Blenheim Passes Air Quality Test, For Now

Friday, 28 March 2025, 8:48 pm
Article: Maia Hart - Local Democracy Reporter

Blenheim’s air quality had a perfect record in 2024, at least to the Government’s targets.

But Marlborough District Council strategic planner Sarah Pearson has warned councillors, in her annual air quality presentation, that the perfect record may not last.

If the national standard for air quality monitoring was changed, as proposed by the Ministry for the Environment in 2020, Blenheim would not be compliant with environmental standards, Pearson told the environment and planning committee.

The council was required to monitor airborne particulate matter known as PM10 under the National Environmental Standard for Air Quality. High exposure to PM10, according to the council, could result in health impacts such as coughing, asthma attacks, bronchitis and high blood pressure.

“There are both human sources and natural sources of those [PM10],” Pearson said.

“Our human sources are burning wood, vehicle exhausts, road dust, quarrying and agricultural spraying.

“Natural sources are sea salt, pollen and windblown dust, and we have all of those here. They're really, really tiny particles.”

Under environmental standards, the limit for PM10 was more than 50mcg of bigger air pollutants per cubic metre of air. Blenheim was allowed to exceed that limit once a year.

Records dating back to 2008 showed Blenheim had always breached the limit at least once, until now.

“The number of exceedances are coming down. Our maximum PM is coming down. And even our annual average is coming down too. So we are making progress,” she said.

However the bigger health concern was the smaller particulate matter of PM2.5, Pearson said. The council started monitoring this in 2017.

“PM2.5 is a part of that PM10, and those can go into our lungs,” she said.

In 2020, the ministry proposed to move the current national standard from PM10 down to PM2.5.

“They looked to a daily average of 25 micrograms and allowing three exceedances over a 12-month period and putting in an annual average,” she said.

Pearson said those proposed changes had not happened yet.

“And I'm not sure, in the state of the reforms at the moment, that air quality is even going to get the blink of an eyelid.

“So I'm not expecting those to come through at this point in time.”

But she expected they would eventually, particularly because the World Health Organisation had brought in PM2.5 guidelines which were much stricter than what the ministry proposed, she said.

Under the PM2.5 proposal, Blenheim would have had 21 exceedances.

So despite Blenheim’s progress, if the national environmental standards changed, Blenheim would be non-compliant, Pearson said.

“I know I keep bashing on about this, but I just want to keep it in your minds.

“We may have to look at further management measures within the airshed to meet that if it does come through. I'm not expecting it to any time shortly but I think we need to be aware of it.”

Pearson had previously said that phasing out older fireplaces – a requirement under the Proposed Marlborough Environment Plan – had helped to improve Blenheim’s air quality.

LDR is local body journalism co-funded by RNZ and NZ On Air.

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