Navigating the Unregulated: A Multi-Tiered Public Health Risk Assessment of PFAS and N-DBPs Utilizing Unregulated Contaminant Monitoring Rule Data

Per- and polyfluoroalkyl substances (PFAS) and nitrogenous disinfection byproducts (N-DBPs) are significant drivers of genotoxic and non-genotoxic health risks, primarily through the ingestion of drinking water containing these contaminants. While risk depends on individual chemical properties rather than broad classifications, the sheer diversity of these compounds presents a critical challenge for human health risk assessments. To assess these risks, average and 95th percentile concentrations of PFAS and N-DBPs were calculated utilizing the United States Environmental Protection Agency (U.S. EPA) Unregulated Contaminant Monitoring Rule (UCMR) 2 and 5 datasets. Compounds were selected based on occurrence and the availability of toxicological parameters, specifically Reference Doses (RfDs) and Cancer Slope Factors (CSFs). Non-carcinogenic and carcinogenic risks for three demographics (i.e., average man, woman, and child) were determined using standard EPA protocols for Hazard Quotient and Lifetime Cancer Risk. To address compounds lacking toxicological data, a novel grouping methodology was developed to evaluate risk assessment results and identify structural patterns impacting toxicodynamics. Results indicate that while long-chain PFAS (e.g., Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS), and Perfluorodecanoic acid (PFDA)) contribute to non-carcinogenic risk, the short-chain Perfluorohexane sulfonic acid (PFHxS) exhibited a Hazard Quotient (HQ) that exceeded the safety threshold by over two orders of magnitude. For carcinogenic risk, N-Nitrosodimethylamine (NDMA) and N-Nitrosodiethylamine (NDEA) were the primary drivers among N-DBPs. PFOA presented the highest risk among PFAS, despite sharing the same chain length with PFOS. This study yields three primary conclusions: (1) sulfonic functional groups contribute to a higher non-carcinogenic risk than carboxylic acid groups; (2) a transition point exists for carboxylate groups where carbon tail hydrophobicity dominates, mimicking the behavior of persistent sulfonates; and (3) serum half-life is a more critical determinant of health risk than chain length alone, providing a vital framework to inform future regulations.

Level thesis:degree_level

Master’s Degree

Year dc:date.issued

2026

Author dc:creator

• Dunn-High, Devynn

Advisor dc:contributor.advisor

• Pagilla, Krishna

Committee members dc:contributor.committeemember

• Dennett, Keith
• Feng, Jia

Language dc:language.iso

en_US, English

Repository record dc:identifier.uri

https://scholarwolf.unr.edu/handle/11714/11830

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/11830