February 20, 2018

expert reaction to study looking at open fireplaces and living room air quality

Researchers publishing in Science of the Total Environment examine the impact of wood combustion in an open fireplace on the air quality of a living room.

Prof Anthony Dayan, Retired Professor of Toxicology, University of London, said:

“The report by Castro and his colleagues reinforces what we have known for some years about the potential risks to health of open fires, especially those burning wood, even in an ordinary room.

“The amount and chemical nature of the smoke and particles emitted will vary depending on factors they did explore and others that were not covered, such as burning different types of wood, the size of the room, the extent of ventilation and draughts through windows, doors and other openings.  The position of exposed subjects in the room will also affect the risk posed by the chemical and particulate pollutants emitted.

“The authors compared the atmospheric findings with industrial workplace standards set in Germany to evaluate the extent of the potential risk but that may not be appropriate because at home people do not normally stay in a room for the period assumed in setting workplace safety limits – 8 hours per day, 5 days per week for up to 40 years.

“However, the new work is to be welcomed for reminding us of the health hazard of open wood burning fires.”

Prof Roy Harrison FRS, Professor of Environmental Health, University of Birmingham, said:

“I have some reservations about the study.  The most significant is that the researchers studied only one fireplace in one home and there is no evidence presented to suggest whether this is typical or an extreme case.  Nonetheless, the results do not come as a particular surprise as earlier research has shown that open fires are liable to contaminate the room with combustion products.

“I am also of the view that some of the instrumentation used here is rather less than state-of-the art, but in other aspects the research was conducted soundly.  The implications for health are not easily evaluated as the effects of short-term exposures to moderately elevated pollutant concentrations are not well defined by the existing epidemiological literature.  It is worth also pointing out that the PM10 concentrations reported are well below those experienced on a regular basis in cities such as Beijing and Delhi in the winter months, and in those cases, the exposures can be far more prolonged.

“My personal view is that the recommendation to wear a mask during lighting and first refuelling of the fire is a rather excessive precaution, although people who wish to minimise their exposure in every way possible might take this advice.  The mask will not give any protection against carbon monoxide which is arguably the most insidious of the pollutants measured, and which is responsible for many deaths each year in the UK due to poorly vented combustion appliances.  In this case, however, the elevated carbon monoxide concentrations persisted only for a few minutes which does not represent a significant threat to health.”

Prof Ian Colbeck, Professor of Environmental Science, University of Essex, said:

“This isn’t a surprising result.  Anyone who grew up in homes where open fires were used as a source of heating will be aware of the problem of smoke blowing into the room when lighting the fire.  Nowadays traditional fires are coming back into fashion despite their extremely low energy efficiency.  The burning of wood and coal in homes accounts for around 40 per cent of particulate matter emitted in the UK.  For wood burning stoves new European wide legislation, with lower emission limits, is due to come into force in 2022.  Defra are currently consulting on the use of solid fuels for domestic heating.  It wants to encourage households to move away from coal and wet wood to less polluting fuels such as low-sulphur coal or dry wood.

“The levels of particulate matter reported in this study are considerably lower than those found in the homes in developing countries where wood or coal is used not only for heating but also for cooking.  The World Health Organization estimate that 4.3 million deaths occur worldwide every year as a result of household exposure to smoke from dirty cookstoves and fuels.”

Prof Paul Monks, Professor of Atmospheric Chemistry and Earth Observation, University of Leicester, said:

“The study clearly demonstrates the impact of wood burning on the indoor environment, in particular in the ignition and clean-up stages and when the system is cold.  Clearly, there will be some variation with fireplace design.  Wood burning is increasing in the UK and open fireplaces are a very inefficient way of heating a room.  Eco-design directive compliant stoves produce more heat and emit fewer particles into the room, though still present a challenge for the outdoor environment.  The study challenges people to think about why they are burning wood in urban areas.  Some caution must be exercised about the recommendation to wear masks.  Many are not very effective at stopping the very small particles.”

Prof Anthony Frew, Professor of Allergy & Respiratory Medicine, Royal Sussex County Hospital, said:

“Open domestic fires are well known to cause high levels of pollution within the home and are a well-recognised cause of COPD (chronic obstructive pulmonary disease), especially in the developing world where women are badly affected by indoor cooking fires.  This paper looks at the fashionable ‘retro’ practice of burning wood in open-fire hearths and shows that they cause high levels of particulate pollution and carbon monoxide exposure within the home, both while burning and while clearing away the resultant ash.  In addition, wood burning contributes to outdoor pollution with particulates, sulphur dioxide and nitrogen oxides, so it affects other people not just those in the room with the fire.  How much this matters in the big picture is not addressed here, but the work is a timely reminder that a cosy fire in the winter is not without health risks.”

Prof Christopher Collins, Professor of Environmental Chemistry, University of Reading, said:

“An interesting study that highlights an issue perhaps overlooked by fireplace users and timely with the recent increase in wood burning stoves in urban areas.  However the study is for an open fireplace and although the levels are considered comparable to textile workers they are only for a short space of time i.e. during ignition, rather than across the working day.  The precautions proposed are rational but perhaps not workable – will people really wear masks when emptying the fireplace?”

Dr Gary Fuller, Environmental Research Group, MRC PHE Centre for Environment and Health, King’s College London, said:

“Although this is an experiment on one open fire it adds to the growing body of evidence on exposure to air pollution from home wood burning.  There is an urgent need for more research to see how the return to wood burning in urban areas could be affecting our health.

“Pollution from wood burning can build up in neighbourhoods.  Studies in the US have pointed to the way that wood smoke coming into your home from your neighbours’ wood burners are also an important exposure route.”

* ‘Impact of the wood combustion in an open fireplace on the air quality of a living room: Estimation of the respirable fraction’ by A. Castro et al. was published in Science of the Total Environment on Tuesday 20 February 2018. 

Declared interests

Prof Anthony Dayan: “I was Professor of Toxicology and Head of Department for 15 years during which I also served on official committees concerned with the health effects of air pollution.  I have been a consultant to many industrial and pharmaceutical firms and to British Gas on Carbon Monoxide but never to any company involved with domestic fires or stoves.”

Prof Roy Harrison: “I am not aware of any interests that I have relevant to this work other than possibly membership of Defra’s Air Quality Expert Group which recently produced a report on the impacts of domestic wood burning on outdoor air.”

Prof Ian Colbeck: “Funding from NERC, EU.  Fellow of the Institute of Physics.”

Prof Anthony Frew: “None relevant to disclose.  Validity to comment: professor of allergy respiratory medicine; air pollution researcher and former government adviser on health effects of air pollution.”

Prof Paul Monks: “I have undertaken EU funded research on wood burning and chair the government science advisory committee on AQ.”

None others received.