Exposure to low levels of pollution may be more harmful than might be expected, according to a new study.
The research says the effects can be worse than simply a reduced form of the effects seen at high levels of exposure.
Scientists at the Universities of Edinburgh and Cambridge and Imperial College London made the warning after discovering that prolonged exposure to low levels of contaminants on soil had a significant effect on earthworms' ability to reproduce.
This impact was larger than expected.
Scientists studied the worms' DNA after exposure to various contaminants, including the metals copper and cadmium, together with fluoroanthene - an industrial pollutant from incinerators - and the weedkiller atrazine.
Lead researchers Professor Mark Blaxter, of the University of Edinburgh's School of Biological Sciences, said: "The worm is the soil equivalent of a canary in a mine - it can alert us to problems before we would notice them.
"We have found that exposure to low levels of pollution for a long time can be harmful, and this must be having an effect on plants and crops, and entering the food chain. High levels of pollution are often easy to spot because they kill animals, but these results show that low levels have important, albeit subtle, effects.
"It is surprising that, despite widespread interest in pollution, it is only now that we are looking to soil animals for indications of the effects of contaminants."
The research is published in the journals BMC Genomics and in Environmental Science and Technology
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