The urban environment and health in a world of increasing globalization: issues for developing countries Anthony J. McMichael1

Urban living is the keystone of modern human ecology. Cities have multiplied and expanded rapidly worldwide over the past two centuries. Cities are sources of creativity and technology, and they are the engines for economic growth. However, they are also sources of poverty, inequality, and health hazards from the environment. Urban populations have long been incubators and gateways for infectious diseases. The early industrializing period of unplanned growth and laissez-faire economic activity in cities in industrialized countries has been superseded by the rise of collective management of the urban environment. This occurred in response to environmental blight, increasing literacy, the development of democratic government, and the collective accrual of wealth. In many low- income countries, this process is being slowed by the pressures and priorities of economic globalization. Beyond the traditional risks of diarrhoeal disease and respiratory infections in the urban poor and the adaptation of various vector-borne infections to urbanization, the urban environment poses various physicochemical hazards. These include exposure to lead, air pollution, traffic hazards, and the ‘‘urban heat island’’ amplification of heatwaves. As the number of urban consumers and their material expectations rise and as the use of fossil fuels increases, cities contribute to the large-scale pressures on the biosphere including climate change. We must develop policies that ameliorate the existing, and usually unequally distributed, urban environmental health hazards and larger-scale environmental problems.

Keywords: urban health; urban population; urbanization; environmental health; environmental pollution; international cooperation; socioeconomic factors; poverty.

Voir page 1124 le re´sume´ en franc¸ais. En la pa´ gina 1124 figura un resumen en espan˜ ol.

Introduction combination of flight from rural poverty and high fertility rates in urban areas. In Latin America, in Homo sapiens is undergoing a radical transformation of contrast, urban growth has been driven more by the its ecology. The proportion of the world’s population pull of industrialization and economic opportunity. living in large towns or cities has grown from around Hence, urban growth has slowed in Mexico City, Sa˜o 5% to 50% over the past two centuries. Demogra- Paulo and Buenos Aires during the past decade of phers estimate that by 2030 approximately two-thirds economic recession (1). of all people will live in large towns or cities. The human population is thus becoming urbanized. In future, urban populations will have a distinctly higher Historical perspective proportion of older people than they do today. Urban migration reflects many things: the Cities have historically been associated with the advent of industrialization, insecurity about the evolution of ideas of public health and practice. The availability of food in rural areas, the search for modern public health revolution began in European refuge from conflict and environmental damage and cities in the 19th century where, under the pressures the lure of jobs, amenities and stimulation. Africa, of industrialization, poverty, crowding and the where the relation between economic development breakdown of traditional ways of living, the condi- and urbanization is weaker than in other regions, is tions of daily life had deteriorated for most people. currently the least urbanized major region in the The economic historian Szreter argues that in world. Nevertheless, it is also the most rapidly England, which led the industrial revolution, rapid urbanizing region. In sub-Saharan Africa much of the economic growth in the first half of the 19th century rapid growth in the urban population reflects a disrupted traditional structures of authority, social relationships and ideologies. This caused urban environmental blight, the flight to the outer suburbs 1 Professor of Epidemiology, Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, by the economically better off, further worsening of Keppel Street, London WC1E 7HT, England (email: tony.mcmichael deprivation in inner urban areas, and increases in @lshtm.ac.uk). disease and death (2). In mid-19th century England Ref. No. 00-0679 those in the suburbs largely ignored the plight of the

