Archive for October, 2013

the solution to beijing’s pollution is…controlling barbecues?

Wednesday, October 16th, 2013

Over the past few months, there have been a few suggestions from Chinese researchers and officials that Beijing’s government should go after cooking, especially outdoor barbecues, as a way of controlling air pollution. Back in May, I was quoted in the WSJ’s China Realtime Report questioning this strategy, noting my opinion that because barbecue emissions are very minor compared with emissions from motor vehicles, power plants, and industrial sources, I think it’s misguided and unfair to target the wonderful Beijing institution of outdoor chuanr. (At a deeper level, I am also concerned about the idea that average people (laobaixing) should be blamed for pollution or should have to “share the burden” to make the skies blue. The primary burden of action for the next decade falls primarily on government and industry.)

In any case, last week, cooking-as-a-pollution-source was back in the news, with another official highlighting the need for Beijingers to contribute to the air quality improvement efforts by, apparently, modifying their cooking practices. (There is even a debate going on about the differing PM2.5 impacts of different regional cuisines.) As noted in a nice summary in the SCMP, the official was widely ridiculed and refuted by both the Beijing EPB and academic researchers.

But before we dismiss this story as a case of a ridiculous official trying to do anything to blame Beijing’s pollution on something other than poor environmental regulation of obvious major sources, let’s take a closer look at whether there is any merit to the claim.

First of all, how much does cooking really matter? The closest I’ve seen to an “official” source apportionment for Beijing’s PM2.5 pollution are numbers cited by Vice Mayor Hong Feng in a January 2013 interview. Cooking isn’t even included, leading me to believe that the Beijing EPB doesn’t see it as a primary culprit:


Here are those data in a pie chart:

The above data, like most citywide inventories I’ve seen, don’t include cooking. But is cooking generally omitted because it truly is insignificant, or simply because most researchers – wrongly – don’t even think about it? At least one researcher would argue the latter. Wang Yuesi, an atmospheric physics researcher at the Chinese Academy of Sciences, has claimed that cooking is responsible for 13% of Beijing’s PM2.5. A detailed breakdown of his numbers were presented at a Clean Air Asia conference earlier this year. Cooking here is shown in red (other sources are in comparable color to the above chart):

Wang Yuesi data on Beijing PM2.5 sources (left: Beijing; right: greater Beijing region)

I don’t know how many other researchers out there would validate this 13% number. Still, this is at least one data point to suggest that cooking is not entirely insignificant and (perhaps) should not be laughed off as quickly and easily as I did earlier this year.

Regardless of the exact contribution of cooking to Beijing’s overall pollution problem, this debate raises an important point that is sometimes forgotten in air quality discussion. When it comes to quality of life and health impacts, what matters is not citywide averages but what people are actually exposed to on a day-to-day basis. (In my work, I often argue that the 22% number thrown around for fraction of PM2.5 from motor vehicles is far smaller than the reality of exposure, since 3/4ths of Beijing’s population lives near a roadway.) Along these lines, my friend Rob Earley took issue with my WSJ comments and e-mailed me the following perspective:

While probably not a big contributor to ambient air pollution across the entire Beijing “airshed”, open-air charcoal fired BBQ is certainly a contributor to local pollution that can directly affect hundreds to thousands of people in areas of high BBQ intensity and high population intensity. As you know, I live directly upstairs from Gui Jie where there is no shortage of BBQing going on at night, and when the wind blows in the right direction, my clothes hanging in the balcony to dry will most definitely take on a smoky, lamby odour. My air purifier agrees that there is something coming through the window to get excited about. While I don’t have the resources to confirm this scientifically, there are research papers that suggest that BBQ smoke does contain significant particulate matter, aromatic compounds and traces of heavy metals. In areas such as gui jie where there are apartment buildings surrounding the BBQ area, there is definitely potential for hundreds of families to be exposed on a daily basis to local high levels of smoke in addition to ambient pollution. I do believe that a major principle of health effects from PM exposure has to do with local conditions – as we’ve discussed before, concentrations of PM are highest within 50 m of major roadways. I expect that PM concentrations would also be very high in areas that supply open-air charcoal BBQ on a regular basis.

In a follow-up, Rob noted that because it’s actually quite challenging to accurately estimate the pollution contributions from different sources in Beijing, people take advantage of the uncertainty to push certain political goals (maybe you have other reasons for wanting to crack down on barbecues) or to dodge responsibility. In the end, the proper solution is probably to go after all the sources you can think of. Although I believe the short and medium-term solutions to improve Beijing’s air quality are to tackle motor vehicles and coal-burning power plants and industrial facilities, that doesn’t mean that effectively controlling these will be sufficient to improve Beijing’s long-term air quality to world-class standards. California, which has notoriously struggled to improve air quality despite stringent emission standards, has regulations affecting a number of unexpected sources like wood-burning, lawnmowers, and, yes, even barbecues.