Mostafa K. Tolba, United Nations Environment Programme,
Nairobi, Kenya and
Osama A. El-Kholy, Cairo University, Egypt
in association with
E. El-Hinnawi, National Research Centre, Egypt,
M. W. Holdgate, IUCN-The World Conservation Union, Switzerland,
D. F. McMichael, Environment and Heritage Consultants, Australia, and
R. E. Munn, University of Toronto, Canada.
Published by Chapman & Hall
on behalf of
The United Nations Environment Programme
The Constitution of the World Health Organization (WHO) defines health as 'a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity'. Such a state is conditioned by a variety of factors ranging from the genetic, the social and the emotional, to the natural and manmade environment. Consequently, consideration of such a state of health will have to take into account factors such as development objectives and strategies, and economic relations (Figure 1) as well as the prevailing social structures, beliefs and value systems in the community.
In this chapter we restrict the discussion to a review of the manner in which human health and well-being have been affected by changes in the human environment over the last two decades. The main elements of the environment involved here are the natural (the air we breathe. the water we drink. the food we eat, the radiations we are exposed to) and the man-made (the habitat, the place of work, the means of transport, the social and recreational facilities). These elements impact on human health in two ways: through physical and chemical agents (radiation, chemical compounds and emissions of gases, liquids or solids) and through pathogenic agents.
The generic impact of these agents on human health has been addressed in the preceding chapters and the responses in different fields and at different levels (scientific, social, national and transnational) are reviewed, and future trends summarized. We proceed here to show the overall results in the health field of these impacts in different parts of the world and over the last two decades.
Although infant and child mortality rates have declined steadily over this period (Figure 2), and life expectancy has increased from an average of 56.7 years in 1970-75 to an average of 61.5 years in l985-90 (Chapter 16), the overall picture is still alarming in many respects (WHO, 1992).
In the developing countries:
On the global scale:
The global figures for infant and child mortality and life expectancy quoted above conceal wide variations from country to country. Moreover, the causes of death differ dramatically between developed and developing countries. Infectious and parasitic diseases are still by far the leading cause of mortality in developing countries. Indeed, in those countries the risk of dying from one of these diseases is virtually identical to the risk in the developed countries of dying from cardiovascular diseases - the leading cause of death in the latter countries (Figure 3).
In developing countries, the commonest diseases are water-related. Eighty per cent of all illness is attributed to unsafe and inadequate water supplies, and half the hospital beds are occupied by people with water-related illnesses (US AID, 1987). As mentioned earlier. diarrhoeal disease is the leading cause of infant and childhood deaths. Cholera, malaria, dracunculiasis (guinea worm) and other parasitic infections remain prevalent. despite eradication campaigns that have achieved some improvement. Furthermore. the ratio of cardiovascular diseases to infectious and parasitic diseases has been increasing steadily of late in developing countries (Figure 4).
In the two decades under review the situation regarding some specific communicable diseases improved while for others it deteriorated. Those diseases that are the target of the expanded programme of immunization (EPI) (viz. poliomyelitis, tetanus, measles, diphtheria, pertussis and tuberculosis) are largely declining as vaccination coverage increases (Figure 5). On the other hand, HIV infection and AIDS, unknown before 1980, are showing alarming increases. Sub-Saharan Africa is suffering the main brunt of this disease, but other regions, both in the developed and developing countries, face similar futures (Figure 6). Cholera has recently flared up in the Americas, with a resulting dramatic increase in the number of cases reported to WHO.
Aggregate global or regional figures tend to hide differences between and within countries. The graphic portrayal of schistosomiasis and malaria hot spots illustrates this (Figures 7 and 8). These problems are largely local in nature, depending on a variety of features among which environmental factors are the most significant. Thus while the global total of malaria cases has been relatively stable over the last decade, important epidemic outbreaks have contributed to the high incidence of illness and death in specific situations.
Similar variations can be found in the developed world. There is, for example, a striking contrast between Eastern and Western Europe. Figure 9 shows, inter alia, the difference in the incidence of cardiovascular disease in the two regions, while Figure 10 shows the regional trends in cardiovascular mortality rates between 1970 and 1988. The rise in cardiovascular disease in Eastern Europe contrasts with the trend in infant mortality, which has declined steadily in both Eastern and Western Europe.
Cancer rates provide similar variations in space and time (Figures 11, 12 and 13). Figure 11 also shows that the incidence of the various kinds of cancer in the developed and developing countries is markedly different. Both stomach and lung cancer show marked trends in Europe. The general decline in stomach cancer (Figure 12) is almost certainly related to dietary habits and changes in food preparation or preservation techniques. Tobacco smoking is the most important cause of lung cancer. In countries with a history of prolonged cigarette usage, 80-90 per cent of lung cancer and 30 per cent of all cancer deaths are attributed to tobacco smoking. The changing mortality from lung cancer in different European countries is shown in Figure 13.
In developed countries. concern over relationships between environment and health has often focused on exposure to pollution, both at work and in the wider environment. The past two decades have seen some improvement in air quality in urban environments of developed countries, although these gains have been partly offset by declining quality in the cities of the developing world and increased ozone levels in some rural areas (Chapter 1). Generally speaking, many of the pollutants that caused concern (sulphur dioxide, particulates, carbon monoxide, lead, mercury and organochlorine pesticides) have come under much closer control over the past two decades and their impacts have been reduced. Fertilizers and industrial effluents are still causes of serious concern. While pesticides, in particular, still cause many deaths in the developing world (Chapters 4 and 5), solid wastes, particularly hazardous wastes, have become a serious health hazard both in developed and developing countries (Chapter 10).
