Collaborative Research: Drinking Water Safety: Occurrence, Formation, and Genotoxicity of New Halocyclopentadiene Disinfection By-Products

Most people in the USA consume disinfected drinking water. While disinfection is vitally important to prevent waterborne disease, disinfection by-products (DBPs) form as an unintended consequence. The U.S.

Environmental Protection Agency currently regulates 11 DBPs in drinking water. In 2022, a new class of DBP called halocyclopentadienes (HCPDs) was discovered in chlorinated and chloraminated drinking water from three U.S. cities. These DBPs were found to be very toxic and likely to accumulate in tissues.

Given these findings, more information is needed to assess the occurrence of these compounds in drinking water and identify conditions that give rise to them. The goal of this research is to conduct a national occurrence study of HCPDs across the USA to uncover the factors that influence HCPD formation and investigate their genotoxicity (potential for cancer).

The results will be used to determine whether HCPDs pose a risk to human health. This goal will be achieved by measuring HCPD concentrations in drinking water collected across the USA, conducting laboratory experiments to understand how HCPDs are formed, and conducting genotoxicity experiments in cells and in laboratory test animals (nematodes). Societal benefits result from a better understanding of the potential risks of these new DBPs.

This information will facilitate long-term engineering solutions to enhance drinking water safety and sustainability. Additional benefits result from science training opportunities for high school and college students to increase scientific literacy and improve the Nation’s STEM workforce.

Water disinfection was the greatest public health achievement of the 20th century. However, chemical disinfection has raised a public health issue resulting from the potential for cancer and reproductive/developmental effects associated with DBPs. In 2022, HCPDs were discovered in chlorinated and chloraminated drinking water from three U.S. cities.

These DBPs were found to be highly cytotoxic and likely to bioaccumulate. Thus, it is important to determine their occurrence in drinking water, along with factors that influence their formation. While the cytotoxicity of three HCPDs is known, their genotoxicity is currently unknown.

The goal of this interdisciplinary research project is to address these knowledge gaps through a three-part study to: i) assess HCPD occurrence in drinking water from across the USA, ii) determine important factors in HCPD formation, and iii) investigate their genotoxicity. To achieve this, HCPD DBPs will be quantified using gas chromatography-mass spectrometry.

Genotoxicity will be assessed using two model organisms. Single cell gel electrophoresis using Chinese hamster ovary cells will be used to assess genotoxicity in vivo, and long amplification quantitative PCR and transgenerational assays will be used to assess genotoxicity in the nematode C. elegans. Results will advance our understanding of the potential risks of this new class of DBP and enable engineering solutions to enhance drinking water safety and sustainability.

The research team will disseminate results to relevant scientific communities, as well as to the lay public and key stakeholders via established outreach programs. Graduate students will be trained to provide research experiences for undergraduate and high school students. These student research and mentoring activities will encourage participation of underserved groups in STEM.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.