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close this bookHealth and Environment in Sustainable Development - Five years after the Earth Summit (WHO, 1997, 258 pages)
close this folderChapter 4: Poor environmental quality, exposures and risks
close this folder4.2 Air pollution
View the document(introductory text...)
View the document4.2.1 Urban ambient air quality: often poor
View the document4.2.2 Indoor air pollution: "rule of one thousand"
View the document4.2.3 Human exposures to particulate air pollution
View the document4.2.4 Health risks of air pollution
View the document4.2.5 Environmental tobacco smoke: on the increase
View the document4.2.6 Ionizing radiation: natural and human-caused exposure
View the document4.2.7 Air quality management: many factors

(introductory text...)

Air pollution is a major environmental health problem affecting developed and developing countries alike (see Sections 3.5 and 3.6). Concern now focuses not only on the ambient air quality of cities but also on indoor air quality, in both rural and urban areas. In fact, the highest air pollution exposures occur in the indoor environment in developing countries.

Air pollution and its effects on health is a very complex subject since there are many different pollutants and their individual effects on health are difficult to discern. But it is known that air pollution impacts heavily on exposed populations. When inhaled, air pollutants affect the lung and respiratory system; they are also taken up by the blood and transported throughout the body. Furthermore, air pollutants are deposited on soil and plants and in water, thereby further contributing to human exposure if contaminated food and water are ingested.

The emphasis in this section is on suspended particulate matter (SPM). Information, in some detail, is presented on global human exposures to this pollutant and of the increased mortality associated with such exposures. The reasons for this focus are that:

· particulate pollution affects more people globally on a continuing basis than any other pollutant

· more monitoring data are available globally on particulate pollution concentrations than on any other pollutant

· more epidemiological evidence has been collected on particulate pollution exposures and their health effects than on any other pollutant and its health effects.

Table 4.1
Common atmospheric pollution sources and their pollutants

Source category

Source

Emitted pollutants

Agriculture

Open burning

SPM, CO, VOC

Mining and quarrying

Coalmining

SPM, SO2, NOx, VOC


Crude petroleum and natural gas production

SO2


Non-ferrous ore mining

SPM, Pb


Stone quarrrying

SPM

Manufacturing

Food, beverages and tobacco

SPM, CO, VOC, H2S


Textiles, leather industries

SPM, VOC


Wood products

SPM, VOC


Paper products, printing

SPM, SO2, CO, VOC, H2S, R-SH

Manufacture of chemicals

Phthalic anhydride

SPM, SO2, CO, VOC


Chlor-alkali

Cl2


Hydrochloric acid

HCl


Hydrofluoric acid

HF, SiF4


Sulfuric acid

SO2, SO3


Nitric acid

NOx


Phosphoric acid

SPM, F2


Lead oxide and pigments

SPM, Pb


Ammonia

SPM, SO2, NOx, CO, VOC, NH3


Sodium carbonate

SPM, NH3


Calcium carbide

SPM


Adipic acid

SPM, NOx, CO, VOC


Lead alkyl

Pb


Maleic anhydride, terephthalic acid

CO, VOC


Fertilizer and pesticide production

SPM, NH3


Ammonium nitrate

SPM, NH3, HNO3


Ammonium sulfate

VOC


Synthetic resins, plastic materials, fibres

SPM, VOC, H2S, CS2


Paints, varnishes, lacquers

SPM, VOC

Manufacture of chemicals

Soap

SPM


Carbon black, printing ink

SPM, SO2, NOx, CO, VOC, H2S,


Trinitrotoluene

SPM, SO2, NOx, SO3, HNO3

Petroleum refineries

Miscellaneous products of petroleum and coal

SPM, SO2, NOx, CO, VOC

Non-metallic mineral products manufacture

Glass products

SPM, SO2, NOx, CO, VOC, F


Structural clay products

SPM, SO2, NOx, CO, VOC, F2


Cement, lime and plaster

SPM, SO2, NOx, CO,

Basic metal industries

Iron and steel

SPM, SO2, NOx, CO, VOC, Pb


Non-ferrous industries

SPM, SO2, F, Pb

Power generation

Electricity, gas, steam

SPM, SO2, NOx, CO, VOC, SO3, Pb

Petrol retail trade

Fuel storage, filling operations

VOC

Transport

Combustion Engines

SPM, SO2, NOx, CO, VOC, Pb

Community services

Municipal incinerators

SPM, SO2, NOx, CO, VOC, Pb

Source: adapted from Economopoulos, 1993.

It must be remembered, however, that the presence of other pollutants in air is closely linked to particulate pollution, and that these other pollutants contribute to the adverse health effects that are observed. Additionally, some specific health effects, such as cardiovascular disease from exposure to carbon monoxide (CO), are primarily attributable to exposures to pollutants other than SPM. A brief mention is therefore also made of the ambient concentrations of other pollutants and of their health effects.

