Potential of water laboratories` Climatic, anthropogenic, and geogenic water pollutants testing performance for ambient water quality management

• The first nationwide assessment of climatic, anthropogenic, and geogenic (CAG) water pollutants testing performance • The CAG water quality parameters established from the Sustainable Development Goal (SDG 6.3.2), with findings supporting SDG 6.3.2 reporting • Revealed key gaps in ambient temperature, pesticide, arsenic, and phytoplankton chlorophyll a testing in Tanzania`s water quality laboratories • Shortcomings and actionable recommendations for strengthening laboratories` water quality testing performance beyond Tanzania Ambient water quality is unceasingly deteriorating due to climatic, anthropogenic, and geogenic (CAG) factors, hampering the achievement of Sustainable Development Goal (SDG) target 6.3 in many African countries, including Tanzania. Laboratory performance in testing CAG water pollutants is fundamental for reliable water governance and SDG 6.3 reporting; however, the CAG testing performance remains underexplored. This study presents the first nationwide assessment of CAG water pollutant testing performance by 17 water laboratories in Tanzania. The World Health Organisation Laboratory Assessment Tool (WHO-LAT) was used, focused on key parameters recommended in SDG 6.3.2. Parameters were grouped into CAG categories, as climatic (Temperature, Dissolved Oxygen, Phytoplankton Chlorophyll a , and Turbidity); anthropogenic (Nitrogen, Phosphorus, Pesticides, and E. coli ); and geogenic (Salinity/Electrical conductivity/TDS, pH, Fluoride, Arsenic). The WHO-LAT's pre-programmed Excel-based data analysis model revealed that laboratories' CAG testing performance ranged from 51% to 81% with an overall mean of 64%. Implying that laboratories had basic to strong testing performance, demanding minor to major performance improvement measures. The financial constraints, political commitment, and the availability and application of methods for testing Arsenic (9%), Pesticides (10%), and Phytoplankton Chlorophyll a (4%) were the critical gaps. This hampers water governance, regulatory enforcement, and the tracking of SDG 6.3.2 indicators. This study's findings provide a scientific benchmark against which future improvements can be measured and enhance progress reporting on SDG 6.3.2. The government can set minimum nationwide benchmarks for laboratory testing performance, ensure accountability, and link funding to measurable improvements. Beyond Tanzania, this work provides a methodological blueprint for other countries seeking to evaluate their laboratories` CAG testing performance. The identified shortcomings and recommended measures may serve as a lesson for other low- and middle-income countries facing similar challenges. Future longitudinal studies are recommended to determine any forthcoming changes in laboratories` testing performance, enabling informed decisions.