March 12, 2009 -- Lead and cadmium found in the hair of wildlife are revealing they are at higher risk from heavy metal pollution than humans, say experts.
Christopher McLean of the University of Wollongong in Australia and colleagues report their study of Australian wildlife in the vicinity of a former lead/zinc smelter, in the journal Science of the Total Environment.
"These two metals accumulate in the hair of animals," said McLean, who did the research while at the University of Newcastle, also in Australia.
McLean said humans are typically exposed to lead and cadmium pollution via the air, especially around sources like smelters.
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In the early 1990s, children around a smelter in the Newcastle suburb of Boolaroo were found to have elevated lead levels. The smelter, which was operated by Pasminco Limited, closed down in 2003.
Much of the contamination from the smelter has since been cleaned up, but McLean said some areas remain polluted.
Lead levels in children were monitored until 2006, which showed that the levels decreased as the air cleared.
Although at last count, four percent of under 13-year-olds and seven percent of under 5-year-olds still had elevated levels.
But, said McLean, heavy metals have accumulated in the environment and animals, which are more likely than humans to feed off plants and insects, remain at risk.
In autumn of 2007, McLean and colleagues analyzed samples of soil and hair from the native brown antechinus and two species of introduced rat in 23 separate sites at different distances from the former smelter.
They washed the animals' hair before testing it to ensure they were only picking up lead that had accumulated in the animal's bodies.
The researchers found the higher the level of soil contamination at a given site, the greater the amount of lead and cadmium were present in the animals' hair.
Evidence from previous studies suggests that the levels present in the animals could interfere with their breeding, says McLean.
He says most studies of heavy metals in animals to date have involved killing the animals, but sampling hair provides a non-invasive method of testing them.
Interestingly, he says, despite differing diets, all three animals showed the same pattern of heavy metal accumulation in their hair.
McLean says the presence of heavy metals in these animals indicates other animals in urban areas -- from brush-tailed possums or rainbow lorikeets -- could also be contaminated.
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