive.org/web/20230101145332/https://www.theaa.com/driving-advice/fuels-environment/lrp |url-status=live }}</ref> An exemption to the ban exists for owners of classic cars.{{cn|date=January 2023}}

Vehicles designed and built to run on leaded fuel often require modification to run on unleaded gasoline. These modifications fall into two categories: those required for physical compatibility with unleaded fuel, and those performed to compensate for the relatively low octane of early unleaded fuels. Physical compatibility requires the installation of [[Hardening (metallurgy)|hardened]] exhaust valves and seats, or by use of additives. Compatibility with reduced octane was addressed by reducing compression, generally by installing thicker cylinder [[head gasket]]s and/or rebuilding the engine with compression-reducing pistons (although modern high-octane unleaded gasoline has eliminated the need to decrease compression ratios {{citation needed|date=September 2021}}), and/or by retarding ignition timing.

Leaded gasoline remained legal as of late 2014<ref name=corrupt-executives>{{cite news |first=Lynne |last=Peeples |date=August 9, 2014 |title=Corrupt Executives Sent To Prison For Pumping Toxic Leaded Fuel Overseas |work=Huffington Post |url=https://www.huffingtonpost.com/2014/08/09/leaded-gas-corruption-innospec_n_5662418.html |access-date=20 February 2020 |archive-date=18 June 2017 |archive-url=https://web.archive.org/web/20170618025101/http://www.huffingtonpost.com/2014/08/09/leaded-gas-corruption-innospec_n_5662418.html |url-status=live }}</ref> in parts of [[Algeria]], [[Iraq]], [[Yemen]], [[Myanmar]], [[North Korea]], and [[Afghanistan]].<ref>{{cite web|title=UNEP 10th general meeting strategy presentation |url=http://www.unep.org/transport/pcfv/PDF/10gpm_CHpresentation_strategy.pdf |archive-url=https://web.archive.org/web/20131203023740/http://www.unep.org/transport/pcfv/PDF/10gpm_CHpresentation_strategy.pdf |archive-date=2013-12-03}}</ref><ref name=leadgroup>{{cite web |url= http://www.lead.org.au/fs/fst27.html |title= Countries where Leaded Petrol is Possibly Still Sold for Road Use |date= 17 June 2011 |author= Robert Taylor |publisher= The LEAD Group |access-date= 12 April 2007 |archive-date= 19 January 2012 |archive-url= https://web.archive.org/web/20120119144013/http://www.lead.org.au/fs/fst27.html |url-status= live }}</ref>{{update inline|date=May 2021}} North Korea and Myanmar purchased their TEL from China, while Algeria, Iraq, and Yemen purchased it from the specialty chemical company [[Innospec]], the world's sole remaining legal manufacturer of TEL.<ref>{{cite web|url=https://www.innospecinc.com/our-markets/octane-additives/octane-additives|title=Octane Additives|website=Innospec|access-date=11 November 2019|archive-date=11 November 2019|archive-url=https://web.archive.org/web/20191111221654/https://www.innospecinc.com/our-markets/octane-additives/octane-additives|url-status=live}}</ref> In 2011 several Innospec executives were charged and imprisoned for bribing various government state-owned oil companies to approve the sale of their TEL products.<ref name=leadgroup /><ref>{{cite web|url=http://www.fcpaprofessor.com/first-enforcement-action-of-2011-involves-a-former-executive-officer|title=First Enforcement Action of 2011 Involves a Former Executive Officer|work=FCPA Professor|date=2011-01-25|access-date=21 December 2015|archive-date=22 December 2015|archive-url=https://web.archive.org/web/20151222145443/http://www.fcpaprofessor.com/first-enforcement-action-of-2011-involves-a-former-executive-officer|url-status=live}}</ref>

{{As of|2016|6}} the [[United Nations Environment Programme|UNEP]]-sponsored phase-out was nearly complete: only Algeria, Iraq, and Yemen continued widespread use of leaded gasoline, although not exclusively.<ref name=":0">{{cite web|url=https://wedocs.unep.org/bitstream/handle/20.500.11822/17542/MapWorldLead_March2017.pdf?sequence=1&isAllowed=y|archive-url=https://web.archive.org/web/20171115235249/http://wedocs.unep.org/bitstream/handle/20.500.11822/17542/MapWorldLead_March2017.pdf?sequence=1&isAllowed=y|archive-date=2017-11-15|publisher=Partnership for Clean Fuels and Vehicles|title=Leaded Petrol Phase-out: Global Status as at March 2017|access-date=2018-04-28}}</ref> In July 2021, Algeria had halted its sale.<ref name="cbc-Aug2021" />

==== Leaded-fuel bans ====
[[File:Lead gasoline phase-out.svg|thumb|300px|link=https://upload.wikimedia.org/wikipedia/commons/1/11/Lead_gasoline_phase-out.svg|Interactive map of the phase-out of leaded gasoline from 1972 to 2021. Click on the image to explore interactivity]]
{{morerefs-section|date=May 2021}}
Leaded-fuel bans for road vehicles came into effect as follows:
{{Col-begin}}
{{Col-break}}

