Editing Gasoline (section)

====Tetraethyl lead====
{{main|Tetraethyl lead}}
<!--This section is linked from [[Lead]]-->

Gasoline, when used in high-[[Compression (physical)|compression]] internal combustion engines, tends to auto-ignite or "detonate" causing damaging [[engine knocking]] (also called "pinging" or "pinking"). To address this problem, [[Tetraethyllead|tetraethyl lead]] (TEL) was widely adopted as an additive for gasoline in the 1920s. With a growing awareness of the seriousness of the extent of environmental and health damage caused by lead compounds, however, and the incompatibility of lead with [[catalytic converter]]s, governments began to mandate reductions in gasoline lead.

In the U.S., the [[Environmental Protection Agency]] issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, scheduled to begin in 1973 but delayed by court appeals until 1976. By 1995, leaded fuel accounted for only 0.6 percent of total gasoline sales and under {{convert|2000|ST|t|abbr=off|sp=us|disp=output only}} ({{convert|{{convert|2000|ST|t|disp=output number only}}|t|ST LT|sp=us|disp=output only}}) of lead per year. 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 in the U.S. The use of TEL also necessitated other additives, such as [[dibromoethane]].

European countries began replacing lead-containing additives by the end of the 1980s, and by the end of the 1990s, leaded gasoline was banned within the entire European Union with an exception for [[Avgas#100LL (blue)|Avgas 100LL]] for [[general aviation]].<ref name="q566">{{cite web | last=Calderwood | first=Dave | title=Europe moves to ban lead in avgas | website=FLYER | date=8 March 2022 | url=https://flyer.co.uk/europe-moves-to-ban-lead-in-avgas/ | access-date=28 July 2024}}</ref> The UAE started to switch to unleaded in the early 2000s.<ref>{{Cite web |title=UAE switches to unleaded fuel |date=January 2003 |url=https://gulfnews.com/uae/uae-switches-to-unleaded-fuel-1.343442 |url-status=live |archive-url=https://web.archive.org/web/20200412131951/https://gulfnews.com/uae/uae-switches-to-unleaded-fuel-1.343442 |archive-date=12 April 2020 |access-date=12 April 2020}}</ref>

Reduction in the average lead content of human blood may be a major cause for falling violent crime rates around the world<ref name="WashingtonPostCrime2">{{cite news |last=Matthews |first= Dylan |date=22 April 2013 |title=Lead abatement, alcohol taxes and 10 other ways to reduce the crime rate without annoying the NRA |newspaper=Washington Post |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/ |url-status=live |access-date=23 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/ |archive-date=12 May 2013 |df=dmy-all}}</ref> including South Africa.<ref name="BusinessDayCrime2">{{cite web |last=Marrs |first= Dave |date=22 January 2013 |title=Ban on lead may yet give us respite from crime |url=http://www.bdlive.co.za/opinion/columnists/2013/01/22/ban-on-lead-may-yet-give-us-respite-from-crime |url-status=dead |archive-url=https://web.archive.org/web/20130406072130/http://www.bdlive.co.za/opinion/columnists/2013/01/22/ban-on-lead-may-yet-give-us-respite-from-crime |archive-date=6 April 2013 |access-date=23 May 2013 |publisher=Business Day |df=dmy-all}}</ref> A study found a correlation between leaded gasoline usage and violent crime (see [[Lead–crime hypothesis]]).<ref name="Reyes2">{{Cite web |last=Reyes |first=J. W. |date=2007 |url=https://www.nber.org/system/files/working_papers/w13097/w13097.pdf |title=The Impact of Childhood Lead Exposure on Crime |work=National Bureau of Economic Research. "a" ref citing Pirkle, Brody, et al. (1994) |access-date=26 May 2024 |archive-date=17 January 2024 |archive-url=https://web.archive.org/web/20240117041241/https://www.nber.org/system/files/working_papers/w13097/w13097.pdf |url-status=live }}</ref><ref>{{cite news |date=28 October 2007 |title=Ban on leaded petrol 'has cut crime rates around the world' |url=https://www.independent.co.uk/environment/green-living/ban-on-leaded-petrol-has-cut-crime-rates-around-the-world-398151.html |url-status=live |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 |archive-date=29 August 2017 |df=dmy-all}}</ref> Other studies found no correlation.

In August 2021, the [[United Nations Environment Programme|UN Environment Programme]] announced that leaded gasoline had been eradicated worldwide, with [[Algeria]] being the last country to deplete its reserves. [[Secretary-General of the United Nations|UN Secretary-General]] [[António Guterres]] called the eradication of leaded petrol an "international success story". He also added: "Ending the use of leaded petrol will prevent more than one million premature deaths each year from heart disease, strokes and cancer, and it will protect children whose IQs are damaged by exposure to lead". [[Greenpeace]] called the announcement "the end of one toxic era".<ref>{{cite web |date=31 August 2021 |title=Highly polluting leaded petrol now eradicated from the world, says UN |url=https://www.bbc.com/news/world-58388810 |url-status=live |archive-url=https://web.archive.org/web/20220125025414/https://www.bbc.com/news/world-58388810 |archive-date=25 January 2022 |access-date=16 September 2021 |work=BBC News}}</ref> However, leaded gasoline continues to be used in aeronautic, auto racing, and off-road applications.<ref>{{cite web |last1=Miranda |first1=Leticia |last2=Farivar |first2=Cyrus |date=12 April 2021 |title=Leaded gas was phased out 25 years ago. Why are these planes still using toxic fuel? |url=https://www.nbcnews.com/business/business-news/leaded-gas-was-phased-out-25-years-ago-why-are-n1264970 |url-status=live |archive-url=https://web.archive.org/web/20210915233641/https://www.nbcnews.com/business/business-news/leaded-gas-was-phased-out-25-years-ago-why-are-n1264970 |archive-date=15 September 2021 |access-date=16 September 2021 |work=NBC News}}</ref> The use of leaded additives is still permitted worldwide for the formulation of some grades of [[aviation gasoline]] such as [[100LL]], because the required octane rating is difficult to reach without the use of leaded additives.

Different additives have replaced lead compounds. The most popular additives include [[aromatic hydrocarbon]]s, [[ether]]s ([[MTBE]] and [[ETBE]]), and [[alcohols]], most commonly [[ethanol]].