writes:

Naptha was used by the dry cleaning industry until the '60s, when it
was discovered to be carcinogenic. Then perchlorethylene (sp?) or
"perc" started to be used. Although perc was also carcinogenic, the
theory was that the machines using it were designed to recover 100% of
it, so the employees wouldn't be exposed to it. But the machines only
did that when they were maintained properly; perc tended to degrade
the rubber seals quickly; and the dry cleaning shop owners didn't want
to spend the money to maintain their machines that well, and they
leaked into the work area. So perc turned out to be carcinogenic "as
applied" (you constitutional law guys will know what that
means. Reading, Jay?)

Naphtha is a petroleum fraction roughly the weight of gasoline, but too
low octane to be useful as a motor fuel. Its composition is variable,
but it can be expected to contain benzene and other aromatics, which are
carcinogenic. It's also as flammable as gasoline, so take care.