The impact of the fourth regulatory determination on vulnerable populations

In March of 2023, the first National Primary Drinking Water Standards for per- and polyfluoroalkyl substances (PFAS) were announced. The fourth Regulatory Determination that led to this development also included several other contaminants for consideration: 1,4-dioxane (dioxane), 1,2,3-trichloropropane (TCP), and strontium, which faced no determination at this time. In this study, the relative risks associated with these three contaminants and the two regulated PFAS, perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), are analyzed on a subregion level, considering socioeconomic and racial factors in national exposure and risk levels for the U.S. population. Results indicate that PFOS and PFOA represent the greatest risk to the population in the subregions in which they are detected. Considering race and ethnicity, living in a majority-minority community may be a risk factor for exposure to strontium, while minority status did not increase exposure risk for dioxane, TCP, PFOS, and PFOA. Additionally, total cancer and non-cancer relative health indicator (RHI) matrices indicate that majority-minority communities face significantly greater risks from strontium exposure. Regression models also confirm results for strontium but place the risk on racial/ethnic minority populations more specifically in regions with greater Hispanic/Latino community percentages. Finally, while greater poverty in a subregion is associated with significantly higher cancer and non-cancer RHI values for dioxane, strontium, and TCP, after controlling for state-level variations, multi-level models reveal that greater poverty is associated with significantly lower risk from these three contaminants.