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Guidance on Searching for Chemical Information

CAS Registry Numbers

 Information Sources
 Locating Studies and Data
 List of Suggested Databases
 CAS Registry Numbers

CAS Registry Numbers were specifically created to uniquely identify chemical substances and have been used since 1965 by the Chemical Abstracts Service (a division of the American Chemical Society).  To date, more than 19 million chemicals have been assigned Registry Numbers by CAS.  Registry Numbers are often used to identify chemical substances in journal articles, handbooks, indexes, databases, and inventories.  Most government agencies, intergovernmental organizations, and research institutes at least cross-reference information about a chemical by its Registry Number when identifying a chemical of interest.

Most chemical databases, both numeric and bibliographic, are indexed by CAS Registry Numbers to enable searching by them.  Many publications include CAS Registry Number indexes so that information can be looked up by a chemical's Registry Number.

For a more complete description of CAS Registry numbers see the the index volumes of Chemical Abstracts or in "Chemical Abstracts Service Registry Numbers" by David W. Weisgerber in the ACS Style Guide: A Manual for Authors and Editors (2nd ed.), Janet S. Dodd (ed.), American Chemical Society, 1997 (pp. 244-246).

HPV Challenge sponsors are required to provide the CAS Registry Numbers for their chemicals as part of the HPV Challenge commitment. Others who are interested in searching for chemical information can obtain CAS Registry Numbers directly from CAS (generally for a charge) or from a number of resources freely available in print or on the Web.  Among the more comprehensive of these is ChemID from the National Library of Medicine.

ChemID (igm.nlm.nih.gov)   National Library of Medicine's Internet Grateful Med igm.nlm.nih.gov 

Select ChemID from the list of databases on the left side of the Internet Grateful Med screen. 

Among print resources, CAS Registry Numbers for selected chemicals can be found in such publications as Chemical Abstracts, the Merck Index, Hawley's Condensed Chemical Dictionary, and others.

Another possible source for a chemical's CAS Registry Number is its Material Safety Data Sheet (MSDS).  MSDS's are required by the Occupational Safety and Health Administration (OSHA) for many chemicals used or handled in the workplace.  Producers and suppliers of chemicals with MSDS's often include CAS Registry Numbers on MSDS's.

CAS Registry Numbers is a registered trademark of the Chemical Abstracts Service.

IMPORTANT: The fact that a resource is included on this list does not mean that EPA or any of the HPV Challenge reviewers is endorsing the source.  Nor does it mean that EPA will automatically accept data included in or referenced by that source.   Studies and data will need to meet the requirements as spelled out in the guidance document on data adequacy in order to be accepted by EPA.

Send comments about this guide to the Chemical Right to Know staff (oppt.chemrtk@epa.gov)

Introduction | Types of Information Sources | Locating Studies and Data| List of Suggested Databases

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