In all countries, nutrition and health are closely related. In poorer regions of developing countries under-nutrition is a major factor increasing vulnerability to infectious and parasitic diseases (see later). By contrast, in developed countries, obesity and high intakes of saturated animal fats are believed to be linked to the high incidence of cardiovascular diseases. understanding of such relationships has advanced considerably over the past two decades.
Finally, mental health is no less important than physical health. Bad housing and a degraded physical and social environment result in psychosocial health disorders, such as depression, drug and alcohol abuse, suicide, child and spouse abuse, delinquency and personal violence. It is now recognized that the environment plays an important role in violent behaviour. Apart from the genetic and societal causes of mental diseases, evidence has been accumulating over the last two decades of the role played by biochemical factors in mental ill-health. Certain biochemical abnormalities are environmentally-induced and some could be inherited. For example, exposure to some heavy metals and synthetic compounds has been linked to brain tumours and abnormal behaviour. Exposure to low doses of lead in childhood has been associated with long-term impairment in the functioning of the central nervous system (Needham et al., 1990).
Rural life styles and health
A key advance in the past twenty years has come through the appreciation of the health significance of land-use changes in the developing world. A large proportion of the world's poor are rural people who work on farms, or do non-farm work that depends in part on agriculture. The relationship between their poverty and their health thus largely depends on agriculture and associated environmental issues. Their health depends particularly on the availability and productivity of farmland, forest resources (especially fuelwood), and water resources, as well as on risks from toxic chemicals, especially pesticides. Some problems of the same kind confront rural populations in high-income countries, but the impacts are slight compared with those in the low-income non industrialized countries, which are more dependent on their natural resources for economic and social growth (Myers, 1989).
Land availability, land use and nutrition
The amount and quality of farmland available is a key environmental asset whose use determines food and cash income for those who own the land and those who work on it. These factors are critical for health. In extreme situations of environmental degradation, where soil depletion, erosion and water scarcity are all present, a whole region s welfare is often jeopardized by the scarcity of food, leading to world-wide calls for emergency action. In less extreme situations, the process of environmental degradation and increasing health vulnerability is more subtle and difficult to characterize. It has often been neglected until disaster strikes - yet it is in just these situations that soil and water conservation measures can be most effective.
Various studies during the past two decades have demonstrated the relationship between land availability and use and health status and vulnerability. The links between access to land and malnutrition are particularly well established (Norse, 1985). Table 1 illustrates the relationship between the absolute amount of land available for agricultural exploitation and childhood nutritional status in Nepal in 1979 (Nabarro, 1981). Similar findings were reported from an area in the Punjab where 54 per cent of the children of landless labourers were moderately or severely malnourished compared to less than 39 per cent of the children of the landowners (Levinson, 1974). In Bangladesh both food consumption and nutrient intake appear to be directly related to landholding, with the landless consuming only around 80 per cent of the calories and protein consumed by those possessing more than 1.2 hectares of land (FAO, 1982).
Figure 14 illustrates the precarious state of cereal food stocks among landless households in Bangladesh (Chowdhury et al., 1981). Among these families, stocks were entirely used up during the critical lean month of October, when rice is most expensive and employment most difficult to obtain. Land-owning families. however, generally had sufficient stocks to maintain adequate family consumption throughout the year without resort to market purchases.
Several studies have illustrated the complexity of the relationship between health status and land usage. Health vulnerability appears greatest among those dependent on paid employment in agriculture (especially when growing cash crops) and less among land-owners and those growing food crops. Generally speaking, cash crops exacerbate maldistribution because they accelerate the processes of social differentiation: cash-crop adopters prosper faster, sometimes at the expense of non-adopters (UN/ACC Sub-committee on Nutrition, 1989).
For example, in Rio Grande do Sul, Brazil, infant mortality rates (IMRs) varied in the late 1970s from 70 deaths per thousand in the south to just over 20 in the northern districts. The pattern was correlated with land holdings and land use. The IMR was highest in areas with large land holdings used for cattle raising, which required much waged labour. These areas also had a higher proportion of low birth-weight babies, and lower mean intake of protein and energy. Areas with small properties, used for crop agriculture with a higher level of self employment had lower IMRs, and better child health and nutrition (Figure 15). Children of land-owners were less likely to be malnourished than children of labourers (Victora et al., 1986). Other studies have demonstrated that where complementary advantage is taken of both cash and food crops, people are less vulnerable from a health point of view (as measured by food security) (Maxwell, 1988).
Health risks often coincide with the seasonality that is so characteristic of rural life. The World Bank notes that incomes in rural households vary substantially according to the season (World Bank, 1990). For example, wage work is readily available only at certain times of the crop year, and it often depends on the weather. In many African countries the dry season puts an extra burden on women, who may have to walk several kilometres to find water or fuelwood. In some busy seasons heavy agricultural work coincides with depleted food stocks and higher prices. Undernutrition and illnesses are more common at certain times of the year. The rains typically increase water contamination and the incidence of waterborne diseases. Acute weight loss during the 'hungry season' has been documented among farmers in The Gambia: adult weight fluctuated as much as 4.5 kilograms within one year. In northeast Ghana, losses of six per cent of body weight were recorded. Among women farmers in Lesotho the figure was seven per cent, and for pastoralists in Niger it was five per cent. For vulnerable groups such as children, the aged, and others whose biological defences are already weakened, seasonal weight change can be extremely damaging (World Bank, 1990).
