Repeated measurements of urinary methylated/oxidative DNA lesions, acute toxicity, and mutagenicity in coke oven workers

We conducted a repeated-measures cohort study of coke oven workers to evaluate the relationships between the traditional exposure biomarker, urinary 1-hydroxypyrene (1-OHP), and a series of biomarkers, including urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG), N7-methylguanine (N7-MeG), acute toxicity, and mutagenicity. A total of eight spot urine samples were collected from each high-exposed (at topside oven area) and low-exposed workers (at side oven area) during the whole working cycle, which consisted of 6 consecutive days of working followed by 2 days off. Our results showed that the high-exposed workers had significantly higher urinary levels of 1-OHP, 8-oxodG, and N7-MeG compared with the low-exposed workers. Acute toxicity and mutagenicity of urine were also found to be markedly increased in the high-exposed workers, as determined by Microtox assay and Ames test, respectively. Multivariate regressions analysis revealed that the urinary 8-oxodG, N7-MeG, or acute toxicity was significantly correlated with 1-OHP concentrations. Overall, the present study showed that exposure to coke oven emissions increased oxidatively damaged DNA products and mutagenicity of urine, and for the very first time, such exposure was also found to increase DNA methylation and urinary acute toxicity. The potential source of methylating agents in coke oven emissions warrants further investigation. Additionally, with repeated measurements, the pattern of time course for urinary 1-OHP was found to be different from those of 8-oxodG and N7-MeG, as well as acute toxicity and mutagenicity. This finding implies that the single measurement that was often conducted in occupational healthy investigations should be used with certain precautions, because single measurement may fail to provide the proper information of interest.