Airborne particulate matter is complex by origin and composition

Particulate Matter (PM) is an air pollutant consisting of a mixture of solid and liquid particles suspended in the air. These suspended particles vary in size, composition and origin. Particles are often classified by their aerodynamic properties because (a) these properties govern the transport and removal of particles from the air; (b) they also govern their deposition within the respiratory system; and (c) they are associated with the chemical composition and sources of particles.

PM can be either directly emitted into the air (primary PM) or be formed in the atmosphere from gaseous precursors (mainly sulfur dioxide, oxides of nitrogen, ammonia and non-methane volatile compounds). Particle mass concentration is usualy expressed as μg/m3. Mostly, particles are sampled and characterized on the basis of their aerodynamic diameter, usually called particle size. PM can be measured with gravimetric devices (measuring the mass of PM per volume unit sampled air) or with devices using light scattering, oscilation frequency or electron attenuation techniques.

Airborne particles are classified by size and/or sampling method

Different names are being used for types or fractions of particulate matter, defined either by particle size or by sampling method. The most commonly used names include:

• TSP (total suspended particulates), comprising all airborne particles;
• PM10, particles with an aerodynamic diameter of <10 μm;
• PM2.5, particles with an aerodynamic diameter of <2.5 μm;
• coarse particles, comprising particles with an aerodynamic diameter between 2.5 μm and 10 μm;
• ultrafine particles, comprising particles with an aerodynamic diameter of <0.1 μm;
• BS (black smoke), a widely used indicator of the “blackness” of aerosols (and therefore as a surrogate for soot);
• BC (black carbon), which is also used as a surrogate for soot.

Smaller particles have more health effects

In general, smaller particles (PM10 and smaller) and combustion-related particles are more important for health effects than larger and mechanically-formed particles. Because PM2.5 can deeper penetrate the airways than PM10, it is assumed that PM2.5 is the more health-threatening fraction. However, both PM2.5 and PM10 fractions have been associated with health effects. Recent studies suggest that BS and BC are also important health-related components.

PM10 concentrations are higher in Southern and Eastern Europe

Annual mean concentrations of PM10 differ between European countries with, in general, lower concentrations in the Northern European countries and higher levels in some Southern as well as some Eastern European countries, as seen in airbase. However, comparisons between countries are hampered by differences in monitoring strategies and sampling methods.

A recent overview of the population exposure to PM10 measured in cities in various European countries can be found on the ENHIS project website. The data refer to the distribution of the population exposed to various levels, and the weighted mean exposure, taking into account this population distribution. The figures are annual averages for 2004 or the latest available year.

This European Environment and Health Information System (ENHIS) project website hosts comparable data and information on priority environment and health issues, selected on the basis of international frameworks on environment and health. The primary focus of the website is on children, see also the EUphocus Children's Health and the Environment.

In most countries, average exposure levels exceed the WHO limit of 20 ug.m3

The data in the ENHIS website show that the country average PM10 exposure levels varied from 13-14 ug/m3 (Finland, Ireland) to 53-56 ug/m3 (Bulgaria, Romania and Serbia). Other countries with averages below 20 ug/m3 include Denmark, Estonia, Latvia, Norway and Sweden. Countries with values over the EU limit value of 40 ug/m3 include, except of the three ones mentioned above, Greece, Italy and Slovenia. The country average levels have not changed substantially over the past few years.

In terms of exposure, this means that almost 90% of people in European cities where PM10 is monitored are exposed to levels exceeding the WHO air quality guideline (AQG) of 20 ug/m3, implying a substantial risk for health. For 14% of the people, the EU limit value of 40 ug/m3 is exceeded.

More information on the occurrence of PM10 in Europe can be found on the European Topic Centre on Air and Climate Change (EIONET) website.

