When I read this article, it just made my blood bowel, to think that our city councils had pissed away rate payers’ money that should have been used wisely to fix a problem that they were well aware of 3 years ago. Rate payers are sick and tired of being the councils personal Piggy bank.

Our ageing cement water pipes are eroding at a higher rate than places overseas and are leaching asbestos fibres into water supplies a study has confirmed. University of Otago school of geography researchers found “abundant evidence” of asbestos fibres in drinking water samples from 35 locations around Christchurch, and say this would be replicated in water supplies around the country. New Zealand currently has 9000 kilometres of asbestos piping in need of replacement, at an estimated cost of $2.2 billion, the study says. Asbestos cement was used for water pipes worldwide from the 1930s until the 1980s, when it became clear they could release asbestos fibres into water supplies when damaged. The vast majority of pipes were now well beyond their use-by date and at risk of failure, the study authors say.

In many parts of New Zealand, water supplies were lower in calcium and magnesium, allowing asbestos cement piping to degrade at a higher rate and release more asbestos fibres, co-author Dr Sarah Mager said. “The rate of that corrosion was quite swift, so the pipes were decaying from the inside much faster than overseas examples.” In the Christchurch study, asbestos fibres were detected in samples from 19 of 20 fire hydrant locations and from three out of 16 domestic water The amounts did not exceed safe levels, according to United States guidelines – the only country with guidelines on asbestos in drinking water samples. The Christchurch water samples were analysed by an international specialist laboratory in the US, which the researchers say was the first time ageing New Zealand asbestos pipes had been correctly assessed for erosion into water supplies. The Christchurch City Council previously sampled 17 hydrants for asbestos fibres in 2017 and found them in one. However, the study authors say the analysis method used was inadequate. While the dangers of airborne asbestos as a carcinogen are well known, the health implications for ingesting it has not been conclusively established, and there is no regulatory threshold for asbestos fibre limits in New Zealand drinking water.

The report, published by the International Water Association’s Water Supply Journal, cites recent studies suggesting a correlation between ingested asbestos and prevalence of gastric and colorectal cancers as well as evidence of asbestos enmeshed in gastrointestinal tissue. The World Health Organisation, the current NZ Guidelines for Drinking Water Quality Management, and the Australian Drinking Water Guidelines state there is insufficient data available worldwide to derive a health-based link to asbestos in drinking water. Despite this, the study co-authors say the impacts of asbestos in drinking water have been under-studied.  “Epidemiological links between asbestos fibres in drinking water and incidence of cancers can only be established if data on asbestos fibres exists: which is not regularly collected.” Asbestos cement pipelines are known to be vulnerable in earthquakes as they are brittle and subject to damage.

The study found the highest concentrations of asbestos fibres in the city’s eastern suburbs, where pipes were laid with native soil back fill rather than gravel. The area experienced strong soil liquefaction in the 2011 Canterbury earthquakes. Christchurch City Council’s acting head of three waters, Tim Drennan, said an “ongoing renewal program” had been increasing since the 1990s and only 21 per cent of the water supply pipes in the city were asbestos cement pipes. “It is very important to reiterate that the asbestos cement pipes in our water supply network are not causing any immediate health concerns.” The council ran a “risk-based prioritisation process”, which considered how significant the impact of failure would be on the community as a whole, Drennan said. “We don’t prioritise based solely on the type of material a pipe is made out of. Drennan said most of the council’s planned water main renewals in the next 27 years would be asbestos cement pipes though.

With limited sampling, the authors were not able to say if the earthquake damage and liquefaction in Christchurch meant the city’s water supplies would have higher levels of asbestos fibres than other areas. However, they recommended all councils “adopt monitoring of asbestos fibres from the reticulated water supply, especially as these pipes reach end-of-life, to detect pipe deterioration and prioritise pipe sections for replacement”. “It’s a national issue because cement asbestos pipes will have the same age and installation – so it’s reasonable to assume the rest of New Zealand is also experiencing the same rates of asbestos release rates,” co-author Michael Knopick said. Mager said the issue of water pipe infrastructure was hidden from public view. “The reality is that it’s underground, it’s hidden, and we don’t think about it until it’s not working properly.

Asbestos in New Zealand’s Urban Water Mains: The Impacts of Aging Infrastructure.

