Scientists are starting to count the health cost of heating our homes with wood. One study, in Canberra in Australia, has found that deaths from everyday exposure to smoke from wood burners is comparable with those during the unprecedented “black summer” bushfires of 2019/2020.
Prof Sotiris Vardoulakis, part of the research team and director of the Healthy Environments and Lives (Heal) National Research Network, described winter in the city: “When I take my two boys to play basketball outdoors in winter, or when we walk the dog before dinner, there is always a smell of wood smoke in the air.”
Vardoulakis and his team found that wood-heating was causing up to a quarter of the particle pollution in Canberra. Combining this information on the health harm from air pollution, they estimated that between 17 and 63 deaths were attributable annually to wood smoke in the Australian Capital Territory, which has a population of about 450,000.
This shortening of life means an annual loss of A$92m to A$333m (£48m to £173m) to Australian society. The health impact of this regular winter burning was comparable to the deaths during the 2019-2020 “black summer” bushfires from smoke.
Vardoulakis said: “Canberra suffers from winter pollution, largely due to wood-heaters. There are many complaints from families with asthma, but also from people without chronic health conditions. They feel hopeless. They cannot open their windows in winter or spend any time outdoors due to the wood smoke.
“The most effective way to reduce community exposure to smoke is by not permitting new wood-heater installations and phasing out existing units. These findings are transferable to other residential areas, where wood burning takes place in the colder months of the year.”
Separate research has estimated that 284 Londoners are dying early each year due to outdoor air pollution from solid-fuel heating. In Greece, many people switched from oil to wood heating during the country’s financial crisis in winter 2012-2013. A study in Thessaloniki found about 200 extra deaths due to the resulting increases in air pollution.
Measurements in homes, including those in the UK, show that stoves and fireplaces increase particle pollution indoors. This adds to pollution from other sources, including cooking and tobacco smoking, but it is less studied compared with outdoor exposure.
A recent study of 50,000 women in the US showed a 43% greater chance of lung cancer for those people who used wood heating compared with those who did not. Increased cognitive impairment, a common symptom of dementia, has also been found in people who use solid-fuel heating in several countries, including China and Ireland.
To understand the overall size of these indoor impacts, two researchers from the University of Lisbon have been estimating how much heating a home with a wood stove or fireplace shortens the lives of the occupants.
Dr Nuno Martins explained what prompted their research: “The initial idea came from hearing a podcast that had Guardian columnist George Monbiot as a guest. We looked more into it and found that there wasn’t much data on how much particle pollution was released by wood-burning equipment into homes.”
Martins and his team started by measuring air pollution from stoves and fireplaces in a small number of homes. This data was used in computer simulations of three homes in north-west Europe: in Birmingham, Groningen and Copenhagen, and combined with data from the health effects of outdoor air pollution.
Heating a living-room open fireplace for four hours each winter’s evening was estimated to shorten the occupant’s life expectancy by between one and 1.6 years. Using a stove could reduce overall life expectancy by up to six months.
This comes with important caveats. Indoor and outdoor air pollution have different sources; chemical composition and exposure. Less is known about how to calculate the impact of air pollution that we breathe in our homes, but the research could help scientists understand the approximate extent of the health impact on people with stoves and fireplaces, as well as possible solutions.
Martins said: “The main message is that open fireplaces should be avoided. An improvement would be to replace them with closed woodstoves or, ideally, replace wood-burning equipment completely.”