Air pollution caused by a spate of uncontrolled burning on the Taieri Plain on 12 May triggered a breach of the National Environmental Standard (NES) for air quality.
Monitoring by the Otago Regional Council (ORC) has shown the 50 microgram per cubic metre of air standard for particulate matter discharges was exceeded, as the result of pollution being caused by low-hanging smoke from several uncontrolled burnoffs on the Taieri near Mosgiel.
Seven such burnoffs are being investigated for possible enforcement action, prompting the council to remind people last week of the ORC rules for discharges to air. These require permit holders not to burn material which causes objectionable and offensive smoke beyond a property boundary.
ORC director of environmental information and science John Threlfall said the breach was the 41st of its kind since continuous air quality monitoring began in 2005.
The daily average for the 12th was 63 micrograms per cubic metre of air. From 7pm until midnight, hourly readings were at times more than 100 micrograms-more than double the permitted level.
During this time conditions were calm, making it difficult for the particulates to disperse, Dr Threlfall said.
"Exceedances have previously happened in May, although it is not a common occurrence for this early in the year," Dr Threlfall said.
"The monitoring results underline the need for people to consider other ways of dealing with autumn prunings and other garden material, such as composting or shredding," he said.
Of the 41 exceedances that have been reported in Mosgiel, last week's ranked 16th in magnitude.
Dr Threlfall said ORC was aware that many people on the Taieri were going to great lengths to retrofit their homes with clean heating systems, so it was disappointing to see that work being undermined by unnecessary burnoffs.
Repeated breaches of the NES could have long-term implications for the wider Taieri community, as the ORC would not be able to issue new consents for discharges to air until they were remedied, potentially affecting local industry.
Dr Threlfall said the issue highlighted that the consequences of air pollution were not just environmental, but could have implications for people's health and economic well-being as well.