PM10 exposure causes a multitude of health effects

In its Report on Health Effects on Air Pollution of 2003, the WHO concluded that there is a causal relationship between PM exposure and adverse health effects. The present information shows that fine particles are strongly associated with mortality, especially premature death in people with heart or lung disease. Other endpoints associated with PM exposure include hospitalization for cardio-pulmonary disease, increased respiratory symptoms, such as irritation of the airways, coughing, difficulties in breathing, decreased lung function, aggravated asthma, development of chronic bronchitis, irregular heartbeat and non-fatal heart attacks.

As indicated by ENHIS, current exposure to PM from anthropogenic sources leads to the loss of 8.6 months of life expectancy, as an average for Europe. The total nuber of premature deaths attributed to PM exposure amounts to around 348.000 annually in the EU-25 countries.

Children, elderly, urban populations people with lung diseases are especially vulnerable

People with heart or lung diseases, young children and older adults are the most likely to be affected by particle pollution exposure. However, even if you are healthy, you may experience temporary symptoms from exposure to elevated levels of particle pollution. For more information, see background document on Susceptible groups.

With respect to children, information given by ENHIS indicates that throughout the WHO European region, around 700 deaths annually from acute respiratory infections in children 0-4 years can be attributed to PM10 exposure. As to morbidity, a preliminary analysis indicates that a reduction of exposure to PM10 to 20 ug/m3 would be associated with a 7% decrease in the incidence of coughs and lower respiratory symptoms in children under 15 years.

Studies have consistently shown that urban populations in cities throughout the world, both in developed and developing countries, suffer adverse health effects from exposure to PM-10.

There is no threshold for health effects of particulate matter

The risk of suffering adverse health effects has been shown to increase with exposure and there is little evidence for a threshold below which no adverse health effects would be anticipated. In fact, the lower range of concentrations at which adverse health effects have been demonstrated is not greatly above the background concentration. Epidemiological evidence shows adverse effects of particles after both short-term and long-term exposures. Current scientific evidence indicates that guidelines cannot be proposed that will lead to complete protection against adverse health effects of particulate matter, as thresholds have not been identified. For updated information, see the WHO Air Quality Guidelines.

Outdoor air pollution is responsible for a substantial part of total mortality and morbidity

In a recent WHO estimate, outdoor air pollution was found to account for approximately 1.4% of total mortality, 0.5% of all disability-adjusted life years (DALYs) and 2% of all cardiopulmonary disease (WHO, 2002h). Such an estimate can be calculated at the level of a country or city, according to locally available exposure and health data, and can be used as input to decision-making regarding, for example, transport options or standard setting in air quality.

This WHO estimate was calculated at the level of urban populations living in cities with more than 100,000 inhabitants and national capitals. The estimated PM10 levels in those cities and yhe calculated attributable yearly mortality can be found on the WHO website.

The CAFE Programme aims to develop a longterm, strategic and integrated policy advice for ‘achieving levels of air quality that do not give rise to significant negative impacts on and risks to human health and the environment’. In this context, the programme has produced estimates of various health endpoints for 2000 and 20020. For details, see the CAFE programme.

The CAFE Programme estimated health effects to support clean air policies

In May 2001, the European Commission launched the Clean Air for Europe (CAFE) Programme – a knowledge based approach with technical/scientific analyses and policy development that will be proposing the adoption of a Thematic Strategy on Air Pollution, fulfilling the requirements of the Sixth Environmental Action Programme. Its aim is to develop a longterm, strategic and integrated policy advice for ‘achieving levels of air quality that do not give rise to significant negative impacts on and risks to human health and the environment’; including ‘no exceedance of critical loads and levels for acidification or eutrophication’.

The report CAFÉ: CBA: Baseline Analysis 2000 to 2020 presents a benefits analysis for the CAFE baseline and the Thematic Strategy. It assesses the state of the environment in 2000 and 2020, and looks at the benefits of current policies over this period.

