Residents fear substance staining homes

Amy Harwood’s South Brighton home has mysterious dark stains on its weatherboards – and she says it is linked to the horrible stench that hangs in the air.

Christchurch City Council is investigating whether ‘‘reports of discoloration or stains’’ it has received are linked to its firedamaged wastewater treatment plant in Bromley.

Parts of the plant, as well as the city’s oxidation ponds, are causing a pungent odour that can be smelt across east Christchurch. Many liken the smell to human faeces.

Jane Davis, the council’s infrastructure, planning and regulatory services general manager, said a specialist firm had been engaged to investigate the reports of stains on homes.

‘‘They will begin sampling next week,’’ she said.

Harwood said she first noticed the ‘‘dreadful’’ stains on her home last weekend.

‘‘I was like, ‘holy hell, where has this come from?’, because it wasn’t there a month ago.’’

She said she had never seen anything like it and she could not wash it off, even with mould remover.

‘‘It is horrible, it is embarrassing,’’ Harwood said. ‘‘If it is doing that to my house, what is it doing to our bodies is kind of my biggest concern.’’

Air tests conducted near the damaged plant show one of the council’s ‘‘gases of interest’’ – hydrogen sulphide – is, in some places, at a level that could cause headaches and nausea.

But the levels remain well below those that would cause serious health effects.

Hydrogen sulphide, also known as sewer gas, was linked to the discoloration and darkening of leadbased paint in a 1966 study.

Christchurch mayor Lianne Dalziel said she recently visited homes in Shortland St, which are next to the stinky wastewater plant, and she could see the ‘‘obvious’’ dark stains.

The health concerns of residents living with the stench was ‘‘a high priority’’, Dalziel said. ‘‘That is the question that we need to 100% know the answer to.’’

Shortland St resident Janet Profit said insurers had taken a sample of the dark material on her home this week.

She wanted to know what the results were. ‘‘Not knowing what it is, is the problem,’’ Profit said.

Helen Beaumont, the city council’s three waters boss, said the council was concerned for the wellbeing of residents living near the damaged plant. Air testing had identified ‘‘gases of interest’’, she said, namely hydrogen sulphide and other reduced sulphur compounds, such as methyl mercaptan – which has a distinctive putrid smell akin to rotten cabbage.

Dr Cheryl Brunton, Canterbury District Health Board’s medical officer of health, said continued exposure to unpleasant odours could also affect mental wellbeing, especially if people could not avoid it.

‘‘It is possible that some of the symptoms being experienced by people from the Bromley area are related to exposure,’’ she said, though she pointed out there could be other reasons for sickness, like the flu.

Brunton said anyone with health concerns should contact their GP.

Hydrogen sulphide, which has a rotten eggs odour, can be smelt at concentrations as low as eight parts per billion (ppb), according to California’s Office of Environmental Health Hazard Assessment. Some studies put the number higher.

The California assessment puts hydrogen sulphide’s threshold for ‘‘annoyance’’ – which includes headaches and nausea – at 40ppb, though people’s sensitivity varies greatly.

These are some hydrogen sulphide levels detected by the city council so far:

■ Shortland St: 91ppb on May 18, not detected on May 25

■ Memorial Park cemetery: 60ppb on May 18, not detected on May 25

■ Affordable Storage in Dyers Rd: 18ppb on May 18, 22ppb on May 25

■ Bromley School: 14ppb on May 18, not detected on May 25

These tests were not done over time and only show a snapshot of what was in the air for a few seconds.

New Zealand’s environment ministry has an ambient air guideline for hydrogen sulphide of 10ppb to prevent ‘‘the resulting impacts on wellbeing rather than specific health effects’’.

Higher levels of hydrogen sulphide have been detected inside the boundaries of the wastewater plant, including 368ppb off the oxidation ponds on May 18, but the gas rapidly dilutes in the air.

Beaumont said a meter allowing continuous sampling of hydrogen sulphide arrived yesterday and would be set up in Bromley immediately.

There were plans to get more of these meters, she said.

‘‘If it is doing that to my house, what is it doing to our bodies.’’

Amy Harwood South Brighton resident