Exposure assessment is the process of estimating or measuring the magnitude, frequency and duration of exposure to an agent, along with the number and characteristics of the population exposed. Ideally, it describes the sources, pathways, routes, and the uncertainties in the assessment. Exposure assessments are typically done for a defined population, for example, the general population of individuals in a country, adults of working age, or children less than 10 years old. In many cases, defined subpopulations have activities or behaviors that make them more likely to be in contact with an agent, such as households that use pesticides frequently or individuals who raise some of their own food. Environmental contaminants are analyzed according to their releases, movement and fate in the environment, and the exposed populations. Consumer products and pharmaceuticals are analyzed in terms of reasonably foreseeable potential exposures. Other residential sources of chemicals can come from household air and water. For example, chemicals in air can deposit on, absorb into, or adsorb onto household materials (such as carpets and foods and food packaging), which can lead to dermal and oral exposures. When chemicals are confined to indoor spaces and not diluted in outdoor air, there can be large differences in indoor versus outdoor levels of a chemical.