The Synergistic Cytotoxicity Of Nano Black Carbon And Perfluorooctanoic Acid (PFOA) To Cultured Human Lung Eptithelial Cells

Air pollution has been recognized as an increasingly serious problem in recent years. The atmospheric fine particles (also called inhalable particles or particulate matter, PM) posed a significantly serious hazard to human health, which have already received people’s concern. What was more, a huge number of epidemiological and toxicological studies demonstrated statistical associations between exposure to inhalable particles and public health. And PM which was smaller than aerodynamic diameter of2.5micrometer (PM2.5) can penetrate into the respiratory airways and has been linked to adverse health effects on the respiratory system. In addition, the large surface area of PM enabled it more easily to adsorb other pollutants. Thus the toxicity of PM2.5appears to be much greater than the toxicity estimated by adding the known toxicity values of the individual substances in a "typical" PM2.5composition. One of the possible explanations for this discrepancy was synergism between the different components of particulate matter. Therefore, it was imperative to assess the potential risk of synergistic effects between the PM and other pollutants to gain further insight into the health effects of PM.In this paper, we chose black carbon nanoparticles (RM2975), the main component of atmospheric aerosol, to represent PM. And as PFOA can be transported to remote regions by attaching to airborne particulate matter, we chose it as a representative of the organic pollutants in PM2.5. Then a thorough physico-chemical characterization of [RM2975](in powder) was performed, using Raman spectra, BET, SEM and STEM. And the size distribution of dispersed [RM2975](in solution) was analyzed by Zetasizer nano. In order to assess the potential risk of human health, we investigated the synergistic toxicity of carbon black and PFOA on the human alveolar epithelial cells line A549. The final conclusions of the experiment are presented as follows:(1) A549cells exposed to black carbon particles alone did not show significant cytotoxicity, and the cell viability maintained above70percent. The half maximal inhibitory concentration of black carbon was over20μg·mL-1. In the mean time, the intracellular ROS and the rate of apoptosis, when induced by black carbon in A549cells, tend to increase with the increase of the concentration of black carbon. Furthermore, we found that the cell viability, the oxidative stress and the rate of apoptosis were well linearly correlated with the diameter of black carbon in solution.(2) The PFOA tend to exhibit the dose-dependent cytotoxicity, but there was no significant effect at the low concentrations. A549cells began to shrink and turn round when they were exposed to PFOA at a concentration over50μg·mL-1. Meanwhile, the cell viability of A549decreased significantly as the concentration increased after exposure to PFOA for24h, while intracellular ROS and rate of apoptosis induced by PFOA in A549cells increased as the concentration of PFOA increased.(3) Co-exposure to carbon black particles and PFOA caused a synergistic cytotoxicity, but the influence of them on each other’s effect was different. A549cells co-exposed to both PFOA and10μg·mL-1of black carbon significantly improved the cytotoxicity of PFOA. However, cells co-exposed to both black carbon and10μg·mL-1of PFOA slightly improved nanoparticles’s cytotoxicity. Therefore, it might be because nano-carbon black had higher toxicity than the organic pollutants.