Toxicants, natural seafood

Seafoods -food toxicants m [FOOD TOXICANTS, NATURALLY OCCURRING] (Vol 11) -iodine in [MINERALNUTRIENTS] (Vo116)... 

Seafood Toxins. Vktually scores of fish and shellfish species have been reported to have toxic manifestations. Most of these toxicities have been shown to be microbiological ki origin. There are a few, however, that are natural components of seafoods. 

Schantz, E.J., Seafood toxicants, in National Academy of Sciences, ed., Toxicants Occurring Naturally In Foods, National Academy Press, Washington, D.C., 1973. 

From the human perspective, HABs are problematic because they cause (1) risks to human health, (2) loss of natural or cultured seafood resources, (3) impairment of tourism and recreational activities, and (4) damage to noncommercial marine resources and wildlife. Exposure pathways include (1) consumption of toxic shellfish that have accumulated phytoplankton toxins filtered from the water, (2) consumption of tropical fish that have accumulated phytoplankton toxins (ciguatera), (3) inhalation of aerosolized toxins ejected from the sea surface, and (4) skin contact resulting in irritations due to allergy-like reactions. Harmful health effects from acute exposures have been relatively well studied. Less well known are the health effects resulting from chronic exposures to low toxin levels. This is of particular concern with regards to marine mammals and seabirds. 

LEFTLEY, J.w. and HANNAH, F. (1998) Phycotoxins in seafood, pp. 182-224 in Natural toxicants in food, CRC/Sheffield Academic Press, ed. D. H. Watson, ISBN 1-85075-862-X. 

Arsenobetaine, arsenosugars and arsenocholine are organoarsenicals less toxic for animals and humans than inorganic arsenic compounds, and have been found in certain marine organisms and in seafoods. They are excreted rapidly in urine (about 70% of the dose in 24h) . Natural arsenic is a pure one-isotope element ( As) and had to be labelled with radioactive arsenic for metabolic studies. As has been chosen as the most suitable isotope for tracer investigations. 

The principal regulatory method to protect consumers from marine toxins in food is the mouse bioassay. It measures the time to death after intraperitoneal injection of a toxic extract, and toxicity is expressed as the amount of toxin (usually in micrograms) or toxin equivalents (eq) per gram (or 100 g) of shellfish tissue, standardized against a reference toxin solution. As it is a reliable indicator of human oral toxicity, the mouse bioassay is obligatory prior to commercialization of seafood in many countries. However, this biological test does not allow for specification of toxins or studies on the formation and effect of individual toxins. In addition, it has a high variability ( 20%) and low sensitivity, lacks specificity, and often has detection limits too near to the accepted threshold. Yet, the major limitation of the mouse bioassay is of ethical and political nature due to the use of live animals. 

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