Two Thousand Water Systems: The Syngenta Atrazine Settlement and Nationwide Herbicide Monitoring Costs
By Paul E. Rosenfeld, M.S., Ph.D., Principal Environmental Chemist, RoseyFields LLC, Santa Monica, California
A herbicide that migrates from field to faucet
Atrazine is among the most widely used herbicides in American agriculture, applied primarily to corn, and it readily migrates from treated fields into surface water and groundwater that supply municipal drinking-water systems. Dr. Paul E. Rosenfeld, M.S., Ph.D. of RoseyFields LLC collected and analyzed the underlying exposure data in the resulting class-action litigation against manufacturer Syngenta.
Nearly two thousand water systems as plaintiffs
The litigation resolved through a $105 million settlement resolving claims brought by nearly 2,000 community water systems across the United States, reached after nearly eight years of litigation, without any admission of liability by Syngenta, reimbursing eligible water providers based on historical atrazine contamination levels and related factors (RoseyFields.com, Syngenta case summary).
Water utilities, not individual residents, as the claimant class
Unlike most environmental exposure litigation, the Syngenta atrazine litigation’s plaintiffs were public water systems themselves, seeking reimbursement for the testing, monitoring, and treatment costs atrazine contamination forced them to incur, a damages theory grounded in utility operating costs rather than individual personal-injury or property-value claims.
Dr. Rosenfeld’s own published atrazine research
This litigation drew on a body of prior research Dr. Rosenfeld had already contributed to: a peer-reviewed conference presentation characterizing atrazine as a persistent pesticide in urban drinking water, examining its occurrence, persistence, and treatment challenges for water utilities well before this litigation began (Sok et al., 2010).
The regulatory drinking-water standard for atrazine
EPA has established a Maximum Contaminant Level of 3 parts per billion (0.003 mg/L) for atrazine in drinking water under the Safe Drinking Water Act, along with a monitoring requirement for community water systems, giving water utilities a specific, enforceable numeric target their treatment and monitoring costs are designed to meet (US EPA, National Primary Drinking Water Regulations).
Why atrazine’s occurrence pattern drives its own monitoring costs
Atrazine’s concentration in surface water is highly seasonal, spiking after spring herbicide application and rainfall runoff events, which means utilities cannot rely on a single annual sample; instead, many systems must conduct intensified seasonal or event-triggered monitoring specifically to capture these atrazine concentration spikes, a substantial driver of the monitoring costs at issue in the litigation.
Treatment technology and its costs
Removing atrazine to below the regulatory limit typically requires granular activated carbon treatment or advanced oxidation processes, both significant capital and operating cost additions for affected water systems, particularly smaller rural utilities serving agricultural communities where atrazine use, and therefore contamination risk, is highest.
The toxicological basis for regulatory concern
EPA’s human health risk assessment for atrazine has identified potential endocrine-disrupting effects and reproductive and developmental toxicity as concerns underlying the current MCL, an evolving area of the compound’s toxicology that has prompted periodic EPA reassessment of the herbicide’s registration and use restrictions (US EPA, Atrazine Interim Registration Review Decision).
How historical contamination levels determined individual settlement shares
Consistent with the exposure-based allocation approach used in other mass environmental settlements, individual water system reimbursement amounts under the Syngenta settlement were tied to each system’s documented historical atrazine contamination levels, requiring a defensible historical concentration record for each of the nearly 2,000 participating utilities.
Why agricultural chemical drinking-water litigation will continue
With atrazine remaining in widespread agricultural use and continuing to be detected in surface water and groundwater supplies nationwide, and with EPA’s ongoing reassessment of its toxicological profile, the monitoring and treatment cost burden on affected water utilities is likely to remain a live issue well beyond this settlement. A fuller account of Dr. Rosenfeld’s drinking-water contamination work can be found at RoseyFields.com.
References
1. In re Syngenta AG MIR162 Corn Litigation and related atrazine drinking-water contamination multidistrict litigation (community water system class action).
2. RoseyFields LLC. $105 Million Settlement — Atrazine Drinking Water Contamination (Syngenta). Santa Monica, CA: RoseyFields LLC; 2026.
3. Sok HL, Waller CC, Feng L, Gonzalez J, Sutherland AJ, Wisdom-Stack T, Sahai RK, Hesse RC, Rosenfeld PE. Atrazine: a persistent pesticide in urban drinking water. Urban Environmental Pollution Conference; June 20-23, 2010; Boston, MA.
4. US Environmental Protection Agency. National Primary Drinking Water Regulations: Atrazine. 40 CFR § 141.61.
5. US Environmental Protection Agency. Atrazine Interim Registration Review Decision. Washington, DC: US EPA Office of Pesticide Programs.
6. US Environmental Protection Agency. Drinking Water Treatment Technologies for Atrazine Removal. Washington, DC: US EPA.
7. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Atrazine. Atlanta, GA: US Department of Health and Human Services; 2003.
8. Safe Drinking Water Act, 42 USC §§ 300f et seq.
9. US Geological Survey. Pesticides in the Nation’s Streams and Groundwater. Reston, VA: USGS.
10. Rosenfeld PE. RoseyFields LLC: Drinking Water Contaminant Fate and Transport Assessment. Santa Monica, CA: RoseyFields LLC; 2026.
11. US Environmental Protection Agency. Revisions to the Guideline on Air Quality Models. 40 CFR Part 51, Appendix W. Fed Regist. 2017;82(10):5182-5235.
12. Rosenfeld PE, Spaeth KR, McCarthy SJ, et al. Camp Lejeune Marine cancer risk assessment for exposure to contaminated drinking water from 1955 to 1987. Water Air Soil Pollut. 2024;235:124.
13. US Environmental Protection Agency. Human Health Risk Assessment for Atrazine. Washington, DC: US EPA Office of Pesticide Programs.
14. US Environmental Protection Agency. Toxicological Review of Benzene (Noncancer Effects). Integrated Risk Information System (IRIS). Washington, DC: US EPA; 2003.