I’m facing a bit of a quandary here. Just last week I was bragging about how air pollution isn’t as much a risk factor to health than much less glamorous topics such as overweight and lack of exercise. Since then, of course, we’ve had the biggest public health emergency I’ve seen in my six years here, with air pollution skyrocketing to an astounding 755 AQI and higher in much of northern China. So does this change anything I said? Can such a dramatic short term toxin change my overall assumptions about long term risks?
To help answer these questions, I emailed C. Arden Pope III, PhD, the Mary Lou Fulton Professor of Economics at Brigham Young University and one of the world’s most cited researchers of air pollution. I’ve based much of my articles on his excellent research, especially his important article comparing health risks of air pollution and smoking. Here’s a bit of our revealing conversation below:
Me: Even with a PM2.5 of 880 ug/m3 recorded last weekend in Beijing, that still only comes out to ~14 mg of PM2.5 per 24 hours, barely the equivalent of one cigarette which has 12 mg on average. Despite the scary news reports about our pollution emergency, is it still accurate to say this is still not even the same risk as 2 cigarettes, and any casual smoker every day is exposing his heart and lungs to much more dangerous levels than even today’s air pollution?
Pope: Yes. Cigarette smoking is an incredibly effective way to expose an individual’s body to very high levels of harmful fine particulate matter and combustion-related nasty stuff. High levels of ambient air pollution are an effective way to expose whole populations to harmful fine particulate matter and associated combustion-related pollutants. These high levels of air pollution that we are seeing in Beijing may be similar, in terms of excess risk, to smoking a cigarette or two per day.
We are learning that just one or two cigarettes per day substantially increases the risk of cardiopulmonary disease. Furthermore, who would suggest that there would not be large adverse health implications of having an entire population, including children, elderly, asthmatics, those with COPD or coronary artery disease, start smoking a cigarette or two per day for a while? Unlike cigarette smoking, exposure to ambient air pollution is involuntary and ubiquitously effects entire populations.
Is it accurate to compare PM2.5 from a cigarette versus air pollution as having the exact same health effects? In general the actual compounds are generally similar enough to compare them, and their morbidity would be equal?
I don’t know for sure, but I think so. I have attached my most recent work (that you already familiar with) that integrates air pollution, second hand cigarette smoke, and active smoking into a single integrated response function for cardiovascular disease and for lung cancer. As you know I think that the best evidence suggests that you can compare them, but for cardiopulmonary disease the response function is not linear. (For a more complete and nuanced discussion, see the discussion section of the attached paper.) It is also interesting to note that in the Institute of Medicine (of the National Academies of Sciences) report that reviews the effects of second hand smoke on cardiovascular disease, they conclude that “Both smoking and air pollution have been associated with heart attacks” providing further evidence of biological plausibility and suggesting that there are similar effects of exposure to fine particulate matter from cigarette smoke and ambient air pollution.
If we only use relative risks of PM2.5, which you generally use in your research, are we ignoring the cumulative RR from other air pollution compounds? Or is PM2.5 an accurate surrogate for overall health effects especially since most morbidity/mortality is associated with PM2.5 and not ozone/NOx/SOx etc? So it’s fair to say that the vast majority of morbidity/mortality from air pollution is from PM2.5?
Again, we don’t know for sure. However, PM2.5 seems to be the best indicator/index, so far, with regards to impact on health.
So there you go. Does this change anything for you? This is actually a very important discussion in terms of public health; isn’t the overall impact of smoking in China in terms of morbidity, mortality, and Disability Adjusted Life Years (DALY) still much worse for smoking than for outdoor air pollution? I think there’s plenty of room for further debate on this. I’m certainly not done with my own research and hope to further discuss with other leaders in their field. Leave your thoughts below…