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EPA ExpoBox

Exposure Assessment Tools by Media - Water and Sediment

Overview

Water

Contaminated media to which people may be exposed include air, water and sediment, soil and dust, food, aquatic biota, and consumer products. Surface water can be contaminated by direct discharges or indirect discharges. Examples of direct discharges are those coming from industrial, commercial, agricultural, or residential sites. Examples of indirect discharges are groundwater contaminants that have migrated to surface water, storm water runoff, or settling of contaminants from the atmosphere.

Pollutants in surface water can sink and contaminate sediments. Groundwater can become contaminated when pollutants in subsoil leach to groundwater. Contaminated surface water or groundwater might be used as a source of drinking water.

Exposure to contaminants in water can occur by direct ingestion (e.g., drinking water) or indirect ingestion (e.g., consuming foods and drinks made with water). Incidental ingestion (e.g., swallowing water while swimming), dermal contact (e.g., during showering or bathing, while swimming or wading in surface water), or inhalation (e.g., inhaling vapors during showering) can also occur.

Exposure to contaminants in sediment would likely occur through dermal contact (e.g., while wading or playing in water). The concentrations of contaminants in water or sediment at the point of exposure may differ from the concentration at the source as a result of fate and transport processes (e.g., dilution, biodegradation).

Various tools are available for evaluating sources and releases of contaminants to water and sediment, fate and transport processes, and potential exposure concentrations. Exposure factors, calculation tools, and guidance for assessing exposure to contaminants in water are also provided.

Information about EPA’s Water Programs can be found here:
Learn About Water and Water Science

The National Primary Drinking Water Regulations (NPDWRs or primary standards) are legally enforceable standards that apply to public water systems to protect public health by limiting the levels of contaminants in drinking water. Maximum Contaminant Levels (MCLs) for various chemicals are available at:
Drinking Water Contaminants

EPA’s Watershed Assessment, Tracking & Environmental ResultS (WATERS) program provides a comprehensive listing of resources for assessing water quality:
Watershed Assessment, Tracking and Environmental Results System (WATERS)

Information from the US Geological Survey on water resources can be found at:
Water Resources of the United States

State, USGS, and EPA Regional water websites are provided in the following tables. 

