Evaluation of the oxidative potential of urban PM and its relation to in vitro induced DNA damage: a spatial and temporal comparison

Some toxic effects of particulate matter (PM) are related to the oxidative potential (OP) of the particles. The electron paramagnetic resonance (EPR) technique was used to evaluate the intensity of paramagnetic species (PS) and EPR plus spin trapping, to evaluate the OP of PM. We evaluated, in parallel, the DNA degradation potential of PM10 and PM25 collected from three regions of Mexico City in 1991 and 2003. Each region had different sources of pollution: industrial, commercial or residential. Both techniques evaluated Fenton-type reactions in the presence and absence of de-feroxamine (DFO). PM10 samples from the industrial region presented similar high OP, independently of sampling year. PM10 and PM25 collected in the commercial and residential regions in 2003 had similarly low OP. The OP induced by PM10 from the industrial region was completely inhibited by DFO, and DFO partially inhibited the OP induced by PM10 from other regions. PM25 OP was not inhibited by DFO. PM from the industrial region was the most potent inductor of DNA degradation, while PM from residential region was the least potent, correlating with the OP. DFO inhibited the degradation of DNA induced by PM. The OP of PM collected in the industrial and residential region correlated with the DNA degradation. The region, size and year of PM collection are linked to observed OP variations and DNA degradation induced by PM.