In a word association game, what would you say when prompted with the word “Beijing”? I suspect most Americans’ responses would include the words “China”, “Olympics”, “city”, and “pollution”. Air pollution was among our chief concerns before moving here. When we spoke with travellers who lived here, we would ask “What’s the deal with the pollution?”. The answer depends on who you ask. Six months into our journey here, we can offer our answer to a question that we’ll probably be answering for years to come.
What’s the deal with the pollution?
The deal is that sometimes it gets really polluted in Beijing. There are two words to that statement that we will dissect. First is the sometimes and second is the really.
Sometimes
Sometimes means that it’s not always polluted here, which is a misconception that I had, and a misconception that is probably shared among many outsiders. When I got out of the Beijing airport and breathed the Beijing air, it reminded me of a forgettable scene from the movie 12 Monkeys, a lesser-known early nineties Brad Pitt flick with a killer soundtrack. The scene I have in mind is towards the end (spoiler alert), when the perpetrator of a biological terror attack opens—upon request by a customs agent—a vile of odorless, clear gas in an airport lobby. The toxin has just silently infected him and the agent, and was now permeating the air around them. The perp’s grimmace as he quietly acknowledges the toxic air around him must have been mirrored in my own face when I surveyed the Beijing air for the first time. WAS IT OKAY TO BREATHE? I slowly took longer and longer breaths as I became comfortable with the fact that the air was just fine. The next morning when we woke up at our friends’ place in Chaoyangmen, Beijing we saw beautiful blue skies. What’s the deal with that?
Roughly speaking, Beijing is only polluted when the air is still for a few days. When there is no wind, the air stagnates and the pollution has nowhere to go. It just builds up. So naturally when Beijing is windy, the pollution gets blown away to somewhere else (sorry rest of the world), and the air is clear.
The change in wind direction and strength can be sudden. Chelsey and I appreciated this for the first time on a scooter ride home from the Modernista Jazz bar on a cool night in October 2015. On the way to Modernista we lamented how bad the pollution was, and donned the conspicuous face masks on our journey. When we left the venue a mere 90 minutes later, the air was crystal clear, and the stars were shining. The wind had abruptly cleared the stagnant air. Our experience was borne out in the data when we consulted our phones later.
The Really part, or “Show me the data”
In order to understand “really”, we need to move from qualitative to quantitative, which is something I am good at: numbers. There are a few numbers that matter here. One is the ubiquitous Air Quality Index, commonly called the AQI. The AQI combines several disparate measures of air quality into a single number, just like how we can summarize the weather with temperature, wind chill factor, or heat index. Unfortunately there is no international standard AQI scale. Each country/region uses slightly different scales, making converting among them as pesky as recalling Fahrenheit to Celsius. The common thread among the AQI scales is the PM2.5, which is the number density of particles with sizes 2.5 micron or below.
Nevertheless, the scale in China is roughly 0-500 AQI. Strictly speaking, a lower bound makes sense (zero particulates in the air), but an upper bound does not make sense, in the same way that an upper bound on temperature does not really make sense. I suppose the upper bound on AQI could be when the air is so dense with particles that fusion can occur, or something less drastic, like our lungs are filled with sand. The truth is that an AQI of 500 effectively means “holy shit it is really freaking polluted.” But then what is the interpretation of AQI 600? We have experienced 3 or 4 of these types of episodes, and they are wild. For those not convinced by data, the AQI 500+ days look like the apocalypse has come. Everything is gray.
To put the numbers in perspective, a random day in Austin Texas has an AQI of about 40. Right now in Beijing, the AQI is about 200. Looking through data for the US, I can find instances of AQI as high as 150, though again with the caveat that the scales are slightly different. The normal state in the US is “good” or 0-50 and green color. The normal in Beijing seems to be closer to the 100-200 mark (orange or red). These categories are considered “unhealthy for sensitive groups”, or just plain old “unhealthy”.
There is a great iPhone App for monitoring the AQI at hundreds of air quality monitoring locations in China. We check this app regularly. My real gut instinct comes from my experience looking at distant buildings from my apartment. If I can see the China Business District (CBD) from our patio, It’s a clear day. If I can see the mountains, it’s an exceptionally clear day.
Health impact effect size
The most important question of all is, “What is the health impact associated with air pollution exposure?”. A recent analysis of 4 months of ground-based air quality monitoring stations across China acknowledged the difficulty of teasing out the effect of air pollution from the many confounding factors that affect health outcomes:
The conversion of pollution concentrations to mortality is complicated.
The above-mentioned Rohde and Muller 2015 study cited two other studies that have measured the differential impact of air pollution on health outcomes. I have only recently discovered this air pollution academic research, which has catalyzed a personal journey to understand the air pollution from a scientific viewpoint. Hopefully that journey will conclude in another blog post here, after I have read and critically assessed the research.
In my experience, the pollution has small or negligible acute side effects, but note that I am not necessarily at risk to acute side effects since I actively reduce my exposure to PM2.5. I can occasionally smell the pollution, like as if a distant fire is burning. Chelsey has an even better sense of smell, so she can pick it out at lower AQI levels than I can. On a few occasions I have felt the pollution like a tickle in my throat. So unfortunately for public health, the health-related effects are only experienced in the long term, a recipe for poor decision making. This absence of prompt feedback would be the ideal place for a nudge from local health officials. One specific nudge could be to include information about air pollution on the TVs in the subway. After 6 months of riding the subway, only a few times have I seen any mention of PM2.5.
Personal protective equipment and exposure dose mitigation
Like any environmental hazard, the health risks associated with air pollution can be mitigated with personal protective equipment (PPE). Imagine you have a job in a NASA cleanroom. You have to wear thick gloves, masks, and splash guards when you handle the hydrofluoric acid, or wear ear plugs when you are in a very noisy environment, or wear insulating gloves when you handle liquid nitrogen. Most Chinese cities would be considered hazardous environments by US standards. So if you are used to US standards, you might elect to don some PPE.
The main form of PPE in Beijing is the face mask. These take many forms, but they are similar to versions used at hospitals or NASA labs. I am familiar with PPE from my experience working in clean rooms, but there was something strange about donning a mask in the outdoors in plain clothes. Most people in Beijing do not wear any form of PPE to protect against air pollution. I put on a mask when the AQI “looks” bad outside, which corresponds with roughly AQI >170. This is not a recommendation, or based on anything scientific, just my personal tradeoffs in comfort and health concerns. This magic number seems to be shared with other friends.
The other major exposure dose mitigation strategy is the air purifier. Chelsey and I found out about a local DIY air purifier kit that is sold at our local fixed gear bike shop. Chelsey and I love these Smart Air filters because they cut the bullshit out of the super expensive air purifiers by simply sticking a HEPA filter in front of a circular fan. Best of all, the Smart Air team put together detailed data about the effiency of the filters with exactly the type of analysis I really wanted to see.
Coda- Quality of life and politics
The Beijing air pollution degrades our quality of life. We cannot run outside as much as we would like to, and I can’t reliably plan a bicycling trip in the nearby mountains. Even just getting some sunshine is slightly less regular that it otherwise would be. There is much more to be said about the politics of pollution, but it will have to wait for another rainy (or polluted) day.