In vitro toxicity and lung cancer risk: Atmospheric particulate matter from a city in southeastern Brazil impacted by biomass burning

The effects of PM₁₀ on human health were investigated using samples collected in São Carlos city (São Paulo state), by the determination of the concentrations of PAHs and derivatives, together with evaluations of cytotoxicity and the formation of ROS in in vitro tests. In 2016, the mean concentrations of PM₁₀, ΣPAHs, Σoxy-PAHs, Σnitro-PAHs, Σsaccharides, and Σions were 21.12 ± 9.90 μg m⁻³, 1.47 ± 1.70 ng m⁻³, 0.37 ± 0.31 ng m⁻³, 0.84 ng m⁻³, 119.91 ± 62.14 ng m⁻³, and 5.66 ± 4.52 μg m⁻³, respectively. The PM₁₀ concentrations did not exceed the limit thresholds set by national legislation, however, the annual lung cancer risk calculated was 2.59 ± 1.22 cases per 100,000 people, in the dry season, which accounts for the annual risk (April to September). Moreover, the carcinogenic activities of the PAHs mixture were more than 1000-fold higher in the dry season (dry season: BaP_eq = 0.30 ng m⁻³; wet season BaP_eq = 0.02 ng m⁻³). The concentrations of most analytes were also higher during the dry season, as had already been demonstrated in the same city. This was due to reductions in precipitation, relative humidity and air temperature, and increased biomass burning, which was the main source of PM₁₀ in the city in 2016 (contribution rate of more than 50%). Toxicological results also showed the negative impacts of PM₁₀, exposure to PM₁₀ extracts for 72 h reduced the viability of A549 and MRC5 cells, and the formation of ROS was observed. The cellular responses obtained using combined and individual extracts of PM₁₀ differed and were sometimes associated with specific compounds. These demonstrate the importance of monitoring PM toxicity using different approaches and the main anthropogenic sources’ contribution. Therefore, to improve air quality and human health, existing legislation needs to be modified to incorporate these tests.