Is Air Pollution Harmful to Your Health? Maybe Not.
Studies of the relationship between air pollution and health have generated an active literature claiming that air pollution and automobile traffic cause heart attack deaths, low birthweights, spontaneous abortions, acute respiratory illness, and chronic social stress in rats. The evolving literature on health effects is being cited as a basis for regulation of energy and transportation that makes both more expensive.
The existing literature relies heavily on cross-sectional statistical analysis. The claims about the deaths or illnesses from air pollution or traffic are arrived at by extrapolating estimated correlations across entire populations. A new study (gated, but with abstract) seems to show that at least some of these claims are exquisitely sensitive to the statistical techniques used to generate them.
Ross McKitrick, a professor at the University of Guelph, Gary Koop of the University of Strathclyde in Glasgow, and Lise Tole of the University of Edinburgh, observed that Canadian air pollution was worse in the 1970s than it is today. They reasoned that if air pollution is as detrimental to health as current researchers would have us believe, and if “today’s air pollution levels are causing thousands of hospitalizations, [then] the effects should have been even stronger in the 1970s when air quality was much worse.”
They examined data from 11 Canadian cities over a 20-year period to look at how air pollution levels affected monthly hospital admission rates for all lung ailments between 1974 and 1994. Unlike other researchers, they controlled for smoking, income, and model uncertainty.
The result?
There is no evidence, at least in their data set, that increases in air pollution levels are associated with increased rates of hospital admissions. The only way they could generate evidence that CO or NO2 had positive effects on lung disease was by cherry picking the data or choosing just the right model form.
The Watts Up With That? blog has a longer article about the study along with Professor McKitrick’s editorial in the National Post. His conclusion is that “the bottom line is that, for the purpose of assessing the link between air pollution levels and hospital admissions, one needs to look closely at the kinds of studies being done and how they did the statistical modeling…we should not be surprised if current estimates of the health effects of air pollution turn out to be in need of major revision.”
Intersting post, Linda. But I’m sure the environmental wackos will be upset by it. Environmentalism has become a religion. Increasingly it has nothing to do with science.
Health statistics get better through time, but it seems unlikely that the improvement is because of less air pollution.
Excellent post. I recently heard a lecture by an environmental science researcher who noted that our air pollution is not much higher than the naturally-occurring levels of air pollution.
Apparently trees (aka pollen) are some of the worst polluters out there. But you don’t see the EPA noting that in their data.
Good post, as usual Linda. I always enjoy reading your contributions here.
Most envirnomentalists know nothing whatever about science. Nor are they very interested in science or the scientific way of thinking.