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, PM(2.5-10 )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 x10 (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 values were dominated by contributions from the inhalation process.