Fracking and Childhood Leukemia: New Evidence Supports Greater Residential Setbacks.

Unconventional oil and gas development (UOGD) has transformed the energy landscape in the United States—and it raises serious public concern over potential health problems. A new study[1] in Environmental Health Perspectives supports earlier reports of an association between UOGD and increased risk of childhood acute lymphoblastic leukemia (ALL), one of three main types of childhood leukemia.[2] The authors say the findings provide new support for limiting UOGD activities near residences.

Hydraulic fracturing (“fracking”) involves pumping highly pressurized water, chemicals, and sand underground to fracture rock formations and release trapped natural gas and oil.[3] Carcinogens such as heavy metals, radionuclides, benzene, and polycyclic aromatic hydrocarbons associated with leukemia have been detected in UOGD air and wastewater emissions; some are used in injection fluids.[4] Accumulating evidence points to links between proximity to UOGD and increased risk of asthma, childhood cancers, and adverse birth outcomes, including preterm delivery, low birth weight, and congenital defects.[5] By one estimate, approximately 4.7 million people live within (about 1 mi) of an active unconventional well in the United States.[6] The new study looked at residence within a slightly greater distance—2 km (1.2 mi).

In 2015, when this photo was taken in Erie, Colorado, the state allowed UOGD operations within (500 ft) of homes, schools, and day care facilities.[13] In 2020, the state legislature passed stringent new setback rules, now requiring (2,000 ft) between new wells and these buildings. However, companies can apply for exceptions.[14] Image: © Steve Nehf/The Denver Post via Getty Images.

The authors of the new paper conducted a registry-based case–control study of children diagnosed with ALL in Pennsylvania between 2009 and 2017. The authors considered whether the children, who were 2–7 years of age at the time of diagnosis, lived within of at least one unconventional oil or gas well during two windows of exposure. They defined a “primary” window of exposure as 3 months preconception to 1 year prior to diagnosis. Within that period, the researchers also looked more narrowly at a “perinatal” window of exposure, defined as 3 months preconception to birth.

The study team estimated that children who lived near a well during the primary or perinatal window had approximately two or three times, respectively, the odds of developing ALL, compared with children who lived farther from a well. The team also developed a new metric to capture drinking water exposures to oil- and gas-related chemicals, says first author Cassandra Clark, a doctoral candidate at Yale University School of Public Health. Use of the water pathway metric produced exposure estimates for both primary and perinatal windows similar to, albeit less precise than, those calculated using the distance metric. “Our findings suggest that drinking water could be an important route of exposure to oil- and gas-related chemicals,” she says.

Lisa McKenzie is senior author of one of the few other papers to assess risk of childhood ALL in relation to residential proximity to UOGD.[7] “Linking back to the birth registry and comparing cancer cases with unaffected controls is especially appropriate for a rare outcome like ALL,” says McKenzie, who was not involved in this research. “The ability to look specifically at the age range with the highest incidence of childhood ALL, another limitation in our study, was also addressed here,” she adds. Even though ALL is relatively uncommon across the population at large, making up less than 0.5% of all cancers diagnosed in the United States each year,[8] it is the most common childhood cancer in the world.[9,10]

Mary Ward, senior investigator at the National Cancer Institute, points to numerous strengths of the study, including the sample size, use of multiple distance metrics, and evaluation of other ALL risk factors and environmental exposures (namely, air pollution and agricultural pesticides). Exposure prevalence was low, limiting the authors’ ability to evaluate an exposure response, adds Ward, who also was not involved in the study. Still, she says, “The study lends further support to the importance of exposures occurring in the perinatal period in the development of ALL. Future studies should also consider exposures at day care facilities and schools.”

Senior author Nicole Deziel, an associate professor of epidemiology at Yale, believes the study shows that existing setbacks—or distances between fracking facilities and structures such as homes and schools—are insufficient to protect children and other vulnerable populations. Current setbacks were established more than a decade ago during the rapid expansion of UOGD, before health implications of exposures could be fully investigated.[11] In Pennsylvania, where the current study was conducted, the setback was extended from () to the current () in 2012.[12] Deziel says, “The consistently elevated odds of [ALL] observed across different buffer sizes and exposure metrics, and after controlling for multiple factors, demonstrate public health significance.”

McKenzie agrees. She concludes that in the context of the broader environmental and epidemiologic literature demonstrating the association between UOGD exposure and adverse health outcomes, policy makers need not wait for further research to enact more protective policies.