"The US Environmental Protection Agency has classified environmental tobacco smoke as a known human (class A) carcinogen, " he added.

BBC: NEWS | UK | Northern Ireland | Legal threat over passive smoking

Data from the US Environmental Protection Agency were used to work out levels of pollution for addresses in California.

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As a result, environmental issues were debated in the Senate for the first time, laying the foundation for the US Environmental Protection Agency.

UNESCO: Intergovernmental Oceanographic Commission

Scientists are working to establish their exact toxicity, but a draft report from the US Environmental Protection Agency indicates dioxins are considered a serious threat to public health.

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In the US, the Environmental Protection Agency (EPA) investigated complaints from residents in Pavillion, Wyoming, who complained that fracking was affecting their drinking water.

BBC: Fracking: Untangling fact from fiction

For example, BP has only been suspended from getting contracts from the Environmental Protection Agency but not the US government, which surprised many lawyers, said Mr Percival.

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