4.2.1 Urban ambient air quality: often poor

The largest sources of human-created air pollution are transportation, energy generation and energy-intensive industrial operations (see Section 3.6). The concentration of these activities in or around cities means that they heavily pollute the outdoor air of many urban areas.

Air pollutants consist of SPM (dust, fumes, mist and smoke), gaseous pollutants and odours. SPM and gaseous pollutants are emitted by a wide range of sources (Table 4.1). In recent years, attention has shifted to that portion of SPM made up of particles that are so small that they can penetrate deeply into the lung. These particles are more closely linked to the health effects of SPM than larger size particles (WHO, 1997f). Accordingly, many countries now monitor and regulate particles smaller than 10 mm (PM10) (see, for example, USEPA, 1996).

Depending on their source and interactions with other components of air, particles can have quite different chemical compositions and health impacts. Yet until recently, understanding of the relationship between the chemical composition of particles and health impacts was limited. As a result, particles have often been treated as a single group. A major exception to this is lead particles, which are known to be especially hazardous to children's health (IPCS, 1995b). Consequently, stringent health-based standards for airborne lead have been established in some countries. Chemical components of SPM that are of concern also include arsenic, nickel, cadmium and those present in diesel exhaust (IPCS, 1996b).

Other health-damaging pollutants include gaseous inorganic pollutants such as sulphur dioxide (SO2), CO, and nitrogen dioxide (NO2), as well as hydrocarbons (HC), such as benzene and butadiene, other volatile organic compounds (VOCs) (see Table 4.1), and secondary pollutants. Secondary pollutants are formed by chemical reactions in the atmosphere. For example, SO2 can oxidize and dissolve in water to form sulphuric acid mist. Reactions between nitrogen oxides (NOx) and HCs in the presence of sunlight produce ozone (O3), the major health-damaging component of photochemical smog (Mage & Zali, 1992; Stanners & Bourdeau, 1995; WHO, 1995d; Loomis et al., 1996).

A major review of air pollution in megacities was undertaken by WHO and UNEP (WHO/UNEP, 1992). Where possible, this information has been updated; the most recent data for 17 large cities are presented in Fig. 4.1.

In developed countries the general picture is one of decreasing SO2 and SPM concentrations, and constant or increasing NOx and O3 concentrations. In many countries in transition and in developing countries, however, not only are SO2 and SPM concentrations rising due to growing fossil fuel combustion, but so too are NOx and O3 concentrations, as a result of increases in traffic exhaust emissions and industrial HC emissions (Schwela, 1996a).


Fig. 4.1 Air pollution in 17 large cities around the world

Source: based on unpublished data from WHO Air Management Information System.

Very severe local air pollution problems involving specific types of pollutants can occur around point sources. Also, periods of dangerously high air pollution levels can occur in areas whose topographical features constrain atmospheric dispersion of pollutants. Under certain meteorological conditions, such as temperature inversion and low wind speed, high air pollution levels can persist for several days or more. Such situations occur periodically in many locations (Mage & Zali, 1992).

Box 4.1
Oil well fires and air quality: Kuwait

Towards the end of the Gulf War in 1991, hundreds of oil wells, tank farms and related oil facilities in Kuwait were destroyed and ignited by the retreating Iraqi forces. Nine million barrels of stored crude oil and refined products were burned immediately, and about 6 million barrels of oil and 100 million m3 of natural gas burned daily until the fires were extinguished about 10 months later. Some 6-65 thousand tons of SO2 and 500-3000 tons of NOx were emitted daily.

Most of the plumes from the fires consisted of dense black smoke, although some were white because of their higher water vapour content and those burning only gas were clear. The combined plumes sometimes reached 3000 m in height and 15 km in width. Most of the plumes emitted at the edge of the oil field were drawn inward toward the centre of the field by winds resulting from the intense "heat island" created by the fires. In calm meteorological conditions, the plumes resulted in dense smoke levels in Kuwait City; visibility dropped markedly and blue skies became heavily overcast. The smoke was frequently trapped between an elevated atmospheric inversion high over the city and the normal nocturnal inversion layer near ground level. At night this entrapment acted as an umbrella over the city, protecting the inhabitants from the worst of the pollution. When north-west winds blew, the smoke was carried to other countries in the region and some of it was even precipitated with snowfall in the Himalayas.

Source: Dr Abdul Rahman Al-Awadi, Executive Secretary, Regional Organization for the Protection of the Marine Environment, Kuwait.

Fires are another source of air pollution and can lead to severe problems if the smoke is blown into populated areas (Box 4.1).

