Environmental epidemiology is the branch of epidemiology concerned with discovery of the environmental exposures that contribute to or protect against injuries, illnesses, developmental conditions, disabilities, and deaths; and identification of public health and health care actions to avoid, prepare for, and effectively manage the risks associated with harmful exposures. Environmental epidemiology studies external factors that affect the incidence, prevalence, and geographic range of health conditions. These factors may be naturally occurring or may be introduced into environments where people live, work, and play. Environmental exposures are involuntary and thus generally exclude occupational exposures and voluntary exposures such as active smoking, medications, and diet. Environmental exposures can be broadly categorized into those that are proximate (e.g. directly leading to a health condition), including chemicals, physical agents, and microbiological pathogens, and those that are more distal, such as social conditions, climate change, and other broad scale environmental changes. Proximate exposures occur through air, food, water, and dermal contact. Distal exposures cause adverse health conditions directly by altering proximate exposures, and indirectly through changes in ecosystems and other support systems for human health.
Environmental epidemiology seeks to:
- understand who is most vulnerable and sensitive to an exposure,
- evaluate mechanisms of action of environmental exposures,
- identify public health and health care policies and measures to manage risks, and
- evaluate effectiveness, costs, and benefits of these policies and measures, as well as provide evidence for accountability.
Environmental epidemiology research can inform risk assessments; development of standards and other risk management activities; and estimates of the co-benefits and co-harms of policies designed to reduce global environment change, including policies implemented in other sectors (e.g. food and water) that can affect human health.
Vulnerability is the summation of all risk and protective factors that ultimately determine whether an individual or subpopulation experiences adverse health outcomes when an exposure to an environmental agent occurs. Sensitivity is an individual’s or subpopulation’s increased responsiveness, primarily for biological reasons, to that exposure. Biological sensitivity may be related to developmental stage, pre-existing medical conditions, acquired factors, and genetic factors. Socioeconomic factors also play a critical role in altering vulnerability and sensitivity to environmentally mediated factors by increasing the likelihood of exposure to harmful agents, interacting with biological factors that mediate risk, and/or leading to differences in the ability to prepare for or cope with exposures or early phases of illness. Populations living in certain regions may be at increased risk because of the physical location and/or environmental characteristics of a region.
See also 
- Environmental health
- Environmental science
- C. Arden Pope
- Occupational safety and health
- Balbus JM, Malina C. 2009. Identifying vulnerable subpopulations for climate change health effects in the United States. J Occup Environ Med 51:33-37.
Further reading 
- Baker, D. and Nieuwenhuijsen, M.J., ed. (2008). Environmental Epidemiology: Study Methods and Application. New York: Oxford University Press. ISBN 978-0-19-852792-3.
- The International Society for Environmental Epidemiology
- International Epidemiological Association
- Journal of Exposure Science and Environmental Epidemiology
- Epidemiology journal
- Environmental Health Perspectives (news and peer-reviewed research journal published by the National Institute of Environmental Health Sciences)