More information :
Pathogen germs
The most frequently-mentioned pathogen bacteria are salmonella, which cause salmonella poisoning. However, there are other pathogen bacteria responsible for stomach flu as well (Shigella species, Escherichia coli pathogens, Yersinia enterolitica, Vibrio bacteria, etc.). When shellfish contain human intestinal viruses, the health risk is even greater for consumers. Some of the infections caused by eating shellfish include hepatitis A and noroviruses, like the Norwalk virus, which causes stomach flu.
Pathogen germs come from urban and farming activity, which release human and animal bacteria and viruses back into the natural environment via relay points in the sea (purification stations, overflowing wastewater or rainwater networks) or surface runoff from urban, farming or port environments. Marine currents can also move contaminated water masses toward sites that are remote from the contamination source.
Phytoplankton toxins
Some marine phytoplankton species produce toxins, referred to as phycotoxins. When present in high concentrations, they can cause a variety of disorders in people who consume contaminated shellfish. In France, the risks to human health are currently known to result from three groups of microscopic algae: Dinophysis, Alexandrium and Pseudo-nitzschia. The Dinophysis variety produces diarrhoea-inducing toxins (DSP), the Alexandrium variety produces paralysis-inducing toxins (PSP) and the Pseudo-nitzschia variety generates amnesia-inducing toxins (ASP).
DSP : Diarrheic ShellFish Poison
ASP : Amnesic ShellFish Poison
PSP : Paralytic ShellFish Poison
Web site: monitoring and state of toxic phytoplankton contamination in France:
http://www.ifremer.fr/envlit/documentation/dossiers/toxines10ans/toxines10.htm
Mineral and organic chemical compounds
These belong to the “micropollutant” family, meaning chemical or biochemical pollutants likely to impact human health at very low concentration. The most frequently encountered in the marine environment are heavy metals, such as mercury, lead and cadmium, and organic molecules such as hydrocarbons, tributyl tin (TBT), polychlorobiphenyls (PCB) and certain pesticides, such as dichlorodiphenylthichloroethane (DDT). They come mainly from the farming industry, where pesticides are concerned, and are discharged into the sea, through rivers and tributaries receiving land pollution. Certain chemical compounds also result from maritime transport (hydrocarbon degassing, and TBT resuspension through the anti-fouling paint used on boats.
Intoxication symptoms due to the aforementioned chemical compounds do not occur immediately after exposure, but develop over the long term, following extended exposure at low doses (on the order of one microgram me/L, or even one monogrammed/L). Micropollutants may impair physiological functions, growth and reproduction. Mercury, for instance, is likely to cause neurological problems, lead can cause neurological and digestive disorders and cadmium can cause renal impairment.
PCB: Polychlorobiphenyls
TBT: Tributyl tin
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