Exclusive: Warning for kids and mums after lab test of Napier's discoloured water shows extremely high manganese level

A lab test of Napier’s discoloured drinking water obtained by 1 NEWS shows extremely high levels of manganese, which some studies and experts say could have serious health implications despite the council insisting it is safe to drink.

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Dr Belinda Cridge, Programme Director of University of Otago's Pharmacology and Toxicology Department, talks about drinking manganese-rich water. Source: 1 NEWS

Napier residents have increasingly reported brown or black discoloured water coming out of their taps over the past year or so, with many growing increasingly frustrated at what they believe is a lack of action from Napier City Council (NCC) to fix the discolouration issues.

The lab test was completed by the Ministry of Health-recognised and IANZ-accredited Analytical Research Lab on December 10 after a resident became fed up with the quality of her tap water and decided to have it tested at her own cost.

Lab test results of discoloured Napier water, left, and a photo from a Napier resident showing how the water often looks. Source: 1 NEWS graphic/Supplied

The resident, whose name has been withheld for privacy reasons, took a sample early in December of "noticeably brown water" after they had flushed their tap for some time. The resident said their water supply has been discoloured more and more frequently, and it is now a weekly occurrence.

"The laboratory rang me prior to emailing the test results, such was their concern," the resident told 1 NEWS.

The test results show a manganese level of 3.52mg/L in the water sampled - almost nine times higher than the Ministry of Health’s (MoH) Maximum Acceptable Value of 0.4mg/L, which is outlined in the Drinking Water Standards for New Zealand.

The result is 88 times higher than the Ministry’s recommended Guide Value of 0.04mg/L. The standards in some cases give this guide value for what they think water supplies should contain, in addition to the maximum value.

The iron content of the water tested was also more than twice the MoH's recommended amount of 0.3mg/L, with a reading of 0.7mg/L.

NCC has maintained the discolouration is the result of "harmless biofilm" being washed out of the pipes during network upgrades and maintenance, and has told residents while the brown water is unsightly, it is purely an aesthetic concern and is technically safe to drink.

The council's advice for people bothered by the colour has been to run the cold tap until the water clears, or to install a filter, and to call the council if the water won't clear. 

Sediment left behind in the home filter system of a Napier resident, including an example of a used filter and a new one, after ten months of use during 2018. Source: Supplied

NCC confirmed 125 complaints about water clarity were received by council in the week to December 9, and Stuff reported in June that 851 complaints were made about water quality in 2017 - an average of more than two per day.

NCC Infrastructure Manager Jon Kingsford told 1 NEWS he was unable to comment specifically on the test results, but said he was sceptical about whether it was performed using approved methods.

He said complaints about water discolouration are "rare" - but also acknowledged that many of the discolouration issues are not being reported to the council.

"We will have a web form available shortly to allow the community to easily log any issues that they are having," he said. "This will allow us to get a clearer understanding of the breadth of the issue."

The sheets of a Napier resident affected by discoloured water - manganese and iron-contaminated water can cause often-irreversible damage to fabrics. Source: Supplied

Mr Kingsford confirmed the discolouration of water in Napier is in fact being caused by high manganese and iron content contained in the biofilm being flushed out of the pipes.

"Biofilm is a collection of organic and inorganic living and dead material attached to the pipes’ surfaces," Mr Kingsford said.

"Bacteria as [biofilm] is harmless (non-pathogenic species), however they accumulate different elements including iron, manganese and their oxides from the water during their life cycle.

"When the bacteria die off, inorganic remains stay there and build up over years – this is what can be found in the sediment after mains cleaning activities or flushing."

Images sent to 1 NEWS by a Napier hairdresser, showing the colour of the water and the sediment left behind after it is drained. She said she is unable to get her clients' hair clean using tap water. Source: Supplied

Mr Kingsford said the council sympathises with affected residents and that council staff members have been affected themselves.

He re-affirmed the council’s stance that the discoloured water is not likely to be harmful to human health, saying "discoloured water in public water pipes does not cause health issues".

