Pollution can be defined as the presence of a substance or agent in the environment that is potentially harmful to health, safety, or comfort. In addition to affecting the health of humans or the ecosystem, pollution may have adverse effects on agricultural products or infrastructure such as buildings or monuments. Pollutants include naturally occurring and industrial chemicals, biological pathogens, and forms of energy such as noise.

The primary significance of pollution to epidemiology lies in its relation to human health. In some cases, this has been well studied, but for thousands of chemicals, it has not. The potential for a pollutant to cause adverse health outcomes is related not only to its toxicity but also on the extent of exposure. Briggs (2003) has estimated that 8% ...