Heavy-duty engine emissions: response.

In his letter, Schaeffer concludes that because of the ongoing changes in diesel technology, "establishing standardized reference materials [of diesel exhaust particles (DEPs)] will be particularly challenging." As amply illustrated by the work of DeMarini et al. (2004) and Singh et al. (2004), which prompted my commentary (Arey 2004), the effort is worth making because multidisciplinary studies on representative DEP samples are needed if meaningful assessments of the health hazards associated with DEPs are to be made. DeMarini et al. (2004) and Singh et al. (2004) highlighted the chemical, physical, and biological differences between two widely used DEP samples, one mainly studied for pulmonary toxicity and the other for genotoxicity; before their studies, the chemical composition and biologic activity of the samples had not been compared.

In his letter, Schaeffer describes the Advanced Collaborative Emissions Study (ACES), an important diesel assessment project currently in the planning stage by the Health Effects Institute (Boston, MA). Perusing Warren's presentation on the project (Warren 2004) cited by Schaeffer, I found that the utility of standard reference materials that allow for collaborations and exhaustive characterization of DEPs is reinforced by several issues Warren highlighted; for example, which of the "794 measurements under consideration" should be made; what should the results be compared to; and what health effect testing should be conducted? Until we fully understand the mechanisms of action of diesel and ambient particles that are involved in their adverse health effects, we need more multidisciplinary, collaborative efforts to study samples that can be shared among researchers.

The author declares she has no competing financial interests.

REFERENCES

Arey J. 2004. A tale of two diesels. Environ Health Perspect 112:812-813.

DeMarini DM, Brooks LR, Warren SH, Kobayashi T, Gilmour MI, Singh P. 2004. Bioassay-directed fractionation and Salmonella mutagenicity of automobile and forklift diesel exhaust particles. Environ Health Perspect 112:814-819.

Singh P, DeMarini DM, Dick CAJ, Tabor DG, Ryan JV, Linak WP, et al. 2004. Sample characterization of automobile and forklift diesel exhaust particles and comparative pulmonary toxicity in mice. Environ Health Perspect 112:820-825.

Warren J. 2004. Update on the ACES Diesel Assessment Program. Available: http://www.healtheffects.org/Slides/ AnnConf2004/Warren.pdf. [accessed 1 July 2004].

Janet Arey

Department of Environmental Sciences

Air Pollution Research Center

University of California, Riverside 

Riverside, California 

E-mail: [e-mail]