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urban poor. The resultant policy stasis and the episodes of air pollution occurred during the mid- growing crisis of urban poverty, disease and over- 20th century in Europe and North America, flowing workhouses precipitated Chadwick’s report including the great London smog during the winter on the conditions of workers (3). of 1952. These experiences ushered in new legisla- Chadwick argued that averting additional tion, which has since led generally to a decrease in air environmental degradation would remedy the social pollution in developed countries. The various major crisis more effectively than would further workhouse categories of air pollutant have followed a multi- ‘‘relief’’ under the provisions of the Poor Law of phasic trajectory (7). Smoke emissions from William 1834, the law that required the unemployed poor to Blake’s ‘‘dark satanic mills’’ of industrialized Europe work for their daily subsistence. Even so, within the began to decline in the early 20th century, and sulfur prevailing laissez-faire ethos, the struggling middle- dioxide emissions declined from the middle of the class representatives of inner urban electorates were century. However, emissions of carbon dioxide and too preoccupied with the immediacies of their own very fine particulates are still rising. commercial survival to embrace grander urban The rise and fall, or ‘‘inverted U’’, trajectory improvement schemes. Hence, Chadwick’s centrally displayed by measurements of smoke and sulfur controlled programme to develop a network of local dioxide is sometimes referred to as the ‘‘environ- boards of health, established under the 1848 Public mental Kuznets curve’’; this refers to the graph Health Act, met with widespread resistance from described by the economist Kuznets in the 1950s of unsympathetic local politicians. The composite the increase and then decrease in income disparities problem of economic deprivation, urban squalor within a country that occurred as industrialized and severe health inequalities was eventually reme- countries grew wealthier. Not all urban environ- died by devolving sanitary powers to local munici- mental pollutants, however, have followed this palities through the Sanitation Act of 1866 (2, 4). trajectory (8). For example, household sanitation Over the next three decades urban authorities in problems in western countries have been on a England, using new sanitary technologies and public downwards trajectory (decreasing) since the early borrowing, transformed sewage and water services stages of industrialization, but carbon dioxide from private enterprises to public services. emissions and consumer wastes are continuing on There is a contemporary relevance to this an upward trajectory (increasing). The current trend historical account: the failure of many large cities in for these latter pollutants will, presumably, turn out to low-income countries to implement similar changes be the up slope of the longer span of the inverted U. has left them with problems of environmental blight, This sequence of rise and fall in environmental inadequate housing, poverty and disease. The process contaminants is not a law of nature. In the megacities has been further slowed in many countries by the of the developing world, such as Mexico City, Sa˜o pressures, distortions and priorities of economic Paulo and Delhi, residents often face the worst of globalization. both the traditional and modern worlds. They Until the second quarter of the 20th century, encounter a wide spectrum of pollution ranging the dominant cause of mortality among industrialized from a lack of sanitation (with exposure to human urban populations was infectious diseases. However, excrement and unsafe drinking-water) to exposure to mortality from infections had begun to decline during hazardous synthetic organic chemicals in their air, the 19th century. McKeown attributes most of the food and water. In Delhi, India, for example, the decline in mortality after the 1850s to improvements coliform count in the city’s main river, the Yamuna, in social and environmental factors (5). He empha- increases 3000-fold from the time it enters the city to sizes that improvements in food supplies and the time it leaves (9). That stretch of the river also nutrition boosted biological defences against infec- receives about 20 million litres of industrial effluent. tious diseases. He notes that better housing, safer Meanwhile, Delhi’s air quality, especially in the colder water supplies, increasing literacy and the idea of months, is among the worst in the world (10). domestic hygiene gave further protection to infants Chaplin argues that there are three reasons why and children. Various commentators have broadly a successful urban sanitation programme has not concurred with McKeown. However, others have arisen in India (4). Firstly, local government in urban emphasized the important role of deliberate public areas lacks the resources and commitment to health interventions including sanitary engineering, counteract problems in inner urban areas that are refuse disposal and vaccination (6). In France, for associated with poverty, overcrowding and hapha- example, substantial gains in life expectancy emerged zard urban growth. The influential middle classes and first in Lyon in the 1850s, then in Paris during the upper classes have relocated to new, leafier, suburbs. 1860s and 1870s (albeit more slowly), and then in In the atmosphere of indifference both corruption Marseille around 1890; each gain was directly and incompetence flourish. Secondly, there is no associated with the deliberate improvement in the manifest political threat from the illiterate, fragmen- supply of public water and sanitation in each of these ted, relatively powerless, urban poor. Thirdly, the cities (7). availability of vaccinations, antibiotics and effective As industrialization intensified the general domestic plumbing have rendered the middle class absence of air quality controls allowed pollution oblivious to the environmental health hazards faced levels to increase in industrialized cities. Spectacular by the poor. Modern medicine and sanitary technol-

1118 Bulletin of the World Health Organization, 2000, 78 (9) Health and the urban environment in a world of increasing globalization ogy insulate the middle class from the threats of sive social relationships. On the other hand, cities are infectious diseases. often impersonal, alienating and sometimes menacing. The three main pathways through which the urban environment impinges on human health are through the social changes that accompany urbanism Microbiological, physical and and the way in which these changes alter behaviour- chemical hazards based risks to health; the way that the physical urban environment poses various microbiological risks and Large cities in the least developed countries typically risks of toxicity; and the way that the larger-scale combine the traditional environmental health pro- environmental impact of modern urban populations blems of poverty, particularly respiratory and enteric creates wider-spread and longer-term risks to health infections, with those of poor quality housing and through their disruption of the life-support systems unregulated industrialization. Residents therefore are of the biosphere. often at risk from diseases and injuries associated with poor sanitation, unsafe drinking-water, danger- ous roads, polluted air, indoor air pollution and toxic Urbanism: changes in social relation- wastes. The United Nations Centre for Human ships and individual behaviour Settlements has written that ‘‘the deterioration in the built environment is sharply in evidence throughout Urbanism potentiates many changes in human most of urban Africa... This trend seems to have been behaviour that affect disease risks. For example, accentuated by the effects of structural adjustment in cities are characterized by high levels of tobacco many countries, according to which urban workers smoking, traffic injuries, fatalities and adult obesity lost more than rural smallholders’’ (16). (11). The increase in the incidence of obesity In developing countries infant mortality is illustrates several aspects of urban living. Among typically four or more times higher in poorer city dwellers, it reflects the combination of easier segments of urban populations than in richer access to energy-dense processed foods and a decline segments. There are also large differences between in physical activity at work, at home, and recreation- richer and poorer populations in the incidence of ally. Typical urban living thus entails an imbalance in environmentally related infectious diseases such as the energy budget that leads to obesity, and this tuberculosis, typhoid and cholera, and in exposure to greatly increases the risk of high blood pressure and local air pollution and indoor air pollution (1). type II (adult onset) diabetes (11, 12). Psychosocial health problems are also related to The urban facilitation of microbial traffic, via income including depression, alcohol and drug abuse, the increased intensity and diversity of human suicide, violence and murder. In large cities every- mobility, contact and sexual behaviours, may have where, poor people are the main victims of property been critical in launching the otherwise poorly crime, assault, rape and murder. In response, the transmissible human immunodeficiency virus richer people raise higher barricades and employ (HIV) in the 1980s (13). Urbanism, increased more security guards. The vulnerability of poor mobility and the relaxation of traditional cultural people then increases further because the adaptive norms yield new patterns of human behaviour, behaviours of crime and violence are inevitable with including changes in sexual activities and the use of high levels of unemployment and poverty. illicit drugs (14). The extensive transmission of the Poverty, then, is more than income depriva- human immunodeficiency virus in the 1980s and tion. Urban poverty is the most important predictor 1990s owed much to the combination of new sexual of environmental health risks when its definition freedoms, movement between urban and rural areas, includes other forms of deprivation such as physical and long distance travel. Similarly, reported rates of assets, political influence, access to basic services and food poisoning have increased in industrialized access to social capital (17). Satterthwaite concluded countries during the past two decades and have that: ‘‘Although considerable progress has been made almost doubled in the United Kingdom between the since 1990 in improving housing conditions for low- mid-1980s and mid-1990s (15). This probably income groups in certain cities and more effective reflects a mixof factors including increasingly long approaches are now being more widely applied, the ‘‘supply lines’’ between production and consumption number of people suffering serious environmental in complexurban social environments, changes in health burdens in urban areas probably increased consumer behaviour and, perhaps, consistently significantly during the 1990s — in part because warmer summers since the 1970s. urban populations continue to grow rapidly in most However, urban life also confers many health of Africa, Asia and Latin America, in part because of benefits. Within cities, there is readier access than in weak and ineffective urban governance, in part rural settings to health services, education, and because of continued increases in urban poverty in financial and social services. Community life can be many nations’’ (18). He argues that what is often rich and fulfilling. The urban environment is diverse, forgotten is the contribution towards reducing stimulating and full of new opportunities. Individual poverty that is made through the health benefits and family mobility make it easier than in a gained by improving housing and providing clean conservative rural community to escape from oppres- water, sanitation and waste removal.

