Climate activists assure us that even if we don’t consider global warming a big problem, we should still support carbon taxes, renewable energy quota, and EPA’s so-called Clean Power Plan (CPP). Such policies, we are told, will save thousands of lives, delivering billions of dollars in net benefits, by coincidentally reducing airborne concentrations of fine particulate matter (PM2.5).
There are three main problems with this “co-benefits” argument. First, EPA’s own data show that total emissions of six principal air pollutants declined 62 percent since 1980 even though carbon dioxide (CO2) emissions increased by 14 percent. What’s more, PM2.5 concentrations declined by 34 percent just since 2000 (the earliest year for which national data are available). History refutes the claim that we need carbon taxes or climate regulations to clean the air.
Second, in the U.S., today’s historically low PM2.5 levels likely pose no threat to human life, as UCLA Prof. James Enstrom and nine other experts argue a letter summarizing their work in the field. Among other points, the Enstrom team explain:
No plausible etiologic mechanism by which PM2.5 causes premature death is established. It is implausible that a never-smoker’s death could be caused by inhalation over an 80 year lifespan of about one teaspoon (~5 grams) of invisible fine particles as a result of daily exposure to 15 µg/m³ [15 micrograms per cubic meter]. This level of exposure is equivalent to smoking about 100 cigarettes over a lifetime or 0.004 cigarettes per day, which is the level often used to define a never-smoker. The notion that PM2.5 causes premature death becomes even more implausible when one realizes that a person who smokes 0.2 cigarettes/day has a daily exposure of about 750 µg/m³. If a 10 µg/m³ increase in PM2.5 actually caused a 0.61 year reduction in life expectancy, equivalent to the claim of Pope [one of the chief studies on which EPA relies], then a 0.2 cigarettes/day smoker would experience about a 45-year reduction in life expectancy, assuming a linear relationship between changes in PM2.5 and life expectancy. In actuality, never-smokers and smokers of 0.2 cigarettes/day do not experience any increase in total death rate or decrease in life expectancy, in spite of a 50-fold greater exposure to PM2.5. Furthermore, hundreds of toxicology experiments on both animals and humans have not proven that PM2.5 at levels up to 750 µg/m³ causes death.
Third, even if we assume PM2.5 pollution in the U.S. poses mortality risks in some locales, EPA’s huge PM2.5 co-benefit estimates are implausible. As Anne Smith of NERA Economic Consulting explains, 99 percent of EPA’s estimated PM2.5 co-benefits occur in areas already projected to be in attainment with the NAAQS for PM 2.5. EPA illegitimately assumes the health benefits of PM2.5 reductions from concentrations already below the national ambient air quality standard (NAAQS) for fine particulate matter are as certain as the benefits of reductions from concentrations above the NAAQS. That is inconsistent with the basic concept of the NAAQS program, which is to set concentration standards at a level “requisite to protect public health . . . allowing an adequate margin of safety.”
Once we factor in the lower probability of PM2.5 health benefits in areas where exposures are already below the NAAQS, the lion’s share of the Power Plan’s purported health benefits disappears. For further discussion, see my blog post “EPA’s PM2.5 Co-Benefits PR Trick Exposed.”