Breathe Life: Tackling short-lived climate pollutants to improve health and climate

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Breathe Life: protecting health and climate by improving air quality, is a new global campaign led by the WHO and Norway to reduce short-lived climate pollutants that are a significant component of air pollution harming both health and climate.

Air pollution is now the world's largest single environmental health risk, responsible for about 7 million premature, preventable deaths every year, according to the latest data from the World Health Organization. Only 12% of cities achieve WHO guideline levels for air quality – and many cities suffer from air pollution levels that are double, triple or even more above WHO guideline limits.

Significantly, many of the most health-harmful air pollutants also exacerbate climate change.  These include black carbon, a component of fine particulate matter emitted by diesel engines, biomass combustion and other sources. Ozone is another air pollutant as well as a climate pollutant. Ozone is formed through the interaction of diverse urban and peri-urban pollution emissions,  including traffic, power plant and building exhaust, as well as emissions of methane (in itself another powerful short-lived climate pollutant) from  waste, sewage and agriculture.

"The good news, however, is that if short-lived climate emissions can be reduced, then their concentrations in the atmosphere drop rapidly. This means a noticeable improvement on people’s health as well as reduced near-term global warming."

Ozone, black carbon and methane are all called ‘short-lived climate pollutants’ (SLCPs) because they ‘live’ in the atmosphere for a relatively short time – about a week to 10 days (for black carbon) and a decade (for methane). The good news, however, is that if short-lived climate emissions can be reduced, then their concentrations in the atmosphere drop rapidly. This means a noticeable improvement on people’s health as well as reduced near-term global warming. While the world urgently needs to reduce CO2 emissions as a long-term solution to climate change, carbon dioxide persists in the atmosphere for a century or more. So reducing SLCPs can help slow the pace of warming, buying time until CO2 emissions reductions begin to have an impact.

In one recent assessment, the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) estimated that the pace of climate change could be reduced by as much 0.5⁰ C (2010-2050) if a range of affordable measures to reduce SLCP emissions were immediately put into place, including diesel engine and fuel improvements, clean cooking and home heating solutions, improved municipal waste management, and others.

Such measures would also have significant health benefits. Take black carbon emissions, for instance. Black carbon is a key component of fine particulate matter (PM2.5). When inhaled, PM2.5 penetrates deep into our lungs, increasing the risk of disease and premature death. Black carbon enters the air as ‘soot’ particles from the incomplete combustion of biomass and fossil fuels in cookstoves and heaters, diesel engines and vehicle operation, open pit waste burning, and brick production. Black carbon particles also contribute to longer-term climate change impacts by absorbing sunlight and warming the atmosphere. Black carbon emissions thus accelerate the melting of glaciers and amplify changes in monsoon cycles – with implications for water availability and agricultural production.

Methane is a very powerful greenhouse gas, especially in the short term, with a warming potential up to 20 times that of carbon dioxide. About 60% of methane emissions are from human sources – primarily agriculture (livestock manure), fossil fuel production and distribution, and municipal solid waste. While methane itself does not directly affect health, it reacts in the atmosphere with other urban and peri-urban or rural pollution emissions to create tropospheric ozone – harmful to respiratory health. And ozone inhibits plant development, leading to declines in agricultural productivity.