On the approach for calculating occupational exposure limits for diesel motor exhaust

In a recent report, Vermeulen and Portengen estimated diesel motor exhaust (DME) exposure levels corresponding to acceptable risk and maximum tolerable risk levels of 4x10^–5 and 4x10^–3 for the lifetime excess risk (LER) of dying from lung cancer.1 According to their calculations, the two exposure levels are in the magnitude of 0.01 and 1.0 µg/m³ elemental carbon, respectively, that is, below contemporary exposure situations in certain occupational settings and in many congested urban areas. These estimates are much too conservative for two main reasons.

First, lung cancer risk due to DME, calculated from three epidemiological studies, is overestimated. A recent review highlights several methodological flaws in these studies and concludes that the currently published studies provide little evidence for a definite causal link between DME exposure and lung cancer risk.2

Second, the methodology for calculating exposure levels corresponding to a certain excess risk employs additive risk models, which are commonly used...

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