Something is not in the air…and it's a good thing.

Air pollution controls put into place in North Carolina in the early 1990s appear to have brought about a drop in death rates from asthma, emphysema, and pneumonia.

“This research indicates that environmental policies not only improve the environment, but can also improve health,” said H. Kim Lyerly, a professor at Duke University Medical School and senior author of the study.

Earlier studies looked at the association between air quality and health over a long period, but they were usually analyses of a specific air pollutant or several pollutants, Lyerly told TheDoctor. He and his colleagues were able to access multiple health and environmental databases, and study the health effects of changes in the levels of a number of air pollutants over the course of about 20 years.

Air pollution controls put into place in North Carolina in the early 1990s appear to have brought about a drop in death rates from asthma, emphysema, and pneumonia.

The researchers analyzed trends in emphysema, asthma, and pneumonia mortality and changes in the levels of ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and particulate matter using monthly data measurements taken at air-monitoring stations across North Carolina between 1993 and 2010.

The decline in emphysema deaths was associated with decreasing levels of sulfur dioxide and carbon monoxide in the air. The decrease in asthma deaths with lower sulfur dioxide, carbon monoxide and particulate matter levels; pneumonia deaths declined with the lowering of sulfur dioxide levels.

Combining databases that previously were not associated with each other is an emerging research method for studying the health effects of pollution control policies. One limitation of the study, according to Lyerly, is that it is possible other factors, in addition to better air quality, could have led to a decrease in the number of deaths from respiratory diseases.

“It would be very difficult to conduct a randomized trial to gather the data for policy changes,” said Lyerly. But by following levels of air pollution and respiratory health over time, the researchers were able to see the types of health benefits the pollution controls helped bring about.

The study was published online in the International Journal of COPD.