For all of you in China: what’s one of the first apps you look at in the morning when you wake up? I’m sure you check your e-mail, WeChat, and the weather, but I’d guess the next one you open up is an air quality monitoring app.
It’s probably one of the most nerve-wracking parts of my morning as I wait for the app to load, not knowing what that magic number is going to be. That number, just as much as the weather forecast, has a big impact on how I spend my day. Is it going to be a relaxing day by the pool or on a bike ride, or am I going to have to deal with foggy glasses all day from breathing into a facemask?
There are many of these apps, but Air.Fresh hosts the most popular. To date, the app monitors air quality in real time across 411 cities in China through 1,887 monitoring stations. In Shanghai, these stations are either the U.S. Consulate on Huai Hai Road or the Chinese Ministry of Environmental Protection in Xujiahui. Both measure air quality using a similar quantitative scale and the app lets you compare the two figures. Most of the time, though, these numbers aren’t exactly the same. Sometimes they are fairly close and you can assume how good or bad the air quality is outside. Other times the numbers are completely skewed.
I wanted to find out why this is. Greenpeace has a fairly recent article explaining the methodologies behind the measurements. As I’m not a scientist, the article only did so much to assuage my curiosity. So, with Typhoon Soudelor rolling in and nothing else to do, I started digging into the figures. Here, dear readers, is my quasi-scientific methodology.
Simple? Sure, but also highly revealing.
After charting all the figures, both the U.S. and Chinese methods follow a similar trajectory over time.
Augusts seem to have low pollution levels, rising through the winter months, and then settling in spring to fall again in the summer. Between 2012 and 2015, seasonal pollution levels have been fairly consistent. The only major outlier was November/December 2013 when pollution levels reached their highest point. For anyone in Shanghai during that time, I’m sure you’ll remember the “white out” of the Bund and Lujiazui noted in just about every newspaper and Weibo post.
Then things start to get funny. These same two charts, while showing similar trends, are noticeably different in one respect: the actual air-quality index. On average, there is a 22.5-point difference between U.S. and Chinese figures. Sometimes the U.S. figures were lower or higher, sometimes the Chinese. The biggest difference happened on October 27, 2012 where the U.S reported an AQI of 250 to China’s 53, a 197 point difference!
I’m not here to argue which side was correct. Again, I’m no scientist but obviously somebody was sleeping at their desk on October 27th. This made me go even further down the rabbit hole.
Looking year-by-year, here is what I found:
All told, the U.S. registered an average AQI reading of 120.41 and China’s MEP a 79.12 between August 1, 2012 and July 31, 2015.
There was something that concerned me even more than the day-to-day figures. Unless it is a highly polluted day, the impact is going to be negligible for most people. The difference of an AQI of 60 and an AQI of 100 is not too important unless you are already sick. What about when the number gets even higher?
On both scales, normal healthy people will begin to feel the impact of pollution with an AQI of 150 or above. When that number reaches 200, masks are needed and those tiny PM2.5 particles are likely dancing around everywhere. Take a look at how the differences in methodologies impact the reporting of these higher numbers.
So, dear reader, I’m left with a quandary. Even with all of this digging and Excel magic, I’m still without an answer to which method is best. Had the two been close I could have averaged things out and called it a day. The differences, though, are too great. I guess it’s all about erring on the side of caution and taking preventative measures when I can. Sure, the typhoon’s winds are blowing through blue skies today, but as we learned the sky is about to go grey in the not-too-distant future.
Maybe one of you knows more about the science behind the numbers. I’d love to get an explanation if you do. Drop me a comment below or an email to firstname.lastname@example.org.