However, some experts have raised concerns about consuming manganese-rich water, and some overseas studies suggest it may be especially harmful to children’s development.

A spokesperson for Hawke's Bay District Health Board said it was unlikely people would be consuming brown water due to the colour or the taste, but agreed there may be a health risk for some people if they do.

They said they have spoken to NCC and asked them to improve their communication with the public over the issue.


Dr Belinda Cridge, programme director of University of Otago's Pharmacology and Toxicology Department, told 1 NEWS there is not a lot of good scientific information around about how much manganese is too much, but that it pays to err on the side of caution.

"The level in of manganese in the water is elevated and this is of concern," she said. "Long term exposure to high levels of manganese is toxic but there is not an easy cut-off point that allows us to say when people will be affected.

"This is because we take in manganese from the diet as well as through our drinking water and exposure varies significantly between people based on what they eat and where food has been grown - also individual factors such as age, pre-existing medical conditions, nutritional status and gender are important.

"There is a lack of really good information about the toxicity of manganese when exposed through drinking water ... The US EPA states a no observed adverse effects level (NOAEL) of 0.14mg/kg/day, which is around 10mg/day for an average adult.

Manganese in its elemental form - a cube and chips after being refined using electrolysis - with the chips showing blue and brown oxidisation. Source: Alchemist-hp/Wikimedia Commons

"What we don't know is the total manganese intake of the people in the area as they will still be taking in some dietary manganese as well as the exposure through the water. Overall, I would be particularly cautious with infants, pregnant women and the elderly.

"My main concern would be for infants on formula and would suggest that concerned residents use bottled water to prepare formula - formula can contain high levels of manganese normally and infants take up manganese more readily than adults so I would always err on the side of caution, but the risks are likely to be low.

"There is some evidence that pregnant women may also be able to take up the manganese more readily and with future generations at risk I always advise a cautionary approach. The elderly, those with liver disease or heart conditions may have a higher risk of toxicity but again this is likely to be a low risk.

"So, I wouldn't panic but I would want to keep an eye on the levels and take special care of babies and infants."

A napier mother sent in this photo of very dark tap water, with her children looking on. Source: Supplied

Dr Nick Kim, senior lecturer in applied environmental chemistry at Massey University, said the results of the test are concerning and that further testing should be undertaken by the council to validate the results and establish whether this is a widespread trend or a one-off.

"It probably would require quite a long-term exposure to get those [harmful] impacts," he said.

"The DHB should get some testing undertaken pretty quickly to get some more representative testing done as a high priority ... before Christmas. They certainly need to investigate.

"Single samples are always suspicious but I think in this case, because they've started chlorination ... it's a major change ... It may be likely that the chlorine is doing something to the reticulation network.

"That may be something that they have no answer for, because it's the whole network ... I think we might be at the beginning of characterising a genuine problem here."

Strongly discoloured water in the white bath tub of a Napier resident. Source: Supplied

The US state of Minnesota’s Department of Health said in March this year that "children and adults who drink water with high levels of manganese for a long time may have problems with memory, attention, and motor skills.

"Infants (babies under 1 year old) may develop learning and behavior problems if they drink water with too much manganese in it."

Researchers in Quebec found in 2010 that children exposed to high concentrations of manganese in drinking water performed worse on tests of intellectual functioning than children with lower exposures.

The study’s authors concluded that "the findings from the present study support the hypothesis that low-level, chronic exposure to manganese from drinking water is associated with significant intellectual impairments in children".

Sediment being left behind inside a water filter filled with Napier tap water. Source: Supplied

In 2011, the World Health Organisation determined that a tolerable level of manganese in drinking water was 0.06mg per kilogram of bodyweight. This is equal to 0.4mg per litre in the case of a 60kg adult drinking two litres of water per day.

People with long-term liver disease such as cirrhosis may have trouble getting rid of manganese in their bodies, and in these people it may build up and cause serious health issues.

In its most extreme form, known as Manganism, symptoms resembling Parkinson’s disease can develop, and they can be irreversible. This condition has been documented in people chronically exposed to manganese through industrial processes like welding.

