Conclusion: PM2.5 pollution is the most serious in winter, and the least in summer in Hangzhou city.

结论：杭州市区PM 2.5污染程度在夏季最轻，春秋季次之，冬季最严重。

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Objective To understand the characteristics of indoor PM2.5 pollution in residential houses in Guangzhou.

目的了解广州市居民室内空气中PM 2.5的污染特征并探讨其污染来源。

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The American Heart Association estimates that in the United States alone, PM2.5 air pollution spark some 60, 000 deaths a year.

美国心脏协会估计，仅在美国，被PM 2.5颗粒污染的空气就导致每年约60,000人死亡。

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Xinhua says that readings in Beijing for the tiniest pollution particles - called PM2.5 - reached more than 400 microgrammes per cubic metre on Thursday, which is considered "dangerous".

BBC: Smog and sandstorm engulf China's capital

Its guidelines say average concentrations of the tiniest pollution particles - called PM2.5 - should be no more than 10 microgrammes per cubic metre but UK standards allow up to 25.

BBC: Dust from recycling plants 'puts residents at risk'