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| Lire aussi la version actualisée du Mise à jour sur les émissions de polluants atmosphériques dans l'Union européenne, leur diminution et leur évolution |
Air quality remains an important issue for public health, the economy and the environment. Exposure to air pollution is largely a multi-pollutant process and poor air quality has a significant impact on health, as it contributes to respiratory and cardiovascular diseases. It has an impact on the economy through medical costs and lost productivity, and it has an impact on the environment as well, affecting directly the health of the ecosystems, or through impacts on the quality of water and soil. European policies of air quality have had considerable success in the past in reducing air pollution. Europe has significantly cut emissions of several air pollutants in recent decades, greatly reducing emissions and exposure to substances such as sulphur dioxide (SO2), carbon monoxide (CO), benzene (C6H6) and lead (Pb).
Despite improvements over several decades, air pollution continues to damage human health and the environment. Particulate matter (PM), ozone (O3), reactive nitrogen substances and some volatile organic compounds (VOC) still pose a significant threat. The long-term EU objective: 'to achieve levels of air quality that do not result in unacceptable impacts on, and risks to, human health and the environment' is still far from being achieved. European citizens often breathe air that does not meet the European regulatory standards. The current pollution levels clearly impact on large parts of the urban population.
What are the main effects of air pollution?
The strongest effects of poor air quality have been felt first in urban areas, where they cause health problems, and second in ecosystems, where air pollution impairs vegetation growth and where eutrophication due to air pollution leads to biodiversity loss.
More specifically, main effects are:
Almost all economic and societal activities produce air pollutants in one form or another. Policies implemented at the level of the European union, of specific countries or of industrial sectors, have resulted over time in decreased emissions of many air pollutants and have led to acceptable air quality levels across Europe for some pollutants, e.g. CO and Pb.
Nevertheless, road transport, industry, power plants, households and agricultural activities continue to emit significant amounts of air pollution. Combustion of biomass by households - burning fuels such as wood and coal - is also an important source of directly emitted particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs, some of which are carcinogenic substances). Agriculture, via the use of fertilizers, is mainly responsible for ammonia (NH3) emissions that can cause health and environmental problems. In the last decade, such emissions, as well as PM from the combustion of fuels to produce energy for domestic needs, have either decreased very little (in the case of agriculture), or not decreased (in the case of domestic fuel combustion). In fact, biomass combustion has become a more important source of air pollution via the emission of PM. This is because wood burning is often relatively cheap, and is thought to be an environmentally friendly source of energy since it is renewable and carbon-neutral.
In recent decades, the EU has introduced and implemented various legal instruments to improve air quality.
Key elements of EU air quality legislation are:
In particular, the Air Quality Directives 2008/50/EC and 2004/107/EC set legally binding limits for ground-level concentrations of outdoor air pollutants.
This report also refers to WHO Air Quality Guidelines, which are often more stringent than EU limit and target values.
Exposure to air pollution is largely a multi-pollutant process, and European citizens often breathe air that does not meet the European regulatory standards. The current pollution levels clearly impact on large parts of the urban population. Air pollution's most important effects on European ecosystems are damages to vegetation resulting from exposure to O3, eutrophication and acidification. Several air pollutants also have an impact on the planet's climate and global warming in the short-term (decades).
The WHO review on the health effects of air pollution of 2013 indicated that health effects can occur at air pollution concentrations lower than those used to establish the 2005 guidelines. It also provides scientific arguments for implementing decisive actions to improve air quality and reduce the burden of diseases associated with air pollution in Europe. Most of the health impact studies reviewed by the WHO focused on respiratory and cardiovascular effects attributed to exposure to air pollution. But evidence is also growing for a range of other effects, caused by exposure to air pollutants at different times of life, ranging from prenatal exposure all the way through childhood and adult life .
Of particular concern in Europe are particulate matter (PM), ground-level ozone (O3), benzo(a)pyrene (BaP) and nitrogen dioxide (NO2).
New estimates of the WHO (2014) indicate that in 2012 worldwide,
around 7 million people died - one in eight of total global deaths – as a
result of air pollution exposure with 4.3 million deaths in households
cooking over coal, wood and biomass stoves. This finding more than doubles
previous estimates and confirms that air pollution is now the world’s
largest single environmental health risk. (…) In particular, the new data
reveal a stronger link between both indoor and outdoor air pollution
exposure and cardiovascular diseases, such as strokes and ischemic heart
disease, as well as between air pollution and cancer.
http://www.who.int/phe/health_topics/outdoorair/databases/FINAL_HAP_AAP_BoD_24March2014.pdf?ua=1
Particulate matter (PM)
In terms of potential to harm human health, PM poses the greatest risk, as given the small size of the particles, it can penetrate deeply into sensitive regions of the respiratory system and can lead to health problems and premature mortality. PM in the air has many sources, including black carbon from from fuel combustion, and is a complex heterogeneous mixture. The sizes and chemical compositions of this mixture can change in time and space, depending on emission sources atmospheric and weather conditions. Emissions of both primary particles and of precursors have decreased in the last decade, but despite those reduction, the percentage of the population exposed to annual levels above the target value has varied between 6 % and 15 % in the period 2009–2011, and when considering the WHO limits, that are more stringent, it is the majority of the urban population that is exposed to health problematic levels of particulate matter.
