New Study Explodes Common Air Pollution Claims

Ten years ago in Air Quality in America: A Dose of Reality on Air Pollution Levels, Trends, and Health Risks, Joel Schwartz and I wrote this:

Air pollution affects far fewer people, far less often, and with far less severity than is commonly believed. . . The air pollution-mortality claim deserves even greater skepticism. First, is is based on the same unreliable correlation moderns that have led medical authorities astray in other areas. Second, even though pollution was correlated with higher premature mortality on average, it seemed to protect against death in about one-third of cities. How could pollution kill people in some cities and save them in others? More likely, both results are chance correlations rather than real effects. Third, researchers have been unable to kill animals in laboratory experiments, even when they expose them to air pollution at levels many times greater than ever occur in the United States. This suggests that air pollution at today’s record-low levels doesn’t pose a risk, and current standards are health-protective with plenty of room to spare.

Well, you can imagine how this was received. The American Lung Association went as far as to ban us from their annual press conference for their egregiously sensational “State of the Air” report that year. They knew we were going to embarrass them.

Well, well. Just out two days ago in Regulatory Toxicology and Pharmacology:

Air quality and acute deaths in California, 2000–2012

S. Stanley YoungRichard L. Smith, and Keneth K. Lopiano.


Many studies have shown an association between air quality and acute deaths, and such associations are widely interpreted as causal. Several factors call causation and even association into question, for example multiple testing and multiple modeling, publication bias and confirmation bias. Many published studies are difficult or impossible to reproduce because of lack of access to confidential data sources. Here we make publically available a dataset containing daily air quality levels, PM2.5 and ozone, daily temperature levels, minimum and maximum and daily maximum relative humidity levels for the eight most populous California air basins, thirteen years, >2M deaths, over 37,000 exposure days. The data are analyzed using standard time series analysis, and a sensitivity analysis is computed varying model parameters, locations and years. Our analysis finds little evidence for association between air quality and acute deaths. These results are consistent with those for the widely cited NMMAPS dataset when the latter are restricted to California. The daily death variability was mostly explained by time of year or weather variables; Neither PM2.5 nor ozone added appreciably to the prediction of daily deaths. These results call into question the widespread belief that association between air quality and acute deaths is causal/near-universal. (Emphasis added.)

This isn’t the first such academic study to reach this conclusion. I am certain environmentalists and regulators will continue to ignore findings like this.