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. 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.
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.
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.
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.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 P10 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.
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 |
Overall, the regional average of urban PM10 did not change substantially in the period 1997–2007. Concentrations of another common urban air pollutant, nitrogen dioxide, fell more consistently, but the reduction was small. This contrasts with the pronounced downward trend evident for sulfur dioxide, indicating that policies aimed at the reduction of sulfur emissions have been more effective than those addressing PM or nitrogen emissions.
WHO’s analysis, based on data from the late 1990s, indicates that throughout the Region around 700 deaths from acute respiratory infections can be attributed to PM10 exposure annually in children aged 0–4 years. Quantifying the effects of PM exposure on illness is more difficult, but a reduction of PM10 exposure to 20 μg/m3 could be associated with a 7% decrease in the incidence of coughs and lower respiratory symptoms and a 2% decrease in respiratory-related hospital admissions in children aged under 15 years. A decrease to 10 μg/m3 is expected to reduce the number of days that children aged 5–14 years suffer lower respiratory symptoms (wheezing, chest tightness, shortness of breath and coughs) by 1.9 days per year per child.
Estimates of the health burden from PM exposure in adults are dominated by the increase in the risk of mortality due to long-term exposure to fine PM2.5. People in Europe are generally unaware of the life-shortening consequences, for them, of air pollution. Current exposure to PM from anthropogenic sources leads to the loss of 8.6 months of life expectancy in Europe – from around 3 months in Finland to more than 13 months in Belgium. The most recent estimates of impacts of PM on mortality, based on PM10 and PM2.5 monitoring data in 40 European countries, indicate that close to 500 000 deaths per year are accelerated due to exposure to ambient PM in those countries. The distribution of these deaths is mapped in a figure below. It is important to note that there is no information on PM levels in many parts of the Region, mainly in the east and including the newly independent states, but approximate estimates for these countries suggest that the burden of disease related to PM exposure will be considerable.
A significant reduction in PM to around 50% of current levels could be achieved if all currently technically feasible emission reduction measures were implemented (the maximum feasible reduction scenario). Although PM10 monitoring data from the 1990s are very scarce in Europe, they do indicate that in the previous decade a significant reduction in pollution has been achieved. For example, mean PM10 measured in United Kingdom cities fell from approximately 36 μg/m3 at the beginning of the 1990s to 23 μg/m3 by 2000.
Ozone is another outdoor air pollutant that causes substantial deaths and illness in the Region. Ozone in lower levels of the atmosphere originates largely from human activity and is not only harmful to humans but has adverse effects on materials and vegetation. It is also a greenhouse gas when in the upper troposphere. Children may be more exposed than adults because of their higher rate of physical activity, the greater amount of time they spend outside and their higher metabolic rate.
Ozone is linked to a number of health problems. Short-term exposure can increase respiratory deaths and the incidence of respiratory symptoms. The consequences of long-term exposure are less well-established but suggestive evidence points to further negative effects.
Despite indications of decreasing frequency of days with high ozone concentrations across much of Europe, ozone continues to contribute substantially to regional health burdens. High ozone concentrations (above 70 μg/m3) are associated with approximately 21 000 deaths and 14 000 respiratory hospital admissions annually in the member states of the EU since 2004 (EU25). The risk is proportional to the indicator which gives the value of the sum of the daily maximum eight-hour mean over 35 parts per billion (SOMO35), presented in the figure below for current O3 levels modelled for 2000 and 2020. High ozone levels aggravate respiratory conditions, with the magnitude of the impact in the range of 8–108 million person-days annually in EU countries.
Current policies are only expected to reduce ozone-related mortality by about 1000 deaths or fewer. Reductions in illness are expected to be greater, with particular benefits in the reduction of cough and lower respiratory symptoms in children (by an estimated 40%). Implementation of all technically feasible pollution reduction measures would, however, halve the current mortality by 2020.
Exposure to indoor air pollution
Second-hand tobacco smoke
Children and adolescents (as well as adults) can be exposed to tobacco smoke indirectly through second-hand tobacco smoke (SHS), which is defined as the involuntary or passive breathing of air contaminated with tobacco smoke by someone who is not smoking. SHS is the dominant form of indoor air pollution in spaces where tobacco is smoked, even where areas are properly ventilated. Tobacco-smoking accounts for approximately 30% of all cancer deaths in the general population as well as for a substantial proportion of cardiovascular and respiratory disease. It is also well-established that exposure to SHS creates a huge burden to health. The most recent calculations indicate that more than 72 000 people in the EU25 alone die each year due to exposure to SHS in the home. In addition to exposure at home, workplace exposure to SHS is also linked to an increased risk of death. In the EU in 2008, 6000 deaths were attributable to SHS in offices, bars and restaurants, 40% of which were in non-smoking staff. These estimates do not include the health burden of customers. The burden of illness related to exposure to SHS in public places can be greatly reduced by smoking bans. A recent study analysing acute coronary events in Italy before and after the implementation of the smoking ban in January 2005 found a statistically significant reduction in acute coronary events, amounting to as much as approximately 11% in people aged 35–64 years and approximately 8% in those aged 65–74 years.
