The Toxic Potential of Diesel Emission Particles and the Significance of Thresholds for the Risk Assessment

Authors

Univ.-Prof. Dr.med. J. Bruch, University Essen and IBE GmbH (Institute for Biological Emission Assessment GmbH), Marl

Year

2005

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 595

Summary

Long-term exposure to ambient particulate matter including diesel emission particles (DEP) is associated with higher risks of cardiovascular diseases and lung cancer. According to the epidemiologists no threshold could be identified. The toxicological data show a mutagenic potential of the organic extracts diesel soot. Chronic inhalation of high concentration of DEP was associated with a dose dependent lung tumor formation in the rat model; however dosimetric calculation points to a predominant contribution of the particulate matter to the tumor numbers. Mechanistic studies clarified the eminent role of inflammatory processes for carcinogenic dust effects including oxidative DNA adducts and mutagenicity. Secondary genotoxic effects are supposed as underlying mechanism. Effective defense processes could be identified which in consequence leads to thresholds in critical intermediate steps in the tumor path. Experimental studies with different design on DEP could confirm thresholds for inflammation, genotoxicity and mutagenicity. In using multi dose assays in a dose doubling step (DDS) manner a reference to a standard low-toxic dust such as corundum could be established. The threshold dose for critical effects of a test sample can be assigned to the applicable DDS, the nocivity is expressed as toxicity dose doubling step category (TDDS). The real world of dust related genotoxicities encompasses TDDS 0 (zero) for the reference corundum and TDDS 4 (four) for the reference crystalline silica DQ12. Ambient particles show a broad range of intrinsic toxicities. In conclusion thresholds for the particle associated genotoxic and mutagenic efficacy of DEP could be identified which can be ranked into a low toxicity category. Different specific toxicity of DEP challenges the development of exhaust technology. The risk assessment should consider the threshold character of the particle toxicity and the specific contribution of the heterogeneous particle population in the ambient air.

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