MUTAGENICITY TESTING OF ORGANIC EXTRACTS OF DIESEL EXHAUST PARTICLES AFTER SPIKING WITH POLYCYCLIC AROMATIC-HYDROCARBONS (PAH)

In the present study, spiking was used as a strategy to evaluate the m utagenicity of individual compounds in a mixture. Mutagenicity of indi vidual polycyclic aromatic hydrocarbons (PAH) was evaluated in an orga nic extract of diesel exhaust particles (DEP). The particles were extr acted with dichloromethane (DCM). After replacing DCM with dimethylsul phoxide (DMSO), the extract was spiked with four individual PAH: benzo (a)pyrene, benzo(a)anthracene, pyrene and fluoroanthene. The PAH were added separately and in various combinations to the extract to determi ne the effects of each variable and to identify possible interactions between the individual PAH and between the PAH and the extract. The st udy was designed as a fractional factorial experiment with the five va riables (the DEP extract and the four PAH), giving 16 (instead of 32) mixtures plus a triplicate centrepoint and background, i.e. a total of 20. The fractionated factorial design used in the present work suppor ts a model with linear and interaction terms. The mixtures were tested for mutagenicity in the Ames assay using four strains of Salmonella t yphimurium in the presence of rat liver xenobiotic enzymes (S9-mix). P rojections to Latent Structures (PLS) was used to quantify the mutagen icity of each compound and possible interactions. The four individual PAH and the DEP extract acted additively in the Ames test with 10% S9- mix.