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U.S. State Water Resources The following links exit the site Exit
State URLs
Alabama Alabama Department of Environmental Management - Water Programs
Alabama Water Science Center - Water Resources of Alabama
Alaska Alaska Department of Environmental Conservation - Division of Water
Alaska Science Center - Water Research
Arizona Arizona Department of Environmental Quality - Water Quality Division
Arizona Water Science Center - Water Resources of Arizona
Arkansas Arkansas Department of Environmental Quality - Water Division
Arkansas Water Resources of Arkansas - Water Resources of Arkansas
California California Environmental Protection Agency - Water Boards
California Department of Public Health - Environmental Management Branch
California Water Science Center - Water Science in California
Colorado Colorado Department of Public Health and Environment - Water Quality Control Division
Colorado Water Science Center - Water Resources of Colorado
Connecticut Connecticut Department of Energy and Environmental Protection - Water
Connecticut Department of Public Health - Drinking Water Section
New England Water Science Center - Connecticut Office - Water Resources of Connecticut
Delaware Delaware's Water Quality
Water Science for Maryland, Delaware and the District of Columbia
Florida Florida Department of Environmental Protection - Water Resource Protection Programs
Florida Water Science Center - Water Resources of Florida
Georgia Georgia Environmental Protection Division - Water Protection Branch
South Atlantic Water Science Center - Georgia - Water Resources of Georgia
Hawaii Hawaii State Department of Health - Clean Water
Pacific Islands Water Science Center - Water Resources of the Pacific Islands
Idaho Idaho Department of Water Resources
Idaho Department of Environmental Quality - Water Quality
National Water Information System - USGS Water Data for Idaho
Illinois Illinois Environmental Protection Agency - Water Quality
Illinois Water Science Center - Water Resources of Illinois
Indiana Indiana Department of Environmental Management - Watersheds and Nonpoint Source Water Pollution
Indiana Department of Natural Resources - Water
Indiana Water Science Center - Water Resources of Indiana
Iowa Iowa Department of Natural Resources - Regulatory Water
Iowa Water Science Center 
Kansas Kansas Department of Health and Environment - Water
Kansas Water Science Center - Water Resources of Kansas 
Kentucky Kentucky Department for Environmental Protection - Division of Water
Kentucky Water Science Center - Kentucky Water Resources Program
Louisiana Louisiana Department of Environmental Quality - Aquifer Evaluation and Protection
Louisiana Water Science Center - Water Resources of Louisiana
Maine Maine Department of Environmental Protection - Water Quality
Maine Division of Environmental Health - Drinking Water
New England Water Science Center, Maine Office - Water Resources of Maine
Maryland Maryland Department of Environment - Water Programs
Water Science for Maryland, Delaware and the District of Columbia
Massachusetts Massachusetts Energy and Environmental Affairs - Water Resources Law and Rules
New England Water Science Center - Massachusetts Office - Water Resources of Massachusetts
Michigan Michigan Department of Environmental Quality - Water Quality Monitoring
Michigan Water Science Center - Water Resources of Michigan
Minnesota Minnesota Pollution Control Agency - Water
Minnesota Department of Health - Drinking Water Protection
Minnesota Water Science Center - Water Resources of Minnesota
Mississippi Mississippi Department of Environmental Quality - Water
Mississippi Water Science Center - Water Resources of Mississippi
Missouri Missouri Department of Natural Resources - Air Protection Program
Missouri Water Science Center - Water Resources of Missouri
Montana Montana Department of Environmental Quality - Water
Wyoming-Montana Water Science Center - Water Resources of Wyoming and Montana
Nebraska Nebraska Department of Environmental Quality - Water Quality Division
Nebraska Water Science Center - Water Resources of Nebraska
Nevada Nevada Division of Environmental Protection - Bureau of Water Pollution Control
Nevada Division of Environmental Protection - Bureau of Water Quality Planning 
Nevada Division of Environmental Protection - Bureau of Safe Drinking Water
Nevada Water Science Center - Water Data and Information
New Hampshire New Hampshire Department of Environmental Services - Water Division
New England Water Science Center - NewHampshire/Vermount Office - Water Resources of New Hampshire and Vermount
New Jersey New Jersey Department of Environmental Protection - Division of Water Quality
New Jersey Department of Environmental Protection - Division of Water Supply and Geoscience
New Jersey Water Science Center - Water Resources of New Jersey
New Mexico New Mexico Environment Department - Ground Water Quality Bureau
New Mexico Environment Department - Drinking Water Bureau
New Mexico Water Science Center - Water Resources of New Mexico
New York New York Department of Environmental Conservation - Water
New York Department of Health - Drinking Water Protection Program
New York Water Science Center - Water Resources of New York
North Carolina North Carolina Department of Environmental Quality - Division of Water Resources
South Atlantic Water Science Center - North Carolina Office - Water Quality Information and Data
North Dakota North Dakota Department of Health - Division of Water Quality
North Dakota Department of Health - Drinking Water Program
North Dakota Water Science Center - Water Quality in North Dakota
Ohio Ohio Environmental Protection Agency - Division of Drinking and Ground Waters
USGS Ohio Water Science Center - Your Source for Water Science You Can Use
Oklahoma Oklahoma Department of Environmental Quality - Water Quality Division
Oklahoma Water Science Center - Water Resources of Oklahoma
Oregon Oregon Department of Environmental Quality - Water Quality
Oregon Health Authority - Drinking Water
Oregon Water Science Center - Water Resources of Oregon
Pennsylvania Pennsylvania Department of Environmental Protection - Water Programs
Pennsylvania Water Science Center - Water Resources of Pennsylvania
Rhode Island Rhode Island Department of Environmental Management - Water Quality
Rhode Island Department of Health - Drinking Water Quality
New England Water Science Center - Rhode Island Office - Water Resources of Rhode Island
South Carolina South Carolina Department of Health and Environmental Control - Water
South Carolina Water Science Center - Water Resources of South Carolina
South Dakota South Dakota Department of Environment and Natural Resources - Water
South Dakota Water Science Center - Water Resources of South Dakota
Tennessee Tennessee Department of Environment and Conservation - Water Quality
Tennessee Department of Environment and Conservation - Drinking Water
Tennessee Water Science Center - Water Resources of Tennessee
Texas Texas Commission on Environmental Quality - Water
Texas Water Science Center - Water Resources of Texas
Utah Utah Department of Environmental Quality - Division of Water Quality
Utah Department of Environmental Quality - Division of Drinking Water
Utah Water Science Center - Water Resources of Utah
Vermont Vermont Department of Environmental Conservation - Watershed Management Division
Vermont Department of Environmental Conservation - Drinking Water and Groundwater Protection Division
New England Water Science Center - New Hampshire/Vermount Office - Water Resources of New Hampshire and Vermount
Virginia Virginia Department of Environmental Quality - Water
Virginia Department of Health - Drinking Water
Virginia Water Science Center - Water Resources of Virginia
Washington Washington Department of Ecology - Water Topics
Washington Department of Health - Drinking Water
USGS Washington Water Science Center - Water Quality
West Virginia West Virginia Department of Environmental Protection - Water and Waste
West Virginia Source Water Assessment and Wellhead Protection Programs
West Virginia Environmental Engineering Division
West Virginia Water Science Center - Water Resources of West Virginia
Wisconsin Wisconsin Department of Natural Resources - Water Topics
Wisconsin Water Science Center - Water Resources of Wisconsin
Wyoming Wyoming Department of Environmental Quality - Water Quality
Wyoming-Montana Water Science Center - Water Resources of Wyoming and Montana

