The health benefits of cycling and walking outweigh the harmful effects of air pollution, a study has suggested.
一项研究表明，骑车和散步对健康的好处大于空气污染对健康造成的伤害。
Air pollution contributes to 40,000 early deaths each year in the UK and we gulp in more of it when we exercise.
英国每年有40000例因空气污染而早逝的案例，而当我们锻炼时会吸入更多污染的空气。
On the other hand, regular exercise reduces the risk of diabetes, heart disease, and several cancers.
另一方面，经常锻炼可以降低糖尿病、心脏病和多种癌症风险。
The University of Cambridge study showed that even in cities with high pollution levels, the benefits outweigh the risks.
剑桥大学的研究表明，即使在空气污染程度较高的城市，锻炼仍是利大于弊。
The researchers used computer simulations to compare data on different kinds of physical activity and different levels of air pollution in locations around the world.
研究人员采用电脑模拟来对比不同体育活动和全球各地不同程度空气污染的数据。
It found that for an average air pollution concentration in an urban area, the tipping point - when the risks begin to outweigh the benefits - comes after a huge seven hours of cycling or 16 hours of walking a day.
研究发现，在市区空气污染平均程度下，临界点-即弊端开始超过益处的临界点-在每天骑车7小时或者散步16小时以后才会出现。
It is far beyond what most people would ever do.
这远远超过了绝大部分人每天的运动量。
"Even in Delhi, one of the most polluted cities in the world - with pollution levels 10 times those in London - people would need to cycle over five hours per week before the pollution risks outweigh the health benefits," said Dr Marko Tainio, the lead author of the study.
“即使在全球空气污染最严重城市之一的德里-污染程度为伦敦的10倍-当人们每周骑车运动5小时以上时，空气污染的风险才会超过锻炼身体带来的好处。”该研究的主要作者马可尼奥博士说。
He added: "We should remember, though, that a small minority of workers in the most polluted cities, such as bike messengers, may be exposed to levels of air pollution high enough to cancel out the health benefits of physical activity."
他补充：“然而我们应记住，在污染最严重的城市中有一小部分工作者，比如自行车信使，他们可能会接受更高程度的空气污染，这种情况下空气污染的弊端就会大于体育锻炼的好处。”
The study, published in Preventive Medicine, said exercise was always beneficial in London.
该研究发表在《预防医学》上，称在伦敦，锻炼总是利大于弊的。
Action still needed’
“仍需行动”
The average air pollution level for cities around the globe is 22 micrograms per cubic metre, according to the World Health Organisation (WHO). In London the air pollution level was recorded at 16 micrograms per cubic metre in 2011.
据世界卫生组织（WHO）称，全球城市空气污染平均水平在22微克/立方米。2011年伦敦空气污染水平为16微克/立方米.
Senior author Dr James Woodcock added: "Whilst this research demonstrates the benefits of physical activity in spite of air quality, it is not an argument for inaction in combating pollution.
资深作者詹姆斯伍德科克博士补充说：“尽管这项研究证明，即使存在空气污染，体育锻炼仍然有好处，但这并不是让我们对空气污染无动于衷。
"It provides further support for investment in infrastructure to get people out of their cars and onto their feet or their bikes - which can itself reduce pollution levels at the same time as supporting physical activity."
“实际上它进一步支持在基础设施上的投资，好让人们走出汽车而步行或骑车-这本身就能够在减少空气污染的同时支持体育锻炼。”
The research was carried out by experts from the University of Cambridge’s Centre for Diet and Activity Research and Medical Research Council Epidemiology Unit, along with researchers from the University of East Anglia.
该项研究由剑桥大学饮食中心、活动及医学研究委员会流行病学单位以及东英吉利亚大学的研究者们共同完成。