The largest sources of PM10 emission include industry, agriculture, transport and domestic sources

For the year 2000, CAFE has estimated that about one third of the primary PM10 emissions (637 kt) in the EU-15 originated from industrial processes and other non-combustion sources (e.g., in agriculture). The transport sector contributes another 521 kt (including non-exhaust emissions), while combustion in the domestic/households sector (mainly fuel wood use in small stoves) is calculated to emit 360 kt. Primary PM10 emissions from stationary combustion of fossil fuels are expected to significantly decline in the coming years. Emissions from mobile sources (including non-exhaust emissions) show a declining, but less steep trend compared to the stationary sources. Overall, it is estimated that PM10 emissions decrease in the scenario with climate measures from 2000 to 2010 by approximately 24 percent in the EU15 and by more than 40 percent in the New Member States. For 2020, total primary PM10 emissions would be 34 percent lower in the EU-15 and 55 percent in the New Member States.

Under current policies, a reduction of health effects caused by air pollution is expected

In the table below, a presentation of estimated total health impacts across the EU25 for the years 2000 and the CAFE Baseline for 2020 is included, as is an outline of the differences between the 2020 and 2000 baselines, i.e. the benefits of current policies.

The health impacts are split into mortality (expressed as premature deaths or life years lost) and morbidity (expressed as a range of health outcomes mainly related to specific diseases). The quantification of health impacts addresses the impacts related to both long-term (chronic) and short-term (acute) exposures.

The results show the number of events that happen in each year (i.e. the annual number of impacts or new cases of premature death and illness), or the change in the number of impacts and cases over time. As outlined in the previous section (consequences for the individual and society), two alternative approaches are used for chronic mortality, to derive years of life lost and premature deaths. These two estimates should not be added.

CBA: Baseline Analysis 2000 to 2020.

LRS = Lower Respiratory Symptoms.

Several groups have increased susceptibility to air pollution

A number of groups within the population have potentially increased vulnerability to the effects of exposure to particulate air pollutants. These groups comprise those who are innately more susceptible to the effects of air pollutants than others, those who become more susceptible (for example as a result of environmental or social factors or personal behaviour) and those who are simply exposed to unusually large amounts of air pollutants. Members of the last group are vulnerable by virtue of exposure rather than as a result of personal susceptibility. Groups with innate susceptibility include those with a genetic predisposition that renders them unusually sensitive.

Young children are especialy sensitive

A WHO Working Group has concluded that very young children and unborn babies are most likely also particularly sensitive to some pollutants (see: Effects of air pollution on children's health and development).

The evidence is sufficient to infer a causal relationship between particulate air pollution and respiratory deaths in the post-neonatal period. Evidence is also sufficient to infer a causal relationship between exposure to ambient air pollutants and adverse effects on lung function development. Both reversible deficits of lung function as well as chronically reduced lung growth rates and lower lung function levels are associated with exposure to particulates.

People with lung and heart disease have enhanced susceptibility to particulate matter

The available evidence is also sufficient to assume a causal relationship between exposure to PM and aggravation of asthma, as well as a causal link between increased prevalence and incidence of cough and bronchitis due to particulate exposure. Groups that develop increased sensitivity include the elderly, those with cardiorespiratory disease or diabetes (Zanobetti & Schwartz, 2001), and those who are exposed to other toxic materials that add to or interact with air pollutants.

When compared with healthy people, those with respiratory disorders (such as asthma or chronic bronchitis) may react more strongly to a given exposure, either as a result of increased responsiveness to a specific dose or as a result of a larger internal dose of some pollutants. In short-term studies, elderly people (Schwartz, 1994) and those with pre-existing heart and lung disease (Dockery et al., 2001; Goldberg et al., 2001) were found to be more susceptible to effects of ambient PM on mortality and morbidity.

In panel studies, asthmatics have also been shown to respond to ambient PM with more symptoms, larger lung function changes and increased medication use compared with non-asthmatics (Pope et al., 2002; Boezen et al., 1999). In long-term studies, it has been suggested that socially disadvantaged and poorly educated populations respond more strongly in terms of mortality (Hoek et al., 2002; Pope et al., 2002; Krewski et al., 2000).

Increased particle deposition and retention has been demonstrated in the airways of people or patients suffering from obstructive lung disease (Brown et al., 2002).

