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EPA-Expo-Box (A Toolbox for Exposure Assessors)

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Water and Sediment

Exposure Factors

To estimate human exposure to contaminants in water, exposure factor information is needed. Exposure factors are human behaviors and characteristics that help determine an individual's exposure to an agent. Several chapters of EPA’s Exposure Factors Handbook: 2011 Edition contain information that might be relevant for a scenario involving exposure to contaminants in water as shown in the table below. Other exposure factors that may be needed for assessing ingestion, inhalation, or dermal exposures include body weight (Chapter 8) and life expectancy values, specifically when evaluating cancer risk (Chapter 18).

Chapter Exposure Factors for Evaluating Exposure to Contaminated Water
Chapter 3: Water Ingestion Rates
  • Ingestion of water consumed as a beverage (direct water intake)
  • Ingestion of water used in preparing foods and beverages (indirect water intake)
  • Water ingestion while swimming (incidental intake)
Chapter 7: Dermal Exposure Factors
  • Skin surface area for assessing dermal exposure to water (e.g., during hand washing, bathing, swimming)
  • Amount of material that adheres to the skin per unit surface area (i.e., sediment loading) when assessing dermal exposure to contaminants in sediment

*Note that chemical-specific factors related to dermal absorption and internal dose are not provided in Chapter 7.

Chapter 6: Inhalation Rates
  • Inhalation rates associated with vapors from tap water (e.g., during showering)
Chapter 16: Activity-Specific Factors
  • Event frequency (e.g., showers per week)
  • Hand washing frequency
  • Number of swimming events per month
  • Time spent doing specific activities

Drinking water ingestion rates are reported in units of mL/day or mL/kg-day (adjusted for body weight). Ingestion rates should be selected to represent the age, lifestage (e.g., pregnant and lactating women), gender (if appropriate), and activity level for the exposure scenario of interest (e.g., water intake among individuals located in hot climates or engaging in high activity levels, ingestion of water while swimming or diving). Drinking water intake rates are provided as per capita or consumer-only data. Per capita rates include all survey participants whether or not they ingested any water from the source during the survey period. Consumer-only rates exclude individuals who did not ingest water from the source during the survey period. Per capita intake rates should be used in exposure assessments of the general population for which average dose estimates are of interest.

Exposure factor data may be accessed from the Exposure Factors Tab of the Indirect Estimation Module..

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