that has not been polluted (= made dirty by harmful substances) 未被污染的;干净的 the unpolluted air of the mountains 山里未受污染的空气 Otters need secluded, unpolluted stretches of river with plenty of fish. 水獭需要隐蔽的、未受污染的、有大量鱼的河流。 The air was fresh and unpolluted. 空气清新,无污染。