The pigeon (Columbia livia) as a monitor for manganese contamination from motor vehicles

Abstract

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn) used in unleaded gasoline in Canada since 1977. It has been suggested that the production of Mn3O4 resulting from the combustion of MMT may become one of the principal sources of manganese contamination in the urban environment. This research evaluates the feral pigeon (Columba livia) as a monitor of Mn contamination in rural (Lachute) and urban (Montreal) environments. Atmospheric Mn concentrations were measured over a 6-month period in the rural and urban areas. Twenty pigeons were captured in each area and the Mn concentrations of several tissues (liver, kidney, lung, pancreas, intestine, brain, down feathers, feces, whole blood, and blood serum) were measured by neutron activation. Biochemical profiles of the blood samples (total protein, aspartate aminotransferase, hematocrit, glucose, and uric acid) were also measured. Air particulate data showed significantly higher Mn levels (p 0.05) in the two groups of pigeons for all the tissues except liver (Lachute=2.42 ppm; Montreal=3.13 ppm) and feces (Lachute=32.2 ppm; Montreal=46.8 ppm); the urban pigeons had about 35% more Mn than the rural pigeons. Aspartate aminotransferase (AST) was also significantly different in the two groups. These results show the importance of the entero-hepatic cycle in the homeostasis of Mn in blood and other tissues. Since the excess of Mn in the feces and liver of the urban pigeons relative to the rural pigeons was similar to the excess Mn in urban air over rural air, pigeon feces and liver appear to be good biomarkers of Mn contamination. Although it is premature to associate this excess Mn with the combustion of MMT, these results nevertheless lead us to consider the pigeon as an interesting indicator of the potential risk to the ecosystem and to human health.