A study has confirmed that our ageing cement pipes are eroding faster than overseas, and that asbestos fibres are seeping into the water supply – but not at dangerous levels yet.
Researchers from the University of Otago’s School of Geography have found “substantial evidence” of asbestos fibres in drinking water samples from 35 sites around Christchurch and say this will be replicated in water supplies across the country.
New Zealand currently has 9000km of asbestos pipes to be replaced at an estimated cost of $2.2 billion, the study said.
Asbestos cement was used in water pipes around the world from the 1930s to the 1980s, when it became apparent that they could release asbestos fibers into the water supply when damaged.
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The study authors say the vast majority of pipes are now well past their useful life and at risk of failure.
Co-author Dr Sarah Mager said that in many parts of New Zealand, the water supply had lower levels of calcium and magnesium, which allowed asbestos cement pipes to degrade at a higher rate and release more asbestos fibres.
“The rate of this corrosion is very fast, so the pipes rot from the inside much faster than the foreign examples.”
In the Christchurch study, asbestos fibers were detected in 19 samples of 20 fire hydrant locations and three of 16 household tap samples.
That amount did not exceed safe levels under U.S. guidelines — the only country with guidelines for asbestos in drinking water.
An international specialist laboratory in the US has analysed water samples from Christchurch in what researchers say is the first time it has correctly assessed the erosion of the water supply from ageing New Zealand asbestos pipes.
Christchurch City Council had previously sampled 17 hydrants for asbestos fibres in 2017 and found them in one.However, the study authors say the analytical methods used were inadequate.
While the hazards of airborne asbestos as a carcinogen are well known, the health effects of ingesting it have not been finalized and there is no regulatory threshold to limit asbestos fibres in drinking water in New Zealand.
The report, published by the International Water Association’s Journal of Water Supply, cites recent studies that show a correlation between ingested asbestos and the prevalence of gastric and colorectal cancers, as well as the presence of asbestos in gastrointestinal tissues. evidence in.
The World Health Organization, the current New Zealand drinking water quality management guidelines and the Australian drinking water guidelines state that there is insufficient data globally to draw a health link to asbestos in drinking water.
Still, the study’s co-authors say the effects of asbestos on drinking water have not been adequately studied.
“The epidemiological link between asbestos fibers in drinking water and cancer incidence can only be established if data on asbestos fibers exist: these data are not routinely collected.”
Asbestos cement pipes are known to be fragile in earthquakes because they are fragile and easily damaged.
The study found the highest concentrations of asbestos fibers were found in the city’s eastern suburbs, where pipes were laid with native soil backfill rather than gravel.The area experienced intense soil liquefaction during the 2011 Canterbury earthquake.
Tim Drennan, acting head of three waters at Christchurch City Council, said there had been an increase in “ongoing renewal programmes” since the 1990s and the city only had 21 per cent of its water supply The pipes are asbestos cement pipes.
“It is important to reiterate that the asbestos cement pipes in our water network do not cause any immediate health problems.”
Drennan said the council runs a “risk-based prioritization process” that considers how much failure affects the community as a whole.
Drennan said most of the water pipe renewals the council planned over the next 27 years would be asbestos cement pipes.
Due to the limited sample, the authors were unable to determine whether the earthquake damage and liquefaction in Christchurch meant that the city’s water supply had higher levels of asbestos fibres than other areas.
However, they recommend that all councils “monitor reticulated water supplies for asbestos fibres, particularly as these pipes reach the end of their useful life, to detect pipe ageing and prioritise the replacement of pipe sections”.
“This is a national problem because cement-asbestos pipes are the same age and installed – so it is reasonable to assume that the rest of New Zealand will have the same rate of asbestos release,” said co-author Michael Nopic.
“The reality is it’s underground, it’s hidden, and we don’t think about it until it doesn’t work.”
Post time: May-18-2022
