Food-chains: it's poisonous at the top

Peregrine petral poo pollutes pristine parklands:

Washington: Seabirds can spread pollutants such as mercury and pesticides across the Arctic in their droppings.

The finding, published in the journal Science, surprised experts, who had presumed that the chemicals were being spread only by atmospheric winds.

It could help explain the high levels of such pollutants found in the bodies of people living in and near the Arctic region, far from the industries that produce them.

The birds eat fish, squid and other animals that concentrate the chemicals in their bodies. The chemicals are concentrated even more in the bodies of the birds.

The birds, some of which range for thousands of kilometres, then rain polluted guano onto once-pristine environments, Jules Blais of the University of Ottawa and colleagues found.

"The effect is to elevate concentrations of pollutants such as mercury and DDT to as much as 60 times that of areas not influenced by seabird populations," said John Smol, a biology professor at Queen's University in Ontario.

Aren't we humans on the top of our food chain and thereby subject to the same problems of toxic accumulation?