===== Europe =====
*Armenia: 2001<ref>{{cite web|title=ՀՀ կառավորության որոշում 913 29.09.2001|language=hy|url=https://www.arlis.am/DocumentView.aspx?DocID=47470}}</ref>
*Austria: 1989
*Belarus: 1998
*Bulgaria: 2002
*Bosnia and Herzegovina: 2009
*Croatia: 2006
*Cyprus: 2004
*Czech Republic: 2001<ref>{{cite book|url=https://books.google.com/books?id=L4_VAgAAQBAJ|title=OECD Environmental Performance Reviews: Czech Republic 2005|date=11 October 2005|publisher=OECD Publishing|via=Google Books|isbn=978-92-64-01179-3|access-date=15 August 2016|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713180336/https://books.google.com/books?id=L4_VAgAAQBAJ|url-status=live}}</ref>
*Denmark: 1994<ref>{{cite web|title=Regulering af brændstoffer|language=da|url=http://mst.dk/borger/luftforurening/biler-busser-og-andre-koeretoejer/regulering-af-braendstoffer/|access-date=13 March 2016|archive-url=https://web.archive.org/web/20140811161933/http://mst.dk/borger/luftforurening/biler-busser-og-andre-koeretoejer/regulering-af-braendstoffer/|archive-date=11 August 2014}}</ref>
*[[European Union]]: 1 January 2000<ref>[[European Union]] Member States which had not already withdrawn it from sale experienced the EU-wide ban from 1 January 2000. Earlier regulation had prevented the sale or production of cars using leaded petrol after 1992.</ref>
*Finland: 1994<ref>{{cite web|url=https://www.neste.com/sites/default/files/attachments/bensiiniopas_2015.pdf|title=Bensiiniopas|language=fi|access-date=28 December 2017|archive-url=https://web.archive.org/web/20151009070249/https://www.neste.com/sites/default/files/attachments/bensiiniopas_2015.pdf|archive-date=9 October 2015|url-status=live}}</ref>
*France: 2000<ref>{{cite book|url=https://books.google.com/books?id=OYbVAgAAQBAJ&q=oecd+environmental+performance+reviews+france+leaded&pg=PA98|title=OECD Environmental Performance Reviews: France 2005|isbn=978-92-64-00914-1|date=2005-09-26|publisher=OECD|access-date=20 October 2020|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713180351/https://books.google.com/books?id=OYbVAgAAQBAJ&q=oecd+environmental+performance+reviews+france+leaded&pg=PA98#v=snippet&q=oecd%20environmental%20performance%20reviews%20france%20leaded&f=false|url-status=live}}</ref>
*Germany: 1996<ref>{{cite news|url=http://www.zeit.de/mobilitaet/2013-11/bleifrei-benzin/komplettansicht|title=Stirbt das Blei, dann lebt der Wald|trans-title=If lead dies, the forest lives|date=8 November 2013|newspaper=Die Zeit|language=de|access-date=10 March 2018|archive-date=11 March 2018|archive-url=https://web.archive.org/web/20180311140700/http://www.zeit.de/mobilitaet/2013-11/bleifrei-benzin/komplettansicht|url-status=live}}</ref>
*Gibraltar: 2001 <ref>{{cite journal |title=Motor Fuel (Composition and Content) Act 2001 |journal=Gibraltar Laws |date=April 5, 2001}}</ref>
*Greece: 2002<ref>{{cite book|url=https://books.google.com/books?id=hWt0uW_a2GIC|title=OECD Environmental Performance Reviews: Greece 2009|date=15 March 2010|publisher=OECD Publishing|via=Google Books|isbn=978-92-64-06133-0}}</ref>
*Hungary: 1999
*Ireland: 1 January 2000
*Italy: 1 January 2002<ref>{{cite book|url=https://books.google.com/books?id=Q4bYAgAAQBAJ|title=OECD Environmental Performance Reviews: Italy 2002|date=29 January 2003|publisher=OECD Publishing|via=Google Books|isbn=978-92-64-19916-3|access-date=15 August 2016|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713182105/https://books.google.com/books?id=Q4bYAgAAQBAJ|url-status=live}}</ref>
*Malta: 2003
*Monaco: 2000
*Netherlands: 1998<ref>{{cite book|url=https://books.google.com/books?id=G1rWAgAAQBAJ&q=oecd+environmental+performance+reviews+norway+leaded&pg=PA207|title=OECD Environmental Performance Reviews: Netherlands 2003|isbn=978-92-64-10100-5|date=2003-06-02|publisher=OECD|access-date=20 October 2020|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713182105/https://books.google.com/books?id=G1rWAgAAQBAJ&q=oecd+environmental+performance+reviews+norway+leaded&pg=PA207#v=onepage&q=oecd%20environmental%20performance%20reviews%20norway%20leaded&f=false|url-status=live}}</ref>
*Norway: 1997
*Poland: December 2000<ref>{{cite web|title=Zakończenie produkcji Etyliny 94|language=pl|date=12 December 2000|url=https://www.orlen.pl/PL/RelacjeInwestorskie/RaportyBiezace/Strony/Zako%C5%84czenieprodukcjiEtyli.aspx|archive-url=https://web.archive.org/web/20201022214134/https://www.orlen.pl/PL/RelacjeInwestorskie/RaportyBiezace/Strony/Zako%C5%84czenieprodukcjiEtyli.aspx|archive-date=22 October 2020}}</ref>
*Slovenia: 2001<ref>{{cite book|url=https://books.google.com/books?id=FOrUeREpU5IC|title=OECD Environmental Performance Reviews: Slovenia 2012|date=6 June 2012|publisher=OECD Publishing|via=Google Books|isbn=978-92-64-16926-5|access-date=15 August 2016|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713182106/https://books.google.com/books?id=FOrUeREpU5IC|url-status=live}}</ref>
*Spain: 1 August 2001<ref>{{cite web|url=http://www.minetur.gob.es/energia/petroleo/Carburantes/Paginas/informacion.aspx|title=Prohibición de la venta de gasolina con plomo|language=es|publisher=Ministerio de Industria, Energía y Turismo|access-date=2 February 2018|archive-date=4 October 2016|archive-url=https://web.archive.org/web/20161004035008/http://www.minetur.gob.es/energia/petroleo/Carburantes/Paginas/informacion.aspx|url-status=live}}</ref>
*Portugal: 1999
*Romania: 2005<ref>{{cite news|title=Dispare benzina cu plumb|language=ro|date=27 July 2004|newspaper=[[Evenimentul Zilei]]|url=http://www.evz.ro/detalii/stiri/dispare-benzina-cu-plumb-657363.html|archive-url=https://web.archive.org/web/20130729085342/http://www.evz.ro/detalii/stiri/dispare-benzina-cu-plumb-657363.html|archive-date=29 July 2013}}</ref>
*Russia: 2003<ref>{{cite web|script-title=ru:Постановление ГД ФС РФ от 15 November 2002 N 3302-III ГД О проекте Федерального закона N 209067-3 "Об ограничении оборота этилированного бензина в Российской Федерации"|language=ru|url=http://www.lawrussia.ru/texts/legal_149/doc149a777x242.htm|archive-url=https://web.archive.org/web/20130729085322/http://www.lawrussia.ru/texts/legal_149/doc149a777x242.htm|archive-date=29 July 2013|access-date=24 March 2013|trans-title=Resolution of the State Duma of the Federal Assembly of the Russian Federation of 15 November 2002 N 3302-III of the State Duma on the Draft Federal Law N 209067-3 "On Limiting the Turnover of Leaded Petrol in the Russian Federation" }}</ref>
*Serbia: 2010<ref>{{cite news | title=Zbogom olovnom benzinu! | trans-title=Goodbye to leaded gasoline! | date=2010-06-08 | author=A. Muslibegović | language=sr | url=http://www.novosti.rs/vesti/naslovna/aktuelno.69.html:275721-Zbogom-olovnom-benzinu | access-date=6 March 2018 | archive-date=6 June 2019 | archive-url=https://web.archive.org/web/20190606221634/http://www.novosti.rs/vesti/naslovna/aktuelno.69.html:275721-Zbogom-olovnom-benzinu | url-status=live }}</ref>
*Sweden: 1995<ref>{{Cite web |date=1995-01-20 |title=Blyad bensin förbjuds från 1 mars |trans-title=Leaded petrol is banned from 1 March |url=https://www.dn.se/arkiv/inrikes/blyad-bensin-forbjuds-fran-1-mars/ |access-date=2022-09-08 |website=[[Dagens Nyheter]] |language=sv |archive-date=8 September 2022 |archive-url=https://web.archive.org/web/20220908114748/https://www.dn.se/arkiv/inrikes/blyad-bensin-forbjuds-fran-1-mars/ |url-status=live }}</ref>
*Switzerland: 2000
*Ukraine: 2003
*United Kingdom: 1 January 2000<ref>{{cite news|title=Four-star petrol banned|date=1 December 1998|author=<!--Staff writer(s); no by-line.-->|publisher=BBC News |url=https://news.bbc.co.uk/2/hi/uk_news/225275.stm|access-date=2 February 2018|archive-url=https://web.archive.org/web/20170810025149/http://news.bbc.co.uk/1/hi/uk/225275.stm|archive-date=10 August 2017|url-status=live}}</ref>
{{Col-break}}

===== North America =====
*Anguilla: 1998
*Antigua and Barbuda: 1991
*Aruba: 1997
*Bahamas: 1996
*Belize: 1997
*Bermuda: 1990
*Cayman Islands: 1999
*Canada: December 1990<ref>{{cite journal | pmid = 9216473 | volume=43 | issue=7 | title=Decline in blood lead in Ontario children correlated to decreasing consumption of leaded gasoline, 1983–1992 | year=1997 | vauthors=Wang ST, Pizzolato S, Demshar HP, Smith LF | journal=Clinical Chemistry | pages=1251–52| doi=10.1093/clinchem/43.7.1251 | doi-access=free }}</ref><ref>{{Cite web|url=https://www.ctvnews.ca/climate-and-environment/article/last-country-on-earth-to-use-leaded-gasoline-in-cars-bans-its-sale/|title=Last country on Earth to use leaded gasoline in cars bans its sale|date=3 September 2021|access-date=2 August 2022|archive-date=2 August 2022|archive-url=https://web.archive.org/web/20220802213617/https://www.ctvnews.ca/climate-and-environment/last-country-on-earth-to-use-leaded-gasoline-in-cars-bans-its-sale-1.5573127|url-status=live}}</ref>
*Costa Rica: 1996<ref>{{Cite web|url=https://www.nacion.com/ciencia/medio-ambiente/combustibles-libres-de-plomo-y-bajos-en-azufre/FDVTM34755CUTO3EIL26A4PTDU/story/|title=Combustibles: Libres de plomo y bajos en azufre|language=es|trans-title=Fuels: Lead free and low in sulfur|date=8 April 2016|access-date=19 November 2021|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713182107/https://www.nacion.com/ciencia/medio-ambiente/combustibles-libres-de-plomo-y-bajos-en-azufre/FDVTM34755CUTO3EIL26A4PTDU/story/|url-status=live}}</ref>
*Dominican Republic: 1999
*El Salvador: 1992
*Guatemala: 1991
*Haiti: 1998
*Honduras: 1996
*Jamaica: 2000
*Mexico: 1998
*Nicaragua: 1995
*Panama: 2002<ref>{{Cite web|url=https://www.panamaamerica.com.pa/economia/gasolina-con-plomo-tiene-los-dias-contados-24656|title=Gasolina con plomo tiene los días contados|language=es|trans-title=Leaded gasoline has its days numbered|date=6 October 2001|access-date=19 November 2021|archive-date=19 November 2021|archive-url=https://web.archive.org/web/20211119071217/https://www.panamaamerica.com.pa/economia/gasolina-con-plomo-tiene-los-dias-contados-24656|url-status=live}}</ref>
*Trinidad and Tobago: 2000
*United States (including Puerto Rico): 1 January 1996
**California: 1992
{{Col-break}}