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U.S. EPA Regional Water Websites
EPA Region URLs
1: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont New England Drinking Water Program
2: New Jersey, New York, Puerto Rico , U.S. Virgin Islands EPA Region 2
3: Delaware, Maryland, Pennsylvania, Virginia, West Virginia, District of Columbia Impaired Waters and TMDLs
4: Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee Impaired Waters and TMDLs
5: Illinois, Indiana, Michigan, Minnesota, Ohio, Wisconsin Impaired Wters and TMDLs
6: Arkansas, Louisiana, New Mexico, Oklahoma, Texas Impaired Waters and TMDLs
7: Iowa, Kansas, Missouri, Nebraska Impaired Waters and TMDLs
8: Colorado, Montana, North Dakota, South Dakota, Utah, Wyoming Drinking Water Operations
9: Arizona, California, Hawaii, Nevada, territories of Guam and American Samoa Pacific Southwest, Region 9 Water Program
10: Alaska, Idaho, Oregon, Washington EPA Region 10

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Sources

Contamination of water and sediment can occur from anthropogenicHelpanthropogenicResulting from human activity. (manmade) sources or natural sources. Examples of anthropogenic sources include point and nonpoint sources. Natural sources that may contaminate water and sediment include volcanic activity, hurricanes and other storms, forest fires, and earthquakes.

  • Point sources involve releases of pollutants to surface water and sediment from a specific source, such as an outfall pipe or ditch. Examples of common point sources of water pollution include sewage treatment plants, industrial facilities, mining operations, construction sites, and storm drains. Contaminants in the surface water column have the potential to settle and contaminate sediments.
  • Nonpoint sources of water contamination are area-wide releases of pollutants to surface water and sediment, including nutrient runoff from agricultural sites or storm water runoff from urban or suburban sites. Storm water runoff can become contaminated when rain water comes into contact with contaminated soil and either dissolves the contamination or carries contaminated soil particles. Surface water can also be contaminated when contaminated groundwater migrates to surface water or when contaminants in the air are deposited on the surface water. Pollutants in the surface water column have the potential to settle and contaminate sediments.

Contamination of groundwater is not classified as resulting from point or nonpoint sources. Contaminants may leach from soil into the groundwater causing contamination of the aquifer.

Contamination of drinking water can occur at the source (surface water or groundwater), during treatment (e.g., byproducts of chlorination), or after treatment (e.g., lead contamination from corrosion of plumbing materials).

For more information on drinking water contaminants, public water treatment systems, primary drinking water regulations, and private drinking water wells, see the text box on the right and the list of resources provided under Guidance in this module.

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Fate and Transport

Fate and transport processes “link” the release of contaminants at a source with the resultant environmental concentrations to which receptors can be exposed. When a contaminant is released from a source, it is subject to transportHelptransportMovement within a medium or between media. and transformationHelptransformationChange in a chemical or physical state. in the environment. Compounds can also transfer from one environmental medium to another.

Migration Process Examples Relevant to Water and Sediment
Transport
  • Dispersion of a contaminant through surface water (transport within a medium)
  • Contaminants in surface water settle and accumulate in sediments or are resuspended in surface water from sediments following disturbance (transport between media)
  • Contaminants in groundwater are discharged to surface water (transport between media)
Transformation
  • Organic breakdown or biodegradation of a compound in sediment by benthic organisms (chemical change)
  • Inorganic metals that dissolve in surface water (physical change)
Transfer – Environment to Biota
  • Contaminants in sediment are taken up by benthic organisms and bioaccumulated
  • Contaminated surface water or groundwater used as a source of drinking water is ingested by animals or humans

For additional information on the uptake of contaminants from water to fish, refer to the Aquatic Biota Module of the Media Tool Set.

