About environment and health

What is environmental health?

Environmental health includes all aspects of human health and disease that are influenced by factors in the environment. These range from the direct pathological effects of chemicals, radiation and some biological agents to the effects - often indirect - of the broad physical, psychological and social environment on health and wellbeing. Environmental health also refers to the theory and practice of assessing and controlling factors in the environment that can potentially affect health.

How can the environment affect human health?

Environmental factors can influence health in different ways. For example, exposure to some pesticides, toxins, asbestos or other chemicals could increase the risk of developing cancer; exposure to lead and mercury can lead to developmental disorders in children. Particulate matters from air pollution are associated with increased mortality, especially from cardiovascular and cardiopulmonary diseases. Obesity, later followed by diabetes development, can also be considered as an environmental health issue because it is caused by lack of exercise as well as by dietary problems.

In some cases, the association between environmental factors and health effects is strong and consistent, however for most cases the relationships and underlying mechanisms are less straightforward. The vulnerability of individuals and communities to environmental health threats also depends on age and health status, genetic factors, diet and well-being.

The environmental burden of disease

The environmental burden of disease represents the amount of disease (morbidity) and mortality that can be attributed to environmental risks. Quantification of the environmental disease burden is important for developing and evaluating policies. The disease burden can be expressed in Disability Adjusted Life Years (DALYs). DALYs allow representation of the disease burden in a single index, combining information on the number of people affected and the duration and severity of their health state. Using such an index allows comparison of the disease burden between different environmental stressors or, for example, between different countries.

The results of international studies on the environmental contribution to the overall burden of disease vary widely, with estimates ranging from about 2 - 5% (Melse and de Hollander, 2001) to 24% (WHO 2006) or even more (eg Smith et al. 1999). The observed variations are mainly caused by differences in methodology (for example, inclusion of certain risk factors in one calculation -such as accidents and injuries- that are excluded in another); and partly related to actual differences in environmental situation of the locations studied.

References

WHO (2006), Prüss-Üstün A. and C. Corvalán. Preventing Disease Through Healthy Environments – Towards an estimate of the environmental burden of disease. WHO, Geneva

Melse JM, de Hollander AEM (2001). Environment and health within the OECD region: lost health, lost money. Background document to the OECD Environmental Outlook. Bilthoven, RIVM (National Institute of Public Health and the Environment,

Smith KR, Corvalan CF, Kjellstrom T (1999). How Much Global Ill Health Is Attributable to Environmental Factors? Epidemiology. 10(5):573, September 1999.