4.2.2 Indoor air pollution: "rule of one thousand"

Indoor air pollution can be particularly hazardous to health because it is released in close proximity to people. The "rule of 1000" states that a pollutant released indoors is 1000 times more likely to reach people's lungs than a pollutant released outdoors. The major source of indoor air pollution in developing countries is household use of biomass and coal for heating and cooking, usually involving open fires or stoves without proper chimneys (see Section 3.6). Pollutant concentrations can be extremely high, exceeding WHO guidelines by more than a factor of 100. Women and children are affected most. It has been estimated that as many as 1000 million people, mostly women and children, are regularly and severely exposed to such concentrations (WHO, 1992f).

In addition to fumes from combustion, indoor pollutants originate from building materials, paints, solvents used in the home and environmental tobacco smoke. Indoor air quality is also affected by outdoor pollution sources. Principal pollutants and their sources are given in Table 4.2

4.2.3 Human exposures to particulate air pollution

Health effects are likely to occur if people are exposed to air pollution for a significant amount of time. In terms of health risk assessment, the duration of exposure is therefore as important as the level of air pollution. Thus if the total exposure of the world's population to air pollution is estimated by relating total person-time spent in different types of setting (i.e. developed or developing country, rural or urban setting, indoor or outdoor) to the average air pollution concentration of these settings, a comparison of total population exposures in different settings can be made, and the populations and settings with the highest health risk identified.

The distribution of the total person-time of the world population in different settings is shown in Fig. 4.2. Few data, however, are available, particularly for developing countries, on the indoor: outdoor time distribution of populations. The information presented in Fig. 4.2 is therefore a gross approximation; it suggests that more than 70% of person-time is spent indoors. The percentage of the population involved in agricultural activities in developing countries was used to estimate the time spent outdoors and indoors in those countries (Smith, 1993).

In addition to time-distribution data, the estimation of human exposures requires information on typical SPM concentrations in different settings, which is provided below.

Urban outdoor: To obtain an indication of human exposure to SPM as a function of the level of development, information on urban SPM concentrations was organized according to the level of national development (Fig. 4.3). Urban outdoor SPM concentrations do not decrease uniformly with development; the peak occurs in the mid-development group as highlighted by the location of cities with high SPM levels (Fig. 4.1). The picture for total exposures is different. These are seen to decrease with increased development levels since the contribution of severe indoor air pollution decreases (Fig. 4.3).

Urban indoor: The relationship between outdoor and indoor air pollution is important for estimating human exposure since urban indoor concentrations are substantially influenced by outdoor concentrations (Table 4.2). Consequently, depending on the kind of household fuel used and amount of tobacco smoke present, they are often as high or higher than outdoor concentrations, sometimes even in developed countries. In many developing country urban areas, particularly in South Asia and East Asia, biomass fuels are commonly used (see Fig. 3.10). In Africa, for instance, many urban households use charcoal, producing substantially lower particulate emissions than wood, but still emitting high CO levels. Fossil fuels are also a major source of urban indoor air pollution. In China, most urban households use coal, often in unvented appliances. Selected indoor air pollution concentrations for China are shown in Table 4.3.

Table 4.2
Principal pollutants and sources of indoor air pollution, grouped by origin

Principal pollutants

Sources: predominantly outdoor

SO2, SPM/RSP

Fuel combustion, smelters

O3

Photochemical reactions

Pollens

Trees, grass, weeds, plants

Pb, Mn

Automobiles

Pb, Cd

Industrial emissions

VOC, PAH

Petrochemical solvents, vaporization of unburned fuels

Principal pollutants

Sources: both indoor and outdoor

NOx, CO

Fuel burning

CO2

Fuel burning, metabolic activity

SPM/RSP

ETS, resuspension of dust, condensation of vapours and combustion products

Water vapour

Biological activity, combustion, evaporation

VOC

Volatilization, fuel burning, paint, pesticides, insecticides, fungicides

Spores

Fungi, moulds

Principal pollutants

Sources: predominantly indoor

Ra

Soil, building construction materials, water

HCHO

Insulation, furnishing, ETS

Asbestos

Fire retardant, insulation

NH3

Cleaning products

Polycyclic hydrocarbons, arsenic, nicotine, acrolein

ETS

VOC

Adhesives, solvents, cooking, cosmetics

Hg

Fungicides, paints, spills or breakages of Hg containing products

Aerosols

Consumer products, house dust

Allergens

House dust, animal dander

Pathogenic organisms

Infections

Source: adapted from WHO, 1995p.

Fig. 4.2
Distribution of time spent by the world population


Developed countries


Developing countries

Here is shown the average time spent during one year in the eight most important environmental settings in the mid-1990s. Note that only about 2%. of all people's time is spent outdoors in developed country cities where the vast bulk of air pollution control efforts have taken place.

