The researchers found that 85% of plotted sampling sites had arsenic contents exceeding WHO guidelines.
Ebonyi had the highest reported concentration of 4.645 milligrams per litre, about 465 times the permissible limit.
Researchers called for water testing statewide and a surveillance system that links water quality data with health information.
A new study has raised alarm over the safety of drinking water in Nigeria after it discovered that around 85 per cent of all sampling sites had arsenic contents over the World Health Organisation’s recommended limit.
Eko Hot Blog reports that findings published in the Journal of Applied Sciences and Environmental Management on September 21, 2026, also found significant gaps in water quality monitoring, with more than one-third of Nigeria’s states and the Federal Capital Territory lacking published data on arsenic contamination.
The team analysed 40 studies carried out in Nigeria, said a joint statement made by the experts on Thursday. Of them, 35 research comprising 945 water samples were included in the analysis.
The greatest arsenic concentration was detected in boreholes in Ebonyi State at values of up to 4.645 milligrams per litre. That’s around 465 times the WHO standard of 0.01 milligrams a litre.
Other states with elevated amounts observed were Abia, Anambra, Kano and Nasarawa. The review looked at water samples from boreholes, wells, rivers and lakes.
But researchers warned that the results do not reflect the degree of arsenic contamination throughout the country as the analysis was based on accessible studies, some of which were carried out in known polluted sites.
The study’s corresponding author, Excel Obumneme Amaefule, said the limited availability of water testing and lack of connection between water quality findings and health records made it difficult to quantify the entire extent of the potential problem.
We’re not saying it’s a national crisis. “We’re saying Nigeria can’t rule one out because in a lot of areas of Nigeria nobody has tested and nobody is comparing water results with health data,” Amaefule added.
Dr Babajide Milton Macaulay said the potential public health implications of arsenic exposure needed urgent consideration, warning that the use of contaminated water could result in serious health concerns even when the quantities seem low numerically.
Romoke Shakirat Ojo also spoke on the significance of the geospatial analysis in the study and asked government entities to make available reliable water quality data to the public to aid research and enhance drinking water policies.
Registered nurse and public health nurse Chioma Dike also cautions that tainted water may seem safe for the households that use it everyday.
She said families may be drinking from contaminated boreholes and wells for years without knowing what was in the water.
The WHO has also associated long-term exposure to inorganic arsenic in drinking water to skin abnormalities and a heightened risk of skin, bladder and lung malignancies. Also long term exposure has been related with cardiovascular problems and diabetes.
In response to the worries, the researchers called for more water testing in jurisdictions that don’t publish contamination data, and water quality checks as a prerequisite for mining and industrial permits.
They also asked for a national surveillance system that would link environmental measures to health information so that authorities could better explore possible connections between contaminated water and illnesses.
The findings point to the need of a more complete monitoring before the level of arsenic pollution in Nigeria can be assessed.
The study does not demonstrate a national water crisis, but researchers say the lack of testing makes it hard to know for certain if water sources across the country are safe.
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