The accuracy and usability of point-of-use fluoride biosensors in rural Kenya.

Geogenic fluoride contaminates the water of tens of millions of people. However, many are unaware of the fluoride content due in part to shortcomings of detection methods. Biosensor tests are a relatively new approach to water quality testing that address many of these shortcomings but have never been tested by non-experts in a "real-world" setting. We therefore sought to assess the accuracy and usability of a point-of-use fluoride biosensor using surveys and field tests in Nakuru County, Kenya. Biosensor tests accurately classified elevated fluoride (≥1.5 ppm) in 89.5% of the 57 samples tested. Usability was also high; all participants were able to use the test and correctly interpreted all but one sample. These data suggest that biosensor tests can provide accurate, meaningful water quality data that help non-experts make decisions about the water they consume. Further scaling of these technologies could provide new approaches to track global progress towards Sustainable Development Goal 6.