The US EPA is conducting research to evaluate field sampling and laboratory approaches for efficiently characterizing and monitoring the exposure risk of toxic benthic cyanobacteria in streams and rivers. In 2024, three spatial extent surveys were designed and conducted to address the primary needs of stakeholders while implementing a synoptic set of sampling and laboratory methods that had been informed by previous work at pilot sampling sites. Sampling campaigns included large sections of the Columbia River, WA, and Ohio River, OH, the entire length of the main stem South Fork Eel River, CA, and throughout the primary drainage network of the Virgin River Watershed, UT, using either a systematic or spatially-balanced random survey design. In 2025, the North Fork of the Shenandoah River watershed will be surveyed. Preliminary data from 2024 for the Columbia River, Virgin River, and Ohio River surveys found detectable anatoxin-a in benthic samples from 77%, 44%, and 20% of the sites sampled, respectively. Benthic toxigenic genes were detected at 95%, 19%, and 27% of sites from the respective surveys. The findings, thus far, complicate the study objective of producing straightforward recommendations for field and lab methods that can be used to confidently characterize relative risk.