In infants and young children, exposure to SHS increases the risk of sudden infant death syndrome, acute lower respiratory tract infections, chronic respiratory symptoms, middle ear disease, reduced pulmonary function and asthma. There is also some evidence that exposure to SHS during childhood may cause lymphoma and brain tumours. Studies in the Region have attributed 25% of all sudden infant death syndrome deaths to SHS and indicate that SHS increases the number of asthma episodes by 6–10%, depending on the underlying smoking prevalence. As a recognized human carcinogen, no level of SHS exposure is considered free of risk.
Recent estimates of children’s exposure to SHS come from the Global Youth Tobacco Survey (GYTS), conducted among young people aged 13–15 years living in countries of central and eastern Europe, central Asia, the Caucasus and the Balkans. According to this study, the proportion of 13–15-year-olds exposed to SHS at home ranged from 37% (in the Czech Republic) to over 90% (in Armenia, the Balkan countries and Georgia), while exposure to SHS outside the home was comparatively higher, ranging from 65% to 96%. Even in countries with relatively low levels of exposure in the home, exposure outside the home is comparatively high. For western Europe, various studies from the late 1990s indicated that the proportion of children aged 0–4 years exposed to SHS at home lay between 20% (Netherlands) and 35% (England), with higher levels often seen in older children.
Unlike some other public health hazards, exposure to SHS is easily preventable. A number of countries worldwide have implemented various forms of smoke-free policies, and research shows that these policies are successful. Smoke-free policies have led to dramatic decreases in exposure to SHS (up to 90% in low-exposure settings) as well as decreases in daily cigarette consumption and in smoking by young people.
Exposure to products of indoor combustion
Cooking and heating with solid fuels, such as dung, wood, agricultural residues, grass, straw, charcoal and coal, is a major source of indoor air pollution. Combustion of such fuels emits a number of different pollutants, but the smallest particles, with a diameter of 2.5 μm or less, appear to have the greatest health-damaging potential. Women and young children, who spend most of their time in the home, are particularly vulnerable. Globally, 52% of the 1.6 million annual deaths related to indoor air pollution in children aged 0–4 years are from the use of solid fuels.
There is consistent evidence that exposure to indoor air pollution from indoor combustion increases the risk of pneumonia, chronic respiratory disease and lung cancer. There is also some evidence for associations with asthma, cataracts, tuberculosis, adverse pregnancy outcomes, ischemic heart disease and cancers of the nose and throat (24). The risks depend partly on the age of those exposed.
The use of solid fuel for cooking in homes in 25 countries of the Region in 2005 for which data were available ranged from just above 0% to almost 50%. Many central Asian countries, where solid fuel is quite frequently used, have recorded substantial drops compared to previous estimates. Another characteristic of the use of solid fuel is that in virtually all countries, the proportion of children exposed in rural areas is many times higher than in cities; in some countries, nearly all the exposure is in rural populations.
Within the Region, the burden of disease attributable to risk factors related to the use of solid fuel is extremely unequally distributed. The highest burden of respiratory illness in children aged 0–4 years occurs in EurB countries,7 both in terms of mortality and illness. These estimates should, however, be interpreted with caution owing to the scarcity of household-level data on use of solid fuels in the other regions.
Mortality and morbidity attributable to cooking with solid fuels in children aged 0–4 years, WHO European Region, 2006
| WHO epidemiological subregion | Burden of disease study, 2006 | |
| Deaths ('000) | DALYs('000) | |
| EurA | 0 | 0 |
| EurB | 11.6 | 319 |
| EurC | <1 | 12.5 |
Moving to cleaner fuels or combustion technologies is the preferred way of preventing the health effects of exposure to the products of indoor combustion. Such a move increases energy efficiency and is often consistent with approaches to reduce greenhouse gas emissions and ambient air pollution.
Exposure to damp
Exposure to damp in the home and to biological contaminants in indoor air arising from dampness is a strong and consistent indicator of risk for a number of respiratory illnesses, including asthma and respiratory symptoms such as cough and wheeze (28). Dampness facilitates the growth of moulds, fungi and bacteria which emit spores, cells, fragments and volatile organic compounds into the indoor air. Moreover, dampness initiates chemical and/or biological degradation of materials, which also causes indoor air pollution. Exposure to microbial contaminants is clinically associated with respiratory symptoms, allergies, asthma and immunological reactions. The risk of a range of respiratory symptoms increases by approximately 50% among the residents of homes suffering from damp. Accordingly, WHO recently released the first Indoor air quality guidelines – dampness and mould. European survey data indicate that exposure to damp is a frequent health risk, with 18% of the EU population exposed in 2007 (vs. 19% in 2005 and 18% in 2006). Exposure varies greatly among countries, however, ranging in 2007 between 5% and 37%. Damp houses are especially frequent in the new EU member states, although many of these also show a notable decrease in exposure over recent years.