The higher figure of seasonal undernutrition and illness among women reported by the World Bank is consistent with many studies that have shown that they are often more vulnerable in rural areas. In most rural areas, their labour is already over-stretched (in Africa. women produce an estimated 60 per cent of the food for household consumption and provide 80 per cent of agricultural labour (ILO 1989a).Any further demands mean lower health and nutritional status, not only for women but also for their children since there is less time for breast feeding, food preparation and child care. These increased demands could be catastrophic within the context of diminishing access to and degradation of environmental resources (land, energy and water)., and the all too common constraints of public expenditure, especially for social services (health, education, child care, etc.).
Cooking fuels and health
The health vulnerability of rural farm-women is aggravated by the fuelwood crisis. Wood, charcoal and other biomass fuels are traditional in lower-income countries and situations. Women are usually responsible for fuel collection, preparation and use, and children in almost all developing societies must help their mothers with these tasks. Girls, in particular, take part in fuel preparation, cooking and tending the fire (Dankelman and Davidson, 1988). The time and energy spent by women and children in collecting firewood means that less time and energy are available for household hygiene, income generation, education and schooling. Furthermore, foods that require longer cooking times may be omitted from the household diet as a fuel-conserving measure, thus further restricting an already limited choice of foods and increasing the risk of disease.
The burning of both biomass and fossil fuels are major sources of air pollution within houses, especially those with open hearths and inadequate ventilation (Chapter 1). Women and children are exposed to the greatest risk because they spend long hours inside, preparing and cooking food and taking care of the house. The most important health effects of air pollution are respiratory, and range from acute infections (particularly in children ) to development of chronic obstructive pulmonary disease in the girls and women who tend the tires. It is estimated that 700 million women and their children are at risk of developing such serious respiratory diseases.
Forests and health
Forests in developing countries often serve as food banks, especially for poor members of local communities. Numerous types of fruits, nuts, leaves, roots and shoots are periodically collected. Forests also harbour many types of mammals, reptiles, birds and insects which can be hunted and consumed, while lakes and rivers in forest areas contain fish and other aquatic animals. These are important sources of protein for many households. By selling them, many households earn significant amounts of much-needed supplementary cash income. Forests are the dominant source of household energy for cooking, heating, construction materials, animal fodder and traditional medicines. They are thus an important source of income and employment within rural areas (Barraclough and Ghimire, 1990).
Forests also provide valuable and sometimes critical resources during hard times. Such resources serve to fill in seasonal shortfalls of food and income as well as providing seasonally crucial agricultural inputs that help in reducing risks and lessening the impacts of drought and other emergencies (FAO, 1989). For example, during the two-month hungry season. the poor forest people of Madhya Pradesh in India rely almost entirely on green leaves gathered in the forests as their main source of food (Cecelski, 1985). Recent studies have shown that the consumption of a variety of indigenous plants was crucial to the survival of many Sudanese during the 1985-86 famine. In particular, a protein-rich dish called 'kawal', made by fermentation of the leaves of the weed Cassia obtusifolia, was frequently the sole support of people whom food shipments failed to reach.
A high proportion of pharmaceutical products originates directly or indirectly from wild species. Apart from the increasing use of plants in the pharmaceutical industry, a much wider range of materials is used world-wide as traditional herbal remedies from wild habitats (Farnsworth et al., 1976).
Water resources development and health
Water is essential for human health, well-being and development. Fresh and marine water yield food, while irrigation is the key to agriculture in many regions (Chapters 4 and 11). Access to safe drinking water and to sanitation are major contributors to general community health, and most water resources development projects have been directed towards these ends. But water also acts as a transport agent for many diseases (Figure 16), and is the habitat for a number of disease vectors.
Of all the diseases associated with irrigation, schistosomiasis is perhaps the best-documented. Apart from the fact that the very nature of irrigation systems creates favourable conditions for the survival of the snails that host the parasite during one phase of its life cycle, the problem is aggravated by social behaviour and poor sanitation practices. Other diseases aggravated by irrigation schemes are onchocerciasis (river blindness) which is endemic in some parts of Africa, Latin America and Yemen. The worm causing the disease is transmitted by black flies of the genus Simulium, which require swift-flowing, well oxygenated fresh water for the survival of their larvae (UNEP, 1986).
Development of water resources has often involved altering water courses, and especially the construction of dams to permit the extension of irrigated agriculture. The dams lead to the inundation of large areas of land and often this results in the displacement of many thousands of people (Goldsmith and Hildyard, 1984) with consequent settlement and health implications. The extensive areas of aquatic habitat created can also lead to an increase in health risks. A good example of what can happen - one of many - is provided by the Diama dam on the Senegal river. This, with a second dam at Manantali in Mali, is intended to allow the irrigation of some 300,000 hectares (Diallo et al., 1990). The Diama dam was completed in August 1986. Disease surveillance began in May 1987. It has since become clear that one of the most important outbreaks of intestinal schistosomiasis in the history of modern West Africa is occurring in this area. The first cases of Schistosoma mansoni infection were reported in early 1988. In the last quarter of 1989, 71.5 per cent of 2.086 passive stools examinations were positive (Talla et al., 1990). Before the construction of the dam, Biomphalaria pfeifferi, the snail vector for S. mansoni, was sparsely present and often not found in the Senegal river basin when looked for. The environmental changes caused by the dam, and believed to be responsible for the change in transmission patterns in the river basin, were changes in river water salinity favouring growth of the snails and stabilization of water level leading to more favourable living conditions for them.
