This article is from the Gasoline FAQ, by Bruce Hamilton with numerous contributions by others.
There are several known toxins in gasoline, some of which are confirmed
human carcinogens. The most famous of these toxins are lead and benzene, and
both are regulated. The other aromatics and some toxic olefins are also
controlled. Lead alkyls also require ethylene dibromide and/or ethylene
dichloride scavengers to be added to the gasoline, both of which are
suspected human carcinogens. In 1993 an International Symposium on the Health
Effects of Gasoline was held . Major review papers on the carcinogenic,
neurotoxic, reproductive and developmental toxicity of gasoline, additives,
and oxygenates were presented, and interested readers should obtain the
proceedings. The oxygenates are also being evaluated for carcinogenicity, and
even ethanol and ETBE may be carcinogens. The introduction of oxygenated
gasoline to Alaska and some other areas of the USA resulted in a range of
complaints. Recent research has been unable to identify additional toxicity,
but has detected increased levels of offensive smell . It should be noted
that the oxygenated gasolines were not initially intended to reduce the
toxicity of emissions. The reformulated gasolines will produce different
emissions, and specific toxins must initially be reduced by 15% all year.
The removal of alkyl lead compounds certainly reduces the toxicity of
exhaust gas emissions when used on engines with modern engine management
systems and 3-way exhaust catalysts. If unleaded gasolines are not
accompanied by the introduction of catalysts, some other toxic emissions
may increase. Engines without catalysts will produce increased levels of
toxic carbonyls such as formaldehyde and acrolein when using oxygenated
fuels, and increased levels of toxic benzene when using highly aromatic
There is little doubt that gasoline is full of toxic chemicals, and should
therefore be treated with respect. However the biggest danger remains the
flammability, and the relative hazards should always be kept in perspective.
The major toxic risk from gasolines comes from breathing the tailpipe,
evaporative, and refuelling emissions, rather than occasional skin contact
from spills. Breathing vapours and skin contact should always be minimised.