Urban environment as a factor modulating metals deposition in the respiratory track and associated cancer risk

The aim of this study was to compare the inhalation cancer risk posed by PM-bound As, Cd, Pb, Ni and Cr(VI) concentrations in typical urban environment and to differentiate this risk between PM size fractions and population age-groups. Additionally inhalation deposition metrics were used to characterize risks posed by PM of highway (H)-, street canyon (SC)- and residential (RA) origin. Aerosol samples were collected in the cities of Zabrze and Katowice (Poland) using Dekati cascade impactors. Regardless of the location metals were primarily associated with particles less than 1 μm. For sites, where the PM size distribution was bi-modal (SC in Zabrze and Katowice and RA in Zabrze) and the maxima of metal mass distribution occurred in both accumulation and coarse modes, the metal was predominantly deposited in head airways region. Sites characterized by an uni-modal distribution (RA in Katowice, H in Katowice and SC in Zabrze) were found to favor pulmonary deposition. The overall mass deposition of metals in the respiratory tract in residential; highway and street canyon environments were: 0.51; 0.54 and 0.61, respectively. Street canyon concentrations were therefore most hazardous. Depending on the specific compartment of the respiratory tract, average metal mass deposition amounts varied from 0.05 to 0.53 of its ambient concentration. ILCR values were up to 10E-03 for adults versus 10E-05 for infants. Adults were mostly exposed near street canyons, while infants and children were mostly susceptible near residential and highway environments.