In recent months The Charlotte Observer has published several articles reporting on issues related to the regulation of “particulate matter” or what is called PM2.5. The most recent article was on December 3.
In spite of the fact that the Observer is aware that evidence regarding the relationship between PM2.5 and lung cancer or heart disease is inconclusive at best, it continues to ignore this fact, arguing that this form of air pollution “prematurely kills thousands of people” annually.
Particulate matter , or soot, is formed primarily from certain power plant emissions. It is speculated that, when inhaled, PM2.5 can cause cardiovascular and lung problems. But from a scientific perspective, this is only speculation. Not noted by the Observer is that there are no studies showing a causal connection, i.e. a scientific link, between PM2.5 and either lung cancer or heart disease. The only research that has shown any connection at all are what are known as epidemiological studies, which are not about science but statistics. Some of these studies purport to show a statistical correlation between PM2.5 and mortality from lung cancer. Correlation refers to the idea that one event occurs in the presence of another with a certain amount of frequency. It does not mean that one event has caused the other. But even epidemiological studies show results that point in different directions. For example, The Charlotte Observer and other papers are quick to point to a study published last year in the Journal of the American Medical Association(JAMA) showing a 14 percent increase in lung cancer due to PM2.5 (misreported by theObserver as a 16 percent increase). On the other hand they never mention a study of 90,000 veterans from 32 cities published in the journal Inhalation Toxicology that shows no relationship at all between lung cancer and PM2.5.
But even the results of the JAMA study tend to be misleadingly reported. News stories typically note the study’s conclusion regarding the 14 percent increase in the chances of getting lung cancer without putting it in context. They don’t report that a non-smoker only has about a 1 in 10,000 chance of getting lung cancer to begin with. A 14 percent increase raises this to a 1.14 in 10,000 chance. Statisticians consider so small an increase to be “insignificant” and possibly the result of either an error in the data or of something other than what is being tested for. Also, there are four specific findings in the JAMA study that put this relationship further in doubt. The study showed no statistically significant association between PM2.5 and lung cancer in women; in people, regardless of gender, with more than a high school education; with people under 60 years old or above 70; or in people who are currently smoking or who have never smoked.
Apparently, PM2.5 is only harmful to men who are uneducated former smokers, between the ages of 60 and 70. For some reason these results are never mentioned by the “advocacy reporting” found in many of our state’s newspapers.
Cordato is vice president for research at the John Locke Foundation.