Objective: the immunological effect of chromium exposure among workers in tanning industry was assessed by studying the incidence of structural chromosomal aberrations in lymphocytes. Early monitoring of immunotoxicity and possibility of
carcinogenecity using the CD40 ligand member of the tumor necrosis superfamily of trans-membrane proteins was evaluated. Methods: levels of chromium in blood (S-Cr) and urine (U-Cr) were measured using the graphite furnace atomic absorption spectrophotometer. The CD40 Ligand (CD40L) was determined using ELISA. Whole blood was treated and chosen metaphases were recorded and scored for morphological aberrations and rearrangements.Results: the study was carried out on 30 workers exposed to chromium in chrome-tanning for 17.13 ± 8.09 years, and a matched group of 28 administrative workers. The mean serum chromium levels (S-Cr) were 4.35 ± 1.46 and 1.89 ± 1.31 μg/dl among exposed and control groups, respectively, and the difference was statistically significant, P<0.00±. The CD40L assessment revealed decreased levels among the exposed population, difference was statistically non-significant. The genotoxic changes in the form of chromosomal and chromatid gaps and breaks as well as dicen-actitricchanges were significantly higher among exposed workers, correlating significantlywith the levels of chromium in both serum and urine after correction for creatinine.A significant negative correlation was reported for the deletions with the level of CD40 ligand. The effect of age, smoking and cumulative exposure indices were dealt with.Conclusion: the use of cytogenetic monitoring of human populations exposed to chemicals has proved to be a useful tool for detecting the chemical's mutagenic effects.CD40L, which is a member of the tumor necrosis factor, may be used as an additional marker to assess the presence of chronic inflammation, an early warning indication of potentially adverse genetic and somatic effects.