Source: Achwela, 1996

Rural indoor: Although many people associate air pollution with outdoor urban environments, some of the highest concentrations actually occur in rural, indoor environments in developing countries (Table 4.4). These high concentrations are often due to the burning of unprocessed biomass fuels (wood, crop residues, dung) that emit considerable quantities of pollutants (see Fig. 3.11). In China, coal burning is a major source of indoor air pollution (Table 4.3). Indeed, so much pollution can be produced by indoor air pollution sources that the outdoor air quality of entire local neighbourhoods and adjoining areas may be highly polluted. Indoor air pollutant concentrations can be high even if ventilation is relatively good. In developed countries, air pollution in rural indoor environments is influenced less by type of cooking fuel than by type of heating stove and the extent of tobacco smoking.


Fig. 4.3 Air pollution trends with development

The line shows that urban outdoor SPM concentrations tend to rise in the first stages of development and then fall at later stages. As shown by the bars, however, actual exposures to city dwellers fall at every stage because indoor sources dominate exposure at early stages of development. Countries have been categorized into four groups according to the Human Development Index (HDI).

Source: Schwela, 1996.

Table 4.3
Indoor particulate air pollution from coal burning in China (sample studies)

Place

Urban/rural

Particulates mg/m3

Shanghai

Urban

500-1000

Beijing

Urban

17-1100*

Shenyang

Urban

125-270

Taiyuan

Urban

300-1000

Harbin

Urban

390-610*

Guangzhou

Urban

460

Chengde

Urban

270-700*

Yunnan

Rural

270-5100

Rural Beijing

Rural

400-1300

Jilin

Rural

1000-1200*

Hebei

Rural

1900-2500

Inner Mongolia

Rural

400-1600*

* particles less than 10 pm in size

Source: adapted from WHO 1995c.

Rural outdoor: In general, SPM concentrations in rural outdoor environments in developed and developing countries are considerably lower than in the other environmental settings. This is because population density is lower than in cities, and large combustion sources generally absent. High levels of air pollution generally occur only on those few days when large-scale agricultural burning is undertaken. Exceptions include village environments influenced by emissions from local households, especially in continental areas with ground-level atmospheric inversions, and communities affected by dust blown from desert or dry areas. Metal smelters, chemical industries and power stations in rural areas may also cause significant local outdoor air pollution.

Total global exposure: Typical SPM concentrations for each of the above types of setting, for developed and developing countries, are listed in Table 4.5. Also shown are the estimated proportions of global human exposure (obtained by combining the typical concentrations of the particular environment with population and time-distribution data) that occur in each setting. Note that about three-fifths of total global exposure apparently occurs in the rural areas of developing countries. The relative level of exposure to SPM from all sources is decreasing as development increases (Fig. 4.3). Changing household energy sources would be the primary means of reducing exposures in developing countries.

4.2.4 Health risks of air pollution

Particular air pollution

In recent years a large number of studies of the health impacts of suspended particulate air pollution have been undertaken in developed country cities (WHO, 1997f). These studies show remarkable consistency in the relationship observed between changes in daily ambient suspended particulate levels and changes in daily mortality. Hopefully, future studies will consider indoor/outdoor differences and also be carried out in developing countries. In the meantime, we can only estimate the health risks of air pollution in these countries. Several uncertainties are involved in such estimation, as explained in Box 4.2, which describes how estimations using two different methods - were made for this report. The results obtained using Method 1 are shown in Fig. 4.4, in the form of an estimate of total global mortality from suspended particulate air pollution exposures.

Divided into the environmental settings presented in Table 4.5, Fig. 4.4 shows that, given the assumptions listed for Method 1 in Box 4.2, about 3 million deaths are due to suspended particulate air pollution globally each year: 2.8 million due to indoor exposures and 0.2 million due to outdoor exposures. In developing countries about 1.9 million deaths each year may be due to indoor exposures in rural areas and 0.6 million to indoor exposures in urban areas. In Table 4.6 estimates based on Method 2 in Box 4.2 of the annual global number of deaths due to air pollution are presented for eight major economic regions. This method arrives at a similar total number (2.7 million). The largest number of deaths is estimated to occur in India, followed by sub-Saharan Africa. The results using either method show clearly that indoor air pollution in developing is most probably the major cause of total excess deaths from exposure to air pollution.

