Public release date: 26-Nov-2007

A new study provides the first evidence that people with higher body mass index (BMI) may have a greater response to ozone than leaner people. Short-term exposure to atmospheric ozone has long been known to cause a temporary drop in lung function in many people. This is the first study in humans to look at whether body weight influenced how much lung function falls after acute ozone exposure. Ozone is formed in the atmosphere in the presence of sunlight from other pollutants emitted from vehicles and other sources.

To examine the question of whether higher body mass index influences ozone responses in humans, the investigators took advantage of an earlier study led by Milan J. Hazucha and colleagues at the Center for Environmental Medicine, Asthma and Lung Biology /UNC and the USEPA Human Studies Facility in Chapel Hill, N.C. From this study, BMI was determined in 197 subjects who had been exposed to ozone for 90 minutes, during which they alternated 20 minutes of exercise with 10 minutes of rest. The subjects’ lung capacity and function were tested immediately before and after the exposure period using spirometry, a basic lung function test that measures the speed and volume of how fast and how much air is breathed out of the lungs.

“It has been known for a long time that in response to short-term exposure to ozone lung function tends to temporarily drop in many people. There has recently been interest in why some people’s lung function drops more than others – – age and perhaps genetics, as well as diet may play a role, ” said NIEHS researcher and co-author Stephanie London, M.D. “We were intrigued by recent mouse studies that showed that obesity increases lung responses to ozone and wanted to see whether this applied in humans.”

The physiologic mechanisms responsible for the decline in lung function after ozone exposure with increasing BMI are not clear, although the authors suggest that perhaps circulatory hormones and other inflammatory factors may play a role. These factors have been shown to affect airway hyper-responsiveness and inflammation in animal models.

Ralph’s note- Can partially explain the increase in asthma rates.