Human exposure to respirable manganese in outdoor and indoor air in urban and rural areas

Methylcyclopentadienyl manganese tricarbonyl (MMT) is used as an additive in gasoline, and its combustion leads to the emission of Mn particles, which increase atmospheric metal concentrations. The objective of this study was to determine the level of outdoor and indoor respirable Mn (MnR) in Montreal, Canada, where MMT has been used since 1976. Ten women were involved in this study: five living in an urban area, near an expressway with high traffic density, and five residing in a rural area characterized by low traffic density. Outdoor and indoor air samples were collected each week (5 in total) during 3 consecutive days; blood samples were collected at the end of the air sampling period. The average concentration of outdoor MnR in the urban area was 0.025 mug/m(3) which is significantly different from the average of 0.005 mug/m(3) found in the rural area. The average indoor MnR concentration was also significantly different between the urban area (0.017 mug/m(3)) and the rural area (0.007 mug/m(3)). The average outdoor MnR concentrations were not significantly different from the average MnR indoor concentrations within both areas. The mean blood Mn concentrations were not significantly different between the two groups. Data suggest that a high outdoor atmospheric MnR leads to a high indoor MnR, but not to an increase in blood Mn levels.