(Xinhua)
Updated: 2007-11-27 10:16

WASHINGTON -- A new study released Monday 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 lung function after acute ozone exposure.

A team of US researchers analyzed data on young (aged 18-35), healthy, non-smoking men and women to see if body mass index (BMI) -- a measure of fatness based on an individual's height and weight -- had an effect on lung response to acute ozone exposure.

The study published in the November issue of journal Inhalation Toxicology found that ozone response was greater with increasing BMI.

"There has recently been interest in why some people's lung function drops more than others (after short-term exposure to ozone) -- age and perhaps genetics, as well as diet may play a role," said co-author Stephanie London.

"We were intrigued by recent mouse studies that showed obesity increases lung responses to ozone and wanted to see whether this applied in humans," he said.

Based on former studies, the research team studied 197 people 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. In general, the higher the BMI, the greater the ozone response, providing one more reason why maintaining a healthy body weight is important to people's health, said the study.

The ozone-related drops in lung function were lowest in underweight people (BMI less than 18.5), greater in normal weight people (BMI 18.5 to 25) and greatest in overweight individuals (BMI above 25).

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.