{"id":6988,"date":"2018-12-03T17:27:57","date_gmt":"2018-12-03T09:27:57","guid":{"rendered":"https:\/\/smartairfilters.com\/?p=6988"},"modified":"2022-07-27T13:49:00","modified_gmt":"2022-07-27T05:49:00","slug":"how-do-people-in-beijing-exercise-with-such-bad-air-pollution","status":"publish","type":"post","link":"https:\/\/smartairfilters.com\/en\/blog\/how-do-people-in-beijing-exercise-with-such-bad-air-pollution\/","title":{"rendered":"This Is When Exercise In Air Pollution Does More Harm Than Good"},"content":{"rendered":"

I\u2019m in Beijing right now, and I\u2019m going to exercise today. So what can I do when the world outside my window looks like this? Would exercise in this air pollution do more harm than good? Is it better to not exercise at all?<\/span><\/p>\n

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1. The point where exercise becomes harmful<\/b><\/h3>\n

Researchers at Cambridge analyzed studies on the benefits of exercise and the harms of air pollution and tried to <\/span>calculate how bad the air has to be<\/a><\/span> <\/span>for exercise to be harmful. There are lots of different types of pollution, but they focused on particle pollution (PM2.5<\/a><\/span>), which <\/span>the WHO says kills more people than any other pollutant<\/a><\/span>. They used biking outdoors as the form of exercise\u2014something I\u2019ve experienced in Delhi.<\/p>\n

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Here\u2019s the cost-benefit analysis in a city with 50 micrograms\/m3 of PM2.5 pollution. That\u2019s about <\/span>the average level in Shanghai<\/a><\/span>. For comparison, the WHO annual limit is <\/span>10 micrograms<\/a><\/span>.<\/span><\/p>\n

First check out the green circle, the tipping point. Biking outside is beneficial to lifespan (in other words, \u201cnot dying\u201d) up to about 70 minutes.<\/p>\n

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Then check out the red circle, the breakeven point.<\/p>\n

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At about 300 minutes it actually starts to become harmful. But at that point you\u2019ve been biking for almost five hours, so you need a break anyway.<\/p>\n

Is exercise as good as pollution is bad?<\/b><\/p>\n

Let\u2019s say you do both. You exercise, but you breathe polluted air. How do those balance out? Are you back to the starting point?<\/p>\n

For a sense of scale, I got statistics on the danger of different behaviors from <\/span>this recent epidemiological study<\/a><\/span>. They don\u2019t have exercise, so I compared eating unhealthy foods. Here\u2019s the years of life lost from PM2.5 versus eating unhealthy foods.<\/p>\n

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The effect of eating a bad diet is worse than air pollution. My guess is exercise is at least as potent as air pollution, if not stronger. That\u2019s why exercise is still helpful in a polluted city.<\/p>\n

But what about really bad days and really bad cities?<\/b><\/p>\n

Hey, 50 micrograms, that\u2019s child\u2019s play!<\/p>\n

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Places like Beijing and Delhi have real man air. The World Health Organization found <\/span>Delhi\u2019s PM2.5 averages 153 micrograms<\/a><\/span>. Beijing easily has days that bad. So how does the calculus change then?<\/p>\n

Here\u2019s a slightly different graph with the tipping point (red) and break-even point (blue). I drew a line for Delhi\u2019s average PM2.5. In Delhi, biking starts to be harmful at just 30 minutes (the breakeven point).<\/p>\n

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The line for the tipping point doesn\u2019t even extend up to Delhi\u2019s PM2.5 levels, so we don\u2019t know at what point it loses its beneficial effect. I tried extending the line up and came up with, maybe 2 minutes?<\/span><\/p>\n

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And keep in mind, <\/span>this is only considering PM2.5 pollution<\/b>. It does not take into account any gas pollutants like ozone or NO2. So the total effect of all air pollutants would be worse.<\/p>\n

Bottom line: <\/span><\/b>This estimate suggests outdoor exercise on bad air days or particularly bad cities becomes harmful after just a few minutes.<\/p>\n

But, but\u2026<\/b><\/p>\n

Keep in mind this is an estimate. It is based on epidemiology research, but it uses lots of assumptions. There are lots of factors that could change the equation:<\/p>\n