Unconventional oil and gas exposure and risk of childhood leukemia in Pennsylvania

Background/Aim. Unconventional oil and gas development (UOGD), commonly known as "fracking,” is a rapidly expanding industry that releases chemicals that have been linked to cancer and childhood leukemia. Despite high community concern, studies of childhood cancer are sparse. We evaluated potential associations between residential proximity to UOGD and risk of acute lymphoblastic leukemia (ALL), the most common form of childhood leukemia, in a large regional sample using UOGD-specific metrics, including a novel metric representing the water pathway. Methods. We conducted a registry-based case-control study of 405 children aged 2-7 years diagnosed with ALL in Pennsylvania between 2009-2017, and 2,080 controls matched on birth year. We used adjusted logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between residential proximity to UOGD (including a new water-specific proximity metric) and ALL in two exposure windows: a primary window (three months pre-conception to one year prior to diagnosis/reference date) and a perinatal window (three months pre-conception–birth). Results. Children with at least one UOG well within 2 km of their birth residence during the primary window had 1.98 times the odds of developing ALL versus those with no UOG wells (95% CI: 1.06-3.69). Children with at least one versus no UOG wells within 2 km during the perinatal window had 2.80 times the odds of developing ALL (95% CI: 1.11-7.05). These relationships were slightly attenuated after adjusting for maternal race and socio-economic status (OR: 1.74 [95% CI: 0.93-3.27], OR: 2.35 [95% CI: 0.93-5.95], respectively). Analyses based on the water-specific metric yielded similar findings. Conclusions. Our large regional study including a novel water-specific metric found UOGD to be a risk factor for childhood ALL. This work adds to mounting evidence of UOGD’s impacts on children’s health, supporting the need to limit UOGD near residences. Keywords. Childhood leukemia, unconventional oil/gas