Vulnerable at risk populations in the clean air act: Understanding the challenge of obesity trends on risks from exposures to particulate matter and ozone

Designating sensitive populations is one of the key actions in Clean Air Act national ambient air quality standards (NAAQS) reviews, conveying whom the standards will protect with an adequate margin of safety. The law directs the U.S. Environmental Protection Agency (EPA) Administrator to address the margin of safety by considering the nature and severity of the health effects, the size of sensitive population at risk, and the uncertainties about the data. Appropriately identifying sensitive populations goes to the very heart of the public health protection afforded by the air quality standards. Two-thirds of American adults are currently overweight or obese. The obesity problem is spreading around the globe while air pollution is increasingly adding to the global burden of disease. The evidence for the pulmonary susceptibility of obese/overweight adults is reason for the EPA to designate these groups as sensitive populations for ozone and particulate matter (PM). Reviews of the scientific literature from the past several decades conclude that obesity has effects on lung function that can reduce respiratory well-being. Studies document the effects of obesity on lung and respiratory system mechanics, the work of breathing, respiratory drive, respiratory muscles, airway closure and gas exchange. As a population, obese and overweight adults may have less reserve than healthy weight adults. The altered physiological, morphological and biochemical states typical of obese populations may place an additional burden on their respiratory systems from air pollution exposures. In the 2012 PM review, this literature was unexplored by EPA. This paper critically examines the evidence regarding obese/overweight populations' pulmonary susceptibility and the implications for setting new standards and the implementation of existing standards, including implications for environmental justice concerns and communication about health effects and air quality indices.