Plant stench ‘causing nausea, headaches’

A putrid stench in east Christchurch is causing physical and mental health effects including nausea, headaches, worsening asthma, and disturbed sleep, Canterbury’s medical officer of health says.

The stench, which many liken to human faeces, is emanating from Christchurch City Council’s damaged wastewater plant in Bromley.

A fire in November 2021 knocked out a large portion of the plant’s ability to treat sewage, and the subsequent stench has plagued residents for months.

Dr Cheryl Brunton, Canterbury’s medical officer of health, said yesterday there was evidence showing the community was suffering physical and mental health effects.

Brunton said the effects were ‘‘very, very consistent’’ with what was expected from exposure to hydrogen sulphide, one of the gases causing the stench.

But long-term health problems from the stench were ‘‘extraordinarily unlikely’’, Brunton said, as hydrogen sulphide did not stay in the body.

She said health effects would be resolved when the stench was no longer there.

Most doctors’ practices near the plant were not reporting an increase in appointments, Brunton said, but people were reporting symptoms when attending for other reasons.

The most commonly reported symptoms were nausea, headaches, eye and throat irritation, skin irritation, worsening asthma and sleep disturbance, Brunton said. ‘‘All of those are very consistent with exposure particularly to hydrogen sulphide at the kind of concentrations that are being measured in the council’s monitoring.’’

The city council carried out air testing near the plant between April 28 and June 8. A handful of samples were shown to be over the 40 parts per billion (ppb) threshold for ‘‘annoyance’’ set by California’s Office of Environmental Health Hazard Assessment.

For example, on June 1, a test result of 139ppb was recorded at Value Plus Meats in Dyers Rd, Bromley. On May 18, a sample recorded 172ppb outside the plant’s Cuthberts Rd gate.

Brunton said the stench had also affected people’s mental wellbeing.

People were reporting ‘‘considerable distress, frustration and a sense of powerlessness’’, she said.

Meanwhile, the city council is ramping up testing of ocean water for contaminants, as the health of the city’s oxidation ponds deteriorates.

Three waters boss Helen Beaumont said conversion work on the plant, which will lessen the

stench from the ponds, was 95% to 98% completed. ‘‘Unfortunately until 100% is in place ... we continue to overload our oxidation ponds.’’

The council’s discharge of treated wastewater into the ocean was exceeding consent limits for faecal coliforms and enterococci, she said. Sampling along the beach had since doubled and shellfish were being sampled too.

‘‘We’re pleased to report that those high bacterial loads going out 3km offshore are not affecting the results at the beach,’’ Beaumont said.

The worst of the stench should be gone in August or the first week of September.