Polycyclic aromatic hydrocarbons are multi-ringed aromatic compounds and are found in e.g. soot, coal, tar, cigarette smoke and barbecue meat. Examples include pyrene and benzo(a)-pyrene. Some of these compounds are known carcinogens.
PAHs have been become increasingly important in research because they are potentially mutagenic or carcinogenic in aquatic organisms and man. They tend to be adsorbed and accumulated by marine organisms. Elevated levels of PAHs are commonly found in coastal and estuarine marine waters near heavily polluted areas. Not all PAHs are known to be carcinogenic, but the environmental effect of most of them remains uncertain, and little is known about how they behave in marine ecosystems.
They tend to adsorb to particles, as these particles sink to the bottom, the sea floor becomes enriched in PAH content. Since PAHs are quite stable in the sediments, bottom dwelling organisms can be exposed by large amounts of PAHs for long periods of time.
Some species (like fish) can excrete PAH rather fast, therefore they have lower body burdens of PAHs than for example shellfish who bioaccumulate PAHs. The most toxic PAHs are pyrene and fluoranthene, followed by phenanthene and anthracene. PAHs with a high molecular weight may cause sublethal effects; such as growth reduction, chronic diseases, reproductive impairment, at very low concentrations in biota: at 5 to 100 ppb (parts per billion) in the tissue of the animal. Concentrations which are considered toxic (0,2 to 10 parts per million) have been found in wild biota from heavily polluted areas .
Environmental standards and legislation
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