===== South America =====
*Argentina: 1998
*Bolivia: 1995<ref name="PMC4643815">{{cite journal |journal=Science Advances |date=6 March 2015 |volume=1 |issue=2 |doi=10.1126/sciadv.1400196 |pmc=4643815 |pmid=26601147 |title=Pb pollution from leaded gasoline in South America in the context of a 2000-year metallurgical history |first1=Anja |last1=Eichler |first2=Gabriela |last2=Gramlich |first3=Thomas |last3=Kellerhals |first4=Leonhard |last4=Tobler |first5=Margit |last5=Schwikowski|article-number = e1400196|bibcode=2015SciA....1E0196E }}</ref>
*Brazil: 1989<ref>{{cite web |url=https://atosoficiais.com.br/anp/resolucao-cnp-n-1-1989-o-substituto-eventual-do-diretor-geral-da-agencia-nacional-do-petroleo-gas-natural-e-biocombustiveis-anp-de-acordo-com-o-disposto-no-3-do-artigo-6-do-anexo-i-ao-decreto-n-2455-de-14-de-janeiro-de-1998-com-base-nas-disposicoes-da-lei-n-9-478-de-06-de-agosto-de-1997-e-na-resolucao-de-diretoria-n-63-de-22-de-fevereiro-de-2005-e |title=Brazilian ANP's Resolution No. 01/1989: Provides for standard gasoline specifications for consumption and emissions tests (including Lead) |location=Brazil |publisher=Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP) |date=January 31, 1989 |access-date=July 16, 2023 |quote= |archive-date=16 July 2023 |archive-url=https://web.archive.org/web/20230716182455/https://atosoficiais.com.br/anp/resolucao-cnp-n-1-1989-o-substituto-eventual-do-diretor-geral-da-agencia-nacional-do-petroleo-gas-natural-e-biocombustiveis-anp-de-acordo-com-o-disposto-no-3-do-artigo-6-do-anexo-i-ao-decreto-n-2455-de-14-de-janeiro-de-1998-com-base-nas-disposicoes-da-lei-n-9-478-de-06-de-agosto-de-1997-e-na-resolucao-de-diretoria-n-63-de-22-de-fevereiro-de-2005-e |url-status=live }}</ref> or 1991<ref name="PMC4643815"/>
*Chile: 2001<ref>{{cite web|title=ENAP dejará de distribuir gasolina con plomo el sabado|language=es|trans-title=ENAP will stop distributing leaded gasoline on Saturday|url=http://www.emol.com/noticias/economia/2001/03/26/50211/enap-dejara-de-distribuir-gasolina-con-plomo-el-sabado.html|access-date=1 August 2014|date=2001-03-26|archive-date=8 December 2015|archive-url=https://web.archive.org/web/20151208175858/http://www.emol.com/noticias/economia/2001/03/26/50211/enap-dejara-de-distribuir-gasolina-con-plomo-el-sabado.html|url-status=live}}</ref> or 2005<ref name="PMC4643815"/>
*Colombia: 1991<ref>{{cite news|newspaper=[[El Tiempo (Colombia)|El Tiempo]]|url=http://www.eltiempo.com/archivo/documento/MAM-615546|title=La gasolina no tiene plomo|language=es|trans-title=Gasoline is unleaded|first=Gabriel Reyes|last=Aldana|date=10 July 1997|access-date=24 May 2014|archive-date=3 February 2019|archive-url=https://web.archive.org/web/20190203201905/https://www.eltiempo.com/archivo/documento/MAM-615546|url-status=live}}</ref>
*Guyana: 2000
*Peru: 2004
*Suriname: 2001
*Uruguay: 2004<ref>{{cite web|url= http://universidad.edu.uy/prensa/renderItem/itemId/43692|archive-url=https://web.archive.org/web/20210521170857/http://universidad.edu.uy/prensa/renderItem/itemId/43692 |title=Udelar y contaminación con plomo: trabajo continuo |language=es |trans-title=University of the Republic and lead contamination: continuous work |date=16 August 2019 |archive-date=21 May 2021}}</ref>
*Venezuela: 2005
{{Col-break}}

===== Asia =====
*Afghanistan: 2016<ref name="bbc.co.uk">{{Cite web|url=https://www.bbc.co.uk/news/world-58388810|title=Highly polluting leaded petrol now eradicated from the world, says UN|website=BBC News|date=31 August 2021|access-date=1 September 2021|archive-date=1 September 2021|archive-url=https://web.archive.org/web/20210901102025/https://www.bbc.co.uk/news/world-58388810|url-status=live}}</ref>
*Bangladesh: 1999
*China: 2000
*Hong Kong: 1999
*India: March 2000<ref name="blogs.wsj.com">{{cite web|last1=Venkatesh|first1=Thuppil|title=A Surprising Source of Lead Poisoning: India's Idols|url=https://blogs.wsj.com/indiarealtime/2015/06/04/an-unlikely-source-of-lead-poisoning-indias-idols/|website=The Wall Street Journal|access-date=18 April 2016|date=2015-06-04|archive-date=6 May 2018|archive-url=https://web.archive.org/web/20180506041349/https://blogs.wsj.com/indiarealtime/2015/06/04/an-unlikely-source-of-lead-poisoning-indias-idols/|url-status=live}}</ref>
*Saudi Arabia: 2001
*Indonesia: 2006
*Iran: 2003
*Iraq: 2018<ref name="wedocs.unep.org">{{cite web |title=Leaded Petrol Phase-out: Global Status March 2018 |url=https://wedocs.unep.org/bitstream/handle/20.500.11822/25422/MapWorldLead_March2018.pdf?sequence=1&isAllowed=y |website=wedocs.unep.org |access-date=1 September 2021 |archive-date=15 September 2021 |archive-url=https://web.archive.org/web/20210915221636/https://wedocs.unep.org/bitstream/handle/20.500.11822/25422/MapWorldLead_March2018.pdf?sequence=1&isAllowed=y |url-status=live }}</ref><ref name="ReferenceA">{{cite web |title=Leaded Petrol Phase-out: Global Status July 2018 |url=https://wedocs.unep.org/bitstream/handle/20.500.11822/25756/MapWorldLead_July2018.pdf?sequence=1&isAllowed=y |access-date=1 September 2021 |archive-date=1 September 2021 |archive-url=https://web.archive.org/web/20210901080729/https://wedocs.unep.org/bitstream/handle/20.500.11822/25756/MapWorldLead_July2018.pdf?sequence=1&isAllowed=y |url-status=live }}</ref>
*Japan: 1986
*Malaysia: 2000
*Myanmar: 2016<ref name="bbc.co.uk"/>
*Nepal: 2000
*North Korea: 2016<ref name="bbc.co.uk"/>
*Pakistan: 2001<ref>{{cite journal|title=Status of children's blood lead levels in Pakistan: implications for research and policy| pmc=2494596 | pmid=18359052|doi=10.1016/j.puhe.2007.08.012|volume=122| issue=7 |year=2008|pages=708–15| last1=Kadir| first1=M. M.| last2=Janjua| first2=N. Z.| last3=Kristensen| first3=S.| last4=Fatmi| first4=Z.| last5=Sathiakumar| first5=N.| journal=Public Health}}</ref>
*Philippines: 2000
*Singapore: 1998
*South Korea: 1993
*Sri Lanka: 1999
*Taiwan: 2000<ref>職業安全衛生法-{{cite web|title=【四烷基鉛中毒預防規則】|url=https://law.moj.gov.tw/LawClass/LawAll.aspx?pcode=N0060019|access-date=15 July 2022|archive-date=16 April 2021|archive-url=https://web.archive.org/web/20210416163534/https://law.moj.gov.tw/LawClass/LawAll.aspx?pcode=N0060019|url-status=live}} <br />法規類別：	行政 ＞ 勞動部 ＞ 職業安全衛生目</ref>
*Thailand: 1996
*Turkey: 2006<ref>{{cite web | url = https://www.resmigazete.gov.tr/eskiler/2004/06/20040611.htm#8 | title = Çevre ve Orman Bakanlığından: Benzin ve Motorin Kalitesi Yönetmeliği (2003/17/AT ile değişik 98/70/AT) | trans-title = From the Ministry of Environment and Forestry: Gasoline and Diesel Quality Regulation (98/70/EC as amended with 2003/17/EC) | publisher = [[Official Gazette of the Republic of Turkey|Resmi Gazete]] | date = 11 June 2004 | access-date = 23 April 2022 | issue = 25489 | language = tr | archive-date = 1 January 2015 | archive-url = https://web.archive.org/web/20150101012357/https://www.resmigazete.gov.tr/eskiler/2004/06/20040611.htm#8 | url-status = live }}</ref>
*United Arab Emirates: 2003<ref>{{Cite web|url=https://gulfnews.com/uae/uae-switches-to-unleaded-fuel-1.343442|title=UAE switches to unleaded fuel|website=Gulf News|date=2003-01-01|access-date=2020-11-28|archive-date=12 April 2020|archive-url=https://web.archive.org/web/20200412131951/https://gulfnews.com/uae/uae-switches-to-unleaded-fuel-1.343442|url-status=live}}</ref>
*Vietnam: 2001 <ref>{{Cite web |date=August 2002 |publisher=Joint UNDP/World Bank Energy Sector Management Assistance Programme (ESMAP) |title=An Overnight Success: Vietnam's Switch to Unleaded Gasoline |url=https://documents1.worldbank.org/curated/pt/441911468762898801/pdf/multi0page.pdf |access-date=2024-06-14 |website=World Bank |archive-date=14 June 2024 |archive-url=https://web.archive.org/web/20240614194104/https://documents1.worldbank.org/curated/pt/441911468762898801/pdf/multi0page.pdf |url-status=live }}</ref>
*Yemen: 2018<ref name="wedocs.unep.org"/><ref name="ReferenceA"/>
{{Col-break}}

