Case Study: Are Low Concentrations of Benzene Disproportionately Dangerous?

It has sometimes been proposed that supralinear dose-response functions—that is, dose-response functions in which low doses are disproportionately potent in causing harm—describe the risks from many well-studied public and occupational hazards including asbestos, benzene, lead, particulate air pollution, and ionizing radiation; and that this implies that exposure concentrations must be driven to zero, or close to it, to adequately protect human health (e.g., Hornung and Lanphear 2014; Lanphear 2017). Some of these concerns have been challenged by other investigators as statistically flawed or as biologically unrealistic (e.g., Waddell 2006). Fors example, studies that identify supralinear dose-response relationships can be questioned if they fail to control fully for important potential confounders, such as misclassified smoking (Hamling et al. 2019). Residual confounding by smoking can create significant associations between some common exposure metrics (e.g., blood lead levels) and adverse health effects (e.g., cardiovascular mortality and morbidity) whether or not the former affect the latter. Misattributing risk caused by a confounder to exposure creates the appearance of a supra-linear dose-response function since risk fails to decline as exposure decreases, in effect spreading the same risk over fewer units of exposure.