In-vitro metabolomics to evaluate toxicity of particulate matter under environmentally realistic conditions

In this pilot study three fractions of particulate matter (PM _0.25, PM _2.5-0.25, and PM _10-2.5) were collected in three environments (classroom, home, and outdoors) in a village located nearby an industrial complex. Time-activity pattern of 20 students attending the classroom was obtained, and the dose of particles reaching the children's lungs under actual environmental conditions (i.e. real dose) was calculated via dosimetry model. The highest PM concentrations were reached in the classroom. Simulations showed that heavy intensity outdoor activities played a major role in PM deposition, especially in the upper part of the respiratory tract. The mass of PM _10-2.5 reaching the alveoli was minor, while PM _2.5-0.25 and PM _0.25 apportion for most of the PM mass retained in the lungs. Consequently, PM _2.5-0.25 and PM _0.25 were the only fractions used in two subsequent toxicity assays onto alveolar cells (A549). First, a cytotoxicity dose-response assay was performed, and doses corresponding to 5% mortality (LC ₅) were estimated. Afterwards, two LC-MS metabolomic assays were conducted: one applying LC ₅, and another applying real dose. A lower estimated LC ₅ value was obtained for PM _0.25 than PM _2.5-0.25 (8.08 and 73.7 ng/mL respectively). The number of altered features after LC ₅ exposure was similar for both fractions (39 and 38 for PM _0.25 and PM _2.5-0.25 respectively), while after real dose exposure these numbers differed (10 and 5 for PM _0.25 and PM _2.5-0.25 respectively). The most metabolic changes were related to membrane and lung surfactant lipids. This study highlights the capacity of PM to alter metabolic profile of lung cells at conventional environmental levels.