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But Canterbury medical officer of health Cheryl Brunton said while there was evidence people were suffering physically and mentally from the foul smell, long-term problems were "extraordinarily unlikely" at current hydrogen sulphide concentrations.
Brunton's district health board colleague, Dr Lucy D'Aeth told a city council committee it was clear people were struggling.
"For the people who have an acutely sensitive sense of smell, this is hell, we acknowledge that," she said.The council asked the DHB to consider establishing a health register in response to community concerns about the months-long stench coming from the plant's two burnt-out trickling filters and overloaded oxidation ponds.
Brunton told the council's finance and performance committee a register would be hard to set up and maintain and would not directly address the problem.
"People who are suffering from the effects of the odour are actually very keen and anxious for that to be acknowledged. A health register doesn't actually address people's health needs," she said.
"A register is actually rather a difficult and clumsy way of ensuring that people have access to care."
The symptoms most commonly reported to GPs were nausea, headaches, eye, throat and skin irritation, worsening asthma and disturbed sleep, Dr Brunton said.
"All of those are very consistent with exposure particularly to hydrogen sulphide at the kinds of concentrations that are being measured in the council's monitoring," she said.
While it was unlikely the health effects would persist long-term at the concentrations measured so far, Dr Brunton said some people would remain particularly sensitive to odour.
"They may experience some of these health effects at very low concentrations in future," she said.
"For those people, it may well be that although the health effects improve they don't completely resolve."
Council head of three waters Helen Beaumont said it could take at least six weeks for the smell from the oxidation ponds to improve.
"We need to wait three weeks for the biomass to establish and then it will take another, at least three weeks and maybe a little longer, for the water to flush through those six ponds," she said.
"It takes a month or so for the water to pass all the way through."
Beaumont said wastewater discharged into the sea was not meeting environmental standards, but tests showed it was not affecting water quality at the beach.
-By Jean Edwards