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Microbiological hazards (1, 24). These may be overt, as in the cases of road As it reshapes modern human ecology, rapid trauma or the increase in asthma attacks that occurs urbanization is expanding the traditional role of cities during episodes of high air pollution, or more as gateways for infections. Crowding and unsanitary insidious, as with exposure to environmental lead. conditions are important amplifiers of the transmis- Environmental lead exposure. In 1997, the sion of infectious diseases: many infectious diseases World Bank made the phasing out of lead in petrol the thrive where there is a lack of water, and inadequate top priority of its 10 main objectives for improving drainage, sanitation and solid waste removal. Popula- health and the environment (25). Exposure to lead has tion movement from rural areas into cities and greater developed in the urban environment over many mobility within cities are bringing new opportunities decades; the lead comes from industrial emissions, for otherwise marginal and obscure microbes (19). house paints and the use of leaded motor fuel (24, 26). Research in Kwa-Zulu Natal, South Africa, has Many high-income countries, including the United shown that the vector-borne disease schistosomiasis States and Australia, have recently set new, lower is spreading to urban areas through the migration of standards for environmental exposure to lead to the rural population to informal settlements around protect young children. However, childhood lead the cities (20). For similar reasons, including poor poisoning — a particular hazard in the neurocognitive sanitary facilities, filariasis, another vector-borne development of children — is an increasing problem infection, (also known as elephantiasis and spread in many low-income countries, especially in urban by a culicine mosquito that breeds in contaminated environments. High concentrations of lead in blood pools of water) has been spreading in towns in Recife, have been observed in cities such as Bangkok, Jakarta, in north-eastern Brazil (21). Yellow fever, plague Taipeh, Santiago and Mexico City (7, 26). In Dhaka, (especially in Madagascar), Lyme disease and cuta- Bangladesh, the airborne lead concentration is one of neous leishmaniasis have all become more urban in the highest in the world, and the mean concentration their distribution, reflecting ongoing changes in of lead in blood in 93 randomly chosen rickshaw human demography and behaviour and in the pullers was 53 mg/dl, five times higher than the environment as urbanization proceeds (22). acceptable limit in high-income countries. The lead A new concern is that as global temperatures content of petrol sold in Africa is the highest in the continue to rise, which they have done over the past world and is associated with high concentrations of quarter of a century, mosquito-borne infections, such lead in the atmosphere, dust and soil. Many other as malaria, will become more prevalent in highland exposures in Africa come from industrial sources, cities in low-latitude countries (such as Nairobi and cottage industries and domestic sources. In recent Harare). Recent movements of such vector organ- surveys, more than 90% of the children in the Cape isms and their diseases to higher altitudes may be an Province, South Africa, had lead concentrations in early response to climate change (23), although causal blood over 10 mg/dl (27). attribution remains difficult because of the limited The best available estimate of the neurotoxicity evidence. Associated with this is the belief held by of lead at low doses in childhood comes from cohort some climatologists that rainfall patterns will inten- studies conducted in industrialized urban popula- sify as a result of global warming and more local tions. These studies indicate that preschool-aged flooding will occur, facilitating the breeding of children whose blood concentrations of lead are in mosquitoes and causing microbiological contamina- the top and bottom quintiles, and which thus differ tion of urban sources of drinking-water. by around 10 mg/dl, have a persistent 2–3% The advance of dengue fever in tropical and difference in measures of intelligence (28). Lead- subtropical zones has been aided by the expansion in induced deficits in children’s intelligence are there- urban areas of breeding sites for the Aedes aegypti fore probably widespread in cities of developing mosquito. This disease is now the most frequently countries that have persistently high levels of occurring vector-borne infectious disease in urban environmental exposure to lead. areas. The more recent spread (particularly via the Urban transport and air pollution. One international trade in used car tyres that contain consequence of the global influence of transnational mosquito eggs) of the second mosquito vector of corporations is that private car ownership is increas- dengue fever, Aedes albopictus, has increased the risk ing spectacularly. In 2000 there are more than of infection in urban settings in several subtropical 750 million cars in the world. This rapid growth in and warmer temperate zones. car ownership reflects the influence of advertising, the power of the roads lobby, the wealth of Physical and chemical hazards consumers and their desire for status, comfort and The modern urban environment combines indus- mobility. In cities where there is no public transport, trialization, crowding, waste generation, and dense private cars are especially desirable. Car congestion is transport systems. This combination, compounded now endemic in cities everywhere (29). In addition to by the periurban poverty that surrounds many cities the fragmentation of neighbourhoods, intrusive in developing countries and the poverty of inner noise, and restrictions on physical exercise, there urban areas in cities in the developed world, are three broad categories of public health hazard introduces many environmental health hazards from urban car traffic. Firstly, over 750 000 people die from car crashes annually, including car occu-