===== Oceania =====
*Australia: 2002<ref>{{cite news|url=http://www.ens-newswire.com/ens/jul2004/2004-07-26-04.asp|title=Australia Cuts Sulfur Content in Transport Fuels|author=<!--Staff writer(s); no by-line.-->|date=26 July 2004|publisher=[[Environment News Service]]|archive-url=https://web.archive.org/web/20050422174432/http://www.ens-newswire.com/ens/jul2004/2004-07-26-04.asp|archive-date=22 April 2005}}</ref>
*New Zealand: 1996
*Guam: 1 January 1996 (USA)
*Samoa: 2001
{{col-end}}

===== Africa =====
*Egypt: 1999
*South Africa: 2006
*Leaded petrol was supposed to be completely phased out continent-wide on 1 January 2006, following a ban initiated from the 2002 Earth Summit.<ref>{{cite news |title = UN hails green triumph as leaded petrol is banned throughout Africa |last = Lean |first = Geoffrey |date = 1 January 2006 |work = [[The Independent]] |url=https://www.independent.co.uk/environment/un-hails-green-triumph-as-leaded-petrol-is-banned-throughout-africa-521255.html |archive-url = https://web.archive.org/web/20101112114249/https://www.independent.co.uk/environment/un-hails-green-triumph-as-leaded-petrol-is-banned-throughout-africa-521255.html |archive-date = 12 November 2010}}</ref> However, in Algeria refineries needed to be altered; as a result, leaded fuel remained available in parts of [[Algeria]],<ref name=leadgroup /> with phaseout scheduled for 2016. After the Algerian Government outlawed the sale of leaded petrol throughout all of Algeria, leaded petrol was finally phased out by July 2021.<ref>{{cite news|title = Africa adopts continent-wide sustainable transport agenda |last = Chandola |first = Priyanka |date = 6 January 2015 |url = http://www.downtoearth.org.in/content/africa-adopts-continent-wide-sustainable-transport-agenda |archive-url = https://web.archive.org/web/20150919192952/http://www.downtoearth.org.in/news/africa-adopts-continent-wide-sustainable-transport-agenda-48089 |archive-date = 19 September 2015 |url-status = live}}</ref><ref>{{Cite web|date=28 September 2020|title=Marketing of Super-Leaded Petrol to stop as of 2021|url=https://www.aps.dz/en/economy/35909-marketing-of-super-leaded-petrol-to-stop-as-of-2021|access-date=24 August 2021|website=Algeria Press Service|archive-date=24 August 2021|archive-url=https://web.archive.org/web/20210824080451/https://www.aps.dz/en/economy/35909-marketing-of-super-leaded-petrol-to-stop-as-of-2021|url-status=live}}</ref><ref>{{cite book |last1=Smil |first1=Vaclav |title=Invention and innovation: a brief history of hype and failure |date=2023 |publisher=The MIT press |location=Cambridge, Massachusetts |isbn=978-0-262-04805-7 |page=34 |quote=The two penultimate holdouts were Venezuela, which initiated a ban in 2005, and Indonesia, which did so in 2006, and it was not until July 2021 that Algeria stopped selling leaded gasoline.}}</ref>

==== In motor racing ====
Leaded fuel was commonly used in professional [[motor racing]], until its phase out beginning in the 1990s. Since 1992, [[Formula One]] racing cars have been required to use fuel containing no more than 5&nbsp;mg/L of lead.<ref>{{cite web|url=https://www.fia.com/regulation/category/110|title=FIA Formula 1 Technical Regulations 2018|date=7 December 2017|access-date=26 October 2018|archive-date=22 February 2019|archive-url=https://web.archive.org/web/20190222080320/https://www.fia.com/regulation/category/110|url-status=live}}</ref>{{verify inline|reason=Publication date was cited using an ambiguous date format. Might actually be 12 July|date=August 2023}}

[[NASCAR]] began experimentation in 1998 with an unleaded fuel, and in 2006 began switching the national series to unleaded fuel, completing the transition at the [[2007 Auto Club 500|Fontana round in February 2007]] when the premier class switched. This was influenced after blood tests of NASCAR teams revealed elevated blood lead levels.<ref>{{cite journal |last1= O'Neil |first1= J. |last2= Steele |first2= G. |last3= McNair |first3=C. S. |last4= Matusiak |first4=M. M. |last5= Madlem |first5= J. |pmid= 16361219 |year= 2006 |pages= 67–71 |issue= 2 |volume= 3 |journal= Journal of Occupational and Environmental Hygiene |title= Blood lead levels in NASCAR Nextel Cup Teams |doi= 10.1080/15459620500471221|bibcode= 2006JOEH....3...67O |s2cid= 33119520 }}</ref><ref>{{cite web|url= http://nascar.about.com/od/cars/a/unleaded08.htm |title=NASCAR to Use Unleaded Fuel in 2008|archive-url=https://web.archive.org/web/20080528131514/http://nascar.about.com/od/cars/a/unleaded08.htm|archive-date=28 May 2008|access-date=5 January 2020}}</ref>

==== Aviation gasoline ====
{{Main|Avgas}}
TEL remains an ingredient of 100 [[octane rating|octane]] [[avgas]] for piston-engine aircraft. The current formulation of 100LL (low lead, blue) aviation gasoline contains {{convert|2.12|g/USgal|g/L}} of TEL, half the amount of the previous 100/130 (green) octane avgas (at 4.24 grams per gallon),<ref>{{cite web|url= http://www.aopa.org/whatsnew/regulatory/reglead.html |title=Issues Related to Lead in Avgas |publisher= Aircraft Owners and Pilots Association |archive-url= https://web.archive.org/web/20110918234831/http://www.aopa.org/whatsnew/regulatory/reglead.html |archive-date= 18 September 2011|date= 2016-03-08}}</ref> and twice as much as the 1 gram per gallon permitted in regular automotive leaded gasoline prior to 1988 and substantially greater than the allowed 0.001 grams per gallon in automotive unleaded gasoline sold in the United States today.<ref>{{cite web |url= http://www.autofuelstc.com/autofuelstc/pa/Information.html |title= Modifications / Octane / Lead Content / Fuel Specs / Limitations / Certification |publisher= Petersen Aviation Inc. |archive-url= https://web.archive.org/web/20120330200056/http://www.autofuelstc.com/autofuelstc/pa/Information.html |archive-date= 30 March 2012}}</ref> The United States Environmental Protection Agency, [[FAA]], and others are working on economically feasible replacements for leaded avgas, which still releases 100 tons of lead every year.<ref>{{cite news |url=http://www.runwaygirlnetwork.com/2014/07/30/us-leads-avgas-effort-for-lead-free-air/ |title=US leads Avgas effort for lead-free air |last1=Bryan |first1=Chelsea |date=30 July 2014 |website=www.runwaygirlnetwork.com |publisher=Kirby Media Group |access-date=31 July 2014 |archive-date=8 August 2014 |archive-url=https://web.archive.org/web/20140808052051/http://www.runwaygirlnetwork.com/2014/07/30/us-leads-avgas-effort-for-lead-free-air/ |url-status=live }}</ref>

==== Alternative antiknock agents ====
Antiknock agents are classed as ''high-percentage'' additives, such as alcohol, and ''low-percentage'' additives based on [[Heavy metal (chemistry)|heavy elements]]. Since the main problem with TEL is its lead content, many alternative additives that contain less poisonous metals have been examined. A manganese-carrying additive, [[methylcyclopentadienyl manganese tricarbonyl]] (MMT or methylcymantrene), was used for a time as an antiknock agent, though its safety is controversial and it has been the subject of bans and lawsuits. [[Ferrocene]], an [[Organometallic chemistry|organometallic]] compound of [[iron]], is also used as an antiknock agent although with some significant drawbacks.<ref>{{cite web|url=http://www.osd.org.tr/14.pdf|archive-url=https://web.archive.org/web/20060505193757/http://www.osd.org.tr/14.pdf|title=Application of fuel additives|archive-date=5 May 2006}}</ref>

High-percentage additives are [[organic compound]]s that do not contain metals, but require much higher blending ratios, such as 20–30% for [[benzene]] and [[ethanol]]. It had been established by 1921 that ethanol was an effective antiknock agent, but TEL was introduced instead mainly for commercial reasons.<ref name="Kitman" /> [[Oxygenate]]s such as [[tert-Amyl methyl ether|TAME]] derived from natural gas, [[MTBE]] made from methanol, and ethanol-derived [[ETBE]], have largely supplanted TEL. MTBE has environmental risks of its own and there are also bans on its use.{{citation needed|date=September 2021}}

Improvements to gasoline itself decrease the need for antiknock additives. Synthetic [[iso-octane]] and [[alkylate]] are examples of such blending stocks. Benzene and other high-octane [[Aromatic hydrocarbon|aromatics]] can be also blended to raise the octane number, but they are disfavored today because of [[toxicity]] and [[carcinogen]]icity.{{citation needed|date=September 2021}}

== Toxicity ==
6&nbsp;mL of tetraethyllead is enough to induce severe [[lead poisoning]].<ref>{{cite web | url=https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+841 | title=TETRAETHYL LEAD - National Library of Medicine HSDB Database | access-date=28 April 2019 | archive-date=28 April 2019 | archive-url=https://web.archive.org/web/20190428172250/https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a%3Fdbs%2Bhsdb:@term%2B@DOCNO%2B841 }}</ref> The hazards of TEL content are heightened due to the compound's volatility and high [[lipophilicity]], enabling it to easily cross the [[blood–brain barrier]].

