SALEM, Ore. — A new report lists four Oregon metro areas among the nation’s worst 50 for air pollution spikes. The Statesman Journal reported that the list from the American Lung Association ranks Eugene, Bend, Portland and Medford-Grants Pass as among the worst for short-term particle pollution — spikes lasting hours to days that increase the risk of heart attacks, strokes and cardiovascular disease. Eugene fared worst among Oregon metro areas — at 24th — and Bend wasn’t far behind at 26th. Forest fires, weather inversions and the use of wood-burning stoves are common reasons for such spikes. The report looked at pollution levels from 2014 to 2016, using data that states report to the U.S.