There's a reason the "this product contains a chemical known to the State of California to cause cancer" warning labels are a bit of a joke, after all.
From the original article: "The toxicity of benzene in humans has been well established for over 120 years. The hematotoxicity of benzene has been described as early as 1897. A study from 1939 on benzene stated that “exposure over a long period of time to any concentration of benzene greater than zero is not safe,” which is a comment reiterated in a 2010 review of benzene research specifically stating “There is probably no safe level of exposure to benzene, and all exposures constitute some risk in a linear, if not supralinear, and additive fashion.”
If you want to adopt a zero tolerance policy for benzene then you’d need to ban petrol. Or stop breathing.
It's benzine. It's a known carcinogen, no need for empiricism here.