Ambient Particulate Matter in Valdivia, Chile: Temporal Analysis and Compared Cytotoxicity in Lung Epithelial Cells

Despite local efforts to replace wood as the main energy source and alleviate the health consequences of their emissions, in most Chilean cities below the 36° S, parallel wood is the main fuel source for home heating and cooking. Valdivia is a city located in the Chilean southern macro-zone where limited research has been carried out to characterize seasonal and daily behavior of atmospheric particulate matter (PM) levels and the potential effects that local PM have over human lung cells. To characterize Valdivia’s ambient PM levels, we assessed daily and hourly PM10 and PM2.5 concentration records in two sampling stations managed by the Chilean Ministry of Environment (VAL-1 and VAL-2). Also, we collected PM2.5 samples from these sites and exposed human lung epithelial cells to assess Valdivia’s PM2.5 effects over lung cell viability. PM10 and PM2.5 daily levels showed a strong seasonality dependance (cold period [April–September] > warm period [October–March]) and for the years with available data (VAL-1 [2008–2021], VAL-2 [2018–2021]), an average trend of reduction was found (0.5–1.6 μg/m3 by year). VAL-1 PM levels surpassed those measured at VAL-2 (cold period > warm period) and surpassed the levels stablished by national standards and recommended by the World Health Organization (WHO). Hourly PM levels showed a minor peak in the morning ( 6–10) and a robust one at night ( 18–3). Weekly PM2.5 ambient samples collected at VAL-1 and VAL-2 were exposed to human lung epithelial cells (A549 and Calu-1) to assess their relative cytotoxicity (cell viability). These samples were compared with standard particulate samples from diesel exhaust (C-DEP), volcanic ashes (MSH), residual oil fly ash (ROFA), and other urban ambient site (Ottawa Dust) through a dose response (ranging 0–100 μg/mL) at 0, 24, 48, and 72 h of exposure. C-DEP and MSH induced a modest reduction in viability (MSH > C-DEP) that was surpassed by VAL-1, VAL-2, and Ottawa Dust which in turn was surpassed by ROFA. Generally, Calu-1 cells and A549 cells were similarly sensitive to ROFA while the A549 cells were more sensitive to ambient samples. Taken together, these results show that PM concentration differences between sites located in Valdivia city present annual and daily peaks consistent with massive wood usage and that ambient PM2.5 samples induced significant cell viability reductions comparable with standard ambient samples.