The level of pollution in the river was falling.

该河流受污染的程度其时正在降低。

《柯林斯英汉双解大词典》

Another difficult question involves what level of pollution is safe.

另一个难题是什么样的污染水平是安全的？

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What concerns the scientists is the increasing level of pollution in our citics.

围绕科学家的是城市的污染日益严重。

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These cores show that the level of pollution, especially soot, in Himalayan glaciers correlates with emissions in Europe and South Asia.

ECONOMIST: Pollution in the Himalayas

The State of the Air report also ranked the Los Angeles-Long Beach- Riverside area as having the third-highest level of annual particle pollution in the nation and the fourth-highest level of short-term particle pollution.

FORBES: Los Angeles Pollution From Car Exhaust Is Down 98%

The level of air pollution caused by vehicles across Sheffield is being monitored at sites across the city.

BBC: Traffic pollution tested across Sheffield