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Data for Economic Analysis of Drinking Water Standards

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Health Effects and Risk Assessment

Health effects data, provided by health scientists and risk assessors, are used in identifying and quantifying health effects for a specific drinking water contaminant (for example, estimating the number of avoided gastrointestinal illnesses from a Cryptosporidium outbreak). 

Using the most current health effects data available allows EPA to:

  • Accurately assess the benefits of a proposed rule
  • Develop regulations that will protect human health

EPA's Integrated Risk Information System (IRIS) contains information on the human health effects of more than 550 carcinogenic and non-carcinogenic chemical substances.

EPA's Exposure Factors Handbook provides information on various physiological and behavioral factors commonly used in assessing an individual's exposure to environemental chemicals. The handbook:

  •  Presents recommended values for the exposure factors
  •  Discusses the underlying data used in developing the recommendations

The Office of Research and Development’s National Center for Environmental Assessment (NCEA) supports the Exposure Factors Handbook.  NCEA also supports the development of tools and databases to improve the scientific basis of exposure and risk assessment by:

  • Identifying exposure factor needs
  • Compiling existing data
  • Exploring ways for filling data gaps

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Finished Water Occurrence

EPA collects information on the geographic distribution and concentration of regulated and unregulated drinking water contaminants. This occurrence data is used in the quantification of both costs and benefits for drinking water standards.  It allows the analyst to calculate a baseline of contaminant occurrence under current conditions.

This baseline, along with other factors, determines:

  • Where and what types of treatment technology would be required under potential regulatory scenarios
  • The affected population size
  • The degree to which health effects will change as a result of a policy

The National Contaminant Occurrence Database (NCOD) is designed to support EPA decisions on identifying contaminants for regulation and subsequent regulation development. The NCOD contains occurrence data from public water systems and other sources (like the U.S. Geological Survey National Water Information System) on physical, chemical, microbial and radiological contaminants.

EPA collects unregulated contaminant occurrence data through the Unregulated Contaminant Monitoring Rule (UCMR) collection process. The UCMR is designed to monitor public water systems for contaminants suspected to be present in drinking water, but not currently having health-based standards set under the Safe Drinking Water Act (SDWA).

The SDWA requires EPA to review each National Primary Drinking Water Regulation (NPDWR) at least once every six years and make revisions if appropriate. This is known as the Six-Year Review (SYR). One component of the SYR is the collection of national SDWA compliance monitoring data for regulated drinking water contaminants from public water supplies. The SYR allows EPA to characterize the national occurrence of contaminants. This helps EPA determine if there may be a meaningful opportunity to improve public health protection.

EPA also maintains two data management systems -- Legacy Data Center (LDC) and the STORET database --that contain water quality information for the nation's ambient waters. The LDC contains historical water quality data dating back to the early part of the 20th century, collected up to the end of 1998. The STORET database contains data collected beginning in 1999, along with older data that has been properly documented and moved from the LDC.

Both systems contain raw biological, chemical and physical data on surface and ground water collected by:

  • Federal government agencies
  • State and local agencies
  • Tribes
  • Volunteer groups
  • Academic scientists

The U.S. Geological Survey (USGS) provides water data it has collected to the public through a system called the National Water Information System (NWIS). Many types of data are stored in the NWIS network, including:

  • Site information
  • Time-series (flow, stage, precipitation, and chemical)
  • Peak flow
  • Ground water and surface water quality measures

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Regulated Community (Water Systems) Baseline

The Federal Safe Drinking Water Information System (SDWIS/FED) is EPA's national regulatory compliance database for the drinking water program.  SDWIS data is drawn from the nation's 160,000 public water systems.  EPA uses this data in assessing costs and benefits of proposed national regulatory options.  The data used include:

  • System location
  • Size
  • Ownership
  • Source water type
  • Population served

The Community Water System Survey (CWSS), conducted periodically by EPA, contains information on:

  • Types of treatment in place
  • Water production and design flow
  • Number and types of water sources
  • Water distribution and storage configurations

This information, along with water system financial data collected in the survey, serves as a baseline against which the effects of newly proposed regulations can be measured.

Non-community water systems are not included in this survey.

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