1120 Bulletin of the World Health Organization, 2000, 78 (9) Health and the urban environment in a world of increasing globalization pants, pedestrians and cyclists, most of them in ranges, from respiratory and cerebrovascular disease developing countries (30). (36). In the greater London area, where daytime Secondly, emissions from vehicles cause local temperatures were higher (and where, as in all large air pollution, particularly photochemical smog during cities, there is less cooling at night), mortality summer. Urban air pollution has, in recent decades, increased by around 15%. The excess mortality risks become a worldwide public health problem, particu- were generally greater among socioeconomically larly in many large cities in the developing world. An deprived groups (37). estimated 130 000 premature deaths and 50–70 mil- There is a need for studies on the impact of lion incidents of respiratory illness occur each year extremes of heat and cold on urban populations living due to episodes of urban air pollution in developing in the developing countries. Most research has been countries, half of them in East Asia (31). done in the United States and Europe. In Mexico City, for example, three-quarters of Agriculture in urban areas. Agriculture in the air pollution is caused by motor vehicle exhaust, urban areas is increasingly prevalent in many and nearly half of the toxins within that pollution developing countries. Typically, between one-quarter come from the same source (32). In Sa˜o Paulo, which and three-quarters of families carry out some type of currently has a population of around 17 million, rapid small-scale gardening for food, usually despite both development has created a culture of car dependency, official disapproval and regulatory prohibition. This with little investment in the subway and rail systems. activity reflects both cultural and economic forces: The proportion of trips in a motorized vehicle taken the maintenance of rural traditions and knowledge by car in Sa˜o Paulo has doubled over the past quarter and as a form of insurance (mostly by women) against of a century, from around 25% to 50%; the number monetary poverty. of vehicles in the city is estimated at five million, two- Urban agriculture has nutritional, economic and thirds of which circulate within the city each day (33). social benefits. It also has health hazards including the Studies elsewhere have shown that increases in potentiation of vector-borne infectious diseases (for airborne nitrogen oxides and fine particulates are example, the development of mosquito breeding sites followed by an increase in the incidence of, and in irrigation channels), exposure to pesticides and mortality from, respiratory diseases in children and various types of contamination of locally grown food the elderly over the ensuing several days. The local caused by the presence of lead and other heavy metals topography and climate exacerbates air pollution in in the soil, and microbiological contamination from winter, when strong thermal inversions trap the the use of human excrement as fertilizer. pollutants close to the ground (33). Thirdly, exhaust emissions contribute to acid rain and to the global accumulation of carbon The larger dimensions of urban dioxide. Each of these have wide ranging conse- impact on environmental health quences for human health. In developed countries, traffic exhaust accounts for approximately one- There is a larger framework within which to consider quarter of all carbon dioxide emissions. health in an urban environment. The impact of Heatwaves, urban vulnerability and mortality. burgeoning urban populations on the wider environ- Heatwaves adversely affect health. The frequency ment is escalating and is bound up with the composite and intensity of heatwaves will likely increase over the process of globalization. This process entails an coming century as world temperatures rise (34). The increase in various types of interconnectedness that impact of heatwaves on mortality is typically greatest transcend national boundaries and other traditional in the centre of large cities, where not only do demarcations (38). The process of globalization, which temperatures tend to be higher than in the suburbs has been evolving over several centuries, has been and surrounding countryside but night-time cooling greatly amplified over the past two decades by the is lessened. This ‘‘heat island’’ effect is caused by the transnational economic reshaping of world trade and large heat-retaining structures and treeless asphalt investment, as free market economics has achieved expanses of inner cities and the physical obstruction ideological and political ascendancy. The concurrent of cooling breezes. revolutions in human mobility and electronic com- Studies of heatwaves have shown that those munications have contributed to this interconnected- who are most vulnerable to heat-related illness and ness. The centrepiece of economic globalization is the death are elderly people, those who are sick and poor new freedom of capital to cross national boundaries people living in urban areas. In the United States in and the accompanying market in international cur- July 1995 more than 460 extra deaths occurred as a rency, now freed from exchange controls. result of a heatwave in Chicago during which Economic globalization has resulted in an temperatures reached 40 oC. The rate of heat-related international division of labour. In particular, the death was much greater among African Americans manufacturing of ‘‘low-end’’ products — such as than the rest of the population and among people footwear, garments, and toys — and the introduction who were confined to their beds or poorly ventilated of low-end processes — such as electronic assembly inner-city apartment blocks (35). In the severe — has been increasingly outsourced by high-income heatwave in England and Wales in 1995, a 10% industrialized countries to poorer countries where excess of deaths occurred, particularly in the adult age labour is cheap and workplace standards are

