Comments On The California Air Resources Board’s Draft Report “Methodology For Estimating Premature Deaths Associated With Long- Term Exposures To Fine Airborne Particulate Matter In California”

This paper provides comments on the California Air Resources Board’s (CARB) draft report “Methodology for Estimating Premature Deaths Associated with Long-term Exposures to Fine Airborne Particulate Matter in California,” which CARB released for public comment on May 22, 2008.

This update of CARB’s methodology for assessing premature mortality due to exposure to fine particulate matter provides an opportunity for CARB to assess the weight of the evidence on the health effects of today’s historically low air pollution levels. Unfortunately, rather than provide such an assessment, CARB has selected and structured information in ways that exaggerate harm from air pollution. CARB accepts uncritically the results of studies claiming to find a causal link between air pollution and mortality. On the other hand, CARB stretches for reasons to discount studies that fail to find harm from PM, often misrepresenting these studies in the process. CARB’s selective marshalling of evidence creates a false appearance that harm from PM2.5 is greater and more certain than is warranted by the actual weight of the underlying evidence from the scientific literature.

CARB’s advisory and peer review process only exaggerates the shortcomings in CARB’s substantive review of air pollution health science. Despite the wide range of scientific opinion on the validity of observational epidemiology studies and air pollution epidemiology in particular, CARB chose as peer reviewers and scientific advisors epidemiologists who believe strongly in the validity of the methods and results of air pollution epidemiology studies, who are supportive of CARB’s regulatory goals, and who have published much of the research CARB and EPA rely on to justify the expansion of their regulatory powers. These selection biases and conflicts of interest ensured that CARB’s PM mortality analysis did not receive a genuine critical review by independent experts.