Early symptoms of acute exposure to tetraethyllead can manifest as irritation of the eyes and skin, sneezing, fever, vomiting, and a metallic taste in the mouth. Later symptoms of acute TEL poisoning include [[pulmonary edema]], [[anemia]], ataxia, convulsions, severe weight loss, [[delirium]], irritability, hallucinations, nightmares, fever, muscle and joint pain, [[cerebral edema|swelling of the brain]], coma, and damage to cardiovascular and renal organs.<ref name="Stasik1969">{{Cite journal|url = https://link.springer.com/article/10.1007/BF00577576|doi = 10.1007/BF00577576|pmid = 5795752|title = Acute tetraethyllead poisoning|journal = Archiv für Toxikologie|volume = 24|issue = 4|pages = 283–291|date = December 1969|last1 = Stasik|first1 = M.|last2 = Byczkowska|first2 = Z.|last3 = Szendzikowski|first3 = S.|last4 = Fiedorczuk|first4 = Z.| bibcode=1969ArTox..24..283S |s2cid = 19189740|access-date = 28 April 2019|archive-date = 12 December 2022|archive-url = https://web.archive.org/web/20221212053742/https://link.springer.com/article/10.1007/BF00577576|url-status = live|url-access = subscription}}</ref>
Chronic exposure to TEL can cause long-term negative effects such as [[memory loss]], delayed reflexes, neurological problems, insomnia, tremors, psychosis, loss of attention, and an overall decrease in IQ and cognitive function.<ref>{{cite journal|pmc=490811|title=Toxic substances and the nervous system: the role of clinical observation|year=1981|doi= 10.1136/jnnp.44.1.1|last1=Le Quesne|first1=P. M.|journal=Journal of Neurology, Neurosurgery & Psychiatry|volume=44|issue=1|pages=1–8|pmid=7009792}}</ref>

The [[carcinogenity]] of tetraethyllead is debatable. It is believed to harm the male reproductive system and cause birth defects.<ref>{{cite web |url=https://nj.gov/health/eoh/rtkweb/documents/fs/1817.pdf |title=Fact sheet |location=New Jersey |publisher=Department of Health |access-date=2019-11-11 |archive-date=1 December 2019 |archive-url=https://web.archive.org/web/20191201003121/https://nj.gov/health/eoh/rtkweb/documents/fs/1817.pdf |url-status=live }}</ref>

Concerns over the [[lead poisoning|toxicity of lead]]<ref>{{Cite journal |title=Low-level lead-induced neurotoxicity in children: an update on central nervous system effects |last=Finkelstein|first=Yoram|date=July 1998 |doi=10.1016/S0165-0173(98)00011-3 |pmid=9622620|volume=27 |issue=2|journal=Brain Research Reviews |pages=168–176|s2cid=15666676}}</ref> eventually led to the ban on TEL in automobile gasoline in many countries. Some neurologists have speculated that the lead phaseout may have caused average IQ levels to rise by several points in the US (by reducing cumulative brain damage throughout the population, especially in the young). For the entire US population, during and after the TEL phaseout, the mean blood lead level dropped from 16 μg/dL in 1976 to only 3 μg/dL in 1991.<ref name="Reyes" /> The U.S. Centers of Disease control previously labelled children with 10&nbsp;μg/dL or more as having a "blood lead level of concern". In 2021, the level was lowered in accordance with the average lead level in the U.S. decreasing to 3.5&nbsp;μg/dL or more as having a "blood lead level of concern".<ref>{{Cite web |date=October 27, 2021 |title=Blood Lead Reference Value |url=https://www.cdc.gov/nceh/lead/data/blood-lead-reference-value.htm |access-date=June 3, 2022 |website=Centers for Disease Control and Prevention |archive-date=8 June 2022 |archive-url=https://web.archive.org/web/20220608165723/https://www.cdc.gov/nceh/lead/data/blood-lead-reference-value.htm |url-status=live }}</ref><ref>{{Cite web |date=May 11, 2022 |title=Blood Lead Levels in Children |url=https://www.cdc.gov/nceh/lead/prevention/blood-lead-levels.htm |access-date=June 3, 2022 |website=Centers for Disease Control and Prevention |archive-date=4 June 2022 |archive-url=https://web.archive.org/web/20220604012038/https://www.cdc.gov/nceh/lead/prevention/blood-lead-levels.htm |url-status=live }}</ref>

== History ==
In 1853, German chemist [[Carl Jacob Löwig|Karl Jacob Löwig]] (1803–1890) first prepared what he claimed was Pb<sub>2</sub>(C<sub>2</sub>H<sub>5</sub>)<sub>3</sub> from [[ethyl iodide]] and an alloy of lead and sodium.<ref>Löwig (1853) [https://scholar.archive.org/work/jqd4mhibvbb2lftuwrwi5jnlwa "''Ueber Methplumbäthyl''"] (On meta-lead ethyl) ''Annalen der Chemie und Pharmacie'', '''88''' : 318-322.</ref> In 1859, English chemist [[George Bowdler Buckton]] (1818–1905) reported what he claimed was Pb(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub> from [[zinc ethyl]] (Zn(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>) and [[lead(II) chloride]].<ref>George Bowdler Buckton (1859) [https://www.jstor.org/stable/111509?seq=1 "Further remarks on the organo-metallic radicals, and observations more particularly directed to the isolation of mercuric, plumbic, and stannic ethyl,"] {{Webarchive|url=https://web.archive.org/web/20230607225234/https://www.jstor.org/stable/111509?seq=1 |date=7 June 2023 }} ''Proceedings of the Royal Society of London'', '''9''' : 309–316. For Buckton's preparation of tetraethyl lead, see pages 312–314.</ref> Later authors credit both methods of preparation with producing tetraethyl lead.<ref>See, for example:
* H. E. Roscoe and C. Schorlemmer, ''A Treatise on Chemistry'', Volume 3, Part 1 (New York, New York: D. Appleton and Co., 1890), [https://books.google.com/books?id=zs0cAQAAIAAJ&pg=PA466 page 466].
* Frankland and Lawrence credit Buckton with synthesizing tetraethyl lead in: E. Frankland and Awbrey Lawrance (1879) "On plumbic tetrethide," ''Journal of the Chemical Society, Transactions'', '''35''' : 244-249.</ref>

=== In fuel ===
TEL remained unimportant commercially until the 1920s.<ref name=Kitman>Kitman, J. (2 March 2000). [https://www.thenation.com/article/archive/secret-history-lead/ "The Secret History of Lead."] {{Webarchive|url=https://web.archive.org/web/20140510105351/http://www.thenation.com/article/secret-history-lead?page=full |date=10 May 2014 }} ''[[The Nation]]''. Retrieved 17 August 2009.</ref> In 1921, at the direction of DuPont Corporation, which manufactured TEL, it was found to be an effective [[antiknock agent]] by [[Thomas Midgley Jr.|Thomas Midgley]], working under [[Charles Kettering]] at [[General Motors Corporation]] Research.<ref>"Leaded Gasoline, Safe Refrigeration, and Thomas Midgley, Jr." Chapter 6 in S. Bertsch McGrayne. ''Prometheans in the Lab''. McGraw-Hill: New York, 2002. {{ISBN|0-07-140795-2}}</ref> General Motors [[patent]]ed the use of TEL as an antiknock agent and used the name "Ethyl" that had been proposed by Kettering in its marketing materials, thereby avoiding the negative connotation of the word "lead".<ref name=Kitman /> Early research into "[[engine knocking]]" (also called "pinging" or "pinking") was also led by A.H. Gibson and [[Harry Ricardo]] in England and Thomas Boyd in the United States. The discovery that [[lead]] additives modified this behavior led to the widespread adoption of their use in the 1920s, and therefore more powerful, higher-compression engines.<ref name=Kovarik2005>{{cite journal |last=Kovarik |first=W. |title=Ethyl-leaded gasoline: how a classic occupational disease became an international public health disaster |journal=Int J Occup Environ Health |volume=11 |issue=4 |pages=384–97 |year=2005 |pmid=16350473 |doi=10.1179/oeh.2005.11.4.384 |s2cid=44633845 |url=http://www.radford.edu/~wkovarik/ethylwar/IJOEH.pdf |archive-url=https://web.archive.org/web/20140711220018/http://www.radford.edu/~wkovarik/ethylwar/IJOEH.pdf |archive-date=11 July 2014}}</ref> In 1924, [[Standard Oil of New Jersey]] (ESSO/EXXON) and General Motors created the [[Ethyl Corporation|Ethyl Gasoline Corporation]] to produce and market TEL. [[Deepwater, New Jersey|Deepwater]], [[New Jersey]], across the river from [[Wilmington, Delaware|Wilmington]], was the site for production of some of DuPont's most important chemicals, particularly TEL. After TEL production at the [[Bayway Refinery]] was shut down, Deepwater was the only plant in the Western hemisphere producing TEL up to 1948, when it accounted for the bulk of the Dupont/Deepwater's production.<ref>{{cite web|url=http://www2.dupont.com/Phoenix_Heritage/en_US/1914_a_detail.html|title=Innovation Starts Here – DuPont USA|author=zk4540|access-date=22 April 2014|archive-date=30 May 2014|archive-url=https://web.archive.org/web/20140530144900/http://www2.dupont.com/Phoenix_Heritage/en_US/1914_a_detail.html}}</ref>

