Human Exposure Assessment and Estimation of Internal Dose

To assess human exposure to chemicals, several important exposure parameters must be considered, including the concentration of chemicals in the air or ingested materials, the duration and frequency of exposure, the fraction of chemicals absorbed through the lungs, gastrointestinal tract, or skin, and the body weight of the exposed individual. Ingestion and dermal exposure also require consideration of the number of chemicals consumed or contacted, as well as the contact rate and surface area of the exposed individual.

To estimate potential exposures, terms such as intake, potential dose, applied dose, dose, and biologically effective dose must be defined. Intake refers to the amount of chemical coming into contact with the visible exterior of the body, while the potential dose is the amount of a chemical in materials that could be absorbed. Applied dose refers to the amount of a chemical in contact with the primary absorption boundaries, and dose is the amount absorbed by the body. Biological effective dose refers to the amount of absorbed chemical that reaches the cells or target site where an adverse effect occurs.

When systemic absorption cannot be estimated, intake and dose are considered to be the same to provide a conservative estimate of actual exposures. Internal dose can be estimated by multiplying intake with an absorption factor.

Review questions:

• What exposure parameters are required for estimating inhalation exposure?
• How do ingestion and dermal exposure differ from inhalation exposure in terms of exposure parameters?
• What is the difference between intake and potential dose?
• Why might intake and dose be considered the same in some cases?
• How is internal dose estimated from intake?