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》

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

这些冰心不仅表明了此地的污染程度，更重要的是说明了喜马拉雅山冰川上的烟灰与欧洲和南亚的排放相关。

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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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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