In a report to the Otago Regional Council’s data and information committee today, council air quality scientist Sarah Harrison said to prepare for new national air quality standards the council trialled low-cost sensors for air quality monitoring that were able to monitor particulate matter in the air only two and a-half microns or less in width (PM2.5).
From July until the end of September last year, 47 outdoor dust information nodes (Odins) were attached to lamp-posts, fences or other structures in 15 airsheds (areas), from Hawea to Green Island.
While not as accurate as the council’s now used "state of the environment" monitoring equipment, which monitors the slightly larger PM10 in seven airsheds, the Odins could be used as a network to produce reliable results for the smaller particles, Ms Harrison said.
All of the monitored airsheds except for Kingston recorded a large evening peak, and a smaller morning peak of PM2.5, indicating home heating was a source, she said.
The PM2.5 concentrations of the airsheds monitored varied; however, Lake Hawea, Luggate, Ranfurly and Oamaru had the highest mean concentrations for the monitoring period.
Lake Hawea recorded the highest 24-hour average PM2.5 concentration of 58 mcg/cum.
"This was the first time in many years that some of these airsheds have been investigated and the concurrent monitoring allowed for direct comparisons between them," Ms Harrison said.
She advised further monitoring and investigations should be considered to understand some of the airsheds in the context of the council’s state of the environment monitoring network, the forthcoming updated national environmental standards, and for future air quality management.
National environmental standards were being updated to include a limit for PM2.5.
The proposed 24-hour limit was 25 mcg/cu m, and the present limit for PM10 was 50 mcg/cu m.
The World Health Organisation (WHO) presently recommended the PM2.5 and PM10 limits should be set at lower levels — 15 and 45 mcg/cu m respectively for 24-hour averages, Ms Harrison said.
The WHO said the lower the levels of air pollution, the better the cardiovascular and respiratory health of the population would be, both in the long-term and short-term.
However, in 2019, 99% of the world’s population was living in places where WHO air quality levels were not met, it said.
Ambient outdoor air pollution in both cities and rural areas was estimated to cause 4.2 million premature deaths worldwide in 2016.
This mortality was due to exposure to PM2.5, which caused cardiovascular and respiratory disease, and cancers, it said.
Meanwhile, the council this week reported the number of days that PM10 exceeded present national limits was down across Otago this year from last year.
However, warmer winter temperatures would have resulted in reduced use of solid-fuel burners for home heating.
Windy weather could also prevent pollution from accumulating, Ms Harrison said.
