Estimating Human Exposure to Chemicals: Factors and Parameters.

The estimation of human exposure to potentially harmful chemicals involves calculating the exposure dose, which is expressed in units of milligrams of chemicals per kilogram of body weight per day.

For chronic exposure, the chronic daily intake is estimated, while for subchronic exposure, the subchronic daily intake is used. Non-carcinogenic effects are evaluated by averaging the exposure dose over the exposure period, while potential carcinogenic effects are calculated by averaging the exposure dose over the assumed lifetime of the receptor. The total dose received by the potential receptors from chemical ingestion is dependent on the absorption of the chemical across the gastrointestinal lining.

Multiple exposure parameters are required to model the various exposure scenarios associated with chemical exposure problems. This includes exposure concentration, contact rate, bioavailability or absorption factor, exposure frequency, exposure duration, body weight, and averaging time. In addition, different age groups are considered in most evaluations, including younger children, older children, and adults.

Review questions:

• What is the exposure dose, and how is it expressed?
• How is the chronic daily intake estimated, and what is it used for?
• What factors affect the total dose received from chemical ingestion?
• Why are different age groups considered in evaluations of chemical exposure?