23. Application of Disability-Adjusted Life Years in Risk Assessment for Total Human Mercury Exposure in China and Japan: A Meta-analysis

For sustainable metal use for the wide industrial sector, benefits and risks need to be managed from the view of life cycle thinking. Knowledge of the present mercury pollution state is significantly required for solution effectiveness assessment in future mercury control. Most previous research about mercury exposure focused on restricted areas. Research on the national or international scale remained as a minority. Disability-adjusted life years (DALY) was seldom used for heavy metal risk assessment before. DALY is capable of quantifying health impact in terms of mortality and morbidity as an endpoint and could be utilized in Life Cycle Impact Analysis. The main objectives of this research are (1) investigation of the average human exposure level to mercury in China and a comparison to Japan, (2) identification of the most important exposure routes to provide a reference for future Hg control, and (3) assessment of DALY for the population in both countries. We conducted a national scale risk assessment of total human exposure to mercury for the Chinese and Japanese populations. A database of concentration in soil, diet, and atmosphere was constructed by a systematic literature review. We evaluated the average exposure doses and health risks in Japan and China. As a result, the average total Hg exposure dose is 1.48 × 10⁻⁴ mg/(kg-BW × day) in Japan, 2.18 × 10⁻⁴ mg/(kg-BW × day) in normal areas in China, and 7.81 × 10⁻⁴ mg/(kg-BW × day) in the vicinity of mercury sources in China. The Chinese population is exposed to a higher mercury level compared to Japan. The most important exposure route for mercury exposure is identified as ingestion exposure in both countries. The general average DALY is 6.91 × 10⁻⁷ years per lifelong exposure, much lower than 6.63 × 10⁻⁶ years in normal areas in China, and 9.96 × 10⁻⁴ years in the vicinity of mercury sources in China. The average DALY for the vicinity of Hg sources in China exceeds the tolerable DALY level. The result of this research indicates the priority in controlling Hg pollution in highly polluted areas in China. DALY, as a health impact factor, could be utilized in future Life Cycle Impact Analysis.