About Substance Registry Services (SRS)

Overview
Providing Quality Substance Identification Information

Substance Registry Services (SRS) is the Environmental Protection Agency's (EPA) central system for information about substances that are tracked or regulated by EPA or other sources. It is the authoritative resource for basic information about chemicals, biological organisms, and other substances of interest to EPA and its state and tribal partners.

The SRS makes it possible to identify which EPA data systems, environmental statutes, or other sources have information about a substance and which synonym is used by that system or statute. It becomes possible therefore to map substance data across EPA programs regardless of synonym.

The system provides a common basis for identification of, and information about:
- Chemicals
- Biological organisms
- Physical properties
- Miscellaneous objects
(See Defining SRS Substance Types under the section What is a Substance? below.)

Basic Information
There is a record in the SRS for every substance that is tracked or regulated at EPA. Each record provides basic information about that substance, such as the Chemical Abstract Service (CAS) number for a chemical or the Taxonomic Serial Number (TSN) for a biological organism. Each record also identifies standardized nomenclature about the substance and any synonyms in use at EPA. When available, there also are links to fact sheets or other documentation available from other web sites.

The SRS provides a range of services to users:
- Search and retrieval of:
- Information about creating machine-to-machine integration between the SRS and other systems
- Outreach and education material to gain a better understanding of the SRS and its services
- Links to related regulatory information within EPA and other federal agencies and states

What is a Substance?
Defining SRS Substance Types

A substance in the Substance Registry System is any chemical, biological organism, or physical property that is tracked or regulated by an EPA program or identified in an environmental statute.
Defining SRS Substance Types

Chemicals

A chemical can be defined as an organic or inorganic material that can be categorized as one of the following:
- A single fully defined chemical substance
- A chemical species
- A chemical substance of known composition
- A chemical substance of variable composition; a chemical substance of unknown composition
- A generic substance, the identity of which typically is protected as confidential business information (CBI)
- A waste, such as what is reported under the Resource Conservation and Recovery Act (RCRA) program
Biological organism

Biological organisms can be categorized as:
- Biota
- Viruses
- Biological groups, such as genera, classes, families, phyla or kingdoms
Physical properties

Physical properties are measurements in the environment that are important for understanding environmental quality. Examples of physical properties are:
- pH
- Light attenuation
- Dissolved oxygen
Miscellaneous objects

Miscellaneous objects are substances that have been reported to EPA programs and are not easily categorized as chemicals or biological organisms.

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Multiple Names for a Single Substance

Substances, particularly chemicals, often have multiple valid names. For example, the scientific name for one chemical is Benzene, methyl. Other names for this chemical include Toluene, Toluol, Phenylmethane, and Methyl benzene. Biological organisms likewise can have a variety of names.

EPA programs may have their own names for substances. Prior to implementing SRS, discovering which EPA program tracked or regulated a particular substance was time-consuming and often required a degree of understanding of chemistry.

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Establishing Standard Substance Names

Recognizing this diversity of names for substances, EPA created two data standards: the Chemical Identification Data Standard for chemicals and the Biological Taxonomy Data Standard for biological organisms.

Each of these standards requires EPA to work with its state partners to identify a core set of identifiers. For chemicals, one of those identifiers is the scientific name (SRS Systematic Name), and one is a common name (SRS Registry Name) if it exists. In the example above, the SRS Systematic Name is Benzene, methyl-, and the SRS Registry Name is Toluene. Toluol, Phenylmethane and Methyl benzene are maintained in SRS as synonyms

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Supporting Discovery and Standardization

SRS, therefore, identifies:
- Which EPA program or environmental statute tracks or regulates a given substance
- The particular name used
The core identifiers for each substance are listed at the top of each SRS record.

New EPA programs have begun to adopt the standardized names for their substance lists. Some older EPA programs have replaced their names with the standardized names.

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Quality
How does SRS Contribute to Quality Information?

