Cytotoxicity and mutagenicity of particulate matter from the open burning of pruning wastes

Burning vegetative debris is a worldwide long-standing practice. The current study was designed to examine the cytotoxicity and mutagenicity of particulate matter with an aerodynamic diameter below 10 µm (PM10) released from the burning of pruning residues common in Portugal and other countries of the Mediterranean region. Field measurements were conducted to collect PM10 samples from open burning of vines, olive, willow and acacia pruning branches. To assess the cytotoxicity of the PM10 total organic extract, the A549 cell line, representative of the alveolar type II pneumocytes of the human lung, was used. The cytotoxicity was checked using two complementary methods: water-soluble tetrazolium (WST-8) test to evaluate the cell metabolic activity and lactate dehydrogenase (LDH) activity assay to assess the loss of cell membrane integrity. The mutagenicity of the PM10-bound polycyclic aromatic hydrocarbons (PAHs) was screened through the Ames test. PM10 organic extracts induced LDH release in a dose-dependent manner. Regarding the cellular metabolic activity, dose-dependency was lacking for the majority of the samples. Combined WST-8 and LDH data indicate that PM10 exposure induce a necrotic cell death pathway in which the cell membrane integrity is lost. Direct and indirect mutagenicity towards the TA98 Salmonella strain has been recorded for the PAH extracts of PM10 collected from combustion of vine and willow branches during the ignition/flaming combustion stage. Significant correlations were found between the cytotoxic responses (WST-8 and LDH) and the PM10 organic component.