Diesel soot particles catalyze the production of oxy-radicals.

The formation of a strong oxidant similar to the OH. radical is catalyzed by diesel soot particles in the presence of cysteine and hydrogen peroxide or in the presence of light. The oxidant(s) formed causes fragmentation of methylthioketobutyric acid measurable as ethylene release. Furthermore, the model carotenoid crocin is bleached and thiobarbituric-acid-reactive material (malondialdehyde) is produced from linolenic acid. All reactions are inhibited by scavengers (propyl gallate, alpha-tocopherol, diazobicyclooctane) and by catalase. The reactions observed suggest that the toxicity and mutagenicity of diesel soot particles is at least in part due to the formation of reactive oxygen species.