Wood heating could be worse than thought for rural air, study suggests

Research at Slovenian village finds particle pollution once air settles in valley reaches levels of the most polluted cities

We think of cities as the places with the worst air pollution, but studies are increasingly highlighting severe air pollution in rural towns and villages, mainly from wood heating. However, government measurement networks mainly focus on cities, overlooking the air breathed by the 20-30% of people in the UK and Europe that live in the countryside.

To plug this gap, a team of scientists moved to the village of Retje in Slovenia for the winter. Retje is home to 690 people, and located in a valley.

Dr Kristina Glojek, from the University of Nova Gorica, described a scene that could be on a Christmas card: “The scenery seems idyllic; a small village with a church on top of a hill surrounded by dense forest and frequently covered with snow. Yet, in the cold part of the year, the village is often enveloped in a brownish fog.”

Public buildings in the village are connected to a district heating scheme but householders burn mainly wood.

Air pollution measurement equipment was installed in the village and on the nearby hillside. For two months, three times a day, Glojek and colleagues set out on a 4-mile (6km) walk carrying a backpack full of measurement equipment. By the end of the investigations they had covered a total of nearly 400 miles.

Glojek explained some of the practicalities: “Low temperatures, early darkness, constant problems with the scientific equipment and also a lot of wildlife, including bears. These hibernate, but not the whole time. When air settled in the valley, particle pollution reached the level of the most polluted cities of the world. After walking for two hours, three times a day we could not wash off the smell. Out of 88 winter days, 34 of them exceeded the legal limits.”

Despite this data, the local perception was quite different. Glojek said: “Seventy per cent believed that air quality in their area was good, and 89% believed that wood smoke did not have a negative effect on health. All the other culprits of local pollution were mentioned, although they are practically non-existent in the area.”

Wood-burning is often portrayed as climate-neutral. In reality it is not. Cutting down trees leads to the loss of an active carbon-sink, and wood-burning also produces climate heating methane. In Retje, the researchers studied the smoke, which contained black soot and brown particles that could absorb the sun’s heat.

Andrea Cuesta, from the Leibniz Institute for Tropospheric Research and part of the research team, said: “We found that the forcing efficiency was positive [warming] and that bright surfaces, such as fresh snow, might be more susceptible to the wood-burning smoke, which could accelerate melting.”

Studies in Ireland and Germany have shown that villages and small towns are especially affected by air pollution from wood and solid-fuel heating during winter.

In Scotland, a proposed ban on stoves as the main source of heating in new homes and extensions has been reversed. Prof Jill Belch, from the University of Dundee, said: “Instead of allowing wood-burning in new builds, rural exceptions, reliable grid expansion, with more generous solar, heat pump, and insulation grants for those off grid or with unreliable power could reduce the significant health hazard of wood-burning for all our people.”

Cover photo: Scientists said 70% of villagers believed air quality in their area was good despite pollution levels exceeding legal limits. Photograph: kud108/Alamy