Toward community-owned optical detection of priority drinking water contaminants: a review

The global water crisis leaves. in. people without safely managed drinking water, with disproportionate impacts on resource-limited nations lacking necessary infrastructure. This review synthesizes recent advances in reagentless optical methods for monitoring WHO priority contaminants, evaluating technologies including autofluorescence, Raman spectroscopy, UV absorbance, and emerging nanomaterial-based approaches. We critically assess their potential for field deployment in disaster areas and low-resource settings, examining both technical performance metrics and barriers to translation. While autofluorescence-based fecal contamination monitoring has advanced to real-time risk classification, achieving UNICEF targets, significant challenges remain for chemical contaminants. Arsenic detection now achieves 0.09 ppb using LSPR sensors with Al2 O3 /graphene oxide nanocomposites, while nitrate monitoring benefits from deep-UV Raman achieving sub-100 ppb detection limits. However, fluoride detection remains constrained by its intrinsic properties, and heavy metal sensing requires further selectivity improvements. Crucially, overcoming the "last mile" barrier depends on non-technical factors: sustainable funding, policy integration, and community engagement. We identify priority research directions, including cold-chain-free nanomaterials, multi-parameter systems with machine learning compensation, and systematic validation pathways from laboratory demonstrations to community-owned solutions.