Current external and internal exposure to naphthalene of workers occupationally exposed to polycyclic aromatic hydrocarbons in different industries

Objectives: External and internal exposure to naphthalene was examined in the most important industries that are typically concerned with polycyclic aromatic hydrocarbon ( PAH)-induced diseases ( cancer). Furthermore, a control collective from the general population was investigated. Methods: External naphthalene was determined by personal air sampling (n = 205). The internal exposure was examined by urinary metabolites 1-naphthol and 2-naphthol (n = 277). Results: Highest median concentrations of naphthalene in air were found in converter infeed (93.2 mu g/m(3)) and coal-tar distillation (35.8 mu g/m(3)). Moderate and low levels were determined in coking plants (14.5 mu g/m(3)) and in the production of refractories (6.1 mu g/m(3)) and graphite electrodes (0.7 mu g/m(3)). Biological monitoring revealed concentrations of the sum of both metabolites [(1+2)-NOL] in smokers to be increased by 1.6 - 6.4 times compared with that in non-smokers at the same workplaces. Among non-smokers we found high median ( 1+ 2)- NOL levels in converter bricklayers ( 120.1 mu g/l), in coal-tar distillation workers (56.0 mu g/l) and in coking plant workers (29.5 mu g/l). ( 1+ 2)- NOL concentrations around 10 lg/ l were found in the production of refractories and graphite electrodes. There was a rough coherency between external and internal naphthalene exposure. In the controls, median ( 1+ 2)- NOL concentrations were 10.9 mu g/l in non-smokers' urine and 40.3 mu g/l in smokers' urine samples. Conclusions: Actual conditions of occupational hygiene at the workplaces investigated in this comprehensive study are better than those that current limit values of 50,000 mu g/m(3) (TLV, TRK) seem to induce. It has become obvious that tobacco smoking is a crucial confounding factor in biological monitoring of naphthalene-exposed humans, making interpretation of occupationally increased naphthol excretions very difficult at low exposure levels.