Abstract
Human exposure to airborne particulate matter (PM) is associated with adverse cardiopulmonary health effects, including lung cancer. Ambient PM represents a heterogeneous mixture of chemical classes including transition metals, polycyclic aromatic hydrocarbons (PAHs) and their derivatives such as nitro‐PAHs, many of which are classified as putative carcinogens. As the primary site of human exposure to PM is the lungs, we investigated the response of two alveolar epithelial cell lines, the tumour‐derived A549 and newly described TT1 cells, to fine and coarse PM collected from background and roadside locations. We show that coarse PM elicits a genotoxic response in the TT1 cells, with the strongest signal associated with the background sample. This response could be recapitulated using the organic extract derived from this sample. No responses were observed in PM‐challenged A549 cells. Fine PM failed to elicit a genotoxic response in either cell line despite the higher PAH concentrations within this fraction. Consistent with the lack of a simplistic association between PM PAH content and the observed genotoxic response, TT1 cells treated with benzo[a]pyrene (BaP) demonstrated no increase in the selected markers. In contrast, a pattern of response was observed in TT1 cells challenged with 3‐nitrobenzanthrone (3‐NBA) similar to that with coarse PM. Together, these data illustrated the suitability of the TT1 cell line for assessing PM‐induced genotoxicity and challenge the contention that fine roadside PM poses the higher cancer risk. Furthermore, the response to 3‐NBA and not BaP suggests a major contribution of nitro‐PAHs to the overall toxicity of PM. Environ. Mol. Mutagen. 59:290–301, 2018. © 2018 The Authors Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society
Highlights
According to the World Health Organization, air pollution contributes to 12.5% of world-wide deaths [World Health Organisation, 2014], making it a major contributor to the global burden of disease
A significant cytotoxic response was seen in TT1 cells exposed to the coarse background Particulate matter (PM) (BG_C) showing approximately 50% decrease in cell viability compared to control cells (Fig. 1A)
A small but non-statistically significant decrease in viability was seen in TT1 cells exposed to the coarse roadside PM (RS_C); no effect on viability was seen in TT1 cells exposed to fine PM or in any of the A549 cell exposures (Fig. 1A)
Summary
According to the World Health Organization, air pollution contributes to 12.5% of world-wide deaths [World Health Organisation, 2014], making it a major contributor to the global burden of disease. In addition the incomplete pyrolysis of carboncontaining compounds, from diesel fuel, is a major source of polycyclic aromatic hydrocarbons (PAHs) and their derivatives, including nitrated PAHs (nitro-PAHs), in ambient PM [Bamford et al, 2003]. Both PAHs and nitro-PAHs have attracted considerable interest with regards to their effects on human health given their ability, following intracellular metabolism, to bind to DNA, and induce mutations [Baird et al, 2005; Nagy et al, 2007]. The International Agency for Research on Cancer (IARC) classified outdoor air pollution and diesel engine emissions as carcinogenic to humans [IARC, 2013, 2016]
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