Autofluorescence spectroscopy meets UNICEF’s target for water quality detection

More than half of the global population lacks access to safe and tested drinking water. Recommended culture-based microbiological water quality assessment methods are impractical in resource-limited settings because they are slow, require costly reagents, infrastructure, and trained personnel. In contrast, measuring the autofluorescence of dissolved organic matter that correlates with microorganisms is a real-time, reagentless, and easy-to-use method, but lacks specificity. Here we show the first method meeting UNICEF's target for rapid water quality detection with a specificity and sensitivity ≥ 85%. The key to this breakthrough is to analyze the dominant fluorescent components in water, and to account for both the radiative and non-radiative energy transfer between these components. The method can be implemented with a portable instrument using a compact spectrometer and an LED for excitation. This widely deployable method empowers stakeholders, especially in resource-limited settings, to improve their water systems, thereby reducing the burden of waterborne diseases.