There’s no need to worry about taking a walk in the neighbourhood for fear of hurting your lungs or your body – even if the air is filled with wood smoke. Short-term exposure to even high concentrations of wood smoke is harmless, argues new study. (Photo: Colourbox)

Short-term exposure to high concentrations of wood smoke has no long-term effect: study

New study suggests that inhaling dense wood smoke for a short duration does not trigger severe symptoms in otherwise healthy people.

Thomas Hoffmann

Numerous studies have shown that wood smoke has the potential to damage our cells, affect our lungs, trigger cancer or even kill us.

Now two Danish studies add a couple of nuances to the debate about how dangerous wood smoke actually is.

The new studies show that if people are exposed to large amounts of wood smoke for three hours, it is certainly uncomfortable and it irritates the lungs, but it has no long-term effect on the lungs’ ability to function, or on our cells or any of our other bodily functions.

“We only observed some very subtle changes in the airways after three hours’ exposure, and the otherwise high concentration we used was not enough to trigger severe symptoms in healthy people. Perhaps the smoke would trigger symptoms in asthmatics, but this was outside the scope of this particular study,” says Torben Sigsgaard, a professor at Aarhus University’s Department of Public Health – Institute of Environmental and Occupational Medicine.

Short-term exposure has no effect on the body
This is how bad it can get in a valley in Tasmania, when (left) there’s a high degree of wood stove pollution and (right) there’s none. If this kind of dense and constant smoke is removed, it reduces mortality rates, say the researchers behind the new study. (Photo: British Medical Journal)

Sigsgaard and his colleagues have studied the airways in 20 people, who were exposed to either clean air, a few particles or many particles from wood smoke, while in sitting in an enclosed room.

In continuation of this study, another team from Copenhagen University has been studying the bodies of the same participants outside of their airways to find out whether the wood smoke e.g. stressed their DNA, created inflammations in the body or affected the blood vessels – effects we already know from traffic-related air pollution.

The results of the examination of the participants’ bodies were just as clear as the examination of their airways: hour-long periods in a room filled with wood smoke does not affect the body – outside of the airways – do a degree that can be measured.

”We have previously observed an effect of traffic pollution at lower concentrations, albeit over a longer period, so we were expecting to be able to measure something here too. But we found no effect at all from exposing people to wood smoke for three hours at a relatively high concentration,” says Professor Steffen Loft, of Copenhagen University’s Department of Public Health.

Higher-than-normal particle concentration

The participants in the study spent three 3-hour sessions in a room where they were exposed to three different types of air: filtered, with a few particles and with many particles.

According to Loft, the high concentration of particles used in the study is higher than what you would be exposed to if you went for a walk on a cold day and your neighbours are firing up their wood-burning stoves.

“The concentration we used can certainly be felt in the airways. The concentration is higher than what you would normally come across, unless your oven is broken, the chimney is malfunctioning or you have an open fireplace indoors,” he says.

Constant wood smoke exposure causes asthma and early death

New research from the US and Australia shows that reducing the emissions of wood smoke in residential areas has a significant effect on the development of asthma in children, and also on mortality.

”So there are still some problems with wood smoke, but since our studies are solid, it appears that we can conclude that short-term exposure to wood smoke is harmless as long as you follow the guidelines,” says Loft.

Both articles about the Danish studies are published in the journal Particle and Fibre Toxicology.

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Read the Danish version of this article at videnskab.dk

Translated by: Dann Vinther

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