What About Diesel PM?
In this assessment, the potential risk from diesel exhaust emissions is not addressed in the same fashion that other pollutants are. This is because data are not sufficient to develop a quantitative estimate of carcinogenic potency for this pollutant. However, EPA has concluded that diesel exhaust is among the substances that the national-scale assessment suggests pose the greatest relative risk. First, several human epidemiology studies link increased lung cancer associated with diesel exhaust. Furthermore, exposures in several of these epidemiology studies are in the same range as ambient exposures throughout the United States.
In addition to the potential for lung cancer risk, there is a significant potential for noncancer health effects as well, based on the contribution of diesel particulate matter to ambient levels of fine particles. Exposure to fine particles has been linked to significant public health impacts, including respiratory and cardiovascular effects, as well as premature mortality. These effects are not specifically presented in the national-scale assessment analysis but are considered in setting and implementing EPA's National Ambient Air Quality Standards for PM-2.5.
In addition, EPA has designated a chronic Reference Concentration (RfC) for diesel particulate of 5 ug/m3 based on specific noncancer effects found in several animal studies, which showed adverse changes in lungs such as inflammation and lesions. The national-scale assessment results show population exposures above this level.
More information on health effects associated with diesel exhaust can be found in the Health Assessment Document for Diesel Exhaust.