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Climate change to increase number of deaths related to poor air quality

October 2017 – An international modelling study lead by the University of North Carolina at Chapel Hill, including the Met Office Hadley Centre, shows that climate change is likely to increase the number of deaths related to poor air quality in the future.

Background

Ozone

Ozone, when in the lower atmosphere, is a secondary pollutant formed by chemical reactions of primary pollutants (such as nitrogen oxides and methane) originating from human activity, such as energy production from fossil fuels.

In people, ozone can irritate the airways and aggravate existing lung conditions such as asthma. At higher concentrations exposure to ozone can lead to inflammations of the airways, shortness of breath and coughing, leading ultimately to irreversible lung damage (RCP, 2016).

Particulate matter

Particulate matter of sizes smaller than 2.5 micrometres (µm) (PM2.5) is a widespread air pollutant. PM2.5 can either be emitted directly (primary PM2.5) or form in the air from gases such as sulphur dioxide. The main human sources, such as fossil-fuel energy production, are similar to those for ozone.

PM2.5 is very harmful to human health because the particles can penetrate deep into the body via the airways. Like ozone, PM2.5 can damage the throat and lungs, but more severe consequences of exposure include diseases of the heart, circulatory system and lungs including lung cancer (RCP, 2016; WHO, 2013).

The impact of future air-pollution emissions on premature mortality has been estimated in a number of studies (e.g. Silva et al. 2016). However the question remains on how much future climate change alone can impact air quality, and consequently, human health.

New Study

A recent study led by the University of North Carolina at Chapel Hill, including the Met Office Hadley Centre, estimates that climate change is likely to increase the number of deaths related to poor air quality in future.

But how? Climate affects the concentration of air pollutants. For example, hotter, drier and more stable conditions can speed up the chemical reactions in the atmosphere that produce pollutants such as ozone and PM2.5. The same conditions can also reduce the efficiency of the processes that remove these pollutants from the atmosphere, such as rainfall.

This study, the most comprehensive to date on this topic, uses multiple climate models to estimate that climate change, under a no-mitigation scenario, could cause approximately 60,000 deaths globally in the year 2030, and over 250,000 deaths in 2100 due to climate change’s effect on global air pollution.

Figure 1. Estimates for mortality due to ozone (top panels) and particulate matter (bottom panels) in 2030 (left panels) and 2100 (right panels).

Figure 1 shows that the increase in mortality is expected to occur in all regions of the world except Africa, with the greatest impacts in India and East Asia.

While the uncertainties around these projections remain very large, this study is the first to use a multi-model approach which increases the robustness of the findings.

The study also shows that mitigating climate change, for instance by reducing emissions of greenhouse gases such as CO2 or methane, would likely reduce impacts on air quality and human health.

References

Royal College of Physicians (RCP). Every breath we take: the lifelong impact of air pollution. Report of a working party. <https://www.rcplondon.ac.uk/projects/outputs/every-breath-we-take-lifelong-impact-air-pollution>. London: RCP, 2016.

Silva, R. A. et al. 2016. The effect of future ambient air pollution on human premature mortality to 2100 using output from the ACCMIP model ensemble. <https://www.atmos-chem-phys.net/16/9847/2016/>. ACP 16: 9847-9862.

World Health Organisation (WHO) Europe. Health effects of particulate matter. Special report for the Joint WHO/ Convention Task Force on Health Aspects of Air Pollution. <http://www.euro.who.int/__data/assets/pdf_file/0006/189051/Health-effects-of-particulate-matter-final-Eng.pdf>. Copenhagen: WHO, 2013.

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