About

Riley Mulhern is an Assistant Professor and INSTAAR Fellow in the Department of Environmental Studies at the University of Colorado Boulder. She holds a PhD in Environmental Sciences and Engineering from the University of North Carolina at Chapel Hill, an MS in Environmental Engineering from the University of Colorado Boulder, and a BS in Physics from Wheaton College. Her research focuses on helping people make decisions to reduce environmental health risks, with particular interest in how drinking water quality varies across social, demographic, and spatial lines. She investigates issues such as private well water quality in the U.S., lead risks in schools, childcare centers, and low-income housing, as well as the presence of per- and polyfluoroalkyl substances (PFAS), community and environmental health impacts of mining, and point-of-use water treatment for reducing drinking water exposures. Mulhern is committed to interdisciplinary approaches that support both grassroots communities and policymakers in risk management decisions, utilizing quantitative risk assessment through data science and machine learning, alongside community-engaged methods to address environmental contamination.

Research topics

• Medicine
• Political Science
• Engineering
• Environmental science
• Computer Science
• Machine Learning
• Environmental engineering
• Business
• Economics
• Economic growth
• Development economics
• Waste management
• Environmental health
• Ecology
• Geology

Selected publications

• Supplemental Information for "Proximity of Informal Worker Housing to Industrial Zones in Hanoi, Vietnam: Associated Environmental Health Risks in Air and Drinking Water"

  Zenodo (CERN European Organization for Nuclear Research) · 2026-03-01

  reportOpen access

  Supplemental Information file to accompany RTI Press journal article titled "Proximity of Informal Worker Housing to Industrial Zones in Hanoi, Vietnam: Associated Environmental Health Risks in Air and Drinking Water"

  PublisherDOI

• Supplemental Information for "Proximity of Informal Worker Housing to Industrial Zones in Hanoi, Vietnam: Associated Environmental Health Risks in Air and Drinking Water"

  Zenodo (CERN European Organization for Nuclear Research) · 2026-03-01

  reportOpen access

  Supplemental Information file to accompany RTI Press journal article titled "Proximity of Informal Worker Housing to Industrial Zones in Hanoi, Vietnam: Associated Environmental Health Risks in Air and Drinking Water"

  PublisherDOI

• Evaluating the effectiveness of point-of-use UVC LED disinfection of activated carbon block filter effluent among private well users

  PLOS Water · 2025-07-31

  articleOpen accessSenior authorCorresponding

  Point of use (POU) water treatment systems are a cost-effective method for providing safe drinking water in the absence of a central water treatment system, such as in homes relying on private wells and low-resource areas where funds for large scale treatment systems are unavailable. Activated carbon block (ACB) filters are a popular method for removing chemical contaminants but have little benefit in controlling microbial contaminants from private well water. This research investigates the effectiveness of a multibarrier approach to POU treatment for private wells by adding a UV disinfection step for treating ACB effluent. An ACB filter followed by an in-line POU Light Emitting Diode (LED) UV disinfection device was installed in 17 homes using well water in North Carolina. Influent and effluent samples were collected monthly for 5 months (Oct 2019-Feb 2020). Total coliforms, heterotrophic plate count (HPC) and male-specific coliphages were measured on paired influent and effluent samples. Mean UV influent (effluent) concentrations were 40 (1.7) MPN per 100 mL, 944 (1172) CFU per 1 mL, and 5.7 (6.8) PFU per 100 mL for coliforms, HPC, and coliphages, respectively. A statistically significant decrease was found in the UV effluent samples for coliforms (Wilcoxon signed rank test, p = 0.029) but not for heterotrophic bacteria or male-specific coliphages. Heterotrophic bacteria exhibited a shift in the microbial community with the species richness decreasing in the UV effluent. Overall, the POU UVC LED device did not achieve health protective levels of disinfection in this study, potentially due to UV-resistant species, viral aggregation, measurement challenges, lamp fouling, and/or other water quality factors. Private well users, policymakers, and/or public health agencies considering UVC LED technology for microbial control in private well water should validate performance in their local context and continue to promote other good well stewardship behaviors to ensure microbiologically safe water.

  PublisherDOI

• Assessment of unregulated drinking water risks in U.S. tap water using non-targeted Total Organic Halogen (TOX) analysis

  2025-08-31

  report1st authorCorresponding
  PublisherDOI

• PFAS in Rural U.S. Well Water: Using Participatory Science to Identify and Communicate Results to Address Risks

  Environmental Science & Technology · 2025-08-07 · 3 citations

  articleOpen access

  = 271) from four U.S. states collected tap water samples for analysis of 25 PFAS. Participants received results report comparing their water to PFAS health guidelines and recommending water filters when guidelines were exceeded. Follow-up surveys asked respondents what actions they took in response. To identify potential PFAS sources, we computed distances from households to PFAS sources recorded in EPA's PFAS Analytic Tools and other public databases and used spatial regression models to analyze relationships between these sources and water quality. PFAS were found in 15% of wells in the area with no known sources, some above a health guideline, and 53-88% of wells at sites with known sources. Total PFAS concentrations were significantly higher in wells closer to PFAS production facilities, Superfund sites, spill sites, and federal facilities. When recommended, 49% installed filters, while none did where water met the guidelines. Our study sheds insight into geographic variation in PFAS in private wells, the influence of potential PFAS sources on well water quality, and private well user decision-making in response to PFAS water quality information.

