Study Highlights Urgent Need to Re-evaluate Latest World Health Organization Drinking Water Guidelines
TORONTO - In a new study published in Environmental Health, researchers from The Hospital for Sick Children (SickKids) and Norwich University report an urgent need to re-evaluate the World Health Organization’s drinking-water guidelines for nine toxic chemicals commonly found in drinking water. In the 2011 edition of its Guidelines for Drinking-water Quality, the World Health Organization (WHO) made guidelines less restrictive for boron, manganese, mercury, molybdenum, nickel, nitrite, selenium, and uranium and did not establish a guideline for aluminum. In the same edition, the WHO did not make any guidelines more restrictive or establish any new guidelines for other chemicals from this family.
Researchers at The Hospital for Sick Children and Norwich University closely examined the WHO’s background documents explaining the rationale for the changes, finding that some of the recent changes to the WHO guidelines did not take into account the occurrence of these chemicals in drinking water or key health studies from the last decade. In other cases, the changes to the guidelines did not follow WHO standard practices for deriving such guidelines. The study authors note that while WHO guidelines are not regulations, they may be used by governments or other stakeholders for setting local standards, and may have greater public health implications, with children being particularly vulnerable.
“The latest WHO guidelines have the potential to adversely affect the health of millions of people, including children, worldwide,” says study team leader and Senior Scientist Emeritus of Molecular Structure and Function at The Hospital for Sick Children, Dr. Bibudhendra Sarkar. “Some countries, especially those with limited resources, use WHO guidelines as de facto standards. Therefore, these guidelines can disproportionately affect the most disadvantaged populations.”
Key study findings
The removal of manganese from the 2011 guidelines was not grounded in comprehensive evidence and may have adverse health implications.
- The 400 micrograms per litre (µg/L) drinking-water guideline for manganese was withdrawn with the assertion that since the health-based guideline value “is well above concentrations of manganese normally found in drinking-water, it is not considered necessary to derive a formal guideline value”. However, manganese at greater concentrations than the former guideline value of 400 µg/L has been reported in over 50 countries, affecting tens of millions of people. Chronic exposure to manganese has been linked to a variety of neurological effects from learning disabilities in children to behavioral disorders, Manganism, Parkinson’s Disease and cognitive decline in adults.
The latest guideline for nickel is based on protection against acute exposures rather than chronic exposures.
- The drinking-water guideline for nickel was made less restrictive (the acceptable concentration raised from 20 µg/L to 70 µg/L) when the several peer-reviewed chronic exposure studies used as the basis for the former guideline were replaced with an unpublished industry-funded study.
The guideline for uranium was made less restrictive despite significant evidence showing increased blood pressure and other adverse effects.
- The drinking-water guideline for uranium was made less restrictive (raised from 15 µg/L to 30 µg/L) based on a 2006 study that found no evidence of renal damage amongst 193 adults who drank water with a median uranium concentration of 25 µg/L for an average of 16 years. However, this nominal “no effect” group showed statistically significant increases in diastolic blood pressure, systolic blood pressure and glucose excretion in urine, and was a subpopulation from a larger 2002 study that found increases in calcium fractional excretion, phosphate fractional excretion, diastolic blood pressure, systolic blood pressure, and diuresis. The new less restrictive guideline was also based on estimated high-end exposures for the 2006 study subpopulation and assumed that the “no effect” finding for the entire group could also be applied to the 10 persons with highest exposures.
The guideline for selenium is based on an allowable limit set specifically for adults and therefore may not provide adequate protection for children.
- The drinking-water guideline for selenium was made less restrictive (increased from 10 µg/L to 40 µg/L) based on a 2000 United States National Academy of Sciences (NAS) recommendation that applies specifically to adults. In the same publication the NAS recommended lower (more restrictive) limits for children based on age-weight differences. Since the WHO did not incorporate the lower limits for selenium exposures to children in its revised guideline, the new WHO guideline may not provide adequate protection for children.
The current guideline for boron has an error in calculation.
- The drinking water guideline for boron was raised from 500 µg/L to 2,400 µg/L. Part of this increase was due to a rounding error in the derivation, in which the Tolerable Daily Intake (TDI) for boron was rounded up before being incorporated into the guideline derivation, contrary to WHO stated policy.
While children are likely to be affected by all of the changed guidelines, the withdrawal of the manganese guideline is especially worrisome, the authors say. As noted in this study, recent research in Canada, Bangladesh, and elsewhere has shown that children’s chronic exposure to manganese through drinking water is associated with decreased ability to learn.
Moreover, high concentrations of chemicals in water may be more widespread than is currently known. The chemicals addressed in the WHO guidelines can occur naturally in drinking water, especially groundwater, due to geologic deposits, or they may result from pollution. Since health effects due to high concentrations of these chemicals may be non-specific or take years to emerge, many water consumers may not be aware of the need to test their drinking water for these chemicals.
Study co-authors Drs. Seth H. Frisbie and Erika J. Mitchell of Norwich University stress, “Regardless of the current WHO drinking-water guidelines, it is vital that owners of private water supplies and managers of public water supplies be aware that these chemicals may be present in their water and that they may be hazardous even if they are not covered by current WHO guidelines or are found at concentrations that are currently deemed safe by the WHO.”
“The WHO Guidelines should be based on a comprehensive review of the literature including the latest data, produced by the most credible research groups. 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,” says global manganese expert, Professor Maryse Bouchard, Department of Environmental Health and Occupational Health, University of Montreal.
Although there is a rolling revision process for WHO guidelines, the next full edition of the WHO Guidelines for Drinking-water Quality is not due to be released until 2020. In the meantime, regulators may choose to revert to earlier editions of the Drinking-water Guidelines, which are more protective of public health, as noted by a previous study by the authors, until the issues raised in this review have been addressed by the WHO.
This article was published in the open-access, peer-reviewed journal Environmental Health. Read the abstract and full article. Journalists interested in the study can find the full embargoed article attached.
About The Hospital for Sick Children
The Hospital for Sick Children (SickKids) is recognized as one of the world’s foremost paediatric health-care institutions and is Canada’s leading centre dedicated to advancing children’s health through the integration of patient care, research and education. Founded in 1875 and affiliated with the University of Toronto, SickKids is one of Canada’s most research-intensive hospitals and has generated discoveries that have helped children globally. Its mission is to provide the best in complex and specialized family-centred care; pioneer scientific and clinical advancements; share expertise; foster an academic environment that nurtures health-care professionals; and champion an accessible, comprehensive and sustainable child health system. SickKids is proud of its vision for Healthier Children. A Better World. For more information, please visit www.sickkids.ca.
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