污染這么嚴重，還要不要鍛煉了？

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.

想要身體好?雖然沒有什么特效藥，但是鍛煉似乎是個很好的方法。體育鍛煉對身體具有深遠的影響，如果你每天運動一段時間，你就比大多數(shù)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)的工作地點在倫敦，所以我能想到騎車去上班，這樣可以換換生活方式。但是考慮到空氣污染，騎車真的會對健康有幫助嗎?還是會損害健康?如果我坐車去上班，就不用聞尾氣。但是騎車時候就不一樣了。

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500萬人因空氣污染死亡，但是此前針對騎車是否有益還沒有定論?，F(xiàn)在，在計算機的幫助下，研究人員通過模擬污染對人的影響來判斷騎車的利弊。

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.

研究人員計算出了“平衡點”，如果騎車時間大于這個平衡點，那么騎車就是有害的。結合WHO的數(shù)據(jù)我們就能知道，在世界上空氣污染最重的城市(德里)，每天騎車時間最好不要超過60分鐘。

“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.”

空氣污染對人體的傷害是毋庸置疑的，但是運動對身體也是有好處的。我們希望能找到一個平衡點，達到雙贏。

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.

但是這項研究也有局限性，因為只考慮了空氣中的PM 2.5，而沒有考慮其他空氣污染物。

“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.

“即使我們將其他因素考慮在內(nèi)，總體上來看也不會有什么改變。可能有些地方污染造成的損害會稍微高一些。”而且一些地形因素也會影響污染的分布，這也會造成結果的偏移。

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

作為世界上第一個權衡運動和污染的分析報告，它想表達的意思也很明確：雖然空氣污染很重，但是我們要堅持運動。