Porphyrin Pattern and Methemoglobin Levels in Columba livia Applied to Assess Toxicological Risk by Air Pollution in Urban Areas

The study has explored two conservative biomarkers, porphyrin pattern in guano and methemoglobin levels in blood of Columba livia , in order to assay their potential use for monitoring toxic effects induced by exposure to urban air pollution. Fieldwork was conducted between October 2003 and June 2005 in the city of Milan, Italy, by sampling the pigeons in different areas almost twice a week. Six air contaminants, CO, PM10, NO 2 , O 3 , SO 2 , and C 6 H 6 , plus polycyclic aromatic hydrocarbons (PAHs) in fine particles, temperature, and UV index, were considered. Protoporphyrins from pigeon excreta sampled outdoors were always higher than in indoor animals, particularly in winter. A positive correlation ( p < 0.001) of protoporphyrin with PAHs was observed. In terms of the values of methemoglobinemia, animals exposed to urban air showed significant differences from season to season but only in summer and autumn did the outdoor pigeons show higher values than indoor animals. In summer, a regression model with a positive correlation between O 3 and benzene was determined ( p < 0.01 ) . The use of Columba livia as a sentinel for urban air pollution as well as for detecting complex interactions between contaminants in the urban air pollutant mixture was discussed.