New Year, New Air

What would a woodsmoke free year feel like?

Wood smoke contains a number of pollutants including nitrous oxides (NOx), polycyclic aromatic hydrocarbons (PAH) and particulate matter (PM). The concentrations of each of these pollutants are monitored by Defra, local authorities, academic institutions and community projects.

Particulate matter is considered to be the most significant pollutant in wood smoke. Particulate matter is everything in the air that is not a gas and the smaller particles, when inhaled, can be transported around your body and lodge in any of your organs, including the brain. Particulate matter is measured by size, and in the UK, we usually measure PM10, particles smaller than 10 micrometres, and PM2.5, particles smaller than 2.5 micrometres. We’ll mostly concentrate on PM2.5 below as these smaller particles are believed to be the most damaging to our health.

We can’t measure all the air in London to get a complete picture of how much PM2.5 there is, and to determine the exact source. Instead we must use a combination of measurements and estimates to build a picture of air quality in London that we can use to plan improvements. Air quality in London is monitored in many ways, including large monitoring stations like the one at Honor Oak Park, council statutory monitoring stations, academic and community sensors, with the network  growing all the time.

Air quality, including particulate matter, has been improving in London for a long time. Our air now is incomparably better than it was in the 1950s, when an estimated 4,000 Londoners died in the weeks following the Great Smog. Polluted air still causes an early death for about 4,000 Londoners each year and we all have a role to play in reducing that toll. The London Atmospheric Emissions Inventory (LAEI) 2019 uses a wide variety of measurements to get a picture of our current air quality and provide the best forecasts of future air quality. This inventory estimates that there were 569 tonnes of small particulate matter (PM2.5) pollution emitted in Greater London in 2019 from domestic wood burning out of a total 3,331 tonnes of PM2.5 emitted in London.  If we gave up burning wood at home this would remove an estimated 17% of the PM2.5 emissions in Greater London.

Chart showing the PM2.5 emissions by source from the LAEI 2019, highlighting that 17% of PM2.5 emissions are estimated to be from domestic wood burning.

That 17% of emissions doesn’t relate exactly to the concentrations of PM2.5 measurable in the air around us. Some particulates settle, or are blown away to other cities, or the nearby countryside, but we know that if we reduce the emissions of PM2.5 in an area, we reduce the concentrations as well.

The World Health Organization (WHO) acknowledges that current evidence suggests that there is no safe level for PM2.5 and has set guidelines for governments to work towards to improve the safety of the air that we breathe. The WHO interim target of 10 µg/m3 was met in parts of outer London for the first time in 2019. However, the WHO target of 5 µg/m3 is not expected to be met, even by 2030, at the current rate of change. It will require concerted action to reduce emissions from all sources if we are going to meet the WHO air quality targets and better protect our health from air pollution, and we all have a role to play. There are many changes that we can make to help meet the WHO targets and to breathe cleaner air this year; leaving fireplaces and wood stoves unlit is one.

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