An epidemiological approach to characterise the human exposure pathways in a contaminated estuarine environment

This study's aim was to develop and implement an integrative epidemiologic cross-sectional study that allows identifying and characterising exposure pathways of populations living and working on the shores of a contaminated estuarine environment. Population residing in Carrasqueira, located on the Sado estuary with known contaminated areas was compared to another population on a noncontaminated estuary (Vila Nova de Mil Fontes - VNMF), considered a nonexposed population. Simple random samples of individuals were selected in each study population from the National Health Service Lists: 140 individuals were selected in Carrasqueira and 219 in VNMF. Participation rates were higher in the exposed group (62.5%, n=102 in Carrasqueira and 48.3%, n=100 individuals in VNMF). The same structured questionnaire was used in both populations, including questions on occupational activities, leisure activities, consumption of food (including fish and mollusks from the estuary) and use of water for human intake and agriculture. Results showed that a significantly higher proportion of Carrasqueira participants reported doing tasks in their job that promote direct (48.8% vs 1.2% in VNMF, p-value<0.001) or indirect (30% vs 11.9% in VNMF, p-value=0.004) contact with water from the estuary. Regarding seafood consumption, the exposed population of Carrasqueira had a higher frequency of consumption of cuttlefish (23.5% vs 9% in VNMF, p-value=0.007), sole (22.5% vs 4% in VNMF, p-value<0.001) and clams (18.6% vs 5.0 in VNMF, p-value=0.004). The comparative study design, with exposed and nonexposed populations living on the shores of two different estuaries allowed us to confirm the hypothesis of a higher risk of contamination from the contaminated estuarine environment. The study design and the selection of both populations were adequate for this type of epidemiologic study of potential routes of human contamination in a mixture of contaminated estuarine environment and can be used in other estuarine areas with similar environmental risk.