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Additional Dermal Pathway-Specific Dose Exposure Parameters
| Exposure Parameters | Description | Exposure Pathways | Guidance Documents |
|---|---|---|---|
| Absorbed dose per event (DAevent)
|
Used to represent the dose of a contaminant absorbed through the skin per event. Dependent on the duration of exposure and on whether the contaminant is organic or inorganic. | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |
| Dermal absorption fraction (ABSd)
|
The amount of a contaminant absorbed into the body through the skin. Included to adjust for the amount of a contaminant that is absorbed into the body through the skin after dermal contact. | Soil/sediment dermal contact
Surface water dermal contact |
Soil/Sediment Dermal Absorption EDG
|
| Gastrointestinal absorption fraction (ABSGI) | The fraction of a contaminant absorbed by the gastrointestinal tract. Used to convert an absorbed dermal dose to an equivalent administered oral dose, which allows health assessors to combine doses from the ingestion and dermal exposure pathway for the same medium (soil/sediment, surface water) to create a total dose, and compare the combined dose to health guidelines or oral cancer slope factors. For most contaminants, ATSDR assumes 100% of the contaminant is absorbed through the GI tract, thus using an ABSGI of 1. For some inorganic compounds, however, ATSDR adjusts the dermal dose using specific absorption factors. |
Soil/sediment dermal contact
Surface water dermal contact |
Soil/Sediment Dermal Absorption EDG
|
| Skin surface area (SA)
|
The amount of skin surface available for dermal contact with contaminants through these media. | Soil/sediment dermal contact
Surface water dermal contact |
Soil/Sediment Dermal Absorption EDG
|
| Soil adherence factor (AF)
|
A measure of soil adherence to the skin. Factors that can impact the soil AF for a site include moisture content, soil type, and the skin barrier. | Soil/sediment dermal contact | Soil/Sediment Dermal Absorption EDG |
| Parameters used to estimate DAevent for Surface Water Dermal Contact Equation | |||
| B ratio | The dimensionless ratio of the permeability coefficient of a contaminant through the stratum corneum relative to its permeability coefficient across the viable epidermis. | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |
| CSW | The chemical concentration in surface water. | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |
| Dermal permeability coefficient (Kp) | The amount of a contaminant that permeates the skin and is absorbed into the body. | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |
| Event duration (tevent) | The duration of exposure for each event in units of hours. The value is site-specific. | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |
| Fraction absorbed (FA) | The amount of a contaminant lost on the skin due to the peeling of the outer layer of skin (called “desquamation”). Without contaminant-specific information, ATSDR uses a default value of 1. | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |
| Lag time per event (τevent) | The contaminant loss due to desquamation as the contaminant crosses the stratum corneum during the absorption process. | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |
| Time to steady state (t*) | The time to reach steady absorption across the skin. For organic contaminants, the equation used to determine DAevent depends on the exposure duration (i.e., the contaminant-specific t* versus the site-specific tevent). | Surface water dermal contact | Surface Water Dermal and Ingestion EDG |