Warning issued on tap water 'dangers'

Cancer-causing trace metals in plumbing fittings -- including lead, cadmium, copper and nickel -- have the potential to leach into drinking water and cause long-term health problems, the Ministry of Health has warned.

Every local council nationwide is now required under the Drinking Water Standards for New Zealand 2005 to alert consumers to the potential danger and advise them how to avoid it.

In a public health notice issued by Porirua City Council today, New Zealand's Director-General of Health Karen Poutasi said some plumbing fittings had "the potential to allow minute traces of metals to accumulate in water standing in the fittings for several hours".

"Although the health risk is small, the Ministry of Health recommends that you flush a mugful of water from your drinking-water tap each morning before use to remove any metals that may have dissolved from the plumbing fittings," Dr Poutasi said.

"We are recommending this simple precaution for all households, including those on public and private water supplies."

Earlier this year, Wellington Regional Council, as the reticulated water supplier for the region, took out a public notice in daily newspapers to advise consumers of the issue, and local bodies have also included notices in rates newsletters.

Drinking water assessor Scott Rostron, from the Wellington Regional Public Health Service, said the potential long-term harmful effects from trace metals in plumbing fittings had been known for a number of years.

The new warnings had not arisen from any changes made by councils to the way water was supplied, he said.

Actual exposure would depend on the age and type of the plumbing fittings in individual houses.

Older fittings could be made of brass, chrome, copper, zinc or even lead, while modern ones tended to be plastic.

Even low-level lead exposure can lead to developmental problems in children and raises blood pressure in adults, causing kidney damage.

The current "maximum acceptable value" for drinking water is 0.01mg per litre.

Council pipework also varied, even within regions, with some made of steel, iron, asbestos cement, to modern plastic piping.

However, council pipework posed less threat to drinking water because the water was always moving, he said.

"I understand that it's when the water is sitting still, such as overnight, that there is the potential for metals to leach into the water."

He said the standards, based on an average 70kg bodyweight, "erred on the side of caution".

"We're not just considering acute short-term exposure but the life-time potential for harm -- what the risk is if you drink two litres a day for 60 to 70 years."

- NZPA