Irrigation schemes increase the extension of land under water, thus providing more breeding sites for vectors and reducing the diversity of habitats that could favour, for example, one species of mosquito rather than another. In a terrain with a moderately fast-flowing river and a wet and a dry season in West Africa, the favoured mosquito would be Anopheles gambiae and malaria transmission would occur mainly during the wet season. Were the river to be dammed, the streams draining into the man-made lake upstream of the dam would be slowed down and the surrounding land would be swampy, thus providing a suitable habitat for A. funestus that would replace the previous species. This new species breeds all year round, and malaria, which was formerly a seasonal disease, becomes permanent. Similar changes in the incidence of diseases may occur in areas where different species of insect prevail due to environmental changes (UNEP, 1986).
Other effects included dramatic increases in the rodent population of irrigated areas. This is of particular importance for several viral and parasitic infections, relapsing fever, leptospirosis and leishmaniasis. Apart from losses in agricultural stocks, the increased rodent population has also caused an increase in bites, especially among children under five years of age.
Agrochemicals and health
Another aspect of rural development is the increasing use of agrochemicals (Chapter 11). While these chemicals have played an important part in increasing food production and thus have contributed positively to human health, many have also proved to be harmful if not used properly. While not as visible as urban chemical contamination, the impact of these chemicals on the health of agricultural workers is of growing importance.
Pesticides cause most health concern, the main hazard being acute poisoning. WHO estimates that some three million people world-wide suffer annually from single, short-term exposure (including that resulting from suicide or attempted suicide) with 220,000 deaths. In 1986, in Sri Lanka as a whole, 57 per cent of admissions of cases of poisoning and 66 per cent of deaths by poisoning, were due to pesticide poisoning. In 1986, pesticide poisoning was the sixth leading cause of death in government hospitals. According to one estimate, in some countries about seven per cent of all agricultural workers involved with intensive pesticide use are likely to experience symptoms of poisoning each year where effective training programmes are not in place (Jeyaratnam et al., 1990). In one survey of acute pesticide poisoning it was found that the proportion of agricultural workers handling pesticides was 29.8 per cent in Indonesia, 91.9 per cent in Malaysia, 38.3 per cent in Sri Lanka, and 41.4 per cent in Thailand (Jevaratnam, 1987). Table 2 demonstrates how deaths due to pesticides have increased in Sri Lanka between 1977 and 1981 (Perera and Gunatilleke, 1990). The fourteen-fold increase in Kurunegala may reflect the fact that this district, in addition to vegetable growing, is one of the largest paddy growing areas with very high and expanding use of agro-chemicals.
Pesticides and other agro-chemicals can also affect human health because of their dispersion in the environment. Women and children are particularly vulnerable since they are the main food producers in many developing countries. The contamination of potable water supplies with pesticides and fertilizers may poison humans and livestock. Persistent chemicals like the organochlorines linger in soil and water for many years and may become concentrated in animals.
Food crops are often directly contaminated by pesticides. It has been estimated that 90 per cent of human pesticide intake has occurred through the food chain (WRI, 1988). UNEP/GEMS has been systematically collecting data on pesticide contamination in a number of foodstuffs, mainly from developed countries. For example, DDT complex levels in the fat of cow's milk showed a marked decline in Japan and the Netherlands in the 197Os. A similar trend was also observed in finfish in Japan and the USA (UNEP. 1986).
Aflatoxin contamination in food is a major hazard in warm humid countries where food storage facilities are inadequate and crops are often left in moist conditions before harvesting. Mycotoxins, in general, have been known to cause serious outbreaks of poisoning but their main significance may well be in long-term exposure to them. Combined with hepatitis B, they may be an important factor in primary cancer of the liver - one of the most common cancers in Asia, and Africa south of the Sahara. Aflatoxins produced by Aspergillus flavus in cereals, peanuts and soya beans are by far the most serious threats to human health (UNEP, 1986).
Urban life-styles and health
Although each person in a city breathes air, drinks water, eats food, sleeps, works and moves about, each does so in a unique familial, socio-cultural and communal environment. That is why different people encounter different environmental hazards. In spite of this, much is known about the general impact of the urban environment on people s health. Epidemiological studies have clearly shown that the odds against child survival and longevity are greater for those city dwellers who are severely exposed to malnutrition, inadequate shelter, poor sanitation, pollution, poor transportation, and the psychological and social stresses resulting from socio-economic deprivation (WHO, 1991a).
Urban poverty is growing in absolute, it not relative, magnitude (Chapter 16). Hundreds of millions of urban dwellers in the Third World now live in what might be termed life and health threatening homes and neighbourhoods (WHO, 1991a). While the picture may not be as dramatic in most cities of the developed world, and the trends are less clear, there are still millions who live in miserable situations in the cities of the North with a quality of life far below that of most of their fellow citizens (Chapter 17).
Health vulnerability in urban slums
One of the advances during the past twenty years has been in understanding the complexity of the causes of health vulnerability in particular situations. All risk groups and factors need to be studied and their changes over time related to changes in health and the environment. Furthermore, factors such as income, employment, assets and educational status, and the social dynamics and behavioral patterns of urban life which lead to exposures to particular risks (sexually-transmitted disease, child abuse, and stress-related illness) need to be taken into account (Cooper Weil et al., 1990). The multi-factoral nature of poverty is well illustrated in a 1986-87 study of an urban slum in Bangladesh (Pryer, 1989, 1990).