=== Initial controversy ===
The toxicity of concentrated TEL was recognized early on, as lead had been recognized since the 19th century as a dangerous substance that could cause [[lead poisoning]]. In 1924, a public controversy arose over the "loony gas", after five<ref>{{Cite magazine|url=https://www.wired.com/2013/01/looney-gas-and-lead-poisoning-a-short-sad-history/|title=Looney Gas and Lead Poisoning: A Short, Sad History|first=Deborah|last=Blum|magazine=Wired|date=5 January 2013|via=www.wired.com|access-date=29 May 2020|archive-date=21 March 2017|archive-url=https://web.archive.org/web/20170321225320/https://www.wired.com/2013/01/looney-gas-and-lead-poisoning-a-short-sad-history/|url-status=live}}</ref> workers died, and many others were severely injured, in Standard Oil refineries in New Jersey.<ref>{{Cite news|url=https://www.bbc.com/news/business-40593353|title=Why did we use leaded petrol for so long?|last=Harford|first=Tim|date=2017-08-28|work=BBC News|access-date=2017-09-03|language=en-GB|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713180346/https://www.bbc.com/news/business-40593353|url-status=live}}</ref> There had also been a private controversy for two years prior to this controversy; several public health experts, including [[Alice Hamilton]] and [[Yandell Henderson]], engaged Midgley and Kettering with letters warning of the dangers to public health.<ref name=Kovarik2005 /> After the death of the workers, dozens of newspapers reported on the issue.<ref>{{cite web|url=https://yarchive.net/chem/tetraethyl_lead.html|title=Tetraethyl lead (Bruce Hamilton)|website=yarchive.net|access-date=11 November 2019|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713182107/https://yarchive.net/chem/tetraethyl_lead.html|url-status=live}}</ref> ''The New York Times'' editorialized in 1924 that the deaths should not interfere with the production of more powerful fuel.<ref name=Kovarik2005 />

To settle the issue, the [[U.S. Public Health Service]] conducted a conference in 1925, and the sales of TEL were voluntarily suspended for one year to conduct a hazard assessment.<ref name=Seyferth /><ref name=Kitman /><ref>Alan P. Loeb, "Paradigms Lost: A Case Study Analysis of Models of Corporate Responsibility for the Environment," Business and Economic History, Vol. 28, No. 2, Winter 1999, at 95.</ref> The conference was initially expected to last for several days, but reportedly the conference decided that evaluating presentations on alternative anti-knock agents was not "its province", so it lasted a single day. Kettering and Midgley stated that no alternatives for anti-knocking were available, although private memos showed discussion of such agents. One commonly discussed agent was ethanol. The Public Health Service created a committee that reviewed a government-sponsored study of workers and an Ethyl lab test, and concluded that while leaded gasoline should not be banned, it should continue to be investigated.<ref name=Kovarik2005 /> The low concentrations present in gasoline and exhaust were not perceived as immediately dangerous. A [[U.S. Surgeon General]] committee issued a report in 1926 that concluded there was no real evidence that the sale of TEL was hazardous to human health but urged further study.<ref name=Kitman /> In the years that followed, research was heavily funded by the lead industry; in 1943, [[Randolph Byers]] found children with lead poisoning had behavior problems, but the [[Lead Industries Association]] threatened him with a lawsuit and the research ended.<ref name=Kovarik2005 /><ref>{{cite journal |last=Silbergeld |first=Ellen |author-link=Ellen Silbergeld |date=February 1995 |title=Annotation: Protection of the Public Interest, Allegations of Scientific Misconduct, and the Needleman Case |journal=American Journal of Public Health |volume=85 |issue=2 |pages=165–166 |doi=10.2105/AJPH.85.2.165 |pmid=7856774 |pmc=1615323 }}</ref>

In the late 1920s, [[Robert A. Kehoe]] of the [[University of Cincinnati]] was the Ethyl Corporation's chief medical consultant and one of the lead industry's staunchest advocates, who would not be discredited until decades later by Dr. [[Clair Patterson]]'s work on human lead burdens (see below) and other studies.<ref name=Kitman /> In 1928, Dr. Kehoe expressed the opinion that there was no basis for concluding that leaded fuels posed any health threat.<ref name="Kitman" /> He convinced the [[Hugh S. Cumming|Surgeon General]] that the [[dose–response relationship]] of lead had "no effect" below a certain threshold.<ref>Bryson, Christopher (2004). ''The Fluoride Deception'', p. 41. Seven Stories Press. Citing historian Lynne Snyder.</ref> As the head of Kettering Laboratories for many years, Kehoe would become a chief promoter of the safety of TEL, an influence that did not begin to wane until about the early 1960s. But by the 1970s, the general opinion of the safety of TEL would change, and by 1976 the U.S. government would begin to require the phaseout of this product.<ref>{{cite web |title=EPA Fuel Regulations (FR-1973-12-06) |url=https://www.govinfo.gov/content/pkg/FR-1973-12-06/pdf/FR-1973-12-06.pdf#page=163 |website=GovInfo |publisher=U.S. Government Publishing Office |access-date=30 December 2024 |page=163}}</ref>

In the late 1940s and early 1950s, [[Clair Patterson|Clair Cameron Patterson]] accidentally discovered the pollution caused by TEL in the environment while determining the [[age of the Earth]]. As he attempted to measure lead content of very old rocks, and the time it took uranium to decay into lead, the readings were made inaccurate by lead in the environment that contaminated his samples. He was then forced to work in a [[cleanroom]] to keep his samples uncontaminated by environmental pollution of lead. After coming up with a fairly accurate estimate of the age of the Earth, he turned to investigating the lead contamination problem by examining ice cores from countries such as [[Greenland]]. He realized that the lead contamination in the environment dated from about the time that TEL became widely used as a fuel additive in gasoline. Being aware of the health dangers posed by lead and suspicious of the pollution caused by TEL, he became one of the earliest and most effective proponents of removing it from use.<ref>{{cite book |last = Bryson |first = B. |year = 2003 |chapter = 10. Getting the Lead Out |title = A Short History of Nearly Everything |publisher = Broadway Books |location = New York |isbn = 978-0-7679-0818-4 |chapter-url-access = registration |chapter-url = https://archive.org/details/shorthistoryofne00brys }}</ref><ref>[https://www.mentalfloss.com/article/94569/clair-patterson-scientist-who-determined-age-earth-and-then-saved-it The Most Important Scientist You've Never Heard Of] {{Webarchive|url=https://web.archive.org/web/20201107223351/https://www.mentalfloss.com/article/94569/clair-patterson-scientist-who-determined-age-earth-and-then-saved-it |date=7 November 2020 }}, BY Lucas Reilly, May 17, 2017, mentalfloss.com.</ref>

In the 1960s, the first clinical works were published proving the toxicity of this compound in humans, e.g. by [[Mirosław Jan Stasik]].<ref name="Stasik1969"/>

===Modern findings===
In the 1970s, [[Herbert Needleman]] found that higher lead levels in children were correlated with decreased school performance. Needleman was repeatedly accused of scientific misconduct by individuals within the lead industry, but he was eventually cleared by a scientific advisory council.<ref name=Kovarik2005 /> Needleman also wrote the average US child's blood lead level was 13.7 μg/dL in 1976 and that Patterson believed that everyone was to some degree poisoned by TEL in gasoline.<ref name="Needleman1999">{{Cite journal |doi = 10.1006/enrs.2000.4069 |pmid = 10991779 |title = The Removal of Lead from Gasoline: Historical and Personal Reflections |journal = Environmental Research |volume = 84 |issue = 1 |pages = 20–35 |year = 2000 |last1 = Needleman |first1 = H.|bibcode = 2000ER.....84...20N }}</ref>

