Size-classified aerosol-bound heavy metals and their effects on human health risks in industrial and remote areas in Japan.

Airborne aerosols were collected in six size classes (PM<0.1 , PM0.1-0.5 , PM0.5-1 , PM1-2.5 , PM2.5-10 and PM>10 ) to investigate aerosol health risks in remote and industrial areas in Japan. We focused on heavy metals and their water-dispersed fractions. The average concentration of heavy metals was 18 ± 25-86 ± 48 ngm-3 for PM<0.1 , 46 ± 19-154 ± 80 for PM0.5-1 ngm-3 , 98 ± 49-422 ± 186 ngm-3 for PM1-2.5 , 321 ± 305-1288 ± 727 ngm-3 for PM2.5-10 and 65 ± 52-914 ± 339 ngm-3 or PM>10 , and these concentrations were higher in industrial areas. Heavy metals emitted from domestic anthropogenic sources were added to the long-range transport component of the aerosols. The water-dispersed fraction of heavy metals contained 3.3-40.1% of the total heavy metals in each size class. The relative contribution of Zn and other species (As, Cd, Cr, Ni, Pb, Mn, V and Cu) increased in the water-dispersed fraction. Smaller particles contained greater proportions of the water-dispersed heavy metal fraction. Carcinogenic risk (CR) and the hazard index (HI) were estimated for each size class. The CR of carcinogens was at acceptable levels (<1 ×10-6 ) for five particle size fractions. The HI values for carcinogens and noncarcinogens were also below acceptable levels (<1) for the same five size fractions. The estimated CR and HI values were dominated by contributions from the inhalation process.