污染这么严重，还要不要锻炼了？

There is no silver bullet in medicine, but exercise comes close. The benefits of physical activity are so far-reaching that, if you do nothing but get some gym time every day, you will live a healthier and longer life than most people.

想要身体好?虽然没有什么特效药，但是锻炼似乎是个很好的方法。体育锻炼对身体具有深远的影响，如果你每天运动一段时间，你就比大多数人健康而且活得更久。

So when I decided to move closer to my office in London, the first thing I thought I’d change about my lifestyle was cycling to work. Yet, given all the harm we know air pollution can cause, does cycling actually help, or could it hurt? After all, I’m not breathing in the foul fumes of a truck when I’m sitting inside an air-conditioned train. I’m certainly not breathing them in deeply, as I would while huffing and puffing on my cycle.

我(原作者)的工作地点在伦敦，所以我能想到骑车去上班，这样可以换换生活方式。但是考虑到空气污染，骑车真的会对健康有帮助吗?还是会损害健康?如果我坐车去上班，就不用闻尾气。但是骑车时候就不一样了。

Air pollution kills more than 5 million people every year, yet there has been no analysis of the costs versus benefits of city cycling. Until now. With the help of advanced computer simulations and data on the effect of pollution on human health, researchers at the University of Cambridge found that, in almost all the cities of the world, the health benefits of cycling and walking far exceed the harm caused by air pollution.

每年有500万人因空气污染死亡，但是此前针对骑车是否有益还没有定论。现在，在计算机的帮助下，研究人员通过模拟污染对人的影响来判断骑车的利弊。

Researchers also calculated the theoretical “tipping point,” after which additional cycling isn’t more beneficial to health, and what they called the “break-even point”—really more of a breaking point—after which cycling is actually more harmful than beneficial. When combined with WHO data on pollution in major cities, the research shows that even in the world’s most polluted cities (like Delhi), that breaking point doesn’t occur until after at least 60 minutes of cycling a day.

研究人员计算出了“平衡点”，如果骑车时间大于这个平衡点，那么骑车就是有害的。结合WHO的数据我们就能知道，在世界上空气污染最重的城市(德里)，每天骑车时间最好不要超过60分钟。

“We are not disputing the fact that air pollution kills,” said James Woodcock, one of the authors of the study. “[But] it would do so even when you are sitting at home. What we find is that being physically active, even in polluted cities, can cut that risk. So it’s a win-win.”

空气污染对人体的伤害是毋庸置疑的，但是运动对身体也是有好处的。我们希望能找到一个平衡点，达到双赢。

The study’s methodology is limited. Researchers only used one pollution metric—the amount of fine particulate matter (PM 2.5)—as a proxy for negative effects, noting that science isn’t developed enough to feed other factors, such as larger particulate matter (PM 10) and gases (such as nitrogen oxides), into a single a computer model.

但是这项研究也有局限性，因为只考虑了空气中的PM 2.5，而没有考虑其他空气污染物。

“Even when we are able to take those factors into consideration, the overall message wouldn’t change,” Woodcock said. “Maybe the harm caused in some cities would be slightly greater, but not by a lot.”Researchers also pegged cyclists’ exposure to harmful pollution as two times the average, but many cities have pockets where pollution levels are much higher.

“即使我们将其他因素考虑在内，总体上来看也不会有什么改变。可能有些地方污染造成的损害会稍微高一些。”而且一些地形因素也会影响污染的分布，这也会造成结果的偏移。

Still, as the first global analysis of physical activity and pollution in cities, the report’s public-health message is clear: Get moving.

作为世界上第一个权衡运动和污染的分析报告，它想表达的意思也很明确：虽然空气污染很重，但是我们要坚持运动。