In the U.S. in 1973, the [[United States Environmental Protection Agency]] issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, which therefore came to be known as the "lead phasedown" program. EPA's rules were issued under section 211 of the [[Clean Air Act (United States)|Clean Air Act]], as amended 1970. The Ethyl Corp challenged the EPA regulations in Federal court. Although the EPA's regulation was initially invalidated,<ref name=Kovarik2005 /> the EPA won the case on appeal, so the TEL phasedown began to be implemented in 1976. Leaded gas was banned in vehicles with [[catalytic converters]] in 1975 due to damage of catalytic converters but it continued to be sold for vehicles without catalytic converters.<ref>{{cite web |title=Gasoline and the environment - leaded gasoline - U.S. Energy Information Administration (EIA) |url=https://www.eia.gov/energyexplained/gasoline/gasoline-and-the-environment-leaded-gasoline.php#:~:text=Because%20leaded%20gasoline%20damages%20catalytic,farm%20equipment%2C%20and%20marine%20engines. |website=www.eia.gov |access-date=23 June 2023 |archive-date=23 June 2023 |archive-url=https://web.archive.org/web/20230623110156/https://www.eia.gov/energyexplained/gasoline/gasoline-and-the-environment-leaded-gasoline.php#:~:text=Because%20leaded%20gasoline%20damages%20catalytic,farm%20equipment%2C%20and%20marine%20engines. |url-status=live }}</ref>  Additional regulatory changes were made by EPA over the next decade (including adoption of a trading market in "lead credits" in 1982 that became the precursor of the Acid Rain Allowance Market, adopted in 1990 for SO<sub>2</sub>), but the decisive rule was issued in 1985.<ref>{{cite web |url=http://yosemite.epa.gov/ee/epa/eed.nsf/fa6512c6e51c4a208525766200639df2/df94392f72ebb26085257746000aff52!OpenDocument |title=Lead Credit Trading |author=<!--Staff writer(s); no by-line.--> |date=c. 2006 |website=National Center for Environmental Economics |publisher=US EPA |access-date=3 October 2014 |archive-date=3 October 2014 |archive-url=https://web.archive.org/web/20141003162827/http://yosemite.epa.gov/ee/epa/eed.nsf/fa6512c6e51c4a208525766200639df2/df94392f72ebb26085257746000aff52!OpenDocument }}</ref> The EPA mandated that lead additive be reduced by 91 percent by the end of 1986. A 1994 study had indicated that the concentration of lead in the blood of the U.S. population had dropped 78% from 1976 to 1991.<ref>{{cite journal |last1= Pirkle |first1= J.L. |last2= Brody |first2= D.J. |last3= Gunter |first3= E.W. |title = The Decline in Blood Lead Levels in the United States: The National Health and Nutrition Examination Surveys (NHANES) |journal= [[JAMA (journal)|JAMA]] |year= 1994 |volume= 272 |pages= 284–291 |doi= 10.1001/jama.1994.03520040046039 |issue= 4 |pmid= 8028141 |display-authors=etal}}</ref> The U.S. phasedown regulations also were due in great part to studies conducted by [[Philip J. Landrigan]].<ref>{{cite journal |last1=Pirisi |first1=Angela |title=Profile Philip Landrigan: children's health crusader |journal=The Lancet |date=9 April 2005 |volume=365 |issue=9467 |page=1301 |doi=10.1016/S0140-6736(05)61015-X |pmid=15823369 |s2cid=35297688 |url=https://www.thelancet.com/pdfs/journals/lancet/PIIS014067360561015X.pdf |access-date=31 August 2021 |archive-date=28 March 2023 |archive-url=https://web.archive.org/web/20230328104415/https://www.thelancet.com/pdfs/journals/lancet/PIIS014067360561015X.pdf |url-status=live }}</ref>

In Europe, Professor [[Derek Bryce-Smith]] was among the first to highlight the potential dangers of TEL and became a leading campaigner for removal of lead additives from petrol.<ref>{{Cite news|url=https://www.theguardian.com/theguardian/2011/jul/19/derek-bryce-smith-obituary|title=Derek Bryce-Smith obituary|newspaper=the Guardian|date=2011-07-19|last1=Gilbert|first1=Andrew|access-date=17 December 2016|archive-date=13 July 2024|archive-url=https://web.archive.org/web/20240713181409/https://www.theguardian.com/theguardian/2011/jul/19/derek-bryce-smith-obituary|url-status=live}}</ref> 

From 1 January 1996, the [[Clean Air Act (United States)|U.S. Clean Air Act]] banned the sale of leaded fuel for use in on-road vehicles although that year the US EPA indicated that TEL could still be used in aircraft, racing cars, farm equipment, and marine engines.<ref>{{cite web |url=https://www.epa.gov/archive/epa/aboutepa/epa-takes-final-step-phaseout-leaded-gasoline.html |title=EPA Takes Final Step in Phaseout of Leaded Gasoline |author=<!--Not stated--> |date=29 January 1996 |website=US EPA Archive |publisher=US EPA |access-date=5 January 2020 |quote=Effective 1 January 1996, the Clean Air Act banned the sale of the small amount of leaded fuel that was still available in some parts of the country for use in on-road vehicles. EPA said fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines. |archive-date=9 September 2021 |archive-url=https://web.archive.org/web/20210909213434/https://archive.epa.gov/epa/aboutepa/epa-takes-final-step-phaseout-leaded-gasoline.html |url-status=live }}</ref> Thus, what had begun in the U.S. as a phase down ultimately ended in a phase-out for on-road vehicle TEL. Similar bans in other countries have resulted in lowering levels of lead in people's [[blood]]streams.<ref>{{Cite journal| title = Blood Lead Secular Trend in a Cohort of Children in Mexico City (1987–2002) |last1= Schnaas |first1= Lourdes |last2= Rothenberg |first2= Stephen J. |first3= María-Fernanda |last3= Flores |first4= Sandra |last4= Martínez |first5= Carmen |last5= Hernández |first6= Erica |last6= Osorio |first7= Estela |last7= Perroni | journal = [[Environ. Health Perspect.]] | year = 2004 | volume = 112 | issue = 10 | pages = 1110–1115 | doi = 10.1289/ehp.6636 | pmid = 15238286 | pmc = 1247386|bibcode= 2004EnvHP.112.1110S }}</ref><ref>{{Cite journal| journal = [[Archives of Environmental Health]] | volume = 59 | issue = 4 | year = 2004 | pages = 182–187 | doi = 10.3200/AEOH.59.4.182-187 | pmid = 16189990 | title = Rapid Drop in Infant Blood Lead Levels during the Transition to Unleaded Gasoline Use in Santiago, Chile | author1 = Paulina Pino |author2=Tomás Walter |author3=Manuel J. Oyarzún |author4=Matthew J. Burden |author5=Betsy Lozoff| s2cid = 25089958 }}</ref>

Taking cue from the domestic programs, the U.S. Agency for International Development undertook an initiative to reduce tetraethyl lead use in other countries, notably its efforts in Egypt begun in 1995. In 1996, with the cooperation of the U.S. AID, Egypt took almost all of the lead out of its gasoline. The success in Egypt provided a model for AID efforts worldwide.<ref>{{cite magazine |last=Franchi |first=Valerie |date=October 1997 |title=Getting the Lead Out |url=https://pdf.usaid.gov/pdf_docs/PNACZ643.pdf |magazine=Front Lines |location=Washington, DC |publisher=USAID |archive-url=https://web.archive.org/web/20170304012340/https://pdf.usaid.gov/pdf_docs/PNACZ643.pdf |archive-date=4 March 2017 |access-date=13 January 2024}}</ref>

By 2000, the TEL industry had moved the major portion of their sales to developing countries whose governments they lobbied against phasing out leaded gasoline.<ref name=Kitman /> Leaded gasoline was withdrawn entirely from the European Union market on 1 January 2000, although it had been banned earlier in most member states. Other countries also phased out TEL.<ref name=meca2003>{{cite web |url=http://www.meca.org/galleries/default-file/lead0103_%28final%29.pdf |title=The Case for Banning Lead in Gasoline |date=January 2003 |publisher=Manufacturers of Emission Controls Association (MECA) |access-date=7 June 2012 |archive-url=https://web.archive.org/web/20120426012900/http://www.meca.org/galleries/default-file/lead0103_(final).pdf |archive-date=26 April 2012 }}</ref> [[India]] banned leaded petrol in March 2000.<ref name="blogs.wsj.com" />

