Airborne inhalable metals in residential areas of Delhi, India: distribution, source apportionment and health risks

Abstract

The inhalable fraction of ambient particles (particulate matter with aerodynamic diameter less than 10μm, denoted by PM10) collected at three residential sites in Delhi, India during December 2008–November 2009 were characterized with respect to 8 major and trace metals (Fe, Mn, Cd, Cu, Ni, Pb, Zn and Cr). Mean annual 24–h PM10 levels varied from 166.5–192.3μg m–3 at the sites (8–10 times of the WHO limit). Weekday/weekend effects on PM10 and associated metals were investigated. Significant seasonal variations (ANOVA, p<0.001) in species concentrations were observed with PM10 and crustal metals peaking in summer while anthropogenic metals peaked in winter. Spatial distributions of metals were influenced mainly by proximity to traffic and industrial areas. Influence of meteorological parameters on ambient metal distributions was also studied. Source apportionment by principal component analysis–multiple linear regression (PCA–MLR) identified three major sources: crustal (49–65%), vehicular (27–31%) and industrial (4–21%). As a part of health risk assessment, calculated theoretical estimates of blood lead levels in children varied from 10.2–13.3μg dL–1, indicating some degree of lead toxicity. Incremental lifetime cancer risk (ILCR) assessment showed that up to 2 908 excess cancer cases (102 for Cd, 2 559 for Cr (VI) and 247 for Ni) are likely in Delhi for lifetime inhalation exposure to these species at their current concentrations.