WHO urged to revisit drinking water guidelines

The World Health Organization’s (WHO) drinking water guidelines for nine common toxic chemicals are inadequate and should be re-evaluated, according to a team of researchers led by Bibudhendra Sarkar at the Hospital for Sick Children in Toronto. The 2011 edition of the WHO’s drinking water quality guidelines were less restrictive for manganese, boron, mercury, molybdenum, nickel, nitrite, selenium and uranium and did not establish a guideline for aluminium.

After examining the agency’s background documents explaining the rationale for the changes, Sarkar’s research team concluded that some of these modifications failed to account for the occurrence of such chemicals in drinking water, or key health studies from the last decade. For example, the scientists suggest that the removal of manganese from the 2011 guidelines is ‘especially worrisome’ because the decision was not grounded in the best science and could harm public health.

Sarkar’s team references the fact that the WHO said it withdrew the 400µg/l drinking water guidelines for manganese because that figure is well above concentrations of the element normally found in drinking water, but the researchers note that manganese has been reported in greater concentrations in over 50 countries. Chronic manganese exposure has been linked to various neurological effects such as learning disabilities in children, Parkinson’s disease and cognitive decline in adults.

Although WHO guidelines are not regulations, they are often used by governments when setting local standards. ‘These are the de facto standards … especially for developing countries that don’t have their own regulations or regulatory agencies,’ Sarkar tells Chemistry World. ‘On the basis of these facts, the WHO should really take this matter very seriously and re-evaluate the guidelines as soon as possible,’ he adds.

Maryse Bouchard, a global manganese expert at the University of Montreal, agreed. ‘The WHO guidelines should be based on a comprehensive review of the literature including the latest data, produced by the most credible research groups,’ she said. ‘This latest edition of the guidelines contains several limits of drinking water contaminants for which questionable risk analysis decisions were made, hence a re-analysis is needed.’ The WHO’s next drinking water guidelines are not due until 2020.