The sample area was an established inner-city slum with a population of 2,200 where environmental conditions were appalling, being overcrowded and unsanitary. A cross-sectional survey of 208 households was conducted. Despite an outward impression of homogeneity it was found that a high degree of inequality existed in the slum, which could be subdivided into three groups. The richest families (34 households), mostly comprising slum landlords and traders, had average monthly incomes more than three times the local food poverty line. A second group (125 households) was in an intermediate position, while the poorest labouring households (49 households) were below this food poverty line. As Figure 17 indicates, the study showed that the poorest households are particularly disadvantaged relative to their better-off neighbours, and even more so with respect to the 'rich' families.
Nutritional and environmental diseases abound in these conditions. Cross-sectional surveys indicate that the prevalence of diarrhoea amongst children under five was 25 per 100 child days. Relatively high rates of ill-health and malnutrition were not, however, exclusively confined to young children - 43 per cent of mothers and 42 per cent of fathers had a Body Mass Index (ratio of weight in kilograms to height in meters squared) below 18, which is considered indicative of adult malnutrition.
Care is needed in interpreting statistics of health trends in urban areas. City health statistics often tend to look better than rural ones. An important reason is that there are usually better health care facilities in urban areas and it is therefore possible for city-dwellers to get treatment for serious illnesses. Another reason is that these statistics usually do not include the inhabitants of slum areas, as these areas are not officially recognized (Basta, 1977). A third reason is that these statistics aggregate all areas of the city, with no separation of groups living in slums and squatter areas from those living in better housing and under more favourable environmental conditions. Changing city politics, alternating between acceptance of squatters and their physical repression, clearly interfere with the gathering of meaningful comparative statistics, especially over time. Nevertheless there have been studies that have been able to look at the city through a finer lens (Wray, 1985; Guimaraes and Fischmann, 1985). The picture that emerges from the first study is that at least in one sample of urban slums in Bangkok, Thailand, malnutrition is far worse than in the rural communities chosen for comparison. The second study revealed
that the levels of infant mortality in a poor shanty town are much higher than in the most affluent part of Porto Alegre, Brazil. The same study demonstrated that infant deaths were especially high near a watercourse called the Moniho Arroyo, where 52.9 per cent of the deaths were attributed to intestinal diseases as compared to 15.9 per cent in the more distant sector. A specific environmental feature, a contaminated watercourse, clearly had a significant impact on mortality patterns.
The health of the homeless
The homeless state, whether in developed or in developing countries (Chapter 17) is clearly characterized by an increased risk to health: little or no protection from the elements; lack of access to basic sanitation or water sources; inadequate nutrition due to the absence of cooking facilities and of money to buy prepared foods; and the spread of disease as a result of overcrowding in temporary accommodation (Cooper Weil et al., 1990). Very often, homeless people are not recognized as official residents and their births and deaths are therefore ignored in official records, which of course leads to serious underestimates of homelessness and the accompanying degree of ill health and premature mortality, and also helps city authorities to continue to ignore the problem (Acheson, 1990).
In the South, the plight of the street children is an extreme case of homelessness, and illustrates the health risks attendant upon this condition. Such children are often a product of massive migration from rural areas and the resultant breakdown of family life, or of the death or separation of their parents. Unsupervised by adults, some children spend their days on the street but are able to return home at night; others have no home to return to and sleep wherever they can find shelter. These abandoned children inevitably suffer the consequences of lack of sanitation and clean water, occupational accidents sexually transmitted disease, drug abuse, crime, and all the other effects of striving to cope alone, resulting in a deep sense of insecurity and emotional conflict (Tabibzadeh et al., 1989).
Health problems in urban settlements of developed countries
One of the main health risks in urban settlements in developed countries is due to the use of certain materials in buildings. The use of asbestos is now completely banned; but some organic materials and metal compounds widely used in paints, pipes and furnishings, as well as others in daily use (such as cleaning agents and solvents) can cause poisoning. Radon emissions pose a serious health hazard, particularly in air-tight buildings (Chapter l). In one study, the concentration of radon indoors was found to be six times higher than its concentration outdoors (Nazaroff and Teichman, 1990). Smokers are at a much higher risk of developing cancer when exposed to radon. Outdoor pollutants are also known to penetrate indoors. Recently, people started complaining of what came to be known as the 'sick building syndrome' which has been shown to be epidemiologically related to sealed buildings that develop high temperatures and levels of dust as well as passive smoking (Chapter 1).
Noise from a variety of sources has become a serious problem in modern urban settlements. Apart from being a nuisance, it can give rise to serious health problems, such as loss of hearing or increased reaction times. Complex tasks are disrupted at relatively low noise levels and higher anxiety levels and risk of hostile reactions have been known to result. High frequency and impulsive noise are usually more disruptive.
Health in unsettled situations
Migration from rural to urban areas is often driven by landlessness, poverty and homelessness. Such unsettled people often live in situations totally lacking the amenities expected in human settlements. Not only are these people exposed to above average health risks, but they can also contribute to the establishment of new disease foci as they move from place to place, a phenomenon no doubt linked with the persistence of malaria in the newly-developed areas of Brazil and the rapid spread of cholera in South America.
