295
5.3.5 Azaspiracid Shellfish Poisoning (AZP)
These toxins accumulate in bivalve molluscs that feed on toxic microalgae of the
genus Protoperidinium. Azaspiracids cause azaspiracid poisoning, an illness like
diarrhetic shellfish poisoning. The toxin may accumulate in the hepatopancreas
(digestive glands), gonads and the adductor muscle. Such contamination can happen during the sample pre-treatment stage, freezing or cooking may damage the
walls of internal organs, thus facilitating the toxin to leach into different tissues
(Hess et al. 2005). An unusual biotoxin was first observed in mussels (Mytilus edulis) from Ireland in 1995 after an illness similar to diarrhetic shellfish poisoning
(DSP) was observed. With the identification of AZA as the causative agent, the illness was named azaspiracid poisoning (AZP). Following the discovery in Risk
Assessment of Azaspiracids (AZAs) in Shellfish: A report of the Scientific
Committee of the FSAI August 2006 mussels, several other bivalve molluscs have
been identified as containing AZAs including oysters (Crassostrea gigas, Ostrea
edulis), scallops (Pecten maximus), clams (Tapes phillipinarium), cockles (Cardium
edule) and razor fish (Ensis siliqua) (Anonymous 2006).
5.4 Chemical Contaminants
5.4.1 Toxic Metals
As a potential source of chemical contaminants in the aquatic environment, industrial wastes and mining activities have accumulation properties and, due to these
properties, can damage the ecosystem and therefore the species diversity in the seas.
The main sources of contaminants are of human origin. Metals (trace elements) are
naturally present in many rocks and minerals (Gueguen et al. 2011). Several sources
of metals can contribute to metal accumulation in marine shellfish, including metal
in the water (or the dissolved phase), metal from prey (such as phytoplankton, small
protozoans, bacteria), and metal in sediment (Wang and Hong Kong University of
Science and Technology 2009). Due to natural weathering of the earth’s crust, they
are found in all environmental compartments, including seawater. Some trace elements that are absorbed by living organisms accumulate in the food chain, and
therefore present a risk to humans, who are the final consumers at the top of the food
chain. Metals, such as mercury, cadmium, lead, copper, and zinc can easily concentrated in shellfish meat (Gueguen et al. 2011).
Marine bivalves are known to pump significant amounts of seawater and thereby
to process particles because of their extremely high filtration activity. Thus, there is
a very close interaction between bivalves and the chemicals in the water. These
contaminants are accumulated through both dissolved phase uptake and particulate
ingestions by shellfish. Bivalve molluscs are exposed to large volumes of water during respiration and feeding. Metals and organic contaminants will thus inevitably
5.4 Chemical Contaminants
5.3.5 Azaspiracid Shellfish Poisoning (AZP)
These toxins accumulate in bivalve molluscs that feed on toxic microalgae of the
genus Protoperidinium. Azaspiracids cause azaspiracid poisoning, an illness like
diarrhetic shellfish poisoning. The toxin may accumulate in the hepatopancreas
(digestive glands), gonads and the adductor muscle. Such contamination can happen during the sample pre-treatment stage, freezing or cooking may damage the
walls of internal organs, thus facilitating the toxin to leach into different tissues
(Hess et al. 2005). An unusual biotoxin was first observed in mussels (Mytilus edulis) from Ireland in 1995 after an illness similar to diarrhetic shellfish poisoning
(DSP) was observed. With the identification of AZA as the causative agent, the illness was named azaspiracid poisoning (AZP). Following the discovery in Risk
Assessment of Azaspiracids (AZAs) in Shellfish: A report of the Scientific
Committee of the FSAI August 2006 mussels, several other bivalve molluscs have
been identified as containing AZAs including oysters (Crassostrea gigas, Ostrea
edulis), scallops (Pecten maximus), clams (Tapes phillipinarium), cockles (Cardium
edule) and razor fish (Ensis siliqua) (Anonymous 2006).
5.4 Chemical Contaminants
5.4.1 Toxic Metals
As a potential source of chemical contaminants in the aquatic environment, industrial wastes and mining activities have accumulation properties and, due to these
properties, can damage the ecosystem and therefore the species diversity in the seas.
The main sources of contaminants are of human origin. Metals (trace elements) are
naturally present in many rocks and minerals (Gueguen et al. 2011). Several sources
of metals can contribute to metal accumulation in marine shellfish, including metal
in the water (or the dissolved phase), metal from prey (such as phytoplankton, small
protozoans, bacteria), and metal in sediment (Wang and Hong Kong University of
Science and Technology 2009). Due to natural weathering of the earth’s crust, they
are found in all environmental compartments, including seawater. Some trace elements that are absorbed by living organisms accumulate in the food chain, and
therefore present a risk to humans, who are the final consumers at the top of the food
chain. Metals, such as mercury, cadmium, lead, copper, and zinc can easily concentrated in shellfish meat (Gueguen et al. 2011).
Marine bivalves are known to pump significant amounts of seawater and thereby
to process particles because of their extremely high filtration activity. Thus, there is
a very close interaction between bivalves and the chemicals in the water. These
contaminants are accumulated through both dissolved phase uptake and particulate
ingestions by shellfish. Bivalve molluscs are exposed to large volumes of water during respiration and feeding. Metals and organic contaminants will thus inevitably
5.4 Chemical Contaminants