RESUMO
Earlier reports described byssinosis syndrome among workers in cotton industry, while recent studies have shown that workers occupationally exposed to cotton dusts have an increased risk of development of many types of cancer. Hence this study was conducted to assess genotoxic effects [as a measure of carcinogenic risk] of chronic cotton dust inhalation in workers with byssinosis and to combine clinical and occupational data with the results of genotoxicity assays in order to reach quantitativness in risk assessment. Clinically, byssinosis was diagnosed mainly in workers employed at early production areas of yarn preparation: opening, blowing and carding [80%] and those working as machine operators [8.5%]. There was significant correlation between the duration of exposure to cotton dusts and the clinical severity of the disease. Study of cytogenetic markers in exposed workers showed significant increase in the percent of total chromosomal breaks and aberrations as well as the mean value of sister chromatid exchanges accompanied with significant decrease in mitotic index value as compared to controls. Assessment of total genomic damage of DNA by visual comparing of the density of released [migrated, damaged] DNA bands and by measuring the optical density of damaged DNA bands using Gel-Pro computer program revealed 20% increase in DNA damage in blood lymphocytes of workers chronically exposed to cotton dusts when compared to non-exposed controls. Also, there was 50% increase in the optical density of the released RNA in blood lymphocytes of exposed workers than controls which might be used as an index of stress of pollution applied on cotton industry workers. Comet assay endpoints revealed more than twice times higher number of migrated DNA spots [damaged, strongly damaged] in blood lymphocytes from cotton industry workers compared to non-exposed subjects. The genotoxicity burden measured as% of total chromosomal breaks, and aberrations, mean values of SCEs/metaphase and DNA damage endpoints [the number of damaged DNA spots and the optical density of damaged DNA] was correlated significantly with the duration of exposure to cotton dusts. Therefore the fact that workers occupationally exposed to cotton dusts have distinctly more chromosomal mutations and DNA damage may be an important indicator in the chronic effect of cotton dust-associated carcinogenesis. Combining the clinical and occupational data with the results of genotoxicity assays showed that the severity of byssinosis syndrome was associated with the degree of genome damage