Penn State scientists believe air pollution levels may have exceeded air quality standards during the development of some Marcellus Shale natural gas wells, according to Penn State News. More than 36,000 may have been impacted in a year during the drilling boom.

More than 20,000 unconventional natural gas wells have been drilled since Pennsylvania’s boom began. Researchers found emissions at some of the sites could have impacted air quality for people who live beyond the 500-foot setbacks required by state regulations.

“We found in one year alone, 36,000 people, or about 1% of the population of Pennsylvania’s Marcellus Shale region, could have been exposed to pollution levels exceeding air quality standards,” Gernand said. “However, we found doubling the required setback distance reduced that number by about half.”

Read the full report: Penn State News > Shale gas development in PA increases exposure of some to air