The new study, published in Cancer Epidemiology, Biomarkers & Prevention, looked at medical records for more than 3,000 children born in Colorado between 1992 and 2019. The researchers found that children who were diagnosed with leukemia between the ages of two and nine were more than twice as likely to live within five kilometers — about three miles — of dense oil and gas development compared to healthy children. The study also found that Children who’d been diagnosed with leukemia during this time period were between 1.4 and 2.64 times more likely to live within 13 kilometers (about eight miles) of dense oil and gas development.