Drinking Water Guidelines Raised
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The World Health Organization has increased the permitted concentration of nickel in drinking
water By Virginia Heffernan
Nickel Magazine, March 2006 -- The trend toward lower permitted concentrations of nickel in drinking water has been broken by the World Health Organization (WHO), which has raised its guideline value to 70 micrograms per liter (μg/liter) from 20 μg/liter.
The WHO focused on two studies produced since the organization’s last guideline revision in 1998: a 2000 review of nickel in drinking water consumed by pregnant rats; and a 1999 study of humans previously diagnosed with nickel contact dermatitis.
The rat study determined that a level of 130 μg/liter, higher than the previous guideline value for nickel, is safe for humans. The increase was justified by the greater level of certainty in the new study over previous reproductive studies used to calculate guideline values.
But the WHO determined that 130 μg/liter, although safe from a reproductive standpoint, may not provide sufficient protection for humans who are highly allergic to nickel. As a result, the organization considered the 1999 study too.
In that study, nickel was given to nickel-sensitive patients under a worst-case scenario: on an empty stomach and/or at levels much higher than would normally be consumed in drinking-water, which generally contains less than 20 μg/liter. From the results, the WHO determined that a 60-kg adult drinking two liters of water per day can consume 70 µg/liter, a level considered protective of the primary group at risk: nickel-sensitive individuals.
Although the WHO revision will have little immediate impact on the use of stainless steels in water systems (which already meet the existing requirements for drinking water), the new guidelines provide a greater degree of comfort to stainless steel users, says Dr. Peter Cutler, European Director, Nickel Use Support for the Nickel Institute.
Bruce McKean, director of sustainable development and product stewardship for the Nickel Institute, agrees: "For the past decade, the regulatory trend has been down, down, down, to the point where we began to worry that even stainless steel would not be acceptable for water distribution. The clouds that users saw on the horizon have now receded."
Cutler says it could be some years before any related revision to the European Union’s Drinking Water Directive finds its way through to national requirements in the EU member states.
Virginia Heffernan is
a Toronto-based freelance writer.
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