Toxic pollutants 'in food chain'
Updated on 12 July 2007
A whole range of toxic pollutants in the food chain that could be harming animals and humans may have been missed by experts, it has been claimed.
Safety limits for persistent organic pollutants (POPs) are currently based on the extent to which chemicals build up in the bodies of fish.
It is this test that led to action to rid the environment of PCBs (polychlorinated biphenyls), used in electrical insulation, and DDT pesticides, both of which have been linked to cancer.
But a new study shows that, without accumulating in fish, some chemicals may become concentrated further up the food chain in birds and mammals.
A third of an estimated 12,000 organic chemicals on sale in Canada fit this category, according to the Canadian scientists.
Levels of the chemicals in body tissue are said to be "biomagnified" with each step up the food chain. As larger animals eat smaller ones, they consume increasingly larger doses of persistent toxins.
The study, published in the journal Science, did not consider whether individual chemicals are actually causing harm.
However, one expert, Dr Lawrence Burkhard from the US Environmental Protection Agency in Duluth, Minnesota, said the work was "really raising a red flag", Science reported.
The authors, led by Dr Barry Kelly, from Simon Fraser University in Burnaby, British Columbia, called for a new regulatory assessment of the "missed" chemicals.
Professor Peter Matthiessen, an independent consultant ecotoxicologist based in the UK, said: "The finding of such biomagnification in terrestrial food chains is not new, but it is nevertheless interesting. However, organisms such as mammals in terrestrial food chains are often able to metabolise and excrete these compounds more efficiently than fish."
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