Water chlorination has saved hundreds of thousands of lives globally and should not be a debate in New Zealand, scientists say.

Chlorine has been used to disinfect water supplies around the world for more than 100 years but is not mandatory in New Zealand and many water supplies are untreated.

Harrison Grierson water and wastewater manager Iain Rabbitts said chlorine should be put in all water supplies in New Zealand.

Globally it has led to the biggest increase in human life span ever, it is vitally important, he said.


"It's the greatest technological advancement of the 20th century. I think chlorine is the absolute minimum we should have in every water supply.

"In a modern society the fact that people are arguing against it is very difficult to comprehend."

The risks from chlorine are so minimal and the risks of bacteria are so high that it should not even be an issue, he said.

Also, the people complaining are generally not those who would be most affected by a bacterial outbreak, such as the young, elderly or vulnerable.

"I think it is very selfish of the people that think it smells or tastes bad.

"It's not a political issue, it's a public health issue. The fact that we have the ability and standards to treat the water - everybody should be able to turn on the tap and get water that's safe to drink."

Water New Zealand chief executive John Pfahlert said he can understand the attractiveness of wanting to drink pure, clean water but the risks are so high.

"It beggars belief that we are still having this conversation here in Havelock North."


"Drinking untreated water is like driving a motor vehicle fast without a seatbelt. You're fine until you're not.

"As long as the community is prepared to take the risk that the water they drink could kill them then, sure, they can choose to."

However, people elected councils and governments to make the best decision for them and therefore there is an obligation on their part to ensure all drinking water is safe by chlorinating, he said.

Massey University epidemiologist David Hayman said if the water in Havelock North had been chlorinated it was most likely that no one would have become sick from campylobacter in the supply.

"Chlorination is one part of the water treatment process, but it's been a remarkably successful one globally in improving public health.

"One study I think that demonstrates this well was a study in the US that determined that water improvement through filtration and chlorination in US cities in the early 20th century was responsible for half the total mortality reduction, including three quarters of the infant mortality reduction and nearly two thirds of the child mortality reduction."