ENVIRONMENTAL AND OCCUPATIONAL EXPOSURE TO MANGANESE - A MULTIMEDIA ASSESSMENT

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic addit ive used in Canada since 1976 as an anti-knock agent in unleaded gasol ine. Its combustion leads to the emission of Mn oxides, especially Mn3 O4. Since no study has assessed the potential risk of chronic exposure to low concentrations resulting from these emissions, the present inv estigation was undertaken to assess the level of environmental and occ upational exposure of the human population. The multimedia exposure of two groups of workers (garage mechanics and blue-collar workers) pote ntially exposed to different levels of Mn from the combustion of MMT w as assessed using personal air samplers, a dietary compilation, water samples at their places of residence, an epidemiological questionnaire and blood and hair samples. Results show that garage mechanics were e xposed on average to higher atmospheric Mn at work (0.42 mu g/m(3)) th an the blue-collar workers (0.04 mu g/m(3)). However, the contribution of atmospheric Mn to the total absorbed dose was less than 1%, and we ll below the standards estabished for occupational or environmental ex posure; food contributes more than 95% of the multimedia dose. The ave rage whole blood Mn concentrations were similar for the two groups (0. 67-0.76 mu g/100 ml) and fall within the normal adult range. The avera ge hair Mn concentrations were significantly higher for the garage mec hanics (0.66 mu g/g) than for the blue-collar workers (0.39 mu g/g). T he contribution of exogenous Mn Versus endogenous Mn is questioned. As judged by the governmental standards or criteria for occupational and non-occupational environments, the current Mn levels in food, water a nd air may not cause any problems for the workers.