The Dose Doesn't Make the Poison?
From bisphenol-A to benzene some researchers are claiming that some toxic substances not only don't have a no observable effect level (NOEL) but also that the shape of the dose response curve for these substances at low levels is supralinear. What that all means is that the bane of any toxic tort litigator, the linear dose response assumption implying that even one molecule poses some risk, understates the actual risk associated with very low levels of exposure.
In "Evidence That Humans Metabolize Benzene via Two Pathways" by Rappaport, et al. hypothesize that at low levels of benzene exposure (less than one ppm) humans metabolize the aromatic molecule much more efficiently than at higher levels due to some as-yet unidentified metabolic pathway. Consequently "true leukemia risks" from exposure to benzene at what are considered acceptable ambient levels may instead pose significantly greater risks than are currently contemplated by regulators, according to the authors.
