Ambient Air Particles: Effects on Cellular Oxidant Radical Generation in Relation to Particulate Elemental Chemistry

Abstract

Epidemiologic studies have reported causal relationships between exposures to high concentrations of ambient air particles (AAP) and increased morbidity in individuals with underlying respiratory problems. Polymorphonuclear leukocytes (PMN) are frequently present in the airways of individuals exposed to particles. Upon particulate stimulation the PMN may release reactive oxygen species (ROS), which can result in tissue damage and injury. In this study a wide range of AAP samples from divergent sources (1, natural dust; 2, oil fly ash; 2, coal fly ash; 5, ambient air; and 1, carbon black) were analyzed for elemental content and solubility in relation to their ability to generate ROS. Elemental analyses were carried out in AAP and dH2O-washed AAP using energy dispersive x-ray fluorescence (XRF). Percent of sample mass accounted for by XRF-detectable elements was 1.2% (carbon black); 22–29% (natural dust and ambient air particles); 13–22% (oil fly ash particles); 28–49% (coal fly ash particles). The major proportion of elements in most of these particles were aluminosilicates and insoluble iron, except oil-derived fly ash particles in which soluble vanadium and nickel were in highest concentrations, consistent with particle acidity as measured in the supernatants. Human blood-derived monocytes and PMN were exposed to AAP and dH2O-washed particles, and generation of ROS was determined using luminol-enhanced chemiluminescence (LCL) assay. All the particles induced chemiluminescence response in the cells, except carbon black. The oxidant response of monocytes induced by AAP (with the exception of oil fly ash particles) was less than the response elicited by PMN. The LCL response of PMN in general increased with all washed particles, with oil fly ash (OFA) and one urban air particle showing statistically significant (p < 0.05) differences between dH2O-washed and unwashed particles. The LCL activity in PMN induced by both particles and dH2O-washed particles was significantly correlated with the insoluble Si, Fe, Mn, Ti, and Co content of particles (p < 0.05). No relationship between LCL activity in PMN and soluble transition metals such as V, Cr, Ni, and Cu was noted. Pretreatment of the particles with a metal ion-chelator, deferoxamine, did not affect LCL in PMN, suggesting that metal ions are not related to the induction of LCL in PMN. Particulate S content and acidity of the particles as measured in the supernatants did not relate to LCL activity in PMN. These results point to the possibility that the insoluble constituents of the particles are related to LCL in PMN. Since some of these dusts are capable of depositing in the lungs and can cause infiltration of PMN, the ability to activate those cells may contribute to particulate toxicity.