Recording heavy-metal deposits from 1772 to the present, the sample showed that the metal content rose exponentially since the 1850s, but decreased slightly after clean-air legislation took effect in Europe and North America in the 1970s.
Still, said the study team — based at the Desert Research Institute in Reno, Nevada — the levels could rise again due to increased coal-burning in Asia. The scientists plan to take more samples to confirm the global pattern.
In the Arctic, heavy metals accumulate in plants and animals, including caribou and whales. People who eat the animals also ingest the metals, which never leave the body. Cadmium is known to cause kidney damage, while thallium is a deadly toxin.
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