Colonization projects, which are initiatives to develop rural areas, have led many hundreds of thousands of people to move. They are being used by many countries to 'redistribute population from densely populated, resource-scarce areas to sparsely populated, resource-rich areas' (Findley, 1984).These projects are fraught with problems, well illustrated by recent colonization experiences in Brazil. This has led to a quadrupling of population in some rural areas over a 20-year period, from under four million in 1970 to over 17 million in 1990. An estimated nine million people have settled in the rural areas of the Amazon along a network of new roads extending over 45,000 kilometres (Wilson and Alicbusan, 1990).
This massive colonization has been accompanied by the spread of malaria (Figure 18), which has, in turn, had a major impact on the colonization process in a number of different ways. Ill workers cannot carry out heavy farm work. The very threat of infection is enough to convince families that they must minimize unnecessary exposure and so, instead of the whole family moving to the settlement area, only the young adults work on the farm, and only when farm work is required. After a number of serious episodes with the disease, many decide to abandon their farms and seek work elsewhere (Sawyer, 1987).
Serious illness requires treatment, which in spite of the presence of extensive anti-malarial services in the area, is often not easily accessible. Transportation costs can be significant, and where private medical services are sought, cost can be prohibitive. An analysis of settlements in the 1970s indicates that many first owners abandoned their farms due to sickness (Henriques, 1988). More recent data from Rondonia show that the cost of malaria treatment represents a major expenditure, especially for low-income households. In one project area, Machadinho, malaria strikes, on average, more than three times per year and one-eighth of family income is used to pay for treatment (Sawyer, 1987). The actual burden on low-income families is likely to be significantly greater. They are less able to afford personal protection (mosquito nets cost $US5 each), to improve their housing, or to clear local breeding sites. In Machadinho, only ten per cent of new settlement plots are in the hands of their original owners.
The malaria epidemic in the Amazon now accounts for more than 60 per cent of all reported malaria cases in the Americas. Within Brazil itself, 97 per cent of the cases come from Amazonia, which has 15 per cent of the population of the country. Two states (Rondonia and Para) report 70 per cent of the cases, and four municipalities of Rondonia and four of Para have more than 60 per cent of the cases of these states.
Malaria. while posing the most serious threat to health in the Amazon, is not the only one. Other diseases - leishmaniasis, schistosomiasis, tuberculosis and leprosy - are also present, and accidental injury, especially during the clearing and burning season, can equally interrupt family settlement.
The story of malaria in the Amazon is not a unique one: many other areas of the world are suffering comparable difficulties. The absence of health care in newly settled areas has serious consequences because the combination of poor sanitation and exposure to an unfamiliar environment results in increased morbidity and mortality rates. In the Selva Lacandona community of Frontera Echevarria, Chiapas, Mexico, the crude death rate was found to be as high as 50 per 1,000 persons. Several surveys also report that colonists have experienced much higher incidence of parasitic and respiratory infections (Findley, 1984). In Thailand, about one million farm households are occupying forest lands as squatters. Lacking secure land ownership, they have less access to credit. Consequently, they cannot borrow money to buy equipment, pesticides or improved seed strains, so their land is less productive. 'Forest malaria' in Thailand is an important health problem and deforestation is an important component of environmental degradation.
The drama of cholera in South America illustrates the threat posed by poor, infected people moving from one poor environment to another, especially when they are carrying the micro-organisms with the potential of starting epidemics in previously disease-free areas. At the end of January 1991, an epidemic of cholera broke out on a continent which had witnessed no outbreak this century. Striking first in the coastal cities of Chancay and Chimbote, north of Lima, Peru, the epidemic then spread with unexpected speed and intensity (WHO, 1992b). Its movement to other countries in South America and the world is shown in Figure 19.
This diagram illustrates the rapidity with which a disease, which is fundamentally linked with a poor environment, especially unsafe water and inadequate sanitation, can spread. Clean water and hygienic practices can break the chain, but these are hardest to come by in unsettled situations, which no doubt has played an important role in this epidemic. In fact, the epidemic in Peru has had a very low mortality rate because of a successful campaign to educate women in the use of oral rehydration therapy.
Industrialization and health
These examples. while capturing many of the features of a variety of human settlements, do not shed much light on two further aspects of development activities which, independently of other deleterious features of urban life, have dramatic effects on human health and the environment, namely industrialization and waste accumulation. Industrial activities, while contributing in many ways to human well-being, also have adverse effects on health through the release of harmful chemical, physical and biological agents. The main pathways of transmission to people are air, water, wastes and contaminated food. Cities, particularly in developing countries concentrate populations and industrial sites (Chapter 12). This combination inevitably leads to higher levels of exposure of a greater number of people.
Most knowledge of the adverse effects of pollutants on health has been obtained in workplaces in developed countries, and relates to single agents (Chapter 10). There is little doubt, however, that the combined effects of multiple exposures, which happens most frequently in highly industrialized areas in both the developed and the developing world, can produce adverse health consequences which are more than simply additive. For example, the effects of sulphur dioxide on health increase in the presence of particulates and, as mentioned earlier, exposure to radon increases the risk of cancer for smokers. In 1984. WHO/UNEP established the 'Human Exposure Assessment Locations' (HEALs) programme (see Chapter 20) in order to monitor total human exposure to pollutants and assess the combined risk from air, food and water pollutants.
In recent years, a number of industrial accidents have alerted the public to the threat posed by the release of large quantities of toxic chemicals. Chapters 9 and 12 deal with natural and industrial hazards and accidents and the various approaches taken to identify hazards, prevent accidents or mitigate their adverse impacts as much as possible through sophisticated risk assessment techniques and adequate preparedness to contain these impacts when accidents do happen.
