In one Central Otago town, a study has found more people are visiting their doctor with respiratory illnesses when wood-fired heating of homes increases.

Which town was the focus of the newly-published and first-of-its-kind study is immaterial, researchers say, and will not be revealed due to ethical considerations.

Public Health South senior public health analyst Dr Vanessa Hammond said the study looked at 812 GP visits from May to August 2014-2018 and found that for some groups, acute respiratory infection risk rose with increasing woodsmoke pollution. 

“Also, it found that areas with a higher density of wood burners per hectare had higher rates of GP visits for acute respiratory infections.”

The woodsmoke pollution of the town was comparable to all mid-size towns across the area but there are ways to reduce risk.

Air quality monitoring comes under the Otago Regional Council’s (ORC) responsibility and in 2019 the council spoke with Public Health South about possible research into links between wood burning and health risks at a local level in Otago, as air quality monitoring showed domestic heating emissions were still prevalent. 

ORC was able to provide air pollution data from a local monitoring site for the study, which was published in the New Zealand Medical Journal last week.

There has never been a study about the effects on an Otago town, according to an ORC media statement. As the first of its kind, it will enable ORC to improve the dialogue between science and monitoring, policy, and physical outcomes.

“We welcome the findings of this study as it fills a data gap we have had in Otago for some time.” ORC policy and science general manager Anita Dawe said.

“The research will also give us good, and importantly local, data as we begin work on our Air Plan review later this year.”

ORC chair Andrew Noone said air quality “can vary immensely” throughout Otago, depending on locations and the time of the year.

“We generally accept we’re able to enjoy good air quality most of the time. However, it’s vital we focus on improving air quality, where required, so it enables us to live in a healthier region.”

Woodsmoke pollution can be reduced when residents burn only dry wood and keep their fire hot and not smouldering. Further reductions in woodsmoke pollution could potentially be made through thermally efficient homes with good insulation.

During winter people want to keep warm and be able to keep burning fuel, but everyone has responsibilities whether as homeowners, landowners, or in industry or business to play their part in improving air quality.

“The survey conclusions provide some missing pieces of the knowledge puzzle,” Andrew said.

Vanessa told The Central App the investigation of health outcomes and disparities in small populations is important but comes with unique ethical considerations. 

“In this case, the study community may be disadvantaged or stigmatised by being identified. We have chosen not to identify the study town in the research paper to avoid this.

The town’s woodsmoke pollution is comparable to all monitored mid-size Otago towns - Alexandra, Arrowtown, Clyde, Cromwell and Milton. For this reason, we believe that the results are highly generalisable to each of these towns.”

She said residents of all of them would benefit from having cleaner air.

“Given the findings of our study and decades of previous research, our advice to anyone, regardless of where they live, is to try to reduce their exposure to woodsmoke.” 

 ORC campaign - dry wood better than wet

Currently, ORC is running its annual campaign highlighting ways to ensure your firewood is dry in time for winter, and the effects that burning wet wood and other items can have on the environment.

 The Council hopes this campaign will encourage residents to consider their health and that of others in their area when using wood burners.

Air quality often degrades during winter due to increased domestic heating emissions, cold calm weather, and the occurrence of inversion layers. 

For this reason, ORC has monitoring sites in seven Otago towns: Milton, Mosgiel, Dunedin, Alexandra, Clyde, Cromwell and Arrowtown. These monitoring sites measure particulate matter (PM10) concentrations in the air. PM10 are solid or liquid particles in the air, smaller than 10 micrometres, and although they include vehicle and industry emissions, and natural sources such as dust and pollen, the main source in Otago is from home heating emissions.

ORC is currently upgrading several monitoring sites to monitor for PM2.5 continuously through the year. PM2.5 (particles smaller than 2.5 micrometres) is a more direct indicator of the smaller sizes of particulate matter that are emitted during combustion.

Vanessa’s paper on the links between woodsmoke and acute respiratory infections can be read at: https://journal.nzma.org.nz/