Resumen de Dietary exposure to neurotoxic and endocrine disruptive effects: the mercury case
Mercury is a strong neurotoxin. It has adverse effects on the nervous and cardiovascular systems, it is also deleterious for several organs, and may act as immunotoxic and hormonal disruptor. This compound is released to the environment by several processes which have generated a widespread contamination throughout the whole planet. However, because of the physical-chemical properties of this metal, semi-volatility and water insolubility, the sink of most of it are the sediments of water bodies, namely marine and lacustrine systems. Bacterial processes transform mercury into methylmercury which is much more deleterious for the organisms and human beings. Methylmercury enters into the food chain and accumulates in fish and from fish into humans. Fish consumption is the main source of mercury for the general population.
The Mediterranean Sea is a hot spot of mercury pollution, but the origin of this metal has not been elucidated. The present PhD dissertation is devoted assessing what is the origin of this metal and which human pollution burden is involved in fish consumption.
To assess the impact of a chlor-alkali plant on a confined environment, fish, sediment and a mammal were collected downstream from the location of a chlor-alkali plant that used a technology that directly releases mercury. Mercury and other metals were examined in the area surrounding the Ebro River and in the marine area located near the mouth of this river. The study has shown that the effects of metal contamination are visible nearby the industrial complex, downriver and in the fish of the Mediterranean area located nearby the Ebro mouth, more than 110 kilometres downriver. This study has also allowed to characterize the specific mercury isotopic composition of chlor-alkali plants.
Subsequently, the study of the fish devoted to human consumption in L’Ampolla, Ametlla de Mar, Alacant, Mallorca, Menorca, Eivissa, Marseille, Genoa, Civitavecchia and Alghero has allowed the contribution characterization of the atmospheric deposition plus the background level and chlor-alkali plants in the fish from Western Mediterranean. The inputs from the chlor-alkali plants represented about 63-100% of total mercury while the inputs from background + atmospheric fallout ranged between 0% and 37%.
The study of 1345 specimens of commercial value sold for human consumption in the above-mentioned locations allowed the characterization of the mercury concentrations in 58 species of lean and cartilaginous fish. 316 samples (23.5% of the total) showed Hg concentrations above the EU recommended limits for human consumption, 0.5 mg kg-1 wet weight (ww) or 1 mg kg-1 ww.
The extrapolation of the mercury concentrations observed in Mediterranean fish to the tolerable provisional weekly intakes of methylmercury showed intakes above the thresholds recommended by EFSA for the three countries where the fish was collected, 152%, 151% and 144% for the populations of Spain, France and Italy, respectively.
Comparison of the mercury content in the different species allowed to define one group of twelve species whose specimens always fulfilled the EU recommended values for human consumption: sardine, anchovie, squid, surmullet, painted comber, blackspot seabream, blue whiting, salema, brown meagre, picarel, pearly razorfish and common dolphinfish. On the contrary, the species showing a high percentage of individuals not fulfilling the EU recommendations were dusky grouper, european barracuda, common dentex, norway lobster, greater forkbeard, common seabream, porbeagle and thornback ray.