Urban waste and health
As the main centres of production and consumption, urban areas naturally generate large quantities of waste. Many major cities world-wide are facing a solid waste crisis as accessible landfills are filling up and rising transportation and processing costs make it harder and harder for services to keep up with the rapid growth of waste. Only between 30 and 70 per cent of solid wastes are currently collected in cities in developing countries. Disease vectors proliferate on waste and in situations where human excreta are added to garbage, increasing health risks considerably.
Particularly dangerous situations are created when hazardous and/or contaminated material, such as clinical wastes and wastes from small chemical and metal processing factories within the city, are mixed with ordinary municipal solid waste, since the latter is normally collected and dumped at a disposal site without much attention being paid to its immediate and long-term environmental consequences. Immediate dangers are faced by waste pickers or scavengers who search through dump sites for wastes of potential use, either directly or after recycling. These people, who are generally poor, living at or near the dump, are of sufficient importance in some cities as to 'play an important role in recovering resources from the waste materials, and thus reducing the waste volume to be ultimately disposed of (Gotoh, 1989). In 1987, 241 people were injured and two died when an abandoned radio-active cancer-treatment device was discovered among rubbish in Goiania, Brazil, and the materials re-utilized (Chapter 9).
The numbers of people engaged in this informal resource recovery are not exactly known (Furedy, 1989). There are estimates, however: 25,000 obtain wastes from Manila's Smokey Mountain dump, with perhaps 60,000 more depending upon these wastes for their basic needs. The waste found is used in diverse ways. It serves as building material for the shelter of the poor. Plastics, tin cans, bottles, bones, feathers, intestines, hair, leather and textile scraps find their way into industries. Families engaged in waste-picking may earn as much as, or more than, an unskilled worker, but this is only achieved by most family members, including young children, working for very long hours.
Few studies of the health status of waste-pickers have been carried out. However, a recent project in Calcutta examined the prevalence of respiratory diseases, diarrhoea, viral hepatitis, intestinal parasites, skin disease, immunization status and nutritional status in this group. A control group was taken from a population with similar socio-economic backgrounds but with different occupations (cultivation and fishing). Figure 20 summarizes the results obtained. While both the control group and the waste-pickers were found to be suffering high levels of ill health, the waste-pickers had greater prevalence of respiratory disease, diarrhoea and intestinal parasites (Nath et al., 1991).
The working environment
The working environment is that part of the human environment in which people spend their working hours every day. Its quality is conditioned by a combination of physical, psychological and socio-economic factors that fall into two main categories. Occupational safety deals with the physical, chemical and biological hazards and mental stresses present in the working environment, and their prevention and control. Working conditions include the organizational framework, length and distribution of working time, contents of work and human relations - all factors that have significant repercussions on the health and well-being of workers. In 1975, the Director General of ILO presented a report entitled Making work more human. This resulted in the 'International Programme for the Improvement of Working Conditions and Environment' (PIACT) (Chapter 12). ILO has since published a series of manuals on occupational health, safety and the working environment in several industries (e.g. ILO 1985, 1989a and 1991).
Occupational hazards depend on the processes involved, the safety precautions taken and the ability to respond effectively to accidents. It has been estimated that there are about 32.7 million occupational injuries and 146,000 deaths at the work-place every year (WHO, 1990a). The main problem in developing countries is the almost complete absence of basic safety measures in the many small workshops that predominate in those countries.
An example is the case of lead poisoning among household members who were exposed to lead-acid battery repair shops in Kingston, Jamaica (Matte et al., 1989; Box 2). The Jamaica study illustrates two important points:
i. The potential of environmental health hazards in the informal work sector, and
ii. the particular vulnerability of children to toxic chemical poisoning.
The first point is of increasing importance given the fact that more and more governments are looking to the informal sector as a source of employment for the growing numbers of unemployed. One major difficulty posed by this sector is the virtual absence of any environmental control measures or standards. The vulnerability of children is due to several factors such as their small ratio of body volume to body surface area, their high metabolic and oxygen consumption rates, their different body composition and the effect of progressive maturation and differentiation of body systems (Belsey. 1987).
The Kingston example is but one of many. Studies in the UK demonstrated elevated levels of lead in people living near to lead smelters, especially the families of workers. Blood lead levels (BLLs) as low as 10 ug/dl, once considered safe, are now known to adversely affect cognitive development and behaviour in children, with potentially long-term consequences. In 1984, an estimated three to four million children in the USA had BLLs greater than or equal to 15 ug/dl (CDC, 1991). It is estimated that a further 675,000 young children in the USA had high concentrations of lead in their blood, and millions world-wide have been exposed to 'potentially toxic amounts of lead' due to the increased use of leaded petrol over the last few decades (Postel, 1986). In those countries that have introduced unleaded gasoline, BLLs have dropped markedly (Chapter 1).
Even though no accurate statistics on occupational diseases are available, there is no doubt that the proliferation of new chemicals whose toxicity is still unknown (Chapters 10 and 12) means that it will be some time before research would reveal the full impact of exposure for long periods of time to what may at first have been considered inoffensive substances. Furthermore, the increasing use of radioactive materials and X-ray machines in industry increases the risks of exposures of increasing numbers of workers to ionizing radiation.
Although noise is not restricted to the workplace, noise levels in factories are generally higher than elsewhere, because of the large number of moving parts and their concentration in a limited space. A great number of developed countries have now adopted noise-limiting standards that reduce both the physical and the psychological ill effects of excessive noise.
