The message that emerges from Linking Environment and Health and Changing Environment, Changing Health is clear: a clean environment supports good health, while a degraded environment increases the likelihood of death and disease. The toll environmental degradation exacts on human health is heavy, especially for children in the poor regions of the world. In the poorest countries, one out of every five children dies before reaching his or her fifth birthday, usually because of an environmentally related – and largely preventable – diseases (1). Improving environmental conditions could thus do much to reduce both death and disease.
Environmental threats to health come from myriad sources, as Linking Environment and Health describes. Many of these threats go hand in hand with poverty and a lack of development; these threats go hand in hand with poverty and a lack of development; these threats tend to be most pronounced at the household or community level. For instance, in impoverished areas, inadequate access to water and sanitation contribute to the 2.5 million childhood deaths each year from diarrhea. Poor drainage and uncollected garbage encourage the proliferation of insect and rodent vectors that carry disease. Household exposure to smoke from burning biomass fuels for heating and cooking contributes to both acute and chronic respiratory disease.
Other environmental risks stem from the processes of economic development and industrialization, when they occur without sufficient safeguards for environmental quality and human health. The three trends discussed in this report – agricultural intensification, industrialization, and rising energy use–are all intimately associated with economic development today. All can contribute enormously to increased prosperity and improved quality of life. Yet, if not properly managed, these trends can also increase risks to human health. Health risks arise not only from direct exposure to polluted air, water, and soil but also indirectly when human activities disrupt ecosystems in unexpected ways. Twenty years ago, for instance, few would have guessed that emissions of chlorofluorocarbons (CFCs) were already damaging the Earth’s protective ozone layer, increasing the risks of developing skin cancer, cataracts, or damage to the immune system (2).
Although the exact contribution of environmental factors to the development of death and disease cannot be precisely determined, the World Health Organization (WHO) has estimated that as much as 23 percent of the global burden of disease is associated with environmental factors (3). Indeed, many of the diseases that each year claim the lives of 11 million children younger than 5 years of age could be prevented by reducing hazards in the environment (4).
Environmental health problems also place significant economic and social burdens on both individuals and societies. In some large urban areas of the developing world, the estimated economic losses each year from air pollution and congestion alone range from US$500 million to US$3.5 billion (5). Exposure to infectious and chemical agents can stunt physical growth, impair cognitive skills, and hamper educational participation and performance, thereby reducing the future potential of individuals and, perhaps, of society as a whole. Preventing these impacts from occurring in the first place is an urgent need because certain impacts such as lowered IQ known to result from exposure to some heavy metals, cannot be remedied.
Because environment and health are so intimately linked, so too should be strategies for improving public health. Yet, with the advent of increasingly sophisticated medical technologies over the past several decades, medical treatment and other clinical interventions have generally received priority over environmental strategies to improve health. Without question, vaccines and drugs have made it possible to prevent or treat diseases that once were certain killers. Indeed, seven major childhood killers – smallpox, diphtheria, tetanus, yellow fever, whooping cough, polio, and measles – have all been brought under varying degrees of control thanks to the development of vaccines (6). Every year, immunization can be credited with saving 9 million lives worldwide (7).
Yet, even in situations where a vaccine or drug exists (and for many environmental threats to human health, one does not), many benefits can be gained by supplementing clinical interventions with environmental management. The rising problem of antibiotic resistance underscores the value of multiple strategies for disease control. Although a specific exposure to an environmental hazard may be the immediate cause of ill health, addressing and correcting the driving forces and pressures contributing to environmental degradation may offer more effective and enduring avenues for improving health over the long term (8). Broad environmental interventions such as ensuring clean air and water will address multiple health conditions and, indeed, may yield other benefits outside of the health arena. Reducing use of fossil fuels, for example, will not only improve air quality for human health today but also may help avert damages from acid rain and mitigate the prospects of future climate change.