Lastly, those exposed to unusually large amounts of air pollutants, including PM, perhaps as a result of living near a main road or spending long hours outdoors, may experience increased vulnerability as a result of their past exposure.

Combustion-derived particles are more harmful than particles from other sources

PM in ambient air has various sources. In targeting control measures, it would be important to know if PM from certain sources or of a certain composition gave rise to special concern from a health perspective, for example owing to its high toxicity. The few epidemiological studies that have addressed this important question specifically suggest that combustion sources are particularly important for health (Laden et al., 2000; Janssen et al., 2002).

Toxicological studies have also pointed to primary combustion-derived particles as having a higher toxic potential (Cassee et al., 2002). These particles are often rich in transition metals and organic compounds, and also have a relatively high surface area (Donaldson et al., 2002).

In contrast, several other single components of the PM mixture (e.g. ammonium salts, chlorides, sulfates, nitrates and wind-blown dust such as silicate clays) have been shown to have a lower toxicity in laboratory studies (Schlesinger & Cassee, 2003).

Yet, the shares of health impacts from different PM sources are difficult to assess

Despite the differences found among constituents studied under laboratory conditions, it is currently not possible to precisely quantify the contributions from different sources and different PM components to the effects on health caused by exposure to ambient PM.

It is therefore prudent to ascertain that proposed control measures do indeed target those components of PM, which have shown relatively toxic, in other words, to check that reductions in PM are not achieved principally by reducing the less toxic fractions).

It is worth noting that some of the components identified as hazardous in toxicological studies can also be found in rural sites in considerable concentrations. These include organic material and transition metals, even though the latter are clearly enriched near sources. However, some of the components with less toxicological activity are also present at considerable levels in aerosols subject to long-range transboundary air pollution, including secondary inorganic aerosols and sea salt.

EU strategies will reduce adverse health effects

There is sufficient evidence to indicate that reducing emissions of major air pollutants leads to reduced levels of particulate air pollution, population exposure and adverse health effects.

In October 2007 the European Commission proposed an ambitious strategy for achieving further significant improvements in air quality across Europe as announced already in a 2005 press release EC press release. For more information, see the following links: EC air quality directive final adoption, EC directive on air quality standards, EC proposal for a directive on ambient air quality and EC directive on ambient air quality The directive is published in the EU's Official Journal in May 2008 alongside a Commission declaration on progress in developing and adopting further measures that address emissions from various sources..

This 'Thematic Strategy on air pollution' aims to cut the annual number of premature deaths from air pollution-related diseases by almost 40% from the 2000 level by 2020. The Strategy aims to reduce the number of premature deaths related to fine particulate matter and ozone from 370,000 a year in 2000 to 230,000 in 2020.

Based on current predictions, as given in the CAFE (Clean Air For Europe) programme, there would still be over 290,000 premature deaths a year in 2020 if no action is taken. It is estimated that the Strategy will deliver health benefits worth at least €42 billion per year through for example fewer premature deaths, less sickness, fewer hospital admissions, improved labour productivity. This is more than five times higher than the cost of implementing the Strategy, which is estimated to cost around €7.1 billion per annum, or about 0.05% of EU-25 GDP in 2020.

Full details of the Strategy and the CAFE programme available on the European Commission’s website, and on the background document on the CAFE programme.

Also relevant are the strategies to improve environmental factors in relation to health with a special focus on children called the Children's Environment and Health Action Plans (CEHAPE). For more details see ENHIS CEHAPE.

Life expectancy

Healthy life expectancy

Cancer survival

Smoking

Children's Health and the Environment

COPD

Lung cancer

Smoking policies

ENHIS European Environment and Health Information System

EIONET European Topic Centre on Air and Climate Change

WHO World Health Organization

EC CAFE European Commission Clean Air for Europe Programme

ENHIS project European Environment and Health Information System

ENHIS CEHAPE Children's Environment and Health Action Plans

Clean Air For Europe, Cost Benefit Analysis