Asbestos cement was a common construction material for water pipes during the twentieth century. Research conducted by the University of Otago, investigated whether aging asbestos cement pipes, used for potable water distribution, are releasing asbestos fibres into New Zealand’s municipal drinking water supplies. It found that 789 km of asbestos cement pressure pipe remains actively in use in the Christchurch water supply network.

Key outcomes from the study are outlined below:

Most of New Zealand’s source waters are soft (low calcium carbonate), making asbestos cement piping vulnerable to internal corrosion. Therefore, local predictive models of pipe lifespan range from 20–60 years rather than the 70 that is usual for piped networks overseas.

Drinking water sampling was targeted to pipes installed before the 1980’s (1930-1970’s) and results found abundant evidence of fibres being released from pipes installed in this period.

20/20 hydrant samples returned positive results for the presence of short chrysotile asbestos fibres (> 0.5 µm) with an average concentration of 6.2 million fibres per litre (MFL). Short asbestos fibers (SAF) had the highest concentrations in drinking water samples, with five hydrant samples exceeding 5 MFL, including the highest concentration measured at 56 MFL.

19/20 hydrant samples showed long asbestos fibres (>10 µm), with an average concentration 0.9 MFL. Asbestos fibres were detected in hydrant samples across all water supply zones (excluding Kainga). The highest concentrations of fibres (as SAF) that exceeded 7 MFL were detected across Christchurch, and there is no discernable clustering at this scale of sampling. Additionally, 15 domestic water taps were also sampled and asbestos fibres were detected at 3 properties, averaging 0.2 MFL (>10 µm) and 3.5 MFL (>0.5 µm). There was no obvious spatial clustering to the positive detections in household water taps.

From this study it is evident that asbestos cement pipes are corroded by the soft, highly aggressive municipal water supply, with mean lifetime corrosion rates of 0.20 mm a-1. The mains water supply in Christchurch is therefore contaminated with (predominantly short >0.5 µm) asbestos fibres from decaying asbestos cement pipes.

Research publicly available from: IWA- Water Supply Journal

Asbestos Cement Pipes

Asbestos was first used in plumbing in 1931. The mineral’s fibres were mixed with concrete slurry to make a tube that was structurally sound. This material was called asbestos cement. By the early 1950’s, these concrete tubes were commonly used in the drinking water distribution networks across cities in many parts of the world. AC pipes contain varying proportions of asbestos fibre, cement and other materials. These include quartz-containing mainly silicon oxide and free lime. Most AC pipes contain between 15 and 20% asbestos fibres [7].

Sources of Asbestos in Drinking Water

In the water supply chain, asbestos can be introduced at two stages:

1. Pre-treatment: Asbestos may be introduced into water by the dissolution of asbestos-containing minerals and ores (geologic erosion) as well as from industrial effluents and atmospheric pollution. However, water filtration processes, when operated properly, have been shown to substantially reduce asbestos fibre concentrations in drinking water.[11] For instance, diatomaceous earth filtration can remove both amphibole and chrysotile fibres, with demonstrated removals as high as 99.99%.[12]
2. Post-treatment: the use of AC pipes is associated with the release of asbestos fibres into drinking water at post water treatment phase. This is a major concern because fibres released post treatment are not eliminated at all. They therefore end up in the distribution points. The amount of asbestos introduced into the distribution system depends on various factors.
   1. Age: The service life expectancy of AC is estimated to be roughly 50 years. While the Chrysotile Institute estimates AC pipe lifespan at 70 years, actual service life depends on pipe condition and working environment.[13] The service life expectancy of most AC pipes depends on many factors such as construction methods, quality of pipe manufacturing, soil corrosivity and water chemistry.[14]
   2. Aggressiveness of water supply: High water flows in the distribution system can lead to the erosion of AC pipes walls. This results in elevation of asbestos fibre counts in water. High flows caused by flushing or firefighting can stir up sediment in AC mains. If this occurs in generally low-flow areas, fibre counts can rise to 10 or even 100 times typical values (Logsdon,1983).
   3. Distribution system operation and maintenance procedures: Unless the pipes are flushed out under pressure, drilling and tapping of AC pipes can introduce and elevate asbestos containing debris into distribution systems.

I have put this information in so you can make an informed decision around your use of water and I will add to this as new information comes in