Modeling Human Exposure to Cadmium and Arsenic in a Zinc Smelter Area-A Belgian Case Study

Abstract

The Northern Campine region in the north-east of Belgium has a long history harboring polluting zinc industry. A recent study showed a significant correlation between cadmium exposure and lung cancer incidence in the area. During the last decades, increasing concerns lead to various measures to limit or eliminate the pollution. In order to assess the present situation concerning cadmium and arsenic pollution and human exposure, a campaign was set up including questionnaires and biomonitoring for 1217 adults and environmental measurements in 100 homes. Based on these data, we developed, implemented and validated a human exposure model, linking external exposure to internal dose using PBPK modelling. Methods: The model included all relevant exposure pathways (inhalation, purchased and homegrown food, water consumption, soil ingestion, smoking). The pharmacokinetic models of Nordberg-Kjellström and Walker and Griffin were used to model the contaminant distribution throughout the human body. Since urinary cadmium is a marker for lifetime exposure, historical exposure was taken into account. Results: Model validation shows good predictive capabilities for cadmium, but less for arsenic. Nowadays, food consumption is a defining exposure pathway for cadmium and arsenic. Inhalation and soil ingestion are of minor importance, but gain importance when taking into account historical exposure. Age, smoking behaviour and consumption of homegrown vegetables correlate with cadmium levels in the human body. Model simulations show that residents younger than 50 have only a small risk of exceeding health-based urinary cadmium limits in the future. We expect marginal health risks for people born nowadays in the exposed area and residing there for life. Conclusion: Historical exposure clearly contributes to urinary cadmium levels, but measures to limit or eliminate the cadmium pollution reduced the current health risks for residents. Consumption of (homegrown) food is a major exposure pathway for cadmium and arsenic.