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comparatively unregulated. Less developed coun- vastly larger than a city itself. Feeding the residents of tries, which have small internal markets, strive to imperial Rome two thousand years ago was depen- generate wealth by exporting goods from light dent on importing more than 1000 tonnes of grain manufacturing to the developed world, where the daily from North Africa. Today, the highly urbanized low price of these products helps maintain low Netherlands consumes resources from a total surface inflation in the developed countries. These practices area equivalent to 15 times larger than itself. The have two main consequences for the less developed consumption of food, wood, paper and fibres by countries. Firstly, socioeconomic stratification is 29 Baltic cities requires a total area 200 times larger widened by supranational economic forces. People than the combined area of the 29 cities; this total area working in favoured sectors (for example, tourism) comprises 17 units of forest, 50 units of arable land prosper; those working in export-led manufacturing and 133 units of marine ecosystems (42). Similarly, earn subsistence wages; and those remaining in Rees estimates that the almost 500 000 residents of sectors not keyed in to the global economy (for Vancouver, Canada, who occupy just 11 400 hec- example, many rural workers) suffer. Many rural tares, actually use the ecological output and services communities thus become marginalized both glob- of 2.3 million hectares (41). This ratio of 207:1 for the ally and nationally. This results in an inevitable urban population is substantially greater than the ratio downward spiral of environmental degradation, of 12:1 for the regional population of the Lower increased poverty, food insecurity, the stunting of Fraser Basin overall, which includes Vancouver as a children’s growth and increasing health risks from whole. infectious diseases. Secondly, the fall of commodity There is nothing intrinsically undesirable about prices and the low prices paid for low-end manu- such ratios, so long as urban populations in aggregate factured goods in a competitive global marketplace can achieve an ecologically sustainable way of life. where trading loyalties no longer count, may consign The scale of the externalities of urban populations is exporting countries to continued poverty. The growing (40, 43). The externalities now include growth of slums and shanty towns in and around massive urban contributions to the world’s problems cities in the developing world is an expression of the of greenhouse gas accumulation, stratospheric ozone persistent and widening economic inequalities in the depletion, land degradation, and destruction of world. coastal zones. Indeed, cities play a central part in Worldwide, poorer residents of large cities bear much of the large-scale pressure that people impose the brunt of the adverse health consequences of on the biosphere’s life-support systems. These environmental degradation. Industrial activities are systems provide environmental stabilization, biolo- often concentrated near impoverished communities gical productivity, the cleansing of water and air, and living on the fringes of urban areas where the the recycling of nutrients. Whereas our predecessors enforcement of environmental standards is weakest. could take these environmental ‘‘services’’ for In South Africa, for example, the industrial pollution granted in a less populated world on which they affecting townships such as Soweto and Mafefe is had less impact, today humankind is introducing well documented (39). Two-fifths of the population unprecedented change to the global environment. of Soweto lives in houses with asbestos roofs. These large-scale changes pose long-term risks to the health of human populations (44). The most prominent of these changes is Urban ‘‘ecological footprints’’: climate change, occurring in response to the human- endangering global sustainability induced accumulation of heat-trapping greenhouse gases in the lower atmosphere (34). The urbanized Urban populations play a dominant role in the developed world, which accounts for one-fifth of the mounting pressures on the world’s ecosystems. world’s population, contributes about three-quarters Girardet says that cities ‘‘are also vast processors of of all human-made emissions of greenhouse gases food, fuels, and the many raw materials that feed a (34). The contributions from urban populations in civilization. With their complexmetabolisms they are developing countries are rapidly increasing, although huge organisms without precedent in nature: their they are starting mostly from a lower base level. connections stretch across the globe’’ (40). Cities A brief consideration of climate change and thus have increasingly large ‘‘ecological footprints’’ health illustrates the nature of these health hazards (41). The ecological benefits of urbanization include (45) and the fact that that, generally, poor populations economies of scale, the shared use of resources and in urban areas will be particularly vulnerable to the opportunities for reuse and recycling. However, there adverse health impacts of climate change (37). An are great externalities, that is environmental and increase in the incidence of heatwaves would cause an social costs not reflected in the market price. Urban increase in heat-related mortality and illness during populations depend on supplies of imported food, the summer. By contrast, less severe cold weather raw materials (timber, metals, fibre, etc.), external would reduce the documented seasonal excess of energy sources (especially fossil fuels) and on being deaths in winter. Hot weather would also amplify the able to dispose of their voluminous wastes elsewhere. production of photochemical smog (for example, Urban populations depend on access to ozone) in urban areas, thereby increasing health risks. environmental goods and services from an area Other impacts of climate change on health would

