WHO:Clean air for health

This text is taken from the WHO report "Health and Environment in Europe: Progress Assessment", 2010, ISBN 978 92 890 4198 0. [1]

Regional priority goal III: We aim to prevent and reduce respiratory disease due to outdoor and indoor air pollution, thereby contributing to a reduction in the frequency of asthmatic attacks, in order to ensure that children can live in an environment with clean air.

Key messages

• The incidence of infant deaths from respiratory disease has been falling in most countries but is still significant (12% of infant deaths overall), particularly in the eastern part of the Region. Asthma and allergies are important and increasing causes of childhood illness.
• Air pollution, especially particulate matter, causes significant health problems throughout the Region, reducing life expectancy in more polluted areas by over one year.
• After substantial decreases in outdoor air pollution in most of the Region in the 1990s, progress in the last decade has been minimal.
• WHO guidelines and EU legislation form the basis for national policies on healthy air throughout Europe. They also drive new policy development, such as that related to second-hand tobacco smoke.
• Damp and mould are now established as major indoor air quality problems which disproportionately affect the health of disadvantaged populations. Although approaches to reduce and eliminate damp and mould from buildings exist, relevant public policies need to be strengthened.
• Even though regulations introducing spaces free of tobacco smoke have proved highly efficient in reducing the health impacts of tobacco, they have yet to be introduced or developed in large parts of the Region.

Clean air and its public health significance – new insights

Knowledge about the links between health and air quality has significantly advanced in the last two decades. There is more evidence about the role of pollutants in the aetiology of respiratory diseases and new insights have been gained into the impacts of fine particulate matter on cardiovascular health. Hundreds of studies throughout the world confirm the association of mortality, or hospital admissions, with levels of the most common urban air pollutants. The results of this research, combined with data on air quality in Europe, indicate that the pollution of air with fine particulate matter leads to a nine-month shortening of life expectancy in Europe. New studies among children indicate that exposure not only increases the prevalence of respiratory symptoms but also raises the incidence of new respiratory diseases. New studies also indicate substantial gains in public health resulting from improvements in air quality, for example, the attribution of 15% of the overall increase in life expectancy to the reduction of fine particulate matter in the United States (2). This evidence has been reviewed and summarized by WHO in the updated Air quality guidelines, and is being used to design new approaches and regulations to reduce the health risks of pollution.

New evidence is also accumulating on the burden of disease due to indoor air pollution. The risks to health of exposure to second-hand tobacco smoke have been widely recognized and are reflected by widespread programmes to eliminate tobacco smoke from indoor spaces. Other hazards common in indoor air, such as biological contaminants arising from damp and mould, have been well characterized by the newly published WHO Guidelines for indoor air quality – dampness and mould. An understanding of these links is an essential element of action to reduce the burden of disease and to benefit public health.

Considering this new research information, this chapter reviews the background patterns of diseases affected by common air pollutants, presents the distribution and trends in exposure in European populations, and characterizes the inherent risks and the opportunities for their reduction.

The burden of respiratory disease

The rates of infant death from respiratory disease have fallen in all sub-regions and in nearly all countries since the mid- to late-1990s. Present rates still, however, account for over 12% of total infant deaths, a substantial burden.

Average post-neonatal death rates from respiratory diseases (per 1000 live births)

There are considerable variations across the Region, with a gradual increase in the death rate from west to east. The poorer economic and environmental situation in eastern Europe contributes to the higher rates seen in that part of the Region. Several countries have virtually eliminated respiratory diseases as a cause of post-neonatal death, indicating the huge potential for further reductions in other countries.

There are significant differences in the causes of respiratory infections between various regions of Europe: bacterial infections are common in developing countries while viral infections cause most acute lower respiratory infections in developed countries. In temperate European countries, there is a marked seasonal variation in acute lower respiratory infections, with a significant rise in incidence in winter months falling to relatively low levels in summer.

Post-neonatal infant death rates due to respiratory diseases in 25 WHO European Member States, 2004−2007 (In Austria, Finland, Luxembourg and Slovenia, reported mortality is 0.)

There is now substantial evidence concerning the adverse effects of air pollution on pregnancy outcomes and infant death. This is sufficient to infer a causal relationship between particulate air pollution and respiratory deaths in the post-neonatal period, as well as with adverse effects on the development of lung function. An increased incidence can be inferred of upper and lower respiratory symptoms (many of which are likely to be symptoms of infection) due to exposure. Older children are also adversely affected by air pollution, and their susceptibility needs to be considered when air pollution regulations are developed.

The effects are attributed to various combustion-related outdoor air pollutants as well as poor indoor air quality, arising in particular from dampness and mould, the use of solid fuel for cooking and heating, tobacco smoke, infectious agents and allergens.

