MANGANESE CONTAMINATION IN MONTREAL IN RELATION WITH TRAFFIC DENSITY

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic deriv ative of manganese used as an additive in unleaded gasoline in Canada since 1977. Moreover, Canada is the only country in the world to have authorized the replacement of lead alkyls by MMT in gasoline. The purp ose of the present study is to assess the importance of air contaminat ion by Mn in relation to other air pollutants (gaseous and particulate s), meteorological variables and traffic density. Tle concentration of both the gaseous (O3, CO, NO, NO2, SO2) and the particulate pollutant s (Mn, Pb, NO3-, SO4--, TSP) had been measured by the Montreal Urban C ommunity in 1990 at seven sampling stations located in high traffic an d low traffic density areas. Data on the meteorological conditions dur ing that same period were also used. Non-parametric correlation, ANOVA and discriminant analyses were used to compare gaseous and particulat e pollutants found between both levels of traffic density. In almost 5 0% of the daily air samples measured in 1990, the Mn concentrations ar e higher than the urban background level estimated at 0.04 mug m-3 and the variations of Mn concentrations are significantly correlated in t ime with traffic density. Moreover, Mn and TSP discriminate the best h igh and low traffic density areas. No significant differences have bee n observed between Pb, O3 and SO2 concentrations in both areas. These results should not be interpreted in terms of potential health effects since it is presently impossible to determine the fate of the Mn in t he environment and its importance in terms of human exposure.