Air pollution

Urban population exposed to air pollutant concentrations above selected EU air quality standards, EU-27 and the UK. Source: EEA, Exceedance of air quality standards in Europe

Health issues

Air pollution emissions have been generally decreasing in Europe. However, exposure to air pollution is seen as the most important environmental risk to human health of the European population (WHO, 2016). Europe’s most serious pollutants, in terms of harm to human health, are particulate matter (PM), nitrogen dioxide (NO2) and ground-level ozone (O3).

Exposure to air pollutants leads to a wide range of diseases, including stroke, chronic obstructive pulmonary disease, trachea, bronchus and lung cancers, aggravated asthma and lower respiratory infections. There is also evidence of links between exposure to air pollution and type 2 diabetes, obesity, systemic inflammation, Alzheimer’s disease and dementia. For more information see: Air pollution: how it affects our health.

Although air pollution affects the whole population, certain groups are more likely to suffer from exposure to it. This includes children, elderly, pregnant women, and people with pre-existing health problems. In large parts of Europe, lower-income groups are more likely to face higher exposure to air pollution live next to busy roads or industrial areas (EEA, 2018).

Observed effects

In 2019, approximately 307 000 premature deaths in EU-27 were attributable to long-term exposure to particulate matter with a diameter of 2.5 μm or less (PM2.5). Nitrogen dioxide (NO2) was linked to 40 400 premature deaths, and ground-level ozone (O3) to 16 800 premature deaths (EEA, 2021).

In recent years, the share of the urban population exposed to air pollutant concentrations above EU limit values, and the resulting health impact, has been decreasing for PM2.5 and NO2 (see figure above). For ground-level ozone, the northern hemispheric background concentration is increasing in Europe, while global peak values are decreasing (Andersson et al., 2017; Orru et al., 2019; Paoletti et al., 2014).

There is increasing evidence that negative health effects of air pollution occur also below the EU ambient air quality directive levels, and this is reflected in the new WHO global air quality guidelines (WHO, 2021). As the updated WHO guidelines are stricter for most pollutants, the share of the urban population exposed to unhealthy air pollutant concentrations and the associated health impact will be larger than previous estimates.

Projected effects

Changes in temperature, precipitation, wind, humidity, or solar radiation associated with climate change affect air quality, potentially worsening it (Fu and Tian, 2019). This happens via altered emissions from natural sources (such as wildfires, mineral dust, sea salt, biogenic volatile organic compounds (BVOC)); emissions from human sources (such as ammonia from agriculture); rates of chemical reactions in the atmosphere; and transport, dispersion and deposition processes of air pollutants (Fortems-Cheiney et al., 2017; Geels et al., 2015).

In relation to human health, the combination of heat stress and air pollution is particularly damaging. Simultanous exposure of population to high temperatures and air pollution (PM, NO2 or O3) has been linked to increased mortality rates due to cardiovascular and respiratory causes (EEA, 2020). The ongoing and projected demographic changes, such as an aging population with increasing prevalence of underlying health problems, will also contribute to an increase of the burden of disease related to air pollution.

Particulate matter

Particulate matter concentrations in the air are projected to increase slightly in the future, albeit with some uncertainty (Doherty et al., 2017; Park et al., 2020). This is because climate change has an impact on the emissions of the precursors of PM: the number and severity of naturally occurring wildfires is expected to increase, as are sea salt emissions. Further, higher temperatures increase biogenic and agricultural ammonia emissions (Geels et al., 2015). Also, the chemical reactions leading to the production of secondary PM are intensified by temperature and humidity changes (Megaritis et al., 2014). Finally, decreases in wind speed, for example projected for parts of the Mediterranean region (Ranasinghe et al., 2021), and decreasing precipitation will reduce the dilution and deposition of PM, resulting in higher air concentration levels (Doherty et al., 2017).

Ground-level ozone

Under the changing climate, higher ground-level O3 concentrations are projected during summer, with the largest increase predicted for the warmest scenarios and for Southern and Central Europe (Fortems-Cheiney et al., 2017; Colette et al., 2015). The peak concentrations are projected to increase, which is relevant for health impacts, as short-term exposure to high peak concentrations of ground-level ozone is linked to respiratory and cardiovascular health problems (Doherty et al., 2017). Up to an 11% increase in ground-level ozone-associated mortality is expected in some countries in Central and Southern Europe in 2050 under the RCP4.5 scenario (Orru et al., 2019).

Ground-level ozone is formed in the atmosphere by photochemical reactions of volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of sunlight. Under climate change, BVOC emissions are likely to increase due to a higher number of hot days; increasing atmospheric CO2 levels may also influence the production of BVOC (Fu and Tian, 2019). Increased global methane concentrations and higher temperatures also accelerate ground-level O3 production. Further, the expected greater influx of stratospheric ozone into the troposphere is projected to raise the ground-level ozone levels further across Europe (Fortems-Cheiney et al., 2017).

Nitrogen dioxide

NO2 concentration levels are not expected to be influenced by climate change.  

Other air pollutants

High levels of humidity and flooding of buildings can support the growth of moulds and increase the prevalence of respiratory diseases (D’Amato et al., 2020). Further, in urban areas air pollution (in particular long-term high NO2 levels) may increase the allergenicity of pollen (Gisler, 2021; Plaza et al., 2020), the concentration and seasonality of which is affected itself by the changing climate.

Policy responses

The revised WHO global air quality guidelines form a solid scientific evidence base for making decisions on clean air policy worldwide.  Within the framework of the European Green Deal, the European Union is revising its Ambient Air Directives to align them more closely with the new WHO guidelines. Mitigation measures for reducing CO2 emissions often have a positive effect on the emissions of air pollutants from traffic, energy production, domestic heating, etc., creating a win-win situation.

Air quality assessments, including health impact, are performed at an annual basis by different authorities. Forecast and early warning systems for air pollution, together with medical advice, can reduce the health risks. They can also be used by healthcare systems to prepare for higher numbers of patients in emergency departments. Forecast and early warning systems are operational at the local level as well as at regional scales, such as e.g. the EEA’s European Air Quality Index. In several European countries ozone concentration levels are included in heat-health action plans.

Citizen science projects on air quality provide evidence-based information and create awareness amongst citizens.

References