Smoke wafts across Essex St, Masterton. PHOTO/FILE


A car driving around Masterton last winter with air quality monitoring equipment on board found pollution is worst in low lying areas of the east, in Lansdowne and Solway South.

The survey was carried out by Greater Wellington Regional Council on eight evenings from June 15 to July 4 last year. The SmokeTrak instrument in the car took 17,839 five second measurements of air with a concentration of particle matter of 2.5 micrometres, known as PM2.5.

Wood smoke is a mix of gas and fine particles that are not completely burnt. They can contain cancer-causing pollutants and if the wood being burnt has been ground treated, harmful pollutants can include arsenic.

“The measurements show that air quality varied strongly over small distances and from night to night,” a GWRC report says.

Masterton’s air quality has been improving but there are challenges during the winter months because 68 per cent of households burn wood for home heating, a separate report to Masterton District Council’s community well-being committee says.

During still, cool weather the smoke doesn’t disperse and topography can contribute to temperature inversions, where smoke is trapped.

Pollution peaks on winter evenings during calm, cold weather.

The GWRC report recommends the areas with high concentrates be prioritised for education.

“The Masterton township has air quality that does not meet New Zealand’s National Environmental Standard for Air Quality,” the GWRC report says.

“It also experiences many days when fine particle air pollution fails to meet World Health Organisation guidelines.”

Some areas had worse pollution than the official air quality monitoring site in Masterton East.

There are two stationary air quality monitoring sites in Masterton, one in the west and one in the east.

There are lower concentrations of particles during the middle of the day, increasing from 4pm to 7pm and peaking about 10pm, then declining with a smaller peak around 9am in the morning.

The highest PM2.5 concentrations are found after 10pm in the evening in lower lying areas of the town – Masterton East, Lansdowne and Solway South.

Clusters of particularly high PM2.5 emissions were identified in some spots that require further investigation. The report recommends a further study using a distributed network of low-cost sensors in “hot spot” areas.

The lowest PM2.5 concentrations were found outside the main urban area and in elevated areas of Lansdowne.