1122 Bulletin of the World Health Organization, 2000, 78 (9) Health and the urban environment in a world of increasing globalization arise from disturbance of the world’s biophysical and opportunity. Cities are sources of ideas, energy, systems, thereby affecting the various foundations of creativity and technology. They can foster enligh- public health, such as the sufficiency of local food tened, congenial multicultural living. However, cities production, the provision of safe and adequate also continue to be sources for poverty, inequality drinking-water, the provision of secure community and environmental health hazards. Populations in the settlements and family shelter, and the ability to cities of less developed countries typically experience control various infectious diseases. Early changes the double environmental health jeopardy of the may well be the result of alterations in the traditional risks from infectious diseases and the geographical range (latitude and altitude) and season- physical and chemical hazards that accompany poorly ality of certain vector-borne infectious diseases, such regulated industrialization, substandard housing, as malaria, dengue fever, schistosomiasis, leishma- traffic hazards, and social violence. niasis, Lyme disease, and various tick-borne viral Urban populations around the world are encephalitides (23, 46). Health would also be increasing the pressure on the natural environment. jeopardized by rising seas and by the displacement As fossil fuel combustion increases, as land is cleared, of populations caused by physical hazards, land loss, a as the number of consumers and their expectations decline in water supplies, economic disruption and rise, so cities are contributing to the degradation of civil strife. These effects, and those caused by altered the world’s natural systems. These large-scale patterns of agricultural yields, would probably not environmental problems should be remedied with become evident for several decades. win-win strategies that also ameliorate the existing, Estimates of the regional impact of climate and usually unequally distributed, urban environ- change have been more difficult to generate because mental health hazards. Poverty is at the heart of this of the peculiarities of the behaviour of climate challenge, but better management of the environ- systems within local environments. However, regio- ment is an important part of the solution (39). nal modelling is becoming more robust. For example, Solutions require radical social and technolo- climatologists estimate that by 2050 the Sahara and gical transformations. These solutions include ex- the semi-arid parts of southern Africa may increase in panding the provision of education and training; the temperature by 1.6 oC. Equatorial countries such as international transfer of appropriate technology; an Cameroon, Uganda and Kenya could experience enhanced role for the state as a modern, efficient and temperatures that are 1.4 oC higher (34). Trends in transparent institution; a more equal redistribution of mean rainfall for 1901–95 show that some regions in income, especially within developing countries; Africa have experienced an increase while others international alleviation of debt; and a true inter- have had a decrease. Projections are that rainfall will national commitment to sharing the world’s common increase in East Africa and decrease in West and property resources (such as the atmosphere and the North Africa (47). These projections are hampered ocean fisheries). This last objective could be achieved by problems in the down-scaling to regional level of via a targeted convergence granting equal access per global predictive models. person, internationally, to the biosphere’s sources There is a flip side to this calculus of health and waste-absorbing sinks. (Both the 1987 Montreal risks. If the world were to comply with targets to Protocol and the 1997 Kyoto Protocol, for con- reduce greenhouse gas emissions then a great deal straining the emission of ozone-destroying gases and less fossil fuel would be burnt in urban environments greenhouse gases, respectively, point in the direction and much of the disease and mortality in urban areas of eventual intercountry convergence in per-person caused by toxic air pollutants would be averted (48). atmospheric emissions.) Estimates for China indicate that if China were to In the 21st century we will undoubtedly modify comply with the 1997 Kyoto Protocol (agreed under the design and use of our cities. City planners will the UN Framework Convention on Climate Change) probably develop approaches to allow us to live in by reducing CO2 emissions, then by 2020 the annual high-density ‘‘urban villages’’ separated by parklands, number of premature deaths from ambient (external) recreation facilities and garden plots, and connected air pollution that could be avoided would range from by light-rail transport. Urban greenery, gardens and 2000 to 16 000; the number of deaths that could be horticulture will thus be reinstated. Urban commu- avoided by simultaneously reducing indoor expo- nity structures and facilities will be recreated on a sures (where coal is currently the main domestic fuel human scale. Environmentally benign technologies and exposures are often extreme) would range from for transport and generating energy will be taken up. 50 000 to 500 000. The width of these ranges reflects Most importantly, both social equity and ecologically both the existence of alternative technological sustainable ways of living will be sought. approaches to emission reductions and the uncer- Cities have become the great contemporary tainties of the dose-specific risks to health (49). focal points of human ecology. They are a fulcrum that allows great leverage in reshaping how humankind lives. Ecologically sustainable cities, Conclusion based on low-impact technologies, social enlight- enment and sharing, are an essential part of our City living is the keystone of human ecology. Humans future survival. n are social animals, craving comfort, security, variety

Bulletin of the World Health Organization, 2000, 78 (9) 1123 Special Theme – Environment and Health

