2.4 times more PM2.5 pollution from domestic wood burning than traffic
Revised figures show domestic wood burning to be the UK’s largest single source of PM2.5 emissions, 2.4 times greater than all PM2.5 emissions from traffic. The new information (33% of PM2.5 emissions in 2013-2014 from domestic wood burning, twice the previous estimate of 17%) highlights the extremely misguided nature of current policies.
The European Environment Agency (EEA) estimates that PM2.5 caused 37,800 premature deaths in the UK in 2012 (420,800 lost years of life), compared to 14,100 premature deaths from NO2 pollution (156,900 lost years of life). The EEA’s estimates were based on methods recommended by the World Health Organization (WHO).
Although perhaps somewhat conservative for NO2 (see note below), these values suggest that current EEC requirements do not reflect the true health costs and are diverting attention away from PM2.5, arguably the most health-hazardous air pollutant. High levels of NO2, O3, and SO2 trigger official public health alerts but high levels of PM2.5 result in ‘notifications’. This might create a false sense of security.
Adding to the confusion, PM2.5 levels up to 35 ug/m3 (well above the WHO guideline of 25 ug/m3) are described as ‘low pollution’. Yet in a study with much lower levels (median PM2.5 of 7.3 ug/m3) an increase of just 3 µg/m3 in annual PM2.5 exposure was associated with a 9% increase in deaths from ischemic heart disease and 3-4.5% increases in all deaths. Describing 35 ug/m3 PM2.5 as low pollution could confuse both the public and policymakers about the most practical and cost-effective ways to reduce the considerable health damage from unhealthy air.
The disproportionate amount of PM2.5 pollution from domestic wood burning continues to escape attention. Few people who install wood stoves are likely to understand that a single log-burning stove permitted in smokeless zones emits more PM2.5 per year than 1,000 petrol cars and has estimated health costs in urban areas of thousands of pounds per year.
Contrary to popular belief, domestic wood stoves also increase the risk that the global temperature rise will exceed the 1.5 or 2 degree limit agreed in Paris. The UN Environment Program and the World Meteorological Organization (UNEP/WMO) recommended phasing out log-burning stoves in developed countries to reduce global warming as well as improve health.
Confusion arises because greenhouse gas inventories have traditionally used a 100-year timescale, despite the fact that current levels of emissions are predicted to cause 1.5 degrees of warming within 15 years and 2 degrees within 35 years. Over the critical period between now and when the temperature limit is likely to be exceeded, the methane, carbon monoxide and black carbon emitted by the average wood stove will cause more global warming than heating half a dozen similar homes with an efficient heat pump.
Rectifying misguided diesel policies will not be easy. Wood stoves last much longer than cars. The sooner policymakers recognize the disproportionate contribution of wood stoves to PM2.5 pollution (a tiny minority of UK households using wood stoves emit over twice as much PM2.5 as all the UK’s cars, trucks and buses), recognize the disproportionate health costs – thousands of pounds per wood stove per year – and consequently heed the UNEP/WMO recommendation to phase our log-burning stoves in developed countries, the better it will be for our health and the health of our planet.
References and additional information
1. UKDEFRA, Department for Environment Food & Rural Affairs. Statistics Release: Emissions of air pollutants in the UK, 1970 to 2014. Available at: https://www.gov.uk/government/statistics/emissions-of-air-pollutants, 2015.
2. EEA, European Environment Agency. Air quality in Europe — 2015 report. EEA Report No 5/2015. Available at: http://www.eea.europa.eu/publications/air-quality-in-europe-2015, 2015.
3. Air Quality News. High particle pollution in London and Birmingham. Available at: http://www.airqualitynews.com/2016/01/20/high-particle-pollution-in-lond.... 2016.
4. London Air. Air Quality Bands Health Information http://www.londonair.org.uk/london/asp/airpollutionhealth.asp?HealthPage... (accessed January 2016_. 2016.
5. Crouse, D.L., et al., Risk of Non-accidental and Cardiovascular Mortality in Relation to Long-term Exposure to Low Concentrations of Fine Particulate Matter: A Canadian National-level Cohort Study. Environ Health Perspect, 2012.
6. 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.
7. 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.
8. Howarth, R.W., Methane emissions and climatic warming risk from hydraulic fracturing and shale gas development: implications for policy. Energy and Emissions Control Technologies, 2015: p. 45-53.
9. AAQG. The Most Effective Ways for Individuals to Reduce their Global Warming. Australian Air Quality Group. Available at: http://woodsmoke.3sc.net/ghg. 2014.
10. WHO, HRAPIE project: recommendations for concentration–response functions for cost–benefit analysis of particulate matter, ozone and nitrogen dioxide, 2013, World Health Organisation. Available at: http://www.euro.who.int/en/health-topics/environment-and-health/air-qual....
11. Pope, C.A., 3rd, et al., Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA, 2002. 287(9): p. 1132-41.
Note: the EEA estimates were based on the World Health Organization (WHO) recommendation to calculate effects of NO2 for levels above 20 ug/m3. PM2.5-related mortality has group A classification with sufficient data to enable reliable quantification of effects. Long-term mortality from NO2 exposure is classed as group B, because there is more uncertainty about the data used to quantify the effects. For example, no effects of long-term exposure to NO2 were identified for the half million subjects in the American Cancer Society study.
Competing interests: No competing interests