Table 4.4
Indoor particulate concentrations from biomass combustion in developing countries

Region

No. of studies

Duration

mg/m3

Pacific

2

12 h

1300-5200

South Asia

15

Cooking period

850-4400**



Cooking

630-820



Non-cooking

880**



24 h

2000-2800**



Various

2000-6800



Urban infants, 24 h

400-520**

China

8

Various

2600-2900



Various

1100-11000**

Africa

8

Cooking/heating

800-1700



Cooking/heating

1300**



24 h

1300-2100**



Urban area, 24 h

400-590**

Latin America

5

Cooking/heating 440-1100**




24 h

720-1200**

* rural unless otherwise stated
** particles less than 10 mm in diameter

Source: adapted from Smith, 1996.

Fig. 4.4
Estimated global annual deaths due to indoor and outdoor pollution exposure


Indoor exposures


Outdoor exposures

Source: Smith, 1996.

Table 4.5
Particulate concentrations and exposures in the eight major global environmental settings

Region

Concentration (mg/m3)

Exposure (%) of global total

Total


Indoor

Outdoor

Indoor

Outdoor


Developed







Urban

100

70

7

1

7


Rural

80

40

2

0

2

Developing







Urban

250

280

25

9

34


Rural

400

70

52

5

57

Total(%)



86

14

100

Note: Population exposures are expressed as a percentage of the world total. Here exposure is defined as equal to the number of people exposed, multiplied by the duration of exposure and the concentration breathed during that time.

Source: updated from Smith, 1993.

The estimated 2.7-3 million deaths due to air pollution represent about 6% of the 50 million global deaths that occur annually (see Section 5.1). However, the uncertainty of these estimates is perhaps a factor of two in either direction. In other words, the estimate of the number of deaths attributable to air pollution ranges from 1.4-6 million annually. As noted in Section 5.2, many of these deaths are due to acute respiratory infections (ARI) in children. Cardiovascular diseases, lung cancer and chronic respiratory diseases in adults also contribute to these deaths (see Sections 5.3 and 5.10). Since there are interactions with other risk factors for all these diseases, a reduction in the number of deaths following improvement in one factor might reduce the number attributable to air pollution, and vice versa. A combination of preventive actions would be the most effective and sustainable means of reducing the number of such deaths.

Box 4.2
Two approaches to determining the global number of deaths due to particulate exposures

The methods used in this book for estimating excess mortality caused by suspended particulate matter (SPM) are presented below.

METHOD I: ENVIRONMENTAL SETTINGS (Fig. 4.4)

The health risks from particulate air pollution exposures have been estimated by Smith (1996), by applying the mean risk per unit ambient concentration determined from the results of a number of urban epidemiological studies (WHO, 1996h; Hong, Corvalán & Kjellström, 1997). The range of risk was found to be 1.2-4.4% increased mortality per 10 mg/m3 incremental increase in the concentration of suspended particulates below 10 mm in diameter (PM10). The total risks were calculated using the mean SPM concentration estimated for the major environmental settings listed in Table 4.5 together with population data and the incremental risk factors. The following assumptions were made.,

· the risks determined for ambient levels are appropriate for total exposures

· risk factors determined for developed-country urban populations are appropriate for other populations

· the health risk is proportional to the exposure

· the true risk is at the lower end of the range of available studies, i.e. 1.2% increased mortality per each incremental increase of 10 mg/m3

· at high concentrations, i.e. above 150 mg/m3, the risk is reduced by 50%

· PM10 levels are half of those indicated for total suspended particulates in Table 4.5s.

METHOD 2: GEOGRAPHIC/ECONOMIC REGIONS (TABLE 4.6)

GEMS/AIR data, combined with data for individual cities from the new WHO Air Management Information System were used by Schwela (1996a, 1996b) to estimate excess mortality caused by exposure to SPM, by economic grouping, for different regions of the world. The model used to estimate the number of excess deaths due to air pollution incorporates the number of people at risk, the number of deaths per 100000 without air pollution influences, and the percentage increase in deaths due to air pollution. The number of people at risk was assumed to be the number of people exposed to SPM concentrations that exceeded the 1987 WHO guidelines for annual mean SPM concentration. Data pertaining to increases in total mortality associated with incremental increases of 100 mg/m3 in SPM in urban areas for China, Central/Eastern Europe, and established market economies, were used (Hong; Corvalán & Kjellström, 1997). The percentage increases in deaths per 100 mg/m3 of SPM were assumed to be approximately the same for China, India, and the South-East Asian/Western Pacific region, while those for Established Market Economies were assumed to be approximately half of those in the eastern Mediterranean, Central/Eastern Europe and Latin America.

Health impacts of other types of air pollution

In addition to particulates, other "classic" air pollutants of concern from a health point of view, include O3, NO2, SO2, and CO.O3 and other photochemical oxidants are formed by the action of short-wave radiation from the sun on NO2. A continuum of health effects at different levels of exposure to O3 may occur, including respiratory symptoms, changes in lung function and airway inflammation. O3 exposure has also been associated with increased hospital admissions for respiratory conditions, including the exacerbation of asthma. Factors such as the time spent outdoors and people's activity level will influence the type of health outcome which may result at a particular concentration level.

