The town is the top town in the region for bad air quality.
At an Otago Regional Council meeting tomorrow, the council will discuss the readings for the towns it monitored during last year’s winter.
Four Otago towns are monitored for particulates in the air which are more than 10 micrometres in diameter.
The recordings measured readings in the Alexandra, Arrowtown, central Dunedin and Mosgiel airsheds in the 2025 calendar year.
Alexandra, Arrowtown and Mosgiel exceeded the National Environmental Standard for Air Quality during the winter months. The standard for the 10 micrometre particles, known as PM10, was 50 micrograms per square metre for a 24-hour average.
Across the four monitored towns, there was a total of 16 exceedances in 2025. Alexandra and Arrowtown recorded four and 10 exceedances, respectively, and Mosgiel recorded two.
The regional council also recorded PM2.5 (particulate matter with a diameter less than 2.5 micrometres) in Arrowtown, Central Dunedin, Clyde, Cromwell, Milton, Mosgiel, Queenstown, Frankton and Wānaka in 2025. The site with the highest annual average was Clyde, with 12 micrograms per square metre.
The site with the highest 24-hour average was Clyde, with 77 micrograms per square metre on July 18.
There are no current standard limits for PM2.5.
Monitoring of black carbon was undertaken in Arrowtown in 2025. Black carbon is a component of particulate matter and affects both climate and human health.
There are no standards or guidelines for it.
The data showed strong seasonal and daily patterns, similar to that of particulate matter. The highest 24-hour average was six micrograms per square metre occurring on July 23.
In Otago, the main source of PM is home heating emissions.
A breakdown in the equipment in Alexandra meant recordings were not taken from May 14 to June 19 last year.
The 10 exceedances recorded in Arrowtown were the equal lowest of the past five years.
