VOA慢速英语:研究发现美国近半污染相关死亡源于外州排放物

source –n. where something comes from

exposure - n. the act of coming into contact with some substance

contributor - n. something that provides or adds to a condition or situation

net - adj. describing an amount that has all reductions and additions accounted for

emissions - n. pollution or gasses that are released from factories or industrial centers

uncertainty –n. a condition of not being sure about something