Health effects (or health impacts) are changes in

health Health has a variety of definitions, which have been used for different purposes over time. In general, it refers to physical and emotional well-being, especially that associated with normal functioning of the human body, absent of disease, p ...

resulting from exposure to a source. Health effects are an important consideration in many areas, such as

hygiene Hygiene is a set of practices performed to preserve health. According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

studies,

occupational safety and health Occupational safety and health (OSH) or occupational health and safety (OHS) is a multidisciplinary field concerned with the safety, health, and welfare of people at work (i.e., while performing duties required by one's occupation). OSH is re ...

, ( utrition and

health sciences The following outline is provided as an overview of and topical guide to health sciences: Health sciences – those sciences that focus on health, or health care, as core parts of their subject matter. Health sciences relate to multiple a ...

in general. Some of the major environmental sources of health effects are

air pollution Air pollution is the presence of substances in the Atmosphere of Earth, air that are harmful to humans, other living beings or the environment. Pollutants can be Gas, gases like Ground-level ozone, ozone or nitrogen oxides or small particles li ...

water pollution Water pollution (or aquatic pollution) is the contamination of Body of water, water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and ...

soil contamination Soil contamination, soil pollution, or land pollution as a part of land degradation is caused by the presence of xenobiotic (human-made) chemicals or other alteration in the natural soil environment. It is typically caused by industrial activit ...

noise pollution Noise pollution, or sound pollution, is the propagation of noise or sound with potential harmful effects on humans and animals. The source of outdoor noise worldwide is mainly caused by machines, transport and propagation systems.Senate Publi ...

and

over-illumination Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. In a descriptive sense, the term ''light pollution'' refers to the effects of any poorly implemented lighting sources, during the day or night. Lig ...

. A non-

stochastic Stochastic (; ) is the property of being well-described by a random probability distribution. ''Stochasticity'' and ''randomness'' are technically distinct concepts: the former refers to a modeling approach, while the latter describes phenomena; i ...

or deterministic health effect has a severity that is dependent on dose and is believed to have a threshold level for which no effect is seen. Stochastic health effects occur by chance, generally occurring without a threshold level of dose, whose

probability Probability is a branch of mathematics and statistics concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1; the larger the probability, the more likely an e ...

is proportional to the dose and whose severity is independent of the dose, such as

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

and genetic effects. Occasionally, lack of exposure to certain effectors has detrimental consequences on an individual's health. Examples of such effectors include sunlight and exercise.

See also