Earthquakes to blame for high smog reading

AIR POLLUTION: Smog over Christchurch at sunset from Cashmere.
AIR POLLUTION: Smog over Christchurch at sunset from Cashmere.

Earthquakes are to blame for most of Christchurch's high smog readings this year, Environment Canterbury (ECan) says.

Considering the mild start to the winter, with the country's warmest May on record and the third-warmest June, Christchurch has had an abnormally high number of high-pollution days. The city experienced its 22nd high-pollution night last night and forecasters were expecting another smoggy night tonight.

This would take the city close to double last year's total for the winter when only 12 breaches of the health guidelines were recorded for particulates in the air, the lowest number since records began in 1999.

Smog over Christchurch at sunrise from Redcliffs.
Smog over Christchurch at sunrise from Redcliffs.

ECan director of investigations and monitoring Ken Taylor said only nine of this year's high-pollution nights were "typical'', with the other 12 related to dust and silt in the air after the  February 22 and June 13 quakes.

Four of the high readings at the city's air-monitoring sites in Woolston and St Albans occurred within a month of February 22, while the air standards were breached on four consecutive days after June 13.

"If you look at the actual number of days of high pollution, if you take out the earthquake-related effects, it's very similar to last year," Taylor said.

Air pollution is measured by the amount of particulates in the air below 10 micrometres, which is about one-seventh the width of a human hair. ECan also measures fine particulates, below 2.5 microns in size.

Taylor said smoke from fires and other heating appliances had a huge component of fine particles. Therefore, if the bulk of particulates were fine on a high air-pollution night, there was a strong likelihood that home heating was to blame, he said.

Soon after the September 4 quake, Energy and Resources Minister Gerry Brownlee said the region's air quality would be boosted by the quake, considering homeowners could use insurance cover to switch to cleaner forms of heating.

About 30,000 chimneys in Canterbury have been damaged or toppled by the quakes.

However, ECan is not rigorously enforcing a ban on using older woodburners and open fires from April and September because of the quakes.

"It may be that people are using appliances that they wouldn't have otherwise been using," Taylor said.

"You may also find people are using appliances more frequently than in the past."

He said that because pollution nights depended on still, cold weather, it was possible to have fewer emissions and have a bad winter.

Canterbury medical officer of health Alistair Humphrey said the theoretical risk of health problems related to liquefaction silt in the air had not increased hospital admissions for respiratory problems.

"It's something we could have expected but it hasn't materialised."

In recent weeks, trucks ladened with demolition debris leaving the central city had been dampened down to prevent dust coming off them, he said.

Air quality and health expert Simon Kingham, associate professor of geography at Canterbury University, said Canterbury's quakes were unusual because they had affected so many urban buildings.

There had not been enough research to reveal any toxicity in the liquefaction dust, he said, but there was the potential for health-related problems.

The Health Research Council and the Canterbury Medical Research Foundation have $600,000 to fund research projects into the health impact of the Canterbury quakes. Applications close tomorrow.

ECan has implemented a series of clean-air measures to tackle Christchurch's pollution problems, including the now-defunct Clean Heat programme.

The Press