Ozone is is not emitted directly by any emission source. It is a secondary pollutant formed in the lower atmosphere (ground level or troposphere) through complex chemical reactions from pollutant precursor gases such as NOX and volatile organic compounds (VOC) emitted from the combustion of fossil fuels. Ozone is a powerful and aggressive oxidising agent, and once exposed to ozone, our bodies try to prevent it from entering our lungs. This reflex reduces the amount of oxygen we inhale, which makes our heart works harder. So for people already suffering from cardiovascular diseases or respiratory diseases, like asthma, high-ozone episodes can be debilitating and even fatal and recent epidemiological studies indicate considerably larger mortality effects than previously thought (WHO, 2013). High levels of O3 can also damage plants, leading to reduced agricultural crop yields and decreased tree growth. Lower atmosphere or ground-level O3 contributes also directly and indirectly to global warming2 . In Europe, the emission of precursor gasses has decreased considerably between 2002 and 2011. However, one of the reasons for this, is increased inter-continental transport of O3 and its precursors in the northern hemisphere, which is likely to mask the effects of European measures to reduce O3 precursor emissions. In the period 2002–2011, between 14 % and 65 % of the EU urban population was exposed to ozone concentrations above the EU target value for protecting human health. When taking the WHO guidelines, in 2011, it is 98% of the urban population that was overexposed.
2 Tropospheric ozone should not be confused with the ozone layer in the high atmosphere, which protects the earth surface from aggressive cosmic radiations. You will also find a presentation on the relation between the ozone layer depletion and climate change on :. URL EXACTE PLEASE www.greenfacts.org/.../could-the-cold-snap-in-december-2010-in-western-europe-be-linked-to-climate-change-in-the-arctic/
Nitrogen oxides are emitted through fuel combustion, such as by vehicle engines, industrial facilities and domestic heating. Nitrogen oxides (NO and NO2) have an impact on health, directly or by contributing to the formation of particulate matter and ozone. Recent studies have documented associations between short-term and long-term exposures to NO2 with mortality and morbidity. Different nitrogen oxide compounds (NOx), emitted but also ammonia, are now the principal acidifying components in our air and cause eutrophication of ecosystems. The ecosystems exposed to eutrophication were reduced by 23 % from 1990 to 2010, and those sensitive to acidification, by 92 % in the same two decades, mainly due to the strong reduction in SO2 emissions. The decrease in NOX emissions (34 % from road traffic sources between 2002 and 2011) is considerably greater than the fall in NO2 annual mean air concentration. This is attributed primarily to the increase in NO2 emitted directly into the air from diesel vehicles.
Sulphur dioxide (SO2)
Sulphur dioxide is emitted when fuels (fossil and biofuels) containing sulphur are burned, or from high temperature industrial processes involving raw materials high in sulphur content (such as smelters). Volcanoes are the most important natural source. It contributes to air acidification, which can affect the respiratory system and reduce lung function. Mortality and hospital admissions for cardiac disease increase on days with higher SO2 levels It is also a major precursor of PM. Large ecosystems that were also at risk of acidification are no longer affected as in the period 2002–2011, EU Member States cut their SOX emissions by 50 %.
Carbon monoxide (CO)
Carbon monoxide is emitted due to incomplete combustion of fossil fuels and biofuels. Exposure to CO can reduce the oxygen-carrying capacity of blood, thereby reducing oxygen delivery to the body's organs and tissues. CO can oxidise into carbon dioxide, contributing to the formation of ozone during this process. Atmospheric concentrations of CO have decreased by 30% in the period 2002–2011. Exposure of the European population to CO concentrations above the limit values to protect human health is very localised and sporadic.
The heavy meare emitted mainly as a result of various combustion processes and industrial activities. They persist in the environment and may bio-accumulate in food chains. This EEA overview covers arsenic (As), cadmium (Cd), mercury (Hg), nickel (Ni) and lead (Pb). Arsenic is not a heavy metal per se but it is regularly added to the list of heavy metals, based on its toxicity. Emissions of all heavy metals have decreased in the 2002-2011 period.
The concentrations of As, Cd, Pb and Ni in air are generally low in Europe but these pollutants contribute to the deposition and build-up of heavy metal levels in soils, sediments and organisms, although the reported estimates of heavy metal emissions are of relatively high uncertainty compared to the main air pollutants. Tobacco smoke may contain As, making it a source of As exposure in ambient air.
Despite a decrease in emissions, there are still a lot of ecosystems that are at risk of heavy metals contamination, in large part because heavy metals are very persistent in the environment.
Benzene (C6H6), and benzo(a)pyrene (BaP)
Benzene is released during incomplete combustion of fuels, and benzo(a)pyrene (a polycyclic aromatic hydrocarbon (PAH)) as a by-product, through the burning of organic materials such as biomass. Benzene and benzo(a)pyrene can cause cancer.
Annual mean concentrations of benzene were highest in 2011 at traffic stations, as petrol is still one of the most important sources of benzene but concentrations measured at traffic and urban background stations decreased steadily until 2007, after which time they stabilised.
Meanwhile, in Europe, BaP pollution is an increasing problem, especially in areas where domestic coal and wood burning is, or becomes more common. Emissions have globally increased by 11 % between 2002 and 2011, due to the 24% increase in emissions from the 'commercial, institutional and household fuels combustion' sector. The annual mean BaP concentration averaged over 13 countries, increased by 36 % from 2007 to 2011. Exposure of the European population to BaP concentrations above the target value, is significant and widespread, especially in Central and Eastern Europe.
Globally, emissions of the main air pollutants in Europe declined in the period 2002–2011. This resulted in improved air quality, at least with respect to certain pollutants. However, a significant proportion of Europe's population lives in cities, where air quality standards are still exceeded regularly. Particulate matter (PM) and ozone (O3) pollution are particularly associated with serious health risks, and exposure to high levels of organic pollutants, in particular BaP is a growing health concern in Europe.
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