International comparisons are difficult with current survey data, so analysis has to focus on national trends. The capacity for international comparisons would be enhanced if procedures for data collection were standardized.
The number of household members, activities such as cooking, laundering and bathing, the use of certain fuels for energy, indoor temperature, amount of insulation, climate, housing characteristics and especially the degree of ventilation all affect the amount of water vapour in indoor air. As is to be expected, poorer population groups are more likely to live in homes with problems of damp in every country surveyed.
Dampness and condensation are connected to other housing quality indicators, and the rehabilitation of housing stock would go a long way towards reducing exposure to indoor air pollution as well as improving other aspects of quality of life. A focus on damp in the homes of poorer residents may yield the greatest health gains. Case studies from around Europe have demonstrated that there are a number of fairly straightforward ways of reducing exposure to damp and mould, which can be successful in a variety of climates.
Two examples of successful programmes to reduce exposure to indoor pollutants
| Mechanical ventilation in Sweden
In Sweden, a country with a relatively cold climate, the impact of mechanical ventilation on indoor humidity, mite allergens and volatile organic compounds in 59 single-family dwellings has recently been assessed. Mechanical ventilation reduced exposure to all three indoor air health risks compared with natural ventilation. National and municipal programmes have been put in place in Sweden based on these findings. |
| Building standards in Israel
Israel, a country with a Mediterranean climate, passed a national thermal insulation standard in 1985 aimed at reducing the risk of surface condensation in dwellings. After implementation of the standard, the proportion of homes with condensation-related mould decreased by 25% and those with extreme mould growth by 20%. The enforcement of the standard created a change in the building market that led to improved building products and to better insulation in new buildings. |
Synergies between climate change mitigation and cleaning the air
There are many links between air pollution, factors affecting the climate and health. The main greenhouse gases (carbon dioxide, methane) are emitted in the same processes that produce air pollutants hazardous to health. Many air pollutants of health concern, such as fine particles or ozone, affect climate directly. On the other hand, air pollutants are often modified by climatic factors (such as temperature and precipitation). For example, temperature modifies the chemical reactions that synthesize ozone, while wind modifies the long-range dispersion of PM. Climatic conditions, such as precipitation or flooding, modify the growth of mould and bacteria and these changes affect the spatial and temporal distribution of allergenic plants. There is growing recognition of the synergies, gains in efficiency and co-benefits of integrated policies and action to mitigate climate change and to alleviate health problems. To achieve the greatest health gains, policies to mitigate climate change should include control of a wider range of combustion-related pollutants in addition to carbon dioxide emissions. A substantial proportion of the major causes of global warming also directly damage health, and it is important to be aware that control of some combustion-related pollutants may lead to quick reductions in global warming.
There is also a potential risk of either the creation, or an increased risk, of health effects from air pollution if climate change mitigation policies do not address health directly. Examples of such potential threat include the proliferation of diesel cars not equipped with appropriate exhaust control systems. While such cars emit less carbon dioxide than petrol-powered cars, they create more fine PM. Similarly, reducing air circulation through buildings to conserve energy could increase the risk of mould.
The consequences of climate change on respiratory disease are difficult to predict but will depend, in part, on the specific region concerned and population-level characteristics. Diseases expected to be affected include asthma, rhinosinusitis, chronic obstructive pulmonary disease and respiratory tract infections. Policies intended to mitigate climate change in various sectors would generally appear to result in net benefits for respiratory health, mainly by reducing population exposure to hazardous air pollutants.
Air quality and health: policy analysis
This policy assessment of outdoor air quality, dampness and mould and SHS is based on responses to the WHO survey on EH policies received from 38 Member States. As with other topics, not all countries submitted information for all policies. The majority completed questionnaires concerning outdoor air quality and SHS, but only 23 countries did so for the dampness and mould questionnaires. No EurG-C countries provided information on this topic.
The policy profiles for these three topics are shown in the figure below. All country groups reported having outdoor air quality policies and a significant number had SHS policies. To some extent, this may reflect the existence of strong EU legislation, the WHO Framework Convention on Tobacco Control and WHO’s air quality guidelines. Implementation of policies addressing dampness and mould generally showed the lowest score – which is of concern, given the importance of this health issue.
