A systematic review of the health effects associated with the inhalation of particle-filtered and whole diesel exhaust

Abstract

Background: Diesel exhaust is a complex mixture comprised of gases and particulate matter and is a contributor to ambient air pollution. To reduce health risks, recent changes in diesel engine technology have significantly altered the composition of diesel exhaust, primarily by lowering emissions of particulate matter. However, animal toxicological studies continue to report health effects following exposure to diesel exhaust from engines employing particulate filters. The cause of these effects remains unclear.

Objective and methods: To gain an understanding of the role of both particle-filtered and whole diesel exhaust on specific health outcomes, we conducted a systematic review in which we examined animal toxicological and controlled human exposure studies that included a comparison between inhalation of particle-filtered and whole diesel exhaust on any health endpoint.

Results: We identified 26 studies that met both the inclusion and study evaluation criteria. For most health outcomes, the particle filtration methods employed in the included studies did not appreciably attenuate the health effects associated with exposure to whole diesel exhaust. There were also several health endpoints for which significant effects were associated with exposure to either particle-filtered or whole diesel exhaust, but not to both.

Conclusions: Overall, the results from this systematic review demonstrate that exposure to different components in diesel exhaust can have distinct and independent health effects. Thus, to better inform human health risk assessments, future studies aimed at elucidating the health effects from diesel exhaust should include exposure to both particle-filtered and whole diesel exhaust.

Keywords:

• Diesel exhaust particles
• filtered exhaust
• particulate matter
• nitrogen dioxide
• traffic-related air pollution

Acknowledgements

The authors thank George Woodall, Stephen Graham, Chad Bailey, Steve Dutton, and John Vandenberg for their review of the manuscript. This manuscript has been reviewed by the U.S. EPA and approved for publication. Approval does not necessarily signify that the contents reflect the views or opinions of the U.S. EPA, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

Disclosure statement

No potential conflict of interest was reported by the author(s).