Spatial analysis of residential location at birth, PFAS in public water, and childhood cancers in Southern California (2000-2019).

[BACKGROUND] Perfluoroalkyl substances exposure via drinking water varies spatially and may be associated with childhood cancer incidence.

[OBJECTIVE] We examined associations between residence at birth and incidence of childhood cancer in Orange and Los Angeles Counties, California, and if these associations change after adjustment for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) detection in public water supplies and other maternal characteristics.

[METHODS] Cancer cases (n = 6448) diagnosed before age 22 years between 2000 and 2019 and controls (n = 13,044) were categorized by PFOS/PFOA detection in residential public water according to the US Environmental Protection Agency third Unregulated Contaminant Monitoring Rule (UCMR3). Referent models using generalized additive models included a bivariable smoothing for location, child birth year, age at diagnosis or index year, and sex. Spatial models were additionally adjusted for PFOS/PFOA detection and maternal characteristics. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) for the effect of location and PFOS/PFOA detection. We also stratified analyses by US-born and Mexico-born mothers.

[RESULTS] Locations with significant increased risk of all cancers, leukemias, lymphomas, and other solid tumors were collocated with PFOS/PFOA contaminated water supplies. Referent ORs for location were attenuated after adjusting for PFOS detection and in stratified analyses for children of US-born mothers but not for Mexico-born mothers. PFOS detection was associated with higher odds of neuroblastoma (OR = 1.51, 95% CI: 1.07, 2.13) and retinoblastoma (OR = 1.83, 95% CI: 1.19, 2.79), whereas all cancers (OR = 1.07; 95% CI: 0.97, 1.18), brain tumors (OR = 1.15, 95% CI: 0.96, 1.37), and other solid tumors (OR = 1.12, 95% CI: 0.98, 1.29) had non-significant associations. PFOA detection was associated with elevated risk of retinoblastoma (OR = 1.85, 95% CI: 1.14, 3.01).

[SIGNIFICANCE] PFOS and PFOA were associated with higher childhood cancer incidence; however, their detection in drinking water did not fully explain observed geographic variations in risk.

[IMPACT] In our population-based study of childhood cancers in Orange and Los Angeles Counties, California, we observed increased risks of all cancers combined and some cancer subtypes (i.e., brain tumors, leukemia, neuroblastoma, and retinoblastoma) among children with birth addresses located in public water systems with PFOS/PFOA contamination. Our results suggest that prenatal PFOS/PFOA exposure may explain some of the cancer risk across the study area, and the effects of PFOS/PFOA adjustment on the spatial patterns of cancer risk were stronger among children of US-born mothers. This work can inform policies to reduce exposure to perfluoroalkyl substances and reduce possible health impacts.