An exposure assessment attempts to answer the following questions for a particular substance or chemical:

• Who or what is exposed (e.g.,people, aquatic ecosystems) ?
• Does the exposure occur through breathing air, drinking water, skin contact or any other routes?
• How much exposure occurs?
• How often and for how long does exposure occur, that is, what is its frequency and duration?

Exposure occurs through contact with a chemical. Such contact can occur by inhaling air, drinking water, eating food, or touching a variety of products that contain the chemical. The concentration of the chemical and the extent of the contact are important components of exposure assessment. The results of an exposure assessment are often considered with a hazard assessment of the chemical. A hazard assessment provides an understanding of the potential for the chemical to cause adverse effects to humans and plant and animal life. Together, the exposure assessment and the hazard assessment can be combined into a risk assessment, which reaches conclusions about the likelihood of adverse effects in the exposed population.