The populations of rich countries also enjoy better general health; the total burden of illness and death from all causes per million people is about half that of developing countries. However, the disease burden from environmental risks is smaller by a factor of ten.

This underscores the basic, although often overlooked, fact that while growth in industry, power generation, transport and other attributes of economic development brings new environmental challenges, the largest environmental threats to human health come from the poor living conditions that result from the lack of development and growth. Environmental health risks, therefore, can be grouped into two broad categories:

• Traditional hazards, related to poverty and lack of development, such as lack of safe water, scant sanitation and waste disposal, indoor air pollution, and a wide spread of disease vectors (e.g. malaria).

• Modern hazards, caused by development that lacks environmental safeguards, such as urban (outdoor) air pollution and exposure to agro-industrial chemicals and waste, including occupational exposure.

Traditional environmental hazards affect developing countries and the poor most. Their impact exceeds that of modern health hazards by a ratio of 10 for Africa, 5 for Asian countries (except for China), and 2.5 for the Middle East (see Figure 2). Water-borne diseases, caused by inadequate water supply and sanitation, impose an especially large health burden in the African, Asian and Pacific regions. In India alone, more than 700,000 children under five years old die annually from diarrhoea. More than half of the world’s households use unprocessed solid fuels, particularly biomass (crop residues, wood and dung) for cooking and heating in inefficient stoves without proper ventilation, exposing people – mainly poor women and children – to high levels of indoor air pollution (see Box). About half of all these deaths – nearly 1 million – occur in India and China. Vector-borne diseases are affected by a range of environmental conditions and factors, including polluted and standing water; open sewers and certain types of sanitation; clogged storm drains; and floods. In Africa alone, malaria is responsible for about 800,000 deaths annually. A study of environmental health in the Indian state of Andhra Pradesh found that the burden of disease from traditional risks falls disproportionately on the poorest 40 per cent of all households. At the same time, environmental health outcomes show significant variations that cannot be simply explained by a household’s economic status, and hence reflect indicators of human development other than income measure alone.

Conversely, modern threats to human health prevail in industrialized countries that have managed drastically to reduce the exposure of their citizens to traditional environmental hazards. More worrying, however, is the fact that the contribution of modern environmental risks to the disease burden in most developing countries is similar to that in rich ones; in quite a few countries it is even greater (see Figure 2). Urban air pollution, for example, hits its highest levels in China, India and in a number of cities in Asia and Latin America.

The urban poor bear the brunt of air pollution because they often live in densely populated neighbourhoods that use dirty household fuels, burn garbage nearby, and are close to traffic corridors or industries. They travel in open vehicles or walk, and spend much more time outdoors. Thus, the world’s poor are increasingly experiencing the ‘double burden’ of both traditional and modern environmental health risks.

Multiple links
Thus environmental health is yet another dimension of the multi-faceted nature of poverty. The links between poor environmental health and other dimensions of poverty are complex and multiple, reinforcing each other in various ways. Poor people typically face greater environmental health risks in their surroundings because they live in unhealthy locations – such as low-lying and marginal lands – and lack basic infrastructure services, like clean water and sanitation. They are more vulnerable because they are less able – as a result of insufficient education and information, daily drudgery and hardship – to adjust their behaviour to moderate their exposure. Additionally, they are the most susceptible to the effects of such exposures because of the simultaneous effect of several factors, such as exposure to indoor smoke and water-borne pathogens, exacerbated by malnutrition and inadequate health care.

Environmental health is yet another dimension of the multi-faceted nature of poverty

Rapid urbanization and the uncontrolled growth of slums are changing the landscape of environmental health concerns and posing significant new challenges in Africa, Asia and Latin America. They increase the ‘double burden’ for the urban and semi-urban poor, adding risks from modern transport and industrial pollution to exposures from dirty cooking fuels, primitive stoves, crowding, and poor access to water and sanitation. Malaria is also becoming an urban issue in some parts of the world, partly as a result of infrastructure failures such as inadequate drainage systems. Climate change is likely to worsen this situation, while globalization and the liberalization of trade may exacerbate the transmission of some diseases.

The environmental challenges of development and globalization require concerted action but the much higher environmental health costs of living in poverty and lacking basic infrastructure and other services must not be neglected. The best policies will address both types of health damage in a synergistic manner. Such policies include those that promote strong growth and the structures for good governance and can both safeguard the environment and respond to the needs of the poor. Trade-offs are sometimes inevitable. However, they should be made with a full understanding of the net health impacts that result.

Mitigating risks
Better infrastructure and energy services for households and communities are key measures in mitigating the most daunting environmental risks to health. So are interventions to improve housing and to control vectors, including effective health-care systems and equitable education policies. For example, measures like improved water and sanitation, household energy, housing, vector control and pollution management could prevent up to 29 per cent of the total burden of disease in sub-Saharan Africa. Health sector interventions that target the disease clusters associated with these environmental risks could reduce it by a further 28 per cent. Providing water supplies to rural households has been found to be among the most cost-effective preventive health interventions in India. Reducing modern risks calls for measures to prevent and abate pollution. These, in turn, require setting and enforcing environmental standards, developing a culture of environmental compliance and creating effective incentives.