Inherent Redox Properties of Diesel Exhaust Particles: Catalysis of the Generation of Reactive Oxygen Species by Biological Reductants

The toxicity of diesel exhaust particles (DEP) can be due to the particle itself, extractable components, or both. Many studies focus on the biological properties of DEP-extractable components although it is possible that chemical properties inherent to the DEP itself can lead to toxicity. Thus, an examination of the chemistry inherent to DEP was carried out. Herein, we report that DEP are capable of catalyzing the consumption of O2 (monitored using a Clarke electrode) by ascorbate and thiols leading to the generation of reactive oxygen species. Consistent with the idea that DEP are capable of catalyzing the generation of reactive oxygen species, they were also found to catalyze DNA strand breakage via an O2- and reductant-dependent process. Significantly, extraction of DEPwith either organic solvent (methylene chloride) or acid (aqueous HCl) did little to abrogate this chemistry. Finally, using electron para-magnetic spectrometry (EPR), DEP were found to have paramag