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EPA Disinfection Byproduct Toxicity Internship

*Applications may be reviewed on a rolling-basis and this posting could close before the deadline. Click here for information about the selection process.

EPA Office/Lab and LocationA research opportunity is available at the Environmental Protection Agency (EPA), Office of Research and Development (ORD), Center for Computational Toxicology and Exposure (CCTE), Chemical Characterization & Exposure Division (CCED) located in Research Triangle Park, North Carolina.

Research Project: Disinfection byproducts (DBPs) occur in chemically disinfected drinking water as a result of reactions between natural components in source waters (organic matter, bromine, iodine) and water disinfectants (e.g., chlorine, chloramine). More than 600 drinking water DBPs have been identified, but only a small subset of those have been characterized regarding their toxicity and potential health effects. Epidemiology studies have consistently found a link between exposure to chlorinated waters containing trihalomethanes (THMs) and other DBPs and an increased risk for bladder cancer, and some associations have also been reported for colorectal cancer and developmental effects. Due to the large number of DBPs, there is a need to prioritize these contaminants for future study and potential regulation based on their toxicities, prevalence in water, exposure potential, and risks for adverse health impacts.

Cultured Chinese hamster ovary (CHO) cells have been utilized to develop a data base and relative ranking of the cytotoxicity and genotoxicity of drinking water DBPs (Wagner and Plewa, 2017, J. Environ. Sci. 58: 64-76). However, CHO cells do not express xenobiotic metabolizing enzymes (XMEs) that can either detoxify or activate these water contaminants. Therefore, the toxicity results reflect only the toxicity of the unmetabolized parent compound. In vivo, some of these DBPs may undergo metabolism that detoxifies the parent and enhances its elimination while others may be metabolized to reactive intermediates that produce cytotoxic and/or genotoxic effects in target cells. A method was recently developed at EPA to introduce human XMEs into a cell line with low endogenous xenobiotic metabolizing capacity via transfection of modified mRNAs in relative proportions similar to human liver expression (DeGroot et al., 2018, J. Pharm. Tox. Methods 92: 77-94).

Therefore, in this research project, CHO cells will be similarly engineered to express key human metabolizing enzymes, exposed to select DBPs, and evaluated for cytotoxicity. These results will be compared to effects of the DBPs in the parent metabolically incompetent CHO cells, and relative toxicity rankings will be established in both cell lines. Enzyme-specific dependency of toxicity will be assessed when possible. The development of relative toxic potency rankings in metabolically competent cells will provide an improved understanding of the usefulness for human health of the data base developed in CHO cells.

Research activities may include: cell culture; assisting with engineering of cells to express human metabolizing enzymes; evaluating toxicity in cells exposed to DBPs using state-of-the-art assays; data analysis and development of presentation/publication graphics and tables.

Learning Objectives: The research participant will have an opportunity to contribute to an important research effort that has the potential to significantly impact drinking water quality and associated public health outcomes in the United States and the world. The participant will also gain: laboratory research experience with state-of-the-art techniques and instrumentation; potential co-authorship of peer-reviewed publications; opportunities to present research findings at meetings or seminars; continual opportunities to learn about environmental health effects research in the U.S. EPA and other leading environmental health institutions in the area via interactions with mentors, seminars, and formal training sessions. 

Mentor(s): The mentor for this opportunity is Dr. Rex A. Pegram ( If you have questions about the nature of the research please contact the mentor(s).

Anticipated Appointment Start Date: Fall 2020. All start dates are flexible and vary depending on numerous factors. Click here for detailed information about start dates.

Appointment Length: The appointment will initially be for one year and may be renewed up to three to four additional years upon EPA recommendation and subject to availability of funding.

Level of Participation: The appointment is full-time.

Participant Stipend: The participant will receive a monthly stipend commensurate with educational level and experience. Click here for detailed information about full-time stipends.

EPA Security Clearance: Completion of a successful background investigation by the Office of Personnel Management (OPM) is required for an applicant to be on-boarded at EPA.

ORISE Information: This program, administered by ORAU through its contract with the U.S. Department of Energy (DOE) to manage the Oak Ridge Institute for Science and Education (ORISE), was established through an interagency agreement between DOE and EPA. Participants do not become employees of EPA, DOE or the program administrator, and there are no employment-related benefits. Proof of health insurance is required for participation in this program. Health insurance can be obtained through ORISE.

Questions: Please see the FAQ section of our website. After reading, if you have additional questions about the application process please email and include the reference code for this opportunity.