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

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Water and Sediment

Exposure Scenarios

People may be exposed to contaminants in water when consuming water directly as a beverage, indirectly from foods and drinks made with water, or incidentally while swimming. Dermal absorption of water contaminants could occur during activities such as hand washing, bathing, and swimming in a pool or surface water body. People could also contact contaminants in sediment while fishing, clamming, wading, or swimming in a lake, river, or other water body. Inhalation exposures to contaminants in tap water through showering or bathing could also occur.

Exposure to contaminants in water can be estimated by first defining the exposure scenario of interest. Exposure scenarios typically include information on the sources and pathways of exposure, as well as the contaminants of concern, and receptor populations. They might describe a receptor population’s location or activities that may affect exposure and the timeframe over which exposure occurs. For example, ingestion of contaminated water may occur at a residence or at work and be associated with different types of activities (e.g., recreational swimming or consuming tap water used to make coffee). Exposures might occur over short durations (e.g., swimming event) or longer timeframes (e.g., a lifetime drinking water scenario). For any exposure scenario of interest, concentrations of the contaminants in the medium are needed to estimate the exposure dose.

After characterizing the exposed population and identifying exposure concentrations, it is important to define all appropriate exposure factor inputs used to estimate potential exposures and risks. These inputs (intake rates, dermal contact rates, and other relevant patterns of behavior) can be obtained from the Exposure Factors Handbook: 2011 Edition (see Exposure Factors tab).

The table below provides some examples of scenarios involving contaminants in water or sediment. The list of examples is not meant to be exhaustive; there are numerous other ingestion, dermal, and inhalation scenarios that may be constructed based on the specific needs of the assessment. There are also numerous variations of the examples provided in the table. Additional information on exposure scenarios involving contaminated water and/or sediment may be found in the Indirect Estimation Module of the Approaches Tool Set in EPA-Expo-Box.

Examples of Exposure Scenarios Involving Water and Related
Exposure Factor Handbook: 2011 Edition Tables
Source/Pathway Population Activity/Timeframe Intake or Contact Rate Exposure Period
Indoor air; volatilization from water while showering Residential adults and children Showering daily
(Table 16-1)
Short-term, activity-specific
(Table 6-2)
Chronic or sub-chronic, depending on lifestage
Outdoor or indoor air; volatilization from swimming pool water Recreational users Swimming over less than lifetime
(Table 16-1)
Short-term, activity-specific
(Table 6-2)
Sub-chronic
Tap water General population; adults Drinking water at home and away from home over lifetime Daily total tapwater intake
(Table 3-1)
Chronic
Tap water; localized School children Drinking water during time at school; elementary school years
(Table 16-17)
Portion of daily community tapwater ingestion rate
(Table 3-1)
Sub-chronic
Swimming pool water Adults and children recreational users Swimming over the short-term
(Table 16-1)
Ingestion rate while swimming
(Table 3-5)
Acute
Tap water General population; adults Showering; lifetime Total surface area
(Table 7-1)
Chronic
Surface water; localized Children Wading Surface area of legs and feet
(Table 7-2)
Subchronic
Swimming pool water Adults and children recreational users Swimming over the short-term
(Table 16-1)
Total skin surface area
(Table 7-1)
Acute
Sediment; localized Adults Clamming Surface area and solid adherence to skin for face, arms, hands, legs, feet
(Table 7-2, 7-4)
Subchronic

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Several resources are available that illustrate ingestion and dermal scenarios involving exposure to contaminants in water and/or sediment.

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