Mercury in Rain Increasing in Western and Central United States: Despite tightening emissions rules, mercury concentrations are rising in rainfall wetting western and central regions of the United States. The pollutant may waft in from Asia, scientists speculate.

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Mercury in Rain Increasing in Western and Central United States: Despite tightening emissions rules, mercury concentrations are rising in rainfall wetting western and central regions of the United States. The pollutant may waft in from Asia, scientists speculate.