Portland's Toxic Air ProblemPortland Air Monitors Find More Toxic Chromium, But Source UnknownBy Rob Manning (OPB)Portland, Oregon April 22, 2016 1:30 a.m.📨 Daily news in your inboxSign up today for OPB’s “First Look” – your daily guide to the most important news and culture stories from around the Northwest.EmailPlease leave this field blankSign up