Very dark, discoloured water coming out of a Napier resident's tap. Source: Supplied


Many residents spoken to by 1 NEWS said they have lived in Napier for decades and have never had discolouration issues prior to the chlorination of the network in 2017.

A chlorine dosing station in use by Hastings District Council. Source: Hastings District Council

Some believe chlorination has had an effect on the balance of substances inside the pipes, leading to increased discolouration, but Mr Kingsford said council does not believe the two issues are related.

However, Christchurch City Council, which in March chlorinated its water supply for similar reasons to Napier, says on its website that "chlorine is a powerful oxidising agent".

"As it travels through the system, it will react with any organic matter, such as slime build-up in the pipes," CCC says.

"It might also react with iron in the old cast iron mains and it will react with any other organic material it comes across."

According to a GNS Science report from 2012, about 12 per cent of Christchurch’s water network is still cast iron, while in Napier about 15 per cent of the network is composed of "poor quality" cast iron or steel pipe installed during a materials shortage after World War II.


Master Plumbers Association CEO Greg Wallace told 1 NEWS his members are seeing hot water cylinders in Christchurch failing at several times the usual rate since chlorination began, and that they are failing due to metal deposits ending up inside tanks, causing corrosive "pitting" of the copper linings.

Close-up images showing the effects of pitting corrosion inside a hot water cylinder, which has been linked to chlorination of the water supply. The images were taken from a University of Canterbury study by Professor Milo Kral. Source: Professor Milo Kral/University of Canterbury Department of Mechanical Engineering

Residents in Hastings and Napier have also complained of failing hot water cylinders.

Mr Wallace said he attended a meeting with Christchurch City Council on Friday to discuss the issue.

"We agree with Christchurch City Council that the presence of chlorine in the water, along with the other factors noted in the University of Canterbury report (such as temperature, details of installation and water chemistry, has contributed to the observed pitting corrosion," he said.

"We similarly agree that pitting corrosion of hot water cylinders is likely to become more frequently observed."

The report referred to is a study completed on October 1 by University of Canterbury’s Professor Milo Kral which was commissioned by hot water cylinder maker Superheat.

It concluded after examining the three provided failed cylinders that chlorination of the water supply was most likely to blame for the failures, and that it was likely to continue.

"In my opinion, due to changes in chlorination, pitting corrosion of copper hot water cylinders is likely to become more frequently observed in Christchurch, and the average life of cylinders will be reduced," Mr Kral concluded.

"The effects of pitting due to chlorination may be observed first in hot water cylinders because these are easily accessed and discovered once leaks occur … however, pitting in copper pipes will also become more frequent, and potentially even more damaging since leaks behind walls and within floors or foundations cause other damage and in locations that are more difficult to repair.

"Even if chlorination treatments are ceased, the damage may already be done."


Mr Kingsford said NCC has "a short and long term plan to address the discoloured water issues that are occurring in Napier.

"Many of the changes we are making to our system following the Havelock North inquiry are still underway.

"A significant programme of work has been identified to address known issues associated with the water supply network that will take a number of years to complete ... Council is currently reviewing the timing of that work to see if it can be brought forward, and are looking at whether additional work may be required.

"Council staff take great care in the work they do and are acutely aware of the impact the water supply operation can have on our community. Staff members have experienced this issue as well. These events are regrettable and we sympathise with those members of our community that have been affected."

Napier City Council decided as part of its 2018-28 Long Term Plan that two chlorine-free public well facilities will be installed in coming years in to-be-determined locations, with the first due to be completed by June next year.

Despite council staff implying in the past that chlorination could only be temporary, Mr Kingsford confirmed it is definitely now permanent.

Many residents are calling for more immediate action, with some asking why they should pay their rates if they are not provided with a clean water supply, and a petition calling on council to fix the discolouration has now reached more than 1000 signatures.

"Changing a major network takes time, funds and resources and a period of review to determine the effectiveness of the changes," Mr Kingsford said.

"Unfortunately, residents are seeing this play out in real time with direct impacts in the network."