Long-term concentrations of airborne cadmium in metropolitan cities in Korea and potential health risks

The long-term concentrations of cadmium (Cd) in total suspended particulate (TSP) were calculated from data obtained from 30 ambient air-monitoring stations (AAMSs) located in seven metropolitan cities throughout Korea. The annual mean levels of Cd in TSP in port cities, industrial cities, and an inland city showed a decreasing trend over the 7-year study period. The overall highest average concentration was observed in Incheon with an annual mean of 3.92 ± 1.62 ng m−3, followed by Ulsan and Busan. The long-term Cd mean levels from international port and/or industrial cities (Incheon, Ulsan, Busan) were much higher than those from inland cities (Seoul, Daegu, Daejeon, and Gwangju). Temporal analysis indicated that there were no significant differences among Cd levels in different seasons. However, in Incheon, the seasonal average concentrations of Cd in spring, winter, and fall were 5.20 (±3.27) ng m−3, 4.01 (±0.93) ng m−3, and 3.5 (±0.77) ng m−3, respectively, which were significantly higher levels than those measured in the other cities for the corresponding seasons. These high concentrations in Incheon are likely due to the combined effects of local industries, traffic, ship emissions, and long-range transported PM from the northeastern industrial regions of China. The long-term summer average concentration in Ulsan, the largest industrial city, was 4.58 ± 1.15 ng m−3, which was significantly higher than the other seasonal values and also the summer averages of the other cities. This can be explained by downwind location effects of prevailing winds that pass through the industrial and port sectors of Ulsan. Excess cancer risk (ECR) estimates indicated that the carcinogenic risk due to inhaled Cd is 7, 6, and 4 persons per million of population in Incheon, Ulsan, and Busan, respectively.