Evidence for a clearly defined concentration-response relationship is lacking for NO2. For acute exposures, only very high concentration levels affect healthy people. Asthmatics and people with chronic obstructive lung disease are more susceptible to acute changes in lung function, airway responsiveness and respiratory symptoms. Epidemiological studies of chronic exposures suggest a range of effects.

The acute effects of SO2 include lung function changes, increases in specific airway resistance and symptoms such as wheezing and shortness of breath. Long-term effects have been more difficult to ascertain as SO2 exposure is most often combined with exposure to SPM.

CO combines with haemoglobin to form carboxyhaemoglobin, which reduces the oxygen carrying capacity of the blood. The binding with other haeme proteins is directly related to changes in the functioning of affected organs, such as the brain and cardiovascular system, and the developing fetus. Neurobehavioural effects of CO include impaired concentration and cognitive performance at certain exposures. In the fetus, the affinity of haemoglobin for CO is increased, and birth weight may be affected.

Health effects have also been demonstrated for many inorganic pollutants including arsenic, cadmium, lead, mercury, manganese and nickel. The health effects of volatile organic pollutants have also been studied. The aforementioned health effects of the "classic" air pollutants, inorganic pollutants, volatile organic pollutants and other classes of air pollutant are discussed in the revised air quality guidelines for Europe, which are due to be published by WHO shortly (WHO, 1996f). In reality, of course, people are exposed to various mixtures of air pollutants, with additive, synergistic or antagonistic effects (see Section 4.10).

Table 4.6
Estimated global annual deaths (in thousands) from air pollution by environmental setting and region*

Environmental setting

Economic regions*


LAC

China

FSE

MEC

EME

India

OAI

SSA

Total

Rural indoor

180

320

n.a.

n.a.

0

496

363

490

1849

Urban indoor

113

53

n.a.

n.a.

31

93

40

32

363

Urban ambient

113

70

100

57

47

84

40

n.a.

511

Total

406

443

100

57

79

673

443

522

2723

na = not available
* according to World Bank classification

Source: Schwela, 1990.

4.2.5 Environmental tobacco smoke: on the increase

Active tobacco smoking is a major cause of ill-health (WHO, 1996s). Concern is also increasing about the effects of passive smoking, i.e. exposure to environmental tobacco smoke (ETS). ETS is that portion of tobacco smoke released into the surrounding air, either directly (side-stream smoke) or after being exhaled by smokers. It is much less damaging per unit of emissions than the mainstream smoke inhaled directly by the active smoker. But since it is often emitted in spaces inhabited by non-smokers, it can have a large impact per unit of emissions even compared to large outdoor sources. Table 4.7 shows the consumption of tobacco per capita across the world and gives an approximate indication of the relative emissions and exposures to ETS for different countries and regions.

Table 4.7
World tobacco consumption per capita (adults 15 years and over)


Cigarettes per adult (over 15 years of age)

Annual % change


1970-1972

1980-1982

1990-1992

1980-1982 to 1990-1992

More developed countries

2860

2980

2590

-1.4

Established market economies

2910

3000

2570

-1.5

Formerly socialist economies of Europe

2450

2830

2770

-0.2

Less developed countries

860

1220

1410

1.4

China

730

1290

1900

3.9

India

1010

1310

1370

0.4

Other Asia and islands

780

1130

1190

0.5

Middle Eastern Crescent

950

1240

1200

-0.3

Sub-Saharan Africa

410

490

500

0.2

Latin America and the Caribbean

1430

1540

1310

-1.6

World

1410

1650

1660

0.1

Source: based on data from WHO, 1990s.

Over 4000 components of cigarette smoke have been identified; many are established carcinogens or other types of toxin. Those of health concern include SPM, CO, nicotine, nitrosamines, benzene, formaldehyde and benzo[a]pyrene. Studies show that the extent of ETS exposure and its health effects are determined by the number of cigarettes smoked in indoor environments. Rough estimates of population exposure to ETS may be inferred from smoking prevalence.

Box 4.3
Successful examples of air quality management in developed countries: USA and Germany

Health-oriented environmental pollution control programmes aim to promote a better quality of life by reducing pollution to the lowest level possible. Environmental pollution control programmes and policies, whose implications and priorities vary from country to country, cover all aspects of pollution (air, water, etc.) and involve coordination among sectors involved in industrial development, city planning, water resources development and transportation planning.