There are two aspects of quality for Substance Registry Services (SRS): improving the quality of substance identification information at EPA and ensuring high quality data in the SRS.
- How does SRS Contribute to Quality Information?
- How is the Quality of the Information within SRS Ensured?
How does SRS Contribute to Quality Information?

Substance identification is an on-going issue at EPA. SRS provides key support to EPA’s efforts to improve quality substance identification information in three areas:
- Standardizing substance identification
- Promoting accurate substance identification
- Mapping substance identification across statues and systems
Standardizing Substance Identification
SRS supports the Chemical Identification Data Standard and the Biological Taxonomy Data Standard. These standards require EPA to establish a set of key fields for each substance to ensure unique identification. Some EPA programs have begun adopting the SRS standardized names, thus reducing the use of synonyms across EPA.

Promoting Accurate Substance Identification
Standardization also promotes improved accuracy. For a subset of substances monitored in the environment, standardization can be difficult. Chemical nomenclature workgroups have striven to identify duplicate substance identities and select valid names for each substance. The result is that, when submitting information about these substances, states and other parties can use the standard identification, thus improving the quality of the incoming data. Additionally, states have begun using SRS to validate substance identification in their own data systems, moving EPA and states toward greater consistency regarding substance information.

Mapping Substance Identification
Over time, Congress has passed different statues to address various environmental concerns. EPA has implemented programs and data systems to implement those environmental statutes. Because each was developed independently of the others, there was no consistency of substance names; each statute and each data system often utilized different synonyms for the same chemical. Mapping substance identification across these statutes and EPA data systems is a key quality concern that is resolved through SRS.

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How is the Quality of the Information within SRS Ensured?

Quality for SRS data is an on-going effort. With approximately 100,000 records in SRS as of June 2008, there are enormous opportunities for error. EPA focuses on quality in three areas for SRS:
- Quality of the information provided by SRS
- Assessment of the accuracy of the synonyms that are used by EPA programs and which are thus published in SRS
- Value of the available information; e.g., links to related websites
Quality of Core Substance Information
Core information is the fundamental metadata about a substance. These data items remain static regardless of environmental statute or EPA system. Examples of core metadata are the SRS Registry Name, the molecular weight, and the EPA Identifier.

The SRS Registry Name (a standard name EPA adopts for each chemical and biological organism) requires high quality. To determine these names and to ensure their accuracy, there are workgroups with representatives from EPA programs and state agencies that meet monthly. The workgroup participants include chemists, staff with extensive knowledge of laboratory analyses, plus other staff with long experience. This complement of diverse skills is necessary for making sound decisions.

Other core data intrinsic to the substance (e.g., molecular weight and molecular formula) are not generated by EPA but are maintained in SRS. To keep this information current and accurate, EPA employs various processes for quality checking and updating of the information.

Maintaining the substance lists in SRS is another area that demands quality assurance. Discovering which substances are named in a particular statute or which substances are tracked by a certain EPA database is a principal use of SRS. EPA has determined that the best approach to managing the substance lists is through stewardship. Each substance list has at least one steward who manages a specific list within SRS. Normally, the steward is from the organization that is responsible for, or has the best information about, the substance list.

Assessing Quality of EPA Synonyms
Future plans include evaluating the quality of the synonyms in the SRS. These synonyms, whether found in environmental statutes or in EPA data systems, are not always correct. A name in an EPA data system, submitted by a facility or other organization, may be misspelled. An environmental law may have used an ambiguous or inaccurate synonym. A review and quality assignment rating (e.g., valid, misspelled, ambiguous) of each synonym will help the users of SRS to decide whether or not to adopt a particular synonym.

Value of Information in SRS
Quality also means ensuring that the information in SRS is of value to users. Since one of the most widely used features of SRS is the fact sheets about substances, SRS will link to additional internal and external sources that provide fact sheets or other documentation about substances.

SRS will also either store other federal agencies’ substance identification information or create links to their substance registries. The result will be the ability to go to SRS as a one-stop registry to discover substance information for the entire Federal government.

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