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EPA Health Assessment Document for Diesel Exhaust approved by the CASAC panel

19 October 2000 | updated 15 November 2000

On its meeting on October 12-13, the EPA Science Advisory Board’s (SAB) Clean Air Scientific Advisory Committee (CASAC), Diesel Review Panel has approved the EPA’s most recent draft Health Assessment Document for Diesel Exhaust (EPA/600/8-90/057E, dated July 2000). The document has been approved with some changes, as outlined in a CASAC review report (the report is expected to be posted in the SAB web site in November—follow the links below). As a result of this decision, which follows a 6-year long review process, the US EPA will finally adopt its formal position on the health effects of diesel emissions.

The July 2000 version of the EPA’s Health Assessment Document follows three earlier drafts, which were published in 1994, 1998 and in November 1999. In all these cases, the CASAC panel found that the document was not scientifically adequate for making regulatory decisions concerning the use of diesel powered engines.

Two classes of possible health effects are discussed in the adopted Health Assessment Document: (1) nonmalignant respiratory effects and (2) carcinogenic effects. The EPA confirmed its earlier findings on the non-cancer effects of ambient PM, such as increased mortality and morbidity. The recommended chronic exposure level without appreciable hazard (inhalation Reference Concentration, RfC) for diesel particulates has been adopted at 5 µg/m3.

A number of conclusions has been drawn on the cancer effects of diesel exhaust particulates, as follows:

The EPA’s position on quantitative cancer risk assessment is in contradiction to the findings of the California Air Resources Board (ARB), which has established unit risk estimates for cancer from diesel exhaust particulates. The ARB estimates are based on some old railroad worker studies, which were later found unsuitable for such purpose by the EPA.

The adopted document is considered by many the most comprehensive, scientifically accurate, and objective summary of current human knowledge on the health effects of diesel emissions. The document will be updated as more information is available in the future, specifically in the area of quantitative cancer risk assessment.

The SAB is an advisory body reporting to the EPA Administrator. The function of the SAB is to provide credible technical advice to the EPA to ensure that EPA regulations are based on solid scientific foundations.

For further information contact Robert Flaak, Clean Air Scientific Advisory Committee, Science Advisory Board, tel (202) 564-4546; fax (202) 501-0582; e-mail flaak.robert@epa.gov.

Source: EPA SAB (EPA draft diesel health assessment | SAB Reports Page)

Preliminary reviewers comments