Evaluation of Cancer Risk of Heavy Metals in the Air of a High Traffic Urban Region and Its Source Identification

Background: Sampling was conducted on particles smaller than ten microns (PM10) in a high-traffic urban region once a week for two years in which fifteen heavy metals were measured. Methods: positive matrix factorization (EPA-PMF5), was used for source apportionment and characterization of the collected PM10. Assessment of cancer risk resulting from metals including arsenic, cadmium, chromium, nickel and lead was conducted in three concentration ranges of maximum, average and minimum. Results: Results for children and adults living in the region indicated that cancer risk indexes at different concentration ranges of carcinogenic metals were between 10-4 to 10-6 for adults and children. Since EPA recommendations suggest that planning should be conducted if cancer risk is in the range of 10-4 to 10-6, using PMF5 model, source characterization of pollutants was implemented by all measured heavy metals. Conclusion: It was found that 41.5% of PM10 resulted from fuel and combustion, 12% from waste dump soil of lead and zinc industries, 35.7% from suspended open soil and 11% from industrial activities. It was also found that cadmium, nickel and, chromium have higher cancer risk than other metals and, suspended open soil, industrial activities and industrial fuel and combustion are the main sources of these metals respectively.