The prevalence of childrens’ ear infections significantly decreased thanks to the Clean Air Act of 1990, which toughened air quality requirements, notes a new study reported on in WebMD Health News.

Researchers analyzed U.S. data on 126,060 children from 1997 to 2007 to determine the amount of ear infections that occurred each year.

Scientists also examined air quality data from the Environmental Protection Agency (EPA) from that same time period and focused on air pollutants such as carbon monoxide, nitrous dioxide, sulfur dioxide and particulate matter—tiny natural or man-made particles of solid or liquid suspended in a gas or liquid.

In a 12-month period, frequent ear infections––known as otitis media––decreased as air quality improved, according to EPA data.

“Otitis media is a major cause of morbidity in children and is one of the most common reasons for children to undergo medical care,” said Neil Bhattacharyya, MD, of the department of otology and laryngology at the Harvard Medical School and the study’s principal investigator.

“The current study reports a statistically significant association between improvements in air quality and a reduction in frequency of ear infections prevalence,” Bhattacharyya concluded.

Previously, smaller studies also made the connection between cleaner air and ear infection reductions.

Researchers looked for but found no association between air quality and respiratory allergy.

Learn how childhood obesity is linked to ear infections here.