"Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula (CH3CH2)4Pb.

TEL is a petro-fuel additive; first being mixed with gasoline (petrol) beginning in the 1920s as a patented octane rating booster that allowed engine compression to be raised substantially. This in turn caused increased vehicle performance and fuel economy.[3][4] TEL had been identified chemically in the mid-19th century, but its antiknock effectiveness was discovered in 1921 by the General Motors research laboratory, which had spent several years attempting to find an additive that was both highly effective and inexpensive. "
https://en.wikipedia.org/wiki/Tetraethyllead

"Le tétraéthylplomb, ou plomb tétraéthyle ou tétraéthyle de plomb, est un liquide incolore, huileux, d'odeur caractéristique de formule brute Pb(C2H5)4 et très toxique. "
https://fr.wikipedia.org/wiki/Tétraéthylplomb

"If the test results are satisfactory, the tank may be 'declassified'. Declassification means that
significant occupational exposures to lead are unlikely during work on the tank. There may
nevertheless be some low-level lead exposure, and the dismantling of the tank may require
additional controls on disposal of lead to the environment. Nevertheless, experience shows
that declassification of tanks, where appropriate, considerably reduces costs, primarily due to the reduced requirement for the use of breathing apparatus, whilst ensuring that the health of the workers is still protected."
Guidance on the declassification of tanks previously ... - Energy Institute
https://publishing.energyinst.org/__.../Pages-from-Guidance-...

"plomb tétraéthyle ou tétraméthyle (plomb organique) "
http://www.sfmu.org/toxin/PROTOCOL/PB/PB0.HTM

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Note added at 11 hrs (2018-09-24 11:33:33 GMT)
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le plomb organique est la substance synthétique antidétonante ajoutée à l'essence...