URINARY-EXCRETION OF MUTAGENS IN COKE-OVEN WORKERS

The influence of occupational exposure to polycyclic aromatic hydrocar bons (PAHs) on urinary mutagenic activity was assessed in 75 coke oven workers, using a highly sensitive bacterial mutagen technique (extrac tion with C18 resin and liquid micro-preincubation test on strain TA98 of Salmonella typhimurium in the presence of metabolizing and deconju gating enzymes). Exposure to PAHs was assessed according to the urinar y excretion of 1-pyrenol; the main confounding factors were checked by the number of cigarettes smoked per day and the levels of nicotine an d its metabolites in urine, or by ascertaining whether recommended die tary restrictions had been followed. Of the 20 urine samples which tur ned out to be positive (producing at least double the number of sponta neous revertants), 19 (95%) belonged to smokers. Only one non-smoker h ad obvious urinary mutagenic activity, and was highly exposed occupati onally to PAHs (urinary 1-pyrenol of 3.930 mu mol/mol of creatinine). Of the five urine samples from subjects who had not followed the recom mended diet, two (40%) were clearly mutagenic, Multiple regression ana lysis (n = 67) showed that the presence of samples positive for urinar y mutagenic activity depended only on smoking habits, if this confound ing factor was assessed according to the number of cigarettes smoked p er day, while the significant influence of exposure to PAH could be sh own when the confounding factor was objectively estimated according to the urinary levels of nicotine and its metabolites, Assessment of the mutagenic potency of urinary extracts (net revertants/mmol creatinine ) confirmed the strong influence of smoking habits on urinary mutageni c activity (all smokers 2156 +/- 2691 versus non-smokers 939 +/- 947 n et revertants/mmol creatinine; Mann-Whitney test: P < 0.01), In smoker s highly exposed to PAHs, greater excretion of mutagens with respect t o low-exposure smokers was revealed (3548 +/- 4009 versus 1552 +/- 122 7 net revertants/mmol creatinine; Mann-Whitney test: P < 0.01). Multip le regression analysis showed that the mutagenic potency of urinary ex tracts of coke oven workers depended on exposure to PAHs, tobacco smok ing habits, and consumption of fried, grilled or barbecued meat, Incre ased urinary mutagenic activity strengthens epidemiological evidence o f the increased risk of renal and urinary tract tumours in these worke rs, The presence of mutagenic metabolites in urine as a result of occu pational exposure to PAH may be demonstrated only by using highly sens itive techniques for assessing urinary mutagenic activity in studies w hich include careful checking of the main confounding factors.