Patricia Nelson was eager for a fresh start when she moved her family from Louisiana back home to Weld County, Colorado, in 2016. Soon after, Nelson’s friend encouraged her to come out to a meeting where Lisa McKenzie, an environmental chemist and epidemiologist at the Colorado School of Public Health, was presenting her research on the health impacts of oil and natural gas drilling.

Weld County has one of the highest concentrations of oil and gas wells in the country — 23,000 within county limits. Its air quality carries an “F” rating from the American Lung Association, with infant mortality rates twice as high as those in surrounding counties. With around 50,000 active wells overall, Colorado just surpassed California to become America’s third-largest oil and gas producer after Texas and North Dakota.

“It was a crash course in fracking,” Nelson told me by phone. Colorado law, she learned, states that drilling operations have to be 1,000 feet away from school buildings, but that ordinance — known as a setback — doesn’t include surrounding school properties, like playgrounds or soccer fields.