Why is there no cancer risk characterization for diesel particulate matter?
While available evidence supports EPA’s conclusion that diesel exhaust is likely to be a human carcinogen, EPA has concluded that the available data are not sufficient to develop a confident estimate of cancer unit risk (i.e., unit risk estimate or URE). (The cancer unit risk is a health assessment value that can be matched with environmental exposure data to estimate environmental risk.) Therefore, EPA cannot provide a quantitative estimate of potential cancer risk associated with environmental exposures to diesel particulate matter as it has for the other 29 carcinogens in the 1996 national-scale assessment. However, the current diesel exhaust hazard information is sufficient to indicate that this pollutant presents a potentially significant public health concern. First, the Agency has concluded that it is a likely human carcinogen. In addition, the general population is exposed to levels close to or overlapping with apparent levels that result in increased cancer risk in epidemiolog
