Frequency of micronuclei and other biomarkers of DNA damage in populations exposed to dusts, asbestos and other fibers. A systematic review.

Airborne particles are small, solid particles projected into the air either by natural forces, or by mechanical or man-made processes, and include fibers and dusts. Their toxicity is usually subsequent to inhalation and can lead to pulmonary dysfunctions and diseases, including cancer. Cytochalasin B blocked micronucleus assay in lymphocytes (L-CBMN) has been shown as a sensitive and reliable technique in assessing genotoxic exposure, An extensive search of the PubMed and Web of Science databases allowed retrieval of 18 articles on occupational or environmental exposure evaluating L-CBMN in subjects exposed to fibers or dusts (asbestos, silica, rockwool, beryllium, tobacco, and wood). For each study, mean L-CBMN levels were compared in exposed subjects vs. unexposed controls providing a point estimate, the Mean Ratio (MR). The high heterogeneity among retrieved studies and their relatively limited number did not allow a quantitative meta-analysis. However, the inter-quartile range of all MRs fell within the interval between 1.25 and 2.23, supporting the hypothesis that exposure to airborne particles increases DNA damage, although mechanisms of genotoxicity should be further investigated. A borderline significant correlation was found with SCE, but not with chromosome aberrations or comet assay. Future research should focus on exposure assessment, in order to perform proper dose-response studies and disentangle the effect of different compounds in mixed exposures. To fully exploit the cytome assay, L-CBMN frequency should be integrated with other endpoints, such as nucleoplasmic bridges and nuclear buds. The use of alternative tissues, such as nasal and buccal mucosa, and the implementation of other cytogenetic assay, may help to understand the effects of this exposure.