In a recently released study, Burying Evidence: The Union of Concerned Scientists' Unscientific Claims about Air Pollution and Health, AEI visiting fellow Joel Schwartz--a former executive in charge of the California state agency charged with evaluating the state's vehicle emissions inspection program and making policy recommendations to the governor and the state legislature--responds to the Union of Concerned Scientists' (UCS) report Digging Up Trouble: The Health Risks of Construction Pollution in California, which asserts that air pollution from construction equipment in California kills more than a thousand people each year and sickens hundreds of thousands.
Schwartz demonstrates that:
- Airborne particulate matter (PM) does not kill animals in laboratory studies, even at levels many times higher than ever occur in the air we breathe. Recent studies with asthmatic human volunteers found no evidence of harm from PM--or diesel smoke specifically--even at levels a few times greater than occur in the most polluted cities.
- UCS bases its findings on results from a much weaker type of study design called an "observational" epidemiological study. Researchers have shown that observational studies tend to give false indications of risk even where no risks in fact exist, thus returning invalid results.
- Studies sponsored by the California Air Resources Board have shown that emissions of oxides of nitrogen (NOx), one of the main pollutants from construction equipment, reduce ozone levels in California.
- Additional evidence further undermines the study's findings. For example, in California and the nation, hospital visits for asthma are lowest during July and August, when ozone levels are at their highest, suggesting that ozone is not be a major cause of asthma exacerbations.
- Finally, the UCS study includes everyone in a county as breathing air that violates federal pollution standards even if only a single county pollution monitor violates the standard. For example, 99 percent of San Diegans breathe air that meets the federal eight-hour ozone standard; only a single rural monitor violates the standard. UCS, however, counts all 3 million San Diego County residents in its "dirty air" tally.
UCS states that it "stands out among nonprofit organizations as the reliable source for independent scientific analysis," yet Schwartz demonstrates that the findings in Digging Up Trouble are unreliable and based on flawed methodology and analysis.