A preliminary assessment of the urban pollution in the Great Lakes region

Trends in emissions of trace elements to the atmosphere in the Great Lakes region are compared with those of ambient concentrations observed in the urban areas of Chicago, Detroit, Cleveland and Toronto from 1982 to 1993. Lead emissions show a steady decrease throughout the region, whereas the emissions of Ni, Cr, Cu, Mn and Cd are following upward trends, and As emissions do not show substantial changes. Our estimates by source category suggest that the emission of trace elements from iron-steel manufacturing, waste incineration and non-ferrous metal production are steadily increasing, whereas emissions from oil combustion are decreasing and that from coal combustion do not show significant changes since 1982. A trend analysis performed on the ambient concentration data from all the urban sites shows a steady decrease of Pb concentrations (3–20%/yr) in all the urban areas, whereas the level of other trace elements is following upward and downward trends depending upon the urban area and sample site locations.