Environmental exposure to toxicants mixtures from a multi-purpose estuary: perspectives for a biomonitoring study in Portugal

This work was focused on a multi-purpose estuarine environment (river Sado estuary, SW Portugal) around which a number of activities (e.g., fishing, farming, heavy industry, tourism and recreational activities) coexist with urban centres with a total of about 200 000 inhabitants. Based on previous knowledge of the hazardous chemicals within the ecosystem and their potential toxicity to benthic species, this project intended to evaluate the impact of estuarine contaminants on the human and ecosystem health. An integrative methodology based on epidemiological, analytical and biological data and comprising several lines of evidence, namely, human contamination pathways, human health effects, consumption of local produce, estuarine sediments, wells and soils contamination, effects on commercial benthic organisms, and genotoxic potential of sediments, was used. The epidemiological survey confirmed the occurrence of direct and indirect (through food chain) exposure of the local population to estuarine contaminants. Furthermore, the complex mixture of contaminants (e.g., metals, pesticides, polycyclic aromatic hydrocarbons) trapped in the estuary sediments was toxic to human liver cells exposed in vitro, causing cell death, oxidative stress and genotoxic effects that might constitute a risk factor for the development of chronic-degenerative diseases, on the long term. Finally, the integration of data from several endpoints indicated that the estuary is moderately impacted by toxicants that affect also the aquatic biota. Nevertheless, the human health risk can only be correctly assessed through a biomonitoring study including the quantification of contaminants (or metabolites) in biological fluids as well as biomarkers of early biological effects (e.g., biochemical, genetic and omics-based endpoints) and genetic susceptibility in the target population. Data should be supported by a detailed survey to assess the impact of the contaminated seafood and local farm products consumption on human health and, particularly, on metabolic diseases or cancer development.