In the past six years that I have lived in Beijing, air quality has become an increasingly popular topic of discussion. The government can regulate it. They cannot regulate it. How bad is it? Can the kids go outside today? Where can I get replacement air filters cheap? Let’s post the AQI level on WeChat. The conversations can drag on and on. Everyone seems concerned about it, but I’ve met few people who can actually define it. So let’s start from the beginning – what is a safe level of particulate matter?
To find out, I did something dangerous and looked up the World Health Organization (WHO) Air Quality Guidelines (AQG), then I looked up particulates on Wikipedia, and then I curled up in the fetal position for a few hours and hid under the covers wearing a mask with the rooms air filters cranked on high.
As I am sure everyone will click the links and read the source material, I’ll be brief. The WHO AQG set the annual mean for PM2.5 of 10 μg/m3 (10 micrograms per cubic meter of air). 10! That’s the high averaged out for the year. For a 24-hour mean, the limit for PM2.5 is 25 μg/m3. To reach a city average of 7 today (Monday) it took winds gusting for 24hours at 70-80km per hour. On Saturday, average PM2.5 was well over 200 μg/m3.
So what? The reason this matters is the well-documented health risks of any exposure. Essentially, the WHO said that there is no known safe level of exposure, but 10 μg/m and under was achievable and presented much lower relative health risks. What about an average of say 15 or 20 μg/m? Wikipedia broke it down like this: In 2013, a study involving 312,944 people in nine European countries revealed that there was no safe level of particulates and that for every increase of 10 μg/m3 in PM10, the lung cancer rate rose 22%. The smaller PM2.5 were particularly deadly, with a 36% increase in lung cancer per 10 μg/m3 as it can penetrate deeper into the lungs.
So who wants to sign up for the long-term health study of exposure levels exceeding PM2.5 of more than 100μg/m3?
Now that we have some terms defined, next time I’ll define what actions we can take, if any, to make our homes, children, and lives a bit safer with respect to Beijing’s overall poor air quality. Stay tuned and try not to breath too much.
Photos: barbourians (flickr)