The characteristics of water and sediment play a large role in the transport processes of contaminants through these media. For example, if surface water is a key exposure pathway, data on flow rates and water characteristics like pH, salinity, water hardness, and levels of dissolved oxygen may be needed.

Environmental factors such as percent organic matter can play a large role in the mobility and bioavailability of contaminants in sediment. Physicochemical characteristics—such as water solubility, octanol/water partition coefficient (Kow), and solid/water partition coefficients (Kd or Koc)—are also important for predicting fate and transport behavior of contaminants in the aqueous phase.

There are a number of sources of information related to the environmental fate and transport of contaminants in surface water and sediment.

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Models

Environmental fate and transport models can be used with monitoring data to help characterize media-specific exposure concentrations. A variety of mathematical methods or models are available to describe the multimedia transport and fate of pollutants in the environment. There are also several resources that contain information on input parameters necessary for fate and transport models.

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Concentrations

Estimates of contaminant concentrations in water and/or sediment are needed for assessing exposure via potential exposure pathways involving these media. These media concentrations may also be needed as data inputs for modeling the fate and transport of contaminants in water and the transfer of contaminants to other media.

Characterizing contaminant concentrations for an exposure scenario is typically accomplished using some combination of the following approaches:

  • Sampling water and sediment and measuring contaminant concentrations
  • Modeling the concentration distribution based on source strength, media transport, and chemical transformation processes
  • Using existing, available measured concentration data collected for related analysis or compiled in databases

EPA ExpoBox provides information on measuring or modeling water and sediment concentrations and on available monitoring data. Information on sampling techniques and analytical methods is available to support the measurement of contaminants in water and sediment.

In some cases, available measurement data may be used alone to estimate exposures. In the absence of monitoring data, a variety of models can be used to estimate contaminant concentrations in these media. Models may also be used in conjunction with monitoring data to estimate water and sediment concentrations at the point-of-contact with receptors considering fate and transport processes.

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Measuring Concentrations

A number of sampling techniques or protocols have been established for monitoring and characterizing water and sediment contamination. Sampling protocols are necessary to ensure that samples are collected in a proper manner using suitable equipment to account for environmental conditions.

Analytical methods for measuring concentrations of contaminants in water and sediment may include methods required for specific contaminants or groups of contaminants that are regulated by EPA, or methods for unregulated contaminants or groups of contaminants of interest.

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Modeling Concentrations

In the absence of monitoring data, models may be used to estimate the concentrations of contaminants in water and sediment, such as the following. By modeling contaminant movement and concentrations in freshwater, marine, and estuarine environments, researchers can better understand how these contaminants affect the quality of water, sediment, and aquatic biota.

Groundwater models simulate groundwater flow through the subsurface (and possible migration to surface water) and inform subsurface contaminant transport models.

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Available Data

There are a number of information sources that provide monitoring data on contaminant concentrations in surface water and sediment (also see the Aquatic Biota Module of the Media Tool Set).

Some of these data come from national surveys that help to characterize the chemical, biological, and physical water quality of the Nation’s waters. They may also identify actions to prevent pollution, and evaluate the effectiveness of protection and restoration efforts

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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 scenarioHelpexposure scenarioA set of facts, assumptions, and inferences about how exposure takes place that aids the exposure assessor in evaluating or quantifying exposure. 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 ExpoBox.

Examples of Exposure Scenarios Involving Water and Related
Exposure Factors 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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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, gender (if appropriate), and activity level for the exposure scenario of interest.

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 are typically 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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Calculation Tools

A variety of tools are available for quantifying exposures (dose) and risks to human populations associated with contaminants in water and/or sediment. These tools have typically been developed for specific situations or program offices but may be tailored to meet the needs of the user.

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Guidance

A number of guidance documents are available to support various components of EPA programs involving water and/or sediment. EPA regularly issues guidelines to states, tribes, territories, and interstate organizations to improve the consistency and comprehensiveness of water quality monitoring, assessment, and reporting methods and to help build stronger water monitoring programs.

General Guidance

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Water Treatment Guidance

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