Cadmium in marine food webs: from inputs to consumers

International audienceCd is a remanent pollutant. Actually, we consider that about 500,000 T of Cd have been disseminated in the environment. Because of the geochemical fluxes, the marine environment is contaminated by Cd which all marine organisms are able to accumulate in their tissues. In this paper, we try to estimate the toxicological risk due to the consumption of Cd contaminated sea foods by top predators including human consumers. In this aim, we studied two different ecosystems where chronic Cd inputs are known to exist. The coastal seawaters of Charente-Maritime are Cd enriched by chronic inputs from the Gironde river. In this area, Cd concentrations have been measured in about 110 benthic marine species collected in the intertidal area. Some mollusc species only showed high Cd concentrations that is mainly dogwells, scallops and oysters. These species may be qualified of " Cd hyper bioaccumulated species ". The Cd intake due to the shellfish consumption has been assessed by the Cd concentrations found in the species commonly eaten by human and has been compared with the Cd Provisional Tolerable Weekly Intake (PTWI) of 7 µg/Kg defined for man by the JECFA. The Cd intakes are not negligible but remain lower than the PTWI. The higher Cd concentrations are transferred to human consumers by the scallops. The limit of 5 µg/g dry weight of Cd has been defined by the European Council for the authorisation of shellfish consumption and protects the consumers. Along the Charente-Maritime coasts, the higher Cd concentrations are encountered in oysters collected in the Gironde estuary where shellfish collection is, by the way, forbidden for 1986. Thus, the Gironde estuary is the unique area of Charente-Maritime where our calculations show that the Cd PTWI could be exceeded for very high shellfish consumers. Polar areas are naturally Cd enriched. In these areas, cephalopods show very high Cd concentrations, mainly in their digestive gland. In this organ, Cd concentrations as high as 400 µg/g dry weigh have been measured. Thus, in polar areas, cephalopods are responsible for the main transfer of Cd to top marine predators (seabirds and marine mammals) which exhibit high Cd concentrations in liver and kidney. As an example, the weekly intake of Cd has been calculated, for the pilot whales of the Faroe Islands. It appeared to be 7 to 220 times higher than intake which is known to induce metabolic diseases in human. A recent study which has shown the presence of Cd enriched granules in the kidney tubules of delphinids collected in the Faroe Islands raises the toxicological risk incured by marine predators, although these organisms which have been exposed for long time to these natural inputs of Cd have probably developed intracellular mechanisms of Cd detoxification. Among pollutants, Cd should be particularly controlled in the marine environment, since because of a natural Cd contamination of our food, the PTWI may easily reached in the case of an anthropogenic input