Motueka air pollution ‘regularly exceeds’ guideline

Fine pollutants in the air above Motueka last winter were, at times, nearly four times over the World Health Organisation guideline, a study has found.

Tasman District Council commissioned the National Institute of Water and Atmospheric Research (Niwa) to monitor pollutants in the air during winter 2019 including coarse PM10 particulate matter and fine PM2.5 fractions.

The report by Niwa says the results indicate the PM2.5 concentrations in Motueka ‘‘regularly exceed’’ the World Health Organisation guideline ‘‘with 24-hour average values nearly four times as high having been recorded’’.

PM10 concentrations were also elevated – a level was recorded at twice the limit of the National Environmental Standards for Air Quality.

‘‘Motueka does appear to have an air quality issue,’’ the Niwa report said.

Higher values on average were recorded in the east of the town. It was unknown if that was due to the prevailing south-westerly winds or a strong local emission source.

In addition, there was evidence of rural burning in the surrounding countryside, particularly around Riwaka, making shortterm and localised ‘‘but significant’’ contributions to poor air quality, which may require further investigation, the report said.

The monitoring across Motueka was done via 22 temporary outdoor sensors.

Monitors were also placed in outlying rural orchard areas including Riwaka and Brooklyn.

A council staff report on the issue said the sensors used were not a recognised method under the National Environmental Standards for Air Quality for assessing compliance ‘‘however, they provide a method to identify if there is an air quality issue which warrants further investigation’’.

Council natural resources policy planner Diana Worthy last week told councillors that based on the hourly averages over a 24-hour period, it appeared home heating was the main source of pollution for the town.

‘‘There’s a peak in the evening time and then a smaller peak first thing in the morning,’’ Worthy said.

In light of the findings and recommendations from Niwa, the council monitoring station would be relocated from the west side of Motueka to the east.

A 2020 autumn-winter monitoring programme would be undertaken to establish a baseline of information using the accredited council monitoring station ‘‘to confirm if there is an air quality issue that requires permanent monitoring’’.

‘‘We’ll be looking in terms of management options going ahead once we’ve done this winter’s monitoring to see if there is actually a need, say for example, to establish an airshed in that area,’’ Worthy said.

Motueka ward councillor Trindi Walker asked if there was a reason Riwaka and Brooklyn were targeted.

‘‘My observations would be it’s not just isolated in those two rural areas,’’ Walker said.

Worthy said the council got ‘‘a lot of complaints’’ about outdoor rural burning in that area.

Meanwhile, council staff would continue to provide education and best-practice advice for home heating and outdoor burning.