text: The receptor-based approach is used in exposure science. It starts by looking at different contaminants and concentrations that reach people. An exposure analyst can use direct or indirect measurements to determine if a person has been in contact with a specific contaminant or has been exposed to a specific risk (e.g. accident). Once a contaminant has been proved to reach people, exposure analysts work backwards to determine its source. After the identification of the source, it is important to find out the most efficient way to reduce adverse health effects. If the contaminant reaches a person, it is very hard to reduce the associated adverse effects. Therefore, it is very important to reduce exposure in order to diminish the risk of adverse health effects. It is highly important to use both regulatory and non-regulatory approaches in order to decrease peoples exposure to contaminants. In many cases, it is better to change peoples activities in order to reduce their exposures rather than regulating a source of contaminants.
  The receptor-based approach can be opposed to the source-based approach. This approach begins by looking at different sources of contaminants such as industries and power plants. Then, it is important to find out if the contaminant of interest has reached a receptor (usually humans). With this approach, it is very hard to prove that a pollutant from a source has reached a target.