Air pollution is also associated with chronic respiratory diseases, which often begin in childhood. Two important chronic respiratory diseases are asthma and allergic rhinoconjunctivitis6. Globally the prevalence of asthma and allergies has increased over the last few decades. Asthma has become the commonest chronic disease in children and is one of the major causes of hospitalization for those aged under 15 years. The increasing prevalence of allergic diseases in children throughout Europe is no longer restricted to specific seasons or environments. The greatest increases are generally seen in urban areas.

Between 1999 and 2004, asthma prevalence rates in Europe ranged from approximately 5% to 20% in children aged 6–7 years and from approximately 5% to 25% in children aged 13–14 years. Allergic rhinoconjunctivitis shows slightly less variation, with a prevalence of approximately 5% to 10% in children aged 6–7 years and from approximately 5% to 20% in children aged 13–14 years. The rates tended to be higher in older children for both asthma and allergies, and wide within-country ranges were often seen in those countries where sufficient data were available. Overall, the correlation between the prevalence of these two conditions was high.

Asthma symptoms adversely affect young patients in a number of ways, including schoolwork and social activities. Early diagnosis and appropriate treatment is vital, as this leads to much better disease control and outcomes. Good management of asthma and allergies, for example by reducing the level of exposure to common risk factors and providing appropriate medication, can control the disorder and enable people to enjoy a high quality of life.

Effects of asthma on patients in EU countries, 2005

There is a complex interaction between genetic and environmental factors in the development of both asthma and allergies. There is evidence of a causal relationship between exposure to air pollution and exacerbation of asthma, mainly due to exposure to particulate matter and ozone. The incidence of allergic symptoms in children is associated with exposure to allergens in indoor environments, including smoke from fires, damp and mould, dust mites, allergens from pets and second-hand tobacco smoke.

Children who are more frequently exposed to poor indoor air may subsequently be at greater risk of being affected by outdoor pollutants. Other factors that may influence the rates of asthma and allergies include lifestyle, dietary habits, socioeconomic status and climatic factors.

Asthma continues to affect many individuals into adulthood, meaning that the prevalence of asthma in adults is also high. Not all chronic respiratory diseases start in childhood, however. Chronic lung diseases that cause limitations in lung airflow (often collectively referred to as chronic obstructive pulmonary disease) tend to begin in mid-life. Although mortality from these diseases is falling in the Region, it still causes 4% of all deaths and contributes to 5% of the overall burden of disease. Globally, their burden is increasing and, should current trends persist, they are projected to become the third leading cause of death by 2030. Currently, the most important risk factors for chronic obstructive pulmonary disease are tobacco-smoking, indoor and outdoor air pollution, and occupational exposure to dusts and chemicals.

It has only become fully apparent in the last decade that air pollution, especially of fine particulates, plays a major role in cardiovascular disease. Over half (52%) of deaths, and 23% of the overall burden of disease in the Region, arises from cardiovascular disease. Even relatively small increases in the risk of cardiovascular disease will translate into huge absolute numbers of additional people suffering more severely from the disease.

Outdoor air pollution and its impact on health in Europe

Various outdoor air pollutants affect health. The impacts of the two widespread pollutants evaluated here, particulate matter and ozone, are the best known but other pollutants (volatile organic compounds, nitrogen oxide, sulfur oxide, etc.) should also be considered for policy action.

Large amounts of particulate matter (PM) are generated by various human activities. Since particles can travel hundreds and thousands of kilometres in the air, and are partly created from gaseous pollutants in the atmosphere, their effects can be seen far from the source. PM consists of solid and liquid particles that vary in their physical and chemical properties and that are classified by particle diameter (in micrometres – μm). When inhaled, PM10 particles (with a diameter of less than 10 μm) penetrate deep into the respiratory system. Finer particles (with a diameter of less than 2.5 μm) then go on to penetrate the lungs and pass into the bloodstream and are carried into other body organs. Concerned that these particles cause a wide range of health impacts, WHO has developed guidelines addressing their risks.

Long-term average exposure to PM is associated with both the risks of chronic effects on children’s health, such as impaired development of lung function, and the frequency of acute effects, such as the aggravation of asthma or incidence of respiratory symptoms (14).Very young children, including unborn babies, are particularly sensitive to air pollutants. Exposure to PM is also associated with increased hospital admissions and mortality in adults. The risk increases linearly with the concentration of pollution, and there is no evidence to suggest a threshold for PM below which no adverse health effects would occur.

Data from 2007 demonstrate that there are important disparities in PM10 exposure in the Region: average country levels varied from 16 μg/m3 (Finland and Ireland) to 45–52 μg/m3 (Bulgaria, Romania and Serbia) and 72 μg/m3 in Turkey. Within-country differences were also substantial. In total, over 92% of the urban population for which PM10 data are available live in cities where the WHO air quality guideline for PM10 is exceeded.

Contribution of key sectors to emission of PM in the EU27, 2007

WHO air quality guidelines for particulate matter

	Annual average	24-hour mean (not to be exceeded >3 days/year)
PM2.5	10 μg/m3	25 μg/m3
PM10	20 μg/m3	50 μg/m3