Asbestos fibres in Christchurch water not 'cause for alarm'

Ryan Boswell
Source: 1News

Asbestos fibres are leaching into Christchurch’s water supply but are “not cause for public health alarm”, according to the University of Otago School of Geography, Te Iho Whenua.

A person is in intensive care after drinking a bleach-like product claimed to cure Covid-19.

Published by the International Water Association’s Water Supply Journal, the new study sampled drinking water from asbestos cement pipes in 35 locations across the city, targeting those laid between the 1930s and 1960s.

It found “abundant evidence” of both short and long asbestos fibre release in all Christchurch water supply zones, except the modern development at Kainga.

Asbestos fibres were identified in drinking water obtained from 19 of 20 fire hydrant locations sampled citywide and in samples from three out of 16 domestic water taps.

The higher amounts of fibres were found in areas which experienced greater levels of liquefaction in the Canterbury earthquakes over a decade ago.

Study co-author Dr Sarah Mager said the presence of asbestos fibres suggests the pipes are being corroded by the soft and highly-aggressive municipal water supply.

She said the findings, while significant, are not cause for public health alarm.

“While there is no regulatory threshold for asbestos fibre limits in New Zealand drinking water, and no maximum acceptable value of ingested asbestos from water yet internationally identified, the amounts detected in this study do not exceed levels of concern for human health. The long asbestos fibre concentrations we found measured below current US-EPA 2015 guidelines,” said Mager.

The World Health Organization, the New Zealand 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.

However, the study found this area of science remains under-studied and that most global piped networks of asbestos cement have exceeded “end of life” status in the past decade.

“Most studies into the quantity of asbestos in drinking water date back 40 years.

“More recent publications suggest precautionary measures should be put in place to limit asbestos fibres in drinking water due to their long latency time,” said Mager.

Vulnerable pipes

Co-author Michael Knopick said asbestos cement pipelines are known to be the most vulnerable in earthquakes as they are brittle and subject to damage and breakdown.

“Ground acceleration, shaking or vibration can cause them to shear, meaning they can degrade both inside and out.

“Christchurch has a moderate to highly aggressive water supply as it’s low in dissolved calcium and magnesium, and that aggressiveness has enhanced internal pipe corrosion. The outer surface of the pipes is also vulnerable to decay, especially in conditions where there are high groundwater tables, which is what happens with prolonged liquefaction,” said Knopick.

Councils across New Zealand are now being urged to investigate.

Mager said it’s crucial to establish which pipes are subject to deterioration and plan for targeted replacement roll-outs as soon as possible, as “many of these pipes have reached the end of their life”.

“Some are up to 80 years old and therefore 20 to 30 years overdue for replacement.

We believe authorities should prioritise replacing pipes over 50 years old to reduce the risk of water-carried asbestos release, and to mitigate any potential risk of asbestos from ingested, contaminated water sources,” said Mager.

The study points out New Zealand currently has 9000 kilometres of asbestos piping requiring replacement, at an estimated total cost of $2.2 billion.