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Widely used pesticides may threaten Earth’s ozone layer

For more than a century, farmers have protected their crops using copper-based chemicals. These pesticides ward off insects and fungi that would damage the plants, boosting harvests. But there’s a catch. These chemicals also may react with soil to release gases that harm Earth’s ozone layer. That’s the finding of a new study.

“We’ve been using copper compounds since the 1800s without fully realizing some of the side effects,” says Robert Rhew. He’s a biogeochemist at the University of California, Berkeley.

Rhew’s team found that copper-soil reactions produce two compounds. One is methyl bromide, which contains bromine. The other is methyl chloride, which contains chlorine. Bromine and chlorine are both highly reactive elements called halogens that share several common traits. One is the ability to form compounds that destroy ozone. As a result, methyl bromide and methyl chloride can both damage ozone in Earth’s atmosphere. That ozone shields life on Earth from the sun’s harmful ultraviolet rays.

“Copper was considered environmentally friendly,” Rhew says. “It probably still is, compared to some alternatives.” But, as his team now shows, copper-based chemicals may threaten a critical region of Earth’s atmosphere. The findings appeared in the January 10 Nature Communications.

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