Environmental epidemiology: An introduction

Epidemiology is increasingly coping with problems correlated with exposures which may have small relative risks. In fact, many chronic diseases, as the most recent common diseases all over the world, may have unknown etiology but also potentially related to environmental exposures. Environmental epidemiology considers the effect of environmental factors on health. More exposure with increasing number of potential environmental hazards has changed the initial application of environmental epidemiology. As a consequence, nowadays it is strongly emphasized on some fields such as molecular epidemiology, but some others have discussed about the importance of its population dimension and the reintegration of epidemiology into public health. Environmental epidemiology research, as a very substantial scope of epidemiology, can consider risk assessments, development of standards and other risk management activities. In addition, it could estimate the co-benefits and co-harms of policies designed to reduce global environment changes, including policies implemented in other sectors (e.g. food and water) affecting human health.1 Environmental epidemiology has indeed several unique features that could make these debates very important. Furthermore, a large number of environmental exposures may require prioritization, with usually very low relative risks.2-3 However, environmental epidemiology has also a more restricted connotation, referring to those environmental factors that are outside of the immediate control of the individual.2 The most important difference of environmental epidemiology with general epidemiology is that the first one could focus more on the living/working environment of people rather than on their personal characteristics or lifestyles. During the recent centuries, environmental epidemiology has achieved remarkable positive health gains by efforts on reduction of the population’s exposure to contaminants in air, water, and soil. However, in the last decades, this concentration has been changed to follow the developments in epidemiology and molecular biology. In fact, with increasing focus on individual exposures and his/her own susceptibility as well as potential mechanisms, environmental epidemiologists may lose their traditional population perspective of disease causation and prevention.