Old pipes add lead to water
Lead from old pipes that date back more than 80 years has been found in drinking water in parts of Christchurch.
The toxic metal was discovered in a small number of water samples taken from the network in Lyttelton in September.
Other areas thought to be affected are older parts of the central city, as well as Sydenham, Beckenham, Merivale, St Albans and Addington.
Canterbury medical officer of health Dr Alistair Humphrey and drinking water assessor Judy Williamson were immediately alerted after the risk was identified. Humphrey deemed the public health risk ‘‘extremely low’’, the city council said, but it is diverting water through alternative, uncontaminated pipes in the network, flushing through those still being used, and replacing pipes in the longer term.
‘‘The chances of anyone having measurable lead poisoning from this is negligible, almost nil,’’ Humphrey told The Press, suggesting harm would require exposure over many years. But he urged anyone with concerns to visit their doctor to allay any health anxieties.
Lead in the blood can cause
anaemia, slow growth, behavioural problems and even lead to death in children, affect the development of babies in the womb, and cause kidney and cardiovascular problems in adults.
Most cities in the world have some amount of lead in their water pipes.
Council head of three waters Helen Beaumont said only ‘‘trace’’ levels of lead had been found during investigations so far, and any danger was not from an ‘‘acute toxicity’’ but a ‘‘chronic, long-acting one’’.
Of 198 samples taken since September in Lyttelton and Sydenham, three were found to be above the maximum acceptable
value (MAV) for lead of 0.01 parts per million. ‘‘The fact we have only found two of 198 samples that are above the MAV does make us feel it is not an enormous problem but that it is an isolated, occasional problem,’’ Beaumont said.
While long-term residents of Lyttelton may be worried about their health, Beaumont said lead levels were not consistently high enough or high for long enough periods so as to potentially cause health problems.
‘‘To get lead poisoning you would have to be drinking it at levels above that MAV all of the time. The health limits are based on a lifetime exposure to dissolved lead in the water supply.
‘‘If we were seeing results over the MAV 90 per cent of the time, that would be of concern.’’
The news comes as it was revealed much of the city will now face chlorination until June, following fresh concerns over safety at reservoirs and the potential for backflow of contaminated water into the network.
Treatment will continue across
70 per cent of the city – the same amount that is currently receiving low-level doses of chlorine – including central and southern areas, Riccarton, Ferrymead and Lyttelton, with the chlorine removed area by area as work is completed.
The lead problem was uncovered during the development of a strict new water safety plan required by the Government.
Previous assessments in the
1990s found no unacceptable levels of the metal in water.
Beaumont said lead had leached into the water from old cast-iron mains pipes that date from the pre1940s. It was used to seal joints between pipes, meaning only a thin sliver is potentially in contact with water supplies, and is thought to be present in about 43 kilometres of the network.
Levels of lead have been found to be fluctuating, so a sample found to be unacceptable at a site on one day might be safe on another day, most likely dependent on how long water has sat in a pipe – meaning a glass of water in the morning could be worse than one in the evening.
‘‘We are still characterising how serious the issue is, that is why we are still investigating.’’
The Ministry of Health advises anyone worried to run taps for a few seconds each morning, after long periods away from home and before drinking or washing dishes to remove any metals that may have dissolved from plumbing fittings. While the lead pollution has only just been uncovered, the council has always known about and managed the risk of contamination from backflow and security worries about reservoirs.
They have only now been deemed of enough concern to require action because of the water safety plan, triggered by the more stringent application of national standards and lower appetite for risk in the wake of the 2016 Havelock North contamination that left 5000 people ill and four dead.
Reservoirs and suction tanks will now have alarmed and locked hatches, while mesh will be put on to vents on overflow pipes to stop animals getting into tanks.
Commercial properties across the city, particularly high-risk sites such as hospitals and abattoirs, are also being inspected to see if they need backflow devices. Chlorination – which cannot be used to treat lead in water – will be continued while work is carried out.