  PublisherOA PDFDOI

• Quantitative Relative Chemical Assessment to Support Risk Frameworks for Water Recycling

  ACS ES&T Water · 2025-03-19 · 1 citations

  articleOpen access

  Water resources around the world are increasingly affected by the pressures of population growth and climate change, with substantial risks of water shortages for public supply, agriculture, energy generation, and industry, with impacts on freshwater ecology. Thus, many water utilities are turning to or considering water recycling to augment existing supplies. It is incumbent on a utility to demonstrate that augmenting its water supply with recycled water does not create undue excess risk compared to existing sources that are considered protective of public health. This research quantified the chemical risks associated with using recycled water as a source of water supply. Linear cancer slope factors and threshold dose values were used with chemical concentrations measured at an advanced water recycling pilot in the southern UK to quantify chemical risk profiles of six waters: two existing drinking water source waters, a secondary treated wastewater effluent serving as the influent to the advanced water treatment pilot, and after each treatment step in the pilot (ultrafiltration, reverse osmosis, and ultraviolet advanced oxidation). This study builds on previous work by considering risks throughout the advanced water recycling treatment train via Monte Carlo simulation and evaluating several approaches to handling censored data sets; the analysis leveraged data from an extensive sampling campaign including 37 cancer risk chemicals and 289 threshold-based risk chemicals. Overall, conclusions around relative risk were relatively insensitive to the approach used for handling censored data, while using a stochastic method provided improved insights into the variability of risk. Cancer and noncancer risk profiles of water treated through the advanced treatment train were comparable or better than existing water supply works source waters. This finding provides strong evidence that use of highly treated recycled water as a source of supply is protective of public health from chemical risks when compared to existing source water supplies.

  PublisherOA PDFDOI

• Predicting the risk of GenX contamination in private well water using a machine-learned Bayesian network model

  UNC Libraries · 2025-05-22

  articleOpen access1st authorCorresponding
  PublisherDOI

• Effect of Community Water Service on Lead in Drinking Water in an Environmental Justice Community

  Environmental Science & Technology · 2024-01-08 · 12 citations

  articleOpen accessSenior author

  Multiple recent studies have found elevated lead (Pb) concentrations in tap water in U.S. homes relying on unregulated private wells. The main Pb source is dissolution from household plumbing, fixtures, and well components. Here, we leverage a natural experiment and citizen science approach to evaluate how extending community water service to an environmental justice community relying on private wells affects Pb in household water. We analyzed Pb in 260 first-draw kitchen tap water samples collected by individual homeowners over a 5-month period in residences that did and did not connect to the community system. Before the community water system was extended, 25% of homes had Pb > 15 μg/L (the U.S. regulatory action level for community water systems) in first-draw water samples. Pb was significantly correlated with nickel (ρ = 0.61), zinc (ρ = 0.50), and copper (ρ = 0.40), suggesting that corrosion of brass fittings and fixtures is the main Pb source. Among homes that connected to the community system, Pb decreased rapidly and was sustained at levels well below 15 μg/L over the study period. Overall, connecting to the municipal water supply was associated with a 92.5% decrease in first-draw tap water Pb.

  PublisherOA PDFDOI

• Effect of Community Water Service on Lead in Drinking Water in an Environmental Justice Community

  Figshare · 2024-10-23

  articleOpen access1st authorCorresponding

  Multiple recent studies have found elevated lead (Pb) concentrations in tap water in U.S. homes relying on unregulated private wells. The main Pb source is dissolution from household plumbing, fixtures, and well components. Here, we leverage a natural experiment and citizen science approach to evaluate how extending community water service to an environmental justice community relying on private wells affects Pb in household water. We analyzed Pb in 260 first-draw kitchen tap water samples collected by individual homeowners over a 5-month period in residences that did and did not connect to the community system. Before the community water system was extended, 25% of homes had Pb > 15 μg/L (the U.S. regulatory action level for community water systems) in first-draw water samples. Pb was significantly correlated with nickel (ρ = 0.61), zinc (ρ = 0.50), and copper (ρ = 0.40), suggesting that corrosion of brass fittings and fixtures is the main Pb source. Among homes that connected to the community system, Pb decreased rapidly and was sustained at levels well below 15 μg/L over the study period. Overall, connecting to the municipal water supply was associated with a 92.5% decrease in first-draw tap water Pb.

  PublisherDOI

• tidywater: Water Quality Models for Drinking Water Treatment Processes

  2024-11-05

  datasetOpen access

  Provides multiple water chemistry-based models and published empirical models in one standard format. Functions can be chained together to model a complete treatment process and are designed to work in a 'tidyverse' workflow. Models are primarily based on these sources: Benjamin, M. M. (2002, ISBN:147862308X), Crittenden, J. C., Trussell, R., Hand, D., Howe, J. K., &amp; Tchobanoglous, G., Borchardt, J. H. (2012, ISBN:9781118131473), USEPA. (2001) &lt;<a href="https://www.epa.gov/sites/default/files/2017-03/documents/wtp_model_v._2.0_manual_508.pdf" target="_top">https://www.epa.gov/sites/default/files/2017-03/documents/wtp_model_v._2.0_manual_508.pdf</a>&gt;.

  PublisherOA PDFDOI

Frequent coauthors

• Jacqueline MacDonald Gibson

  11 shared

• Andrea McWilliams

  RTI International

  6 shared

• Jennifer Hoponick Redmon

  RTI International

  6 shared

• Keith E. Levine

  MetroHealth Medical Center

  6 shared

• R. Scott Summers

  University of Colorado Boulder

  6 shared

• F. Weber

  RTI International

  6 shared

• Erica Wood

  6 shared

• Laurie Stella

  RTI International

  5 shared

Education

• Ph.D., Environmental Sciences and Engineering

  University of North Carolina at Chapel Hill

• M.S., Environmental Engineering

  University of Colorado Boulder

• B.S., Physics

  Wheaton College