Apoptosis and DNA damage induced by silica nanoparticles and formaldehyde in human lung epithelial cells

Human exposure to silica nanoparticles (SNPs) and formaldehyde (FA) is increasing and this has raised some concerns over their possible toxic effects on the exposed working populations. Notwithstanding several studies in this area, the combined toxicological effects of these contaminants have not been yet studied. Therefore, this in vitro study was designed to evaluate the SNPs and FA combined toxicity on human lung epithelial cells (A549 cells). The cells were exposed to SNPs and FA separately and in combined form and the single and combined toxicity of SNPs and FA were evaluated by focusing on cellular viability, DNA damage, and apoptosis via MTT, DAPI staining, DNA ladder, and Annexin V-FITC apoptosis assays. The results showed a significant increase in cytotoxicity, DNA damage, and chromatin fragmentation and late apoptotic/necrotic rates in combined treated cells compared with SNPs and FA-treated cells (P value < 0.05). Two-factorial analysis showed an additive toxic interaction between SNPs and FA. Eventually, this can be deduced that workers exposed simultaneously to SNPs and FA may be at high risk compared with exposure to each other.