Some countries, such as the USA and Germany, have based air pollution management on a clean air implementation plan, consisting of the following elements:

· description of area with respect to topography, meteorology, socioeconomic conditions
· emissions inventory
· comparison of emission concentrations with emission standards
· air pollutant concentrations inventory
· simulated air pollutant concentrations
· comparison of air pollutant concentrations with air quality standards
· inventory of air pollution impacts
· causal analysis of compounds and sources responsible for observed effects
· control measures
· cost of control measures
· cost of public health and environmental effects
· cost-benefit analysis of control measures versus public health and environmental effects
· transportation and land-use planning
· enforcement plan
· resource commitment
· projections for the future regarding population, traffic, industries, fuel consumption
· follow-up strategies.

The impact of clean air implementation plans in the USA and Germany (known as State Implementation Plans in the former) have resulted in the following reductions in air pollution:

USA

1985®1994

Germany

1975®1994

National average CO levels

28%



SO2

75%



National total CO emissions

15%



NO2

10%



Pb concentrations in urban areas

86%



Suspended particulate (PM10)

40%



Total Pb emissions

75%



Lead

80%



Total NOx emissions

3%



Cadmium

80%



Highway vehicle NOx emissions

9%





Fuel combustion emissions

8%





National composite mean for O3

12%





Exceedances of the ozone National Ambient Air Quality Standard

56%





Particulate (PM10) (1988-1994)

20%





Estimated PM10 emissions from traditional inventories

12%





National annual mean SO2

25%





National total SO2

9%






Source: adapted from Schwela & Köth-Jahr, 1994

In adult non-smokers, chronic exposure to ETS increases mortality from lung cancer by between 20-30% (US EPA, 1992) (see also Section 5.9). Other likely health effects may also ensue, such as cardiovascular disease, chronic respiratory disease, pulmonary lung function reduction in adults, and ARI in children. This implies that about 3% (100000) of the global air pollution deaths in Fig. 4.4 could be attributed to ETS exposure. As smoking rates are rising in many developing countries (Table 4.7), the health risks of ETS can be expected to increase.

4.2.6 Ionizing radiation: natural and human-caused exposure

The contribution of natural, medical and industrial sources of radiation to human exposure is shown in Table 4.8. Exposure to ionizing radiation can occur due to uranium mining and milling, reactor operation and fuel reprocessing, when radionuclides are released into air. However, total emissions are small compared with those emitted by natural sources (UNSCEAR, 1996). Of course, the converse can be true in the event of a nuclear accident. (see Section 3.6).

Table 4.8
Annual average adult radiation doses

Source of exposure

Annual effective dose (mSv)


Typical

Elevated*

Natural sources




Cosmic rays

0.39

2.0


Terrestrial gamma rays

0.46

4.3


Radionuclides in the body (except radon)

0.23

0.8


Radon and its decay products

1.3

10.0


Total of natural sources

2.4

16.9

Sources related to human activities




Medical

0.3

1-2


Occupational

0.001

10


Nuclear power

0.001

0.02


Large fuel reprocessing plants

0.2

0.5


Nuclear tests

0.005

0.2

* elevated values are representative of large regions; even higher values occur locally

Source: based on data from UNSCEAR, 1993.

The health effects of ionizing radiation exposures have been studied intensively, but uncertainty remains about the exact health risks at low exposure rates (see also Section 5.9.6). If it is assumed that an increase in mortality is proportional to exposure all the way down to natural levels, then the current pattern of (nonradon) human-caused exposure (mostly medical X-rays and medical use of radioactive isotopes) implies an attributable global number of cancer deaths of 0.12 million per year (ICRP, 1990).

In some areas of the world, such as the Arabian Sea coast of Kerala in India and the Atlantic coast of Espírito Santo in Brazil, high natural ionizing radiation dose rates in air of up to 4000 n Gy/h (due to the thorium or uranium content of mineral sands) have been recorded.

Only in recent years has the extent of the largest naturally-occurring exposure - radon in residences - been realized (UNSCEAR, 1996). Radon gas (222Rn) is radioactive, has a half-life of 3.8 days, and can accumulate in homes. Elevated indoor radon levels in buildings originate from radon in underlying rocks and soils, and sometimes from outdoor air. Radon levels may also be elevated due to the presence of radon in building materials, tap water or domestic gas supplies. National surveys have shown that the average indoor radon concentration in residences ranges from 10 to 140 Bq/m3 (EC, 1995b), with maximum concentrations greater than 100000 Bq/m3 having been detected in individual dwellings in some countries. Remedial action is recommended if radon exposure in dwellings exceeds a yearly average concentration of 200-600 Bq/m3 Of 222Rn in air (ICRP, 1990; IAEA, 1996).