Conditions of work have come to receive more attention of late. in almost all industrialized countries, working time has been reduced, either by legislation or by collective agreements. Perhaps the most important development has been in the developed countries where problems of work organization and job content have received a good deal of in-depth analysis. With the increasing recourse to better-educated workers doing more sophisticated jobs and the decline in dependence on motor skills and dexterity, job satisfaction now becomes a major concern of the new generations of workers in knowledge-intensive fields. This is quite different from previous emphasis on the discomfort, fatigue or stress of less skilled workers in the older industries.
In the previous chapters, whether those dealing with the major environmental issues (Part One of this volume) or the impacts of developments in the different sectors of socio-economic activity (Part Two), the responses to environmental problems, including those impacting on human health, have been addressed. These responses have ranged from better monitoring of impacts of various activities on the environment and better understanding of the manner in which the environment is affected, to measures of mitigating undesirable impacts through combinations of actions on both the technological and social fronts. On the technological front, action has involved minimization or treatment of emissions, effluents and wastes; reduced material and energy inputs; cleaner technologies and recycling. On the social front, new regulations and legislation to reduce pollution and wasteful use of resources have been enacted at the national, regional and international levels (Chapters 22 and 23); economic incentives and penalties have been applied, and technical and advisory services and public awareness campaigns have been initiated.
At the higher level of integrating development, health and the environment, a start was made with the 'Primary Health Care' approach for achieving health for all, adopted at the international Conference on Primary Health Care, held in Alma-Ata, USSR, in 1978. This has shaped and defined present-day thinking regarding the place of health development in overall national development. The meeting concluded that any distinction between economic and social development was no longer tenable:
'Economic development is necessary to achieve most social goals and social development is necessary to achieve more economic goals. Indeed, social factors are the real driving force behind development. The purpose of development is to permit people to lead economically productive and socially satisfying lives. Only when they (people) have an acceptable level of health can individuals, families and communities enjoy the other benefits of life. Health development is therefore essential for social and economic development, and the means for attaining them are intimately linked' (WHO, 1978).
Most health care systems have found it very difficult to move in the direction outlined at Alma-Ata because they have been overwhelmed by the basic problem of running their curative services. Few, if any, low-income countries have been able to establish an adequate public health capacity, even of the most rudimentary kind. Most still lack the necessary full-time staff with public health and related skills, or the logistical and communication capacity to collect and analyse data of the kind required. For many of them the austerity measures imposed by structural adjustment requirements have made the situation even more difficult, leading to lowered staff morale and motivation.
Following a recent review by WHO of the world situation, the WHO Director General called for a New Paradigm for Health, embracing a world view, in which health is seen as central to development and to the quality of human life. As such, health should become a major political issue at cabinet level of government. Health, as a human right, cannot be left entirely to market forces, because the most disadvantaged will become even worse off. Furthermore, the new paradigm must be people-oriented:
'We must humanize our approach to health development - a process that begins and ends with the people themselves. This means paying due attention to the individual, the family and the community, but especially to the underprivileged and those who are at risk, such as women and children and the elderly. It means building a sustainable health infrastructure, 'bottom-up', in communities where people live and work, with appropriate response and support from district and more central levels, thus closing the existing gap between programme delivery and community initiatives' (Nakajima, 1991).
A 'post Alma-Ata' period of reflection has started. The desired features of the health sector's contribution to national development are now being examined critically, publicly and sectorally. A contribution is called for which is more in tune with today's political, economic and social realities. Central to this will be the prevention and control of health problems deriving from a rapid and widespread degradation of the human environment.
The health sector will have considerable difficulty in contributing effectively to the process of 'post Alma-Ata' reflection. Few national health sectors are organized to address development issues from a truly holistic perspective that goes beyond the delivery of curative services. It will take considerable political adroitness within the health sector to mobilize the human and financial resources required to address the issues identified above. The necessary action programme covers a range of policy issues that still lack the information and analysis needed for discussion and decisions.
At the level of the health sector itself, certain strategic lines can be suggested. These include mapping health-environment linkages so as to relate health vulnerability to specific economic development programmes through the intermediary factors of environmental degradation (e.g. better understanding of the interrelationship between rural, urban and unsettled contexts). This means that the capacity of ministries of health has to be strengthened so that action can be initiated to prevent or mitigate the adverse health consequences of the impacts of development activities.
Effective handling of health-environment interactions can only be achieved, particularly in most developing countries, if the issue of poverty is addressed seriously. As has been argued in several parts of this book, poverty is not only the result of scarcity of resources and population growth - important as these are. Social organization, national goals and development strategies, as well as international economic relations, are also important factors in environmental degradation and the resulting poverty and deteriorating health standards. This is related directly to consumption patterns and life-styles, both in the developed regions and amongst those groups in developing regions that adopt such consumption patterns and life-styles. It is these that impact on the economies and the environment of the developing countries, particularly those that rely mainly on the export of commodities for economic survival (Chapters 11 and 16).
It is also these life-styles that are mainly responsible for the emergence of a whole range of new health problems associated with, for example, eating and drinking habits, leading a more sedentary life and the hazards brought about by chemical or radioactive emissions, effluents and solid wastes, whether in the home or the work and leisure environments. This, in turn, relates to the quality and quantity of material and energy inputs and the technologies used in satisfying the social demand for goods and services in different walks of life.
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