Re´ sume´ La sante´ en milieu urbain : conse´ quences de la mondialisation pour les pays en de´ veloppement Le mode de vie urbain est la clef de vouˆ te de l’e´ cologie terme. A ce phe´nome`ne s’ajoute celui de la mondialisa- humaine moderne. Au cours des deux derniers sie`cles, les tion observe´ sur la plus grande surface du globe dans les villes se sont multiplie´esetde´veloppe´ es rapidement dans domaines social, politique et e´conomique et qui, a` son le monde entier. Berceau de la cre´ ativite´etdela tour, cre´ e de nouvelles de´pendances dans les pays technologie et moteur de la croissance e´conomique, elles pauvres qui s’efforcent de faire face a` la concurrence sur engendrent aussi la pauvrete´, des ine´galite´ s et des le marche´ mondial. Il s’ensuit que les normes risques pour la sante´ lie´s a` l’environnement. Depuis environnementales sur le lieu de travail et la protection longtemps, les populations urbaines servent a` la fois de l’environnement sont insuffisantes et que les e´carts de d’incubateur et de porte d’acce`s aux maladies infectieu- revenu se creusent, autant de facteurs qui influent sur la ses. Les citadins des pays en de´veloppement sont donc sante´ des populations. doublement expose´s : aux risques classiques de maladie Les consommateurs devenant de plus en plus diarrhe´ ique et d’infection respiratoire ; aux risques nombreux et exigeants, les villes contribuent dans une physiques et chimiques des temps modernes, lie´s a` une tre`s large mesure aux agressions que subit la biosphe`re industrialisation mal controˆle´e, a` de mauvaises condi- et notamment aux changements climatiques. Les villes tions de logement, a` la circulation routie`reeta` la violence des pays de´veloppe´s, qui abritent un cinquie`me de la sociale. population mondiale, e´mettent les trois quarts environ La croissance non planifie´e et la politique des gaz a` effet de serre ge´ne´re´s par l’activite´ humaine. e´conomique de laisser-faire des de´buts de l’e`re Bien que ge´ne´ ralement plus faibles au de´ part, les industrielle ont fait place a` une gestion collective du e´missions imputables aux populations urbaines des pays milieu urbain, en re´action a`lade´gradation de en de´veloppement augmentent rapidement. l’environnement et du fait de l’alphabe´ tisation, de L’e´volution du climat de la plane` te aura toutes l’ave`nement de la de´mocratie et de l’accumulation de sortes de re´percussions sur la sante´ humaine, pour la richesses. Dans de nombreux pays a` faible revenu, ce plupart ne´fastes. D’une manie`re ge´ne´ rale, les plus progre`s est freine´ par les impe´ratifs et les tendances anti- vulne´rables seront les populations pauvres des zones corporatistes de la mondialisation de l’e´conomie. urbaines. On peut re´ partir les effets du milieu urbain sur la Pour re´soudre ces proble`mes e´ cologiques de sante´ en trois grandes cate´gories. La premie`re concerne grande ampleur, il faut des strate´gies avantageuses les changements sociaux dont s’accompagne l’urbanisa- pour tous qui visent aussi a`re´duire les ine´galite´s et les tion et la fac¸on dont ils modifient les risques pour la sante´ risques pour la sante´ auxquels sont expose´ s nombre de lie´s au comportement. Le re´gime alimentaire, l’activite´ citadins au niveau local. La solution passe par des physique, les comportements toxicomaniaques, la changements sociaux et technologiques radicaux, sexualite´ et la nature de l’engagement social changent. notamment une ferme volonte´, au niveau international, Le risque de maladie cardio-vasculaire, de diabe` te sucre´, de mettre en commun les ressources de la plane` te, telles de certains cancers, d’infection sexuellement transmis- que l’atmosphe` re et les peˆcheries en mer. sible et de proble`mes mentaux e´volue lui aussi. Il y a tout a` parier que notre conception et l’usage La deuxie`me cate´gorie concerne les risques que nous faisons de la ville changeront au XXIe sie`cle. Les microbiologiques et les risques de toxicite´ pre´sents dans urbanistes imagineront probablement des solutions nous le milieu urbain. A la menace que constituent permettant de vivre dans des « villages urbains » a` forte habituellement les maladies infectieuses pour les citadins densite´ de population, se´pare´s par des espaces boise´s, pauvres s’ajoutent des dangers de nature physico- des aires de loisir et des jardins, et relie´s entre eux par un chimique tels que l’exposition au plomb (dans l’air, le sol re´seau de transports ferroviaires le´gers. On re´introduira et l’eau), la pollution atmosphe´rique, les accidents de la ainsi les espaces verts, les jardins et l’horticulture ; les circulation et l’amplification des vagues de chaleur dans infrastructures collectives seront de taille humaine ; les les zones urbaines. modes de transport et les sources d’e´nergie seront sans Troisie`me point : l’influence des populations danger pour l’environnement. Mais surtout, on tendra urbaines modernes sur l’environnement atteint une telle vers l’e´quite´ sociale et un mode de vie e´cologiquement ampleur qu’elle entraıˆne, par la destruction des milieux viable. vitaux de la biosphe`re, des risques pour la sante´a` long

Resumen La salud y el entorno urbano en un mundo cada vez ma´ s globalizado: problemas para los paı´ses en desarrollo El modo de vida urbano es la piedra angular de la de creatividad y tecnologı´a y motores del crecimiento ecologı´a humana moderna. En todo el mundo, las econo´ mico. Sin embargo, tambie´n son fuente de ciudades se han multiplicado y extendido ra´ pidamente a pobreza, desigualdades y peligros medioambientales lo largo de los dos u´ ltimos siglos. Las ciudades son fuente para la salud. Durante mucho tiempo, las poblaciones

