Environmental epidemiology is the branch of epidemiology concerned with the 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 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 microbiologicalpathogens, 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 skin 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 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 due to location and the environmental characteristics of a region.
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