Radon exposure increases the risk of lung cancer (UNSCEAR, 1996) (see Section 5.9.6). Quantifying the health impact from radon exposure is difficult, though, because the risk due to radon exposure interacts heavily with the risk due to active smoking. In the USA, for example, most lung cancer due to radon exposure seems to occur in the 25% of the adult population who smoke. Applying the US risk ratios to the world population indicates that approximately 0.2 million lung cancer deaths (80% in smokers) could be attributable to radon exposure (UNSCEAR, 1996). (The health effects of non-ionizing radiation are discussed in Section 5.9.7.)

Box 4.4
Successful air quality management in a developing country: Chile

The Chilean government has restructured its environmental legislation. New legislation is based upon the Framework Environmental Law, which is intended to provide the basis for a gradual improvement in environmental quality, but avoiding conflict between industry, government and pressure groups.

Specific measures already implemented to reduce industrial emissions of air pollutants include the Ministry of Mining Decree 185. Adopted in 1992, this decree seeks to drastically reduce 502 emissions, to ensure that air quality meets United States Environmental Protection Agency standards in the mining areas in the north of the country, and the strict Scandinavian standards for the protection of forests in the south. An estimated 90% of 502 emissions in Chile originate from copper smelting, a process which is also responsible for high ambient concentrations of heavy metals, such as arsenic.

Pollution in the capital city

It is generally agreed that diesel vehicle emissions represent an important source of air pollution in Santiago, and have increased significantly since the deregulation of the city's bus services in the 1980s. Poor engine maintenance and the use of second-hand engine parts has exacerbated the problems created by the doubling of bus numbers between 1980 and 1988. Vehicle bans are applied during air pollution episodes; the more severe the air pollution, the more rigorous the ban. In addition to restrictions on vehicle use during air pollution episodes, the emergency bans also stipulate 20-50% cuts in industrial emissions and in the use of polluting domestic fuels. These measures have been implemented on several occasions but their success is hard to evaluate. Chile has also established a number of ambient air quality standards which are very similar to US National Ambient Air Quality Standards.

Overall, Santiago has good and improving air quality management capabilities with an excellent monitoring network, an emissions inventory and improving regulatory and administrative structures. The proliferation of highly polluting sources in the city combined with extremely unfavourable meteorological and topographical features continue, however, to result in high concentrations of a number of pollutants.

Source: adapted from MARK, 1996

4.2.7 Air quality management: many factors

Air quality management aims at the elimination or reduction to acceptable levels of airborne pollutants whose presence in the atmosphere can adversely affect human health, animal or plant life, the environment and materials of economic value.

Beyond considerations of emissions from fixed or mobile sources, air quality management programmes should also take into account a wide variety of factors, including topographical and meteorological conditions which influence pollutant concentration levels in particular localities, the socio-demographic characteristics of exposed groups, and community and government participation in air pollution control efforts. For example, meteorological conditions can greatly affect ground-level pollutant concentrations. Additionally, air pollution sources may be scattered over a community or a region and their control may necessitate the involvement of more than one administrative or political unit.

Comprehensive air pollution control programmes that adopt a multidisciplinary approach, and that are based on the collaborative efforts of different entities, both private and governmental, are therefore called for. These will normally need to be based on inventories of emissions and sources, knowledge of concentration levels of pollutants, their potential health-and-environment effects, and so on. Comprehensive monitoring programmes need to be in place which yield information on trends in pollutant concentrations over space and time, and which are relevant also to likely exposures. Proposed source control measures and abatement strategies need to take into account their technical feasibility, as well as social, economic and other considerations. Various technical, legal, and economic instruments can be used to control pollution, in combination with improved administrative and jurisdictional arrangements that aim at more coordinated and integrated air pollution control. Generally, the various sectoral responsibilities for aspects of control at different tiers of government must be clarified, and communities and the private sector involved in control strategies.

Examples of air quality management and some of the factors that such activity should take into account are given in Boxes 4.3 and 4.4.

The management of indoor air quality is usually left primarily to building occupants. This is in direct contrast to protection of the ambient environment, which is usually considered a government responsibility (Krzyzanowski, 1995). The decisions of the latter tend to be driven by the household economics, convenience or habits, rather than a desire to minimize health risks relating to specific activities and materials used indoors. Expecting that all health hazards will be eliminated from households and that adverse health impacts will be avoided completely, following optimal decisions taken by the individuals involved, is therefore unrealistic. Instead, public health professionals must identify the most prevalent conditions adversely affecting health in a given population and propose coordinated efforts for reducing the health risks, using the most efficient means. In developed countries, legislative and economic mechanisms are already in place to encourage individuals and building administrators, to manage indoor environments in a health-promoting way. In developing countries, the actual air quality situation should be assessed in order to inform policymakers, create awareness of indoor air problems, assess their magnitude, provide information on health effects, and develop remedial actions and education programmes.