1124 Bulletin of the World Health Organization, 2000, 78 (9) Health and the urban environment in a world of increasing globalization urbanas han servido de incubadora y vı´a de entrada imperante en la mayor parte del mundo, que a su vez para las enfermedades infecciosas. Y en particular las crea nuevas dependencias para los paı´ses ma´ s pobres, poblaciones urbanas de los paı´ses en desarrollo corren los cuales esta´ n luchando por competir en el mercado en general un doble peligro, pues esta´ n expuestas tanto mundial. Las deficiencias resultantes en lo tocante a la a los riesgos tradicionales, desde las enfermedades calidad del entorno laboral y a la proteccio´ n medioam- diarreicas a las infecciones respiratorias, como a los biental, ası´como el recrudecimiento de las disparidades peligros modernos, fı´sicos y quı´micos, que traen consigo en materia de ingresos, tienen consecuencias para la una industrializacio´ n mal regulada, unas viviendas en salud de la poblacio´n. malas condiciones, el tra´ fico y la violencia social. Debido al aumento del nu´ mero de consumidores y La primera fase de la industrializacio´ n, caracteri- de sus expectativas, las ciudades contribuyen enorme- zada por un crecimiento no planificado de las ciudades y mente a las presiones a gran escala que sufre la por la economı´a del laissez-faire, ha dado paso a la bioesfera, en particular al cambio clima´ tico. El mundo gestio´ n colectiva del entorno urbano. Esto ha sucedido desarrollado urbanizado, que cuenta con una quinta como respuesta al deterioro del entorno, paralelamente parte de la poblacio´ n mundial, produce unas tres cuartas al aumento de la alfabetizacio´ n, el desarrollo de partes de todas las emisiones de gases termoactivos de gobiernos democra´ ticos y el crecimiento de la riqueza. origen humano. La contribucio´ n de las poblaciones En muchos paı´ses de ingresos bajos este proceso es ma´s urbanas de los paı´ses en desarrollo a ese feno´ meno esta´ lento debido a las presiones y las prioridades anti- aumentando ra´ pidamente, aunque en la mayorı´a de los corporativas de la globalizacio´ n econo´ mica. casos el punto de partida es ma´ s bajo. Existen tres vı´as principales a trave´s de las cuales el Las alteraciones del clima mundial ocasionara´n entorno urbano afecta a la salud humana. La primera son muchos cambios en la salud humana, la mayorı´a de ellos los cambios sociales que entran˜ a la urbanizacio´n y el adversos. En general, la poblacio´ n pobre que vive en modo en que dichos cambios inciden en los riesgos zonas urbanas sera´ particularmente vulnerable. comportamentales para la salud. Estos cambios afectan Deberı´a ponerse remedio a estos problemas a los ha´ bitos de alimentacio´ n, a la actividad fı´sica, los medioambientales en gran escala mediante estrategias comportamientos adictivos, la conducta sexual y que beneficien a todas las partes, y que adema´ s reduzcan diferentes tipos de compromisos sociales. Tambie´n las desigualdades existentes y los peligros locales para la varı´an los riesgos de padecer enfermedades cardiovas- salud a que esta´ n expuestos muchos habitantes de las culares, diabetes mellitus, algunos ca´ nceres, infecciones zonas urbanas. Las soluciones exigira´ n transformaciones de transmisio´ n sexual y problemas de salud mental. sociales y tecnolo´ gicas radicales, incluido un verdadero La segunda vı´a tiene que ver con el entorno fı´sico compromiso internacional de compartir los recursos urbano y sus diversos riesgos microbiolo´ gicos y de mundiales de propiedad comu´ n, tales como la atmo´ sfera toxicidad. Adema´ s del riesgo tradicional que suponen las y la pesca del oce´ano. enfermedades infecciosas para los pobres de las zonas En el siglo XXI modificaremos sin duda el disen˜ode urbanas, el entorno urbano tambie´n esconde diversos las ciudades y las usaremos de otro modo. Los urbanistas peligros fisicoquı´micos, como por ejemplo la exposicio´n probablemente desarrollara´ n criterios que nos permitira´n al plomo (a trave´s del aire, la tierra y el agua), la vivir en «aldeas urbanas» de alta densidad separadas por contaminacio´ n del aire, los peligros del tra´ fico y la parques, instalaciones recreativas y zonas verdes, y amplificacio´ n que de las olas de calor provoca la bo´ veda comunicadas mediante formas de transporte ferroviario te´rmica urbana. ligero. Reaparecera´ n la vegetacio´ n urbana, los jardines y La tercera vı´a guarda relacio´ n con el impacto la horticultura. Se volvera´ n a crear estructuras y servicios medioambiental a gran escala de las poblaciones comunitarios urbanos a escala humana. Se adoptara´n urbanas modernas; la perturbacio´ n de los sistemas de tecnologı´as electro´ genas y de transporte respetuosas del la bioesfera necesarios para la vida provoca riesgos para medioambiente. Y lo que es ma´ s importante, se la salud a ma´ s largo plazo. Esto coincide con la procurara´ fomentar tanto la equidad social como la globalizacio´ n social, polı´tica y econo´ mica general adopcio´ n de modos de vida ecolo´ gicamente sostenibles.

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