By 2011, the United Nations announced that it had been successful in phasing out leaded gasoline worldwide. "Ridding the world of leaded petrol, with the United Nations leading the effort in developing countries, has resulted in $2.4 trillion in annual benefits, 1.2 million fewer premature deaths, higher overall intelligence and 58 million fewer crimes", the United Nations Environmental Program said.<ref name=":1">{{cite web|date=27 October 2011|title=Phase-out of leaded petrol brings huge health and cost benefits|url=https://www.un.org/apps/news/story.asp?NewsID=40226&Cr=pollutant&Cr1=#.UZdkooJAsR4|access-date=2020-11-28|website=UN News|archive-date=27 January 2022|archive-url=https://web.archive.org/web/20220127192850/https://news.un.org/en/story/2011/10/393292-phase-out-leaded-petrol-brings-huge-health-and-cost-benefits-un-backed-study#.UZdkooJAsR4|url-status=live}}</ref><ref>{{Cite journal |url = http://www.unep.org/transport/pcfv/PDF/Hatfield_Global_Benefits_Unleaded.pdf |last1 = Tsai |first1 = P.L. |last2 = Hatfield |first2 = T.H. |title = Global Benefits From the Phaseout of Leaded Fuel |journal = Journal of Environmental Health |volume = 74 |number = 5 |pages = 8–14 |date = December 2011 |access-date = 28 May 2014 |archive-date = 23 December 2016 |archive-url = https://web.archive.org/web/20161223134750/http://www.unep.org/transport/pcfv/PDF/Hatfield_Global_Benefits_Unleaded.pdf }}</ref> The announcement was slightly premature, as a few countries still had leaded gasoline for sale as of 2017.<ref name=":0" />  On 30 August 2021 the [[United Nations Environment Programme|United Nations Environment Program]] announced that leaded gasoline had been eliminated.  The final stocks of the product were used up in Algeria, which had continued to produce leaded gasoline until July 2021.<ref>{{cite news |title=Highly polluting leaded petrol now eradicated from the world, says UN |url=https://www.bbc.co.uk/news/world-58388810 |work=BBC News |date=31 August 2021 |access-date=31 August 2021 |archive-date=1 September 2021 |archive-url=https://web.archive.org/web/20210901102025/https://www.bbc.co.uk/news/world-58388810 |url-status=live }}</ref><ref>{{cite web |title=Era of leaded petrol over, eliminating a major threat to human and planetary health |date=30 August 2021 |url=https://www.unep.org/news-and-stories/press-release/era-leaded-petrol-over-eliminating-major-threat-human-and-planetary |publisher=United Nations Environment Programme |access-date=31 August 2021 |archive-date=29 December 2021 |archive-url=https://web.archive.org/web/20211229100350/https://www.unep.org/news-and-stories/press-release/era-leaded-petrol-over-eliminating-major-threat-human-and-planetary |url-status=live }}</ref>

=== Effect on crime rates ===
{{Main|Lead–crime hypothesis}}

Reduction in the average blood lead level is believed to have been a major cause for falling violent crime rates in the United States.<ref name="WashingtonPostCrime">{{cite news | url=https://www.washingtonpost.com/blogs/wonkblog/wp/2013/04/22/lead-abatement-alcohol-taxes-and-10-other-ways-to-reduce-the-crime-rate-without-annoying-the-nra/ | title=Lead abatement, alcohol taxes and 10 other ways to reduce the crime rate without annoying the NRA | newspaper=The Washington Post | date=22 April 2013 | access-date=23 May 2013 | author=Matthews, Dylan | archive-date=12 May 2013 | archive-url=https://web.archive.org/web/20130512052321/http://www.washingtonpost.com/blogs/wonkblog/wp/2013/04/22/lead-abatement-alcohol-taxes-and-10-other-ways-to-reduce-the-crime-rate-without-annoying-the-nra/ | url-status=live }}</ref> A statistically significant correlation has been found between the usage rate of leaded gasoline and violent crime: the violent crime curve virtually tracks the lead exposure curve with a 22-year time lag.<ref name="Reyes">Reyes, J. W. (2007). [https://www.nber.org/papers/w13097 "The Impact of Childhood Lead Exposure on Crime". National Bureau of Economic Research.] {{Webarchive|url=https://web.archive.org/web/20240713181409/https://www.nber.org/papers/w13097 |date=13 July 2024 }} "a" ref citing Pirkle, Brody, et. al (1994). Retrieved 17 August 2009.</ref><ref>{{cite news|url=https://www.independent.co.uk/environment/green-living/ban-on-leaded-petrol-has-cut-crime-rates-around-the-world-398151.html|title=Ban on leaded petrol 'has cut crime rates around the world'|last=Lean|first=Geoffrey|date=27 October 2007|work=[[The Independent]]|access-date=15 September 2017|archive-date=29 August 2017|archive-url=https://web.archive.org/web/20170829032830/https://www.independent.co.uk/environment/green-living/ban-on-leaded-petrol-has-cut-crime-rates-around-the-world-398151.html|url-status=live}}</ref> After the ban on TEL, blood lead levels in U.S. children dramatically decreased.<ref name="Reyes" /> Researchers including [[Amherst College]] economist Jessica Wolpaw Reyes, [[Department of Housing and Urban Development]] consultant Rick Nevin, and Howard Mielke of [[Tulane University]] say that declining exposure to lead is responsible for an up to 56% decline in crime from 1992 to 2002.<ref>{{cite web |url=http://www.chicagotribune.com/news/watchdog/ct-lead-poisoning-science-met-20150605-story.html |title=Lead poisoning linked to violent crime |work=Chicago Tribune |date=6 June 2015 |first=Michael |last=Hawthorne |access-date=17 December 2015 |archive-date=17 December 2015 |archive-url=https://web.archive.org/web/20151217065850/http://www.chicagotribune.com/news/watchdog/ct-lead-poisoning-science-met-20150605-story.html |url-status=live }}</ref> Taking into consideration other factors that are believed to have increased crime rates over that period, Reyes found that the reduced exposure to lead led to an actual decline of 34% over that period.<ref name="AmherstCrime">{{cite web |url = http://www3.amherst.edu/~jwreyes/papers/LeadCrimeNBERWP13097.pdf |title = Environmental Policy as Social Policy? The Impact of Childhood Lead Exposure on Crime |last = Wolpaw Reyes |first = Jessica |publisher = [[National Bureau of Economic Research]] |date = May 2007 |access-date = 23 May 2013 |archive-date = 29 September 2007 |archive-url = https://web.archive.org/web/20070929131323/http://www.amherst.edu/~jwreyes/papers/LeadCrimeNBERWP13097.pdf |url-status = live }}</ref><ref>{{cite web |url=https://www.motherjones.com/environment/2013/01/lead-crime-link-gasoline |title=America's Real Criminal Element: Lead |last=Drum |first=Kevin |work=[[Mother Jones (magazine)|Mother Jones]] |date=January–February 2013 |access-date=4 January 2013 |archive-date=12 May 2014 |archive-url=https://web.archive.org/web/20140512040918/https://www.motherjones.com/environment/2013/01/lead-crime-link-gasoline |url-status=live }}</ref>

=== Lingering issues over time ===

Although leaded gasoline has long since ended its history of regular use in U.S. transportation, it has left high concentrations of lead in the [[soil]] adjacent to roads that were heavily used prior to its phaseout. These contaminated materials present health dangers even when merely touched or when components of it get [[Breathing|breathed in]]. Children, especially those in [[Poverty in the United States|poverty inside of the U.S.]], are particularly at risk.<ref>{{cite web|url=http://lead.tulane.edu/lead_soil.html|title=Lead's Urban Legacy|publisher=[[Tulane University]]|access-date=12 May 2024|date=2013}}</ref>

== See also ==
{{Portal|Chemistry}}
* [[Elmer Keiser Bolton#World War I and E.I. du Pont de Nemours and Company|Elmer Keiser Bolton]]
* [[Lead abatement]]
* [[List of petrol additives]]

== References ==
{{Reflist}}

== Further reading ==
{{Refbegin}}
* {{cite book|last1=Filella |first1= Montserrat|last2=Bonet|first2=Josep|chapter= Chapter 14. Environmental Impact of Alkyl Lead(IV) Derivatives: Perspective after Their Phase-out|pages=471–490
|publisher= de Gruyter|date= 2017|series= Metal Ions in Life Sciences|volume=17|title=Lead: Its Effects on Environment and Health|editor1-last=Astrid|editor1-first= S.|editor2-last=Helmut|editor2-first=S.|editor3-last=Sigel |editor3-first= R. K. O.|doi=10.1515/9783110434330-014|pmid = 28731307|isbn = 978-3-11-043433-0}}{{Refend}}

==External links==

===Media articles===
*[https://www.pbs.org/wgbh/nova/article/herbert-needleman/ The Man Who Warned the World About Lead] (PBS / NOVA)
* [https://www.mentalfloss.com/article/94569/clair-patterson-scientist-who-determined-age-earth-and-then-saved-it The Most Important Scientist You've Never Heard Of], BY Lucas Reilly, May 17, 2017, mentalfloss.com
* [https://www.npr.org/2021/08/30/1031429212/the-world-has-finally-stopped-using-leaded-gasoline-algeria-used-the-last-stockp The World Has Finally Stopped Using Leaded Gasoline. Algeria Used The Last Stockpile], August 30, 2021, Heard on All Things Considered, Camila Domonoske, NPR.

===Official documents===
*U.S. Gov't, National Institute for Occupational Safety and Health. [https://www.cdc.gov/niosh/npg/npgd0601.html NIOSH Pocket Guide to Chemical Hazards]

===Scientific papers and journal articles===
*Kovarik, Bill (1999). [https://web.archive.org/web/20060708163208/http://www.radford.edu/~wkovarik/papers/kettering.html Charles F. Kettering and the 1921 Discovery of Tetraethyl Lead]
*[https://www.aopa.org/advocacy/advocacy-briefs/regulatory-brief-avgas-100ll-alternatives True unleaded alternative for 100LL needed for general aviation]
*Jamie Lincoln Kitman: ''[https://www.thenation.com/article/archive/secret-history-lead/ The Secret History of Lead]''. In: The Nation, 2 March 2000.

{{Chemical agents}}
{{Neurotoxins}}
{{Motor fuel}}
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[[Category:Organolead compounds]]
[[Category:Antiknock agents]]
[[Category:Ethyl compounds]]