Another misguided policy - wood stoves: as many PM2.5 as roads & increased global warming
The misguided nature of favourable tax regimes for diesel vehicles was demonstrated by a comprehensive review that concluded: “global warming has been negatively affected, and air pollution has become alarming in many European locations.” Policymakers failed to take account of the serious health effects of PM2.5 air pollution,(known since 1993 when the Six Cities study was published), and the additional global warming from increased NOx, O3 and black carbon emissions.
We continue to make equally misguided mistakes. Emissions from domestic wood burning are increasing in the UK. They accounted for 17% of PM2.5 emissions in 2013, only marginally less than the 18% from all road transport.
The UN Environment Program and the World Meteorological Organization recommended phasing out log-burning stoves in developed countries to reduce global warming as well as dangerous air pollution. Even if the wood is from a sustainable source, methane and black carbon emissions from log-burning stoves cause more global warming than a gas heater or electric heat pump.
There is much concern about the NO2 standard, yet fine particles (PM2.5) are believed to affect more people than any other pollutant, with chronic exposure causing the most deaths from serious disease. The estimate of 29,000 UK deaths from air pollution is for PM2.5 (not NOx) pollution.
Effective policies should aim to achieve the greatest possible reduction in health damage for the available resources. London’s PM2.5 average (15.5 μg/m3) is much higher than the World Health Organization guideline of 10 μg/m3, which is now considered inadequate. An analysis of 268,050 deaths of people living in areas with 10 μg/m3 or less PM2.5 found that, compared with 6 μg/m3, exposure to 10 μg/m3 increases death rates by 3.7%. New studies using high-resolution PM2.5 data generally show larger increases in mortality than COMEAP’s estimate of 0.6% per 1 μg/ m3 additional annual PM2.5 exposure.
PM2.5 pollution also increases the risk of lung diseases, heart attacks, strokes, cancer and even neurological diseases. A recent study found Alzheimer’s increased by 15% for every 1 μg/ m3 increase in annual PM2.5 exposure.
The annual mean concentration of PM10 from wood burning (1.1 μg/ m3) in London is more than 6 times greater than the city-wide reduction of 0.17 μg/m3 predicted from the first two phases of the London Low Emission Zone to reduce PM from traffic. With 17% of PM2.5 emissions from wood burning and 18% from road transport, solving the wood burning problem could generate more benefits for less cost than solving the problem of diesel emissions.
Instead, misguided policies are allowing the problem to get worse. Log-burning stoves permitted in smokeless zones emit more PM2.5 per year than 1,000 petrol cars, with estimated annual health costs of thousands of pounds per stove per year. Buyers often think log-burning stoves are good for the environment, but in reality they create alarming levels of PM2.5 pollution and their methane and black carbon emissions increase the risk of exceeding 2 degrees of global warming.
Dr Gary Fuller studied sources of PM2.5 pollution in the UK, commenting: “Home wood burning needs to be addressed before more people invest in stoves or make open fires a feature in their living rooms.”
BMJ readers and other health professionals need to convey this message to policymakers so that future policies do not repeat the mistakes of the past, but instead use the best and most cost effective ways to minimize the public health damage from air pollution.
1. Cames, M. and E. Helmers, Critical evaluation of the European diesel car boom - global comparison, environmental effects and various national strategies. Environmental Sciences Europe, 2013. 25(1): p. 15.
2. Dockery, D.W., et al., An association between air pollution and mortality in six U.S. cities. N Engl J Med, 1993. 329(24): p. 1753-9.
3. Department for Environment Farming and Rural Affairs, Emissions of air pollutants in the UK 1970 to 2013. Available at: www.gov.uk/government/uploads/system/uploads/attachment_data/file/388195.... . 2014.
4. UNEP/WMO, Integrated Assessment of Black Carbon and Tropospheric Ozone. Summary for Decision Makers. UN Environment Program & World Meteorological Organization. http://www.unep.org/dewa/Portals/67/pdf/Black_Carbon.pdf (accessed 13 March 2012). 2011.
5. AAQG. The Most Effective Ways for Individuals to Reduce their Global Warming. Australian Air Quality Group. Available at: http://woodsmoke.3sc.net/ghg. 2014.
6. American Heart Association. Long-term exposure to air pollution may harm your brain. Available at: http://newsroom.heart.org/news/long-term-exposure-to-air-pollution-may-h.... 2015.
7. Hawkes, N., Air pollution in UK: the public health problem that won’t go away. Vol. 350. 2015.
8. DEFRA. FOI release. Anthropogenic and non anthopogenic PM2.5 estimates for England. Department for Environment, Food & Rural Affairs and Dan Rogerson. Produced by uk-air.defra.gov.uk. Available at: https://www.gov.uk/government/publications/anthropogenic-and-non-anthopo.... 2013.
9. Shi, L., et al., Low-Concentration PM2. 5 and Mortality: Estimating Acute and Chronic Effects in a Population-Based Study. Environmental health perspectives, 2015.
10. COMEAP, Committee on the Medical Effects of Air Pollutants. The mortality effects of long-term exposure to particulate air pollution in the UK. www.gov.uk/government/uploads/system/uploads/attachment_data/file/304641.... 2010.
11. AAQG. Health experts advise that current wood heater models are too polluting to be allowed. Australian Air Quality Group. Available at: http://woodsmoke.3sc.net/health. 2015.
12. Kioumourtzoglou, M., et al., Long-term PM2.5 Exposure and Neurological Hospital Admissions in the Northeastern United States. Environ Health Perspect; http://dx.doi.org/10.1289/ehp.1408973. 2015.
13. Fuller, G.W., et al., Contribution Of Wood Burning To PM10 In London. Atmospheric Environment, 2014.
14. Fuller, G.W., Pollutionwatch: Please don’t keep the home fires burning, in The Guardian. Available at: http://www.theguardian.com/environment/2015/jan/11/pollutionwatch-dont-k....
Competing interests: No competing interests