Tear gas at Portland protests raises concern about pollution

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FILE - In this July 25, 2020, file photo, a protester carries an umbrella as federal police officers deploy tear gas during a protest at the Mark O. Hatfield U.S. Courthouse in Portland, Ore. Federal agents have left Portland, but city officials are still learning about and cleaning tear gas residue that lingers in the streets, dirt and possibly storm drains that empty into the Willamette River. (AP Photo/Marcio Jose Sanchez, File)