Exposure is the contact between a cell and a substance, a microorganism or radiation. In humans, this can occur through ingestion (swallowing), inhalation (breathing in), skin or eye contact. Exposure can be short-term (acute exposure), of moderate duration or long-lasting (chronic).

Exposure is the contact of a person, an animal or a plant with a substance, a microorganism or radiation. Exposure can be short-term (acute exposure), of moderate duration or long-lasting (chronic exposure).

A distinction is made between external and internal exposure.

External exposure refers to the total dose to which an organism is exposed.

Internal exposure refers to the proportion of the original substance dose that was absorbed via the bloodstream and distributed in the body.

With the help of epidemiology, we can identify links between a disease and a person's exposure. This helps us to control health problems and prevent them through targeted preventive measures against exposure.

To find out whether there is a causal relationship between exposure and disease, different study designs are used and exposed and non-exposed individuals are compared. For diseases such as chickenpox, sunburn or aspirin overdose, it is easy to determine the association between exposure and disease. It is more difficult with diseases that have a long latency period (i.e. that occur much later after the risk has affected them).

The measure for a certain amount of exposure is called dose. In toxicology it is referred to as the lowest known toxic dose TDLo; in toxicology it is referred to as the lethal dose LD.