Air pollution controls help to save lives, a U.S. study suggests, as death rates from emphysema, asthma and pneumonia fell dramatically as air quality improved..

Most research has focused on a specific air pollutant or a couple of pollutants over short time periods. Now, researchers in North Carolina have cross-referenced data from air quality monitoring stations and vital statistics registries and found associations between levels of several air pollutants and deaths from respiratory diseases from 1993 to 2010.

Coal Ash Spill North Carolina

Air quality in North Carolina improved after a series of federal and state acts reduced emissions. (Randall Hill/Associated Press)

Air quality has improved in North Carolina since the mid-1990s as U.S. and state regulations for heavy-duty truck engines, fuels and coal-burning generators were enacted. Levels of air pollutants started to drop and so did death rates.

"Our results support the hypothesis that improvement in air quality, especially declines in sulphur dioxide, carbon monoxide and [a type of] particulate matter levels in the air, contributed to the improved respiratory health of the North Carolina population," Dr. Kim Lyerly, a professor of surgery at Duke University in Durham and his team concluded in Monday’s issue of the International Journal of Chronic Obstructive Pulmonary Disease.

The findings show environmental policies work if the goal is to improve health as well as the environment, he said.

Lyerly said emphysema and asthma deaths fell by roughly half and pneumonia deaths were cut by a third over the study period.

The findings are dramatic and maybe not entirely due to decreases in pollution, said Dr. Christopher Carlsten, who studies the health effects of air pollution at the University of British Columbia in Vancouver.

"I think the study adds to the limited but growing body of evidence that the air pollution improvements in North American have had tangible benefits," said Carlsten, who holds a chair in occupational and environmental lung disease at UBC. "It would bolster the idea that we certainly shouldn't relax them."

Carlsten said the Duke study wasn’t designed to fully account for falling smoking rates, which the researchers acknowledged as a limitation.

The Duke findings confirm previous studies, such as a higher prevalence of visits to emergency departments for COPD and emphysema where sulphur dioxide levels are higher.

Pollutants such as carbon monoxide, nitrogen dioxide and sulphur dioxide are considered major public health concerns that play a role in an estimated 1.4 per cent of deaths worldwide, and two per cent of all cardio-pulmonary deaths worldwide, according to the World Health Organization.

The study was funded by a philanthropic donation by Fred and Alice Stanback.

With files from CBC's Pauline Dakin