CAS

CAS is an identification system for chemical substances developed to provide unique numeric identifiers for organic, inorganic, coordination, and alloyed materials. It was created to enable disambiguation among substances mentioned in scientific literature, patent filings, regulatory documents, and industrial inventories, supporting indexing, retrieval, and cross-referencing across databases maintained by organizations such as Chemical Abstracts Service, American Chemical Society, United States Patent and Trademark Office, and European Medicines Agency. The registry links chemical names appearing in publications like Journal of the American Chemical Society, Nature, and Science to stable numeric records referenced by researchers from institutions including Massachusetts Institute of Technology, Max Planck Society, and University of Cambridge.

History

The identifier system originated in the mid-20th century during efforts by Chemical Abstracts Service to organize the burgeoning output of chemical literature, patent activity at the United States Patent and Trademark Office, and catalogues from industrial firms like Dow Chemical Company and DuPont. Early milestones include integration with indexing operations at periodicals such as Chemical Reviews and collaboration with library systems at institutions like Library of Congress and British Library. Over subsequent decades the registry expanded alongside initiatives at World Intellectual Property Organization, the Organisation for Economic Co-operation and Development, and national agencies such as Environmental Protection Agency to accommodate new classes of substances originating from laboratories at Harvard University, Stanford University, and University of Tokyo.

Purpose and Scope

The registry’s primary purpose is to provide a unique numeric handle for each discrete chemical substance reported in the literature, patent filings, trade catalogues, and regulatory submissions from bodies like European Chemicals Agency, Food and Drug Administration, and Health Canada. This enables consistent referencing across bibliographic indexes such as Scopus, Web of Science, and PubMed and interoperability with material databases maintained by organizations like NIST and industrial consortia including IUPAC. The scope covers small molecules, polymers, coordination compounds, alloys, isotopically labeled variants, and stereoisomers described in works from laboratories at California Institute of Technology, ETH Zurich, and Korea Advanced Institute of Science and Technology.

Structure and Numbering System

Each identifier follows a numeric format partitioned into three blocks separated by hyphens, designed to minimize collision and support machine validation used in systems deployed by Elsevier, Clarivate, and proprietary platforms at corporations like BASF. The numbering logic enables automated parsing by cheminformatics tools developed at institutions such as Scripps Research Institute and companies like ChemAxon and OpenEye Scientific Software. Indexing workflows incorporate connections to nomenclature standards from IUPAC and substance descriptions appearing in monographs published by Springer Nature and Wiley. Cross-links to spectroscopic libraries curated by Royal Society of Chemistry and crystallographic records from Cambridge Crystallographic Data Centre support the mapping between numeric identifiers and experimental data.

Applications and Uses

Researchers at universities including Columbia University and University of California, Berkeley, analysts at regulatory agencies such as European Medicines Agency, and patent examiners at United States Patent and Trademark Office use the identifiers for literature searches, regulatory submissions, supply chain management, and patentability assessments related to inventions handled by law firms with ties to World Intellectual Property Organization. Pharmaceutical developers at companies like Pfizer, Novartis, and GlaxoSmithKline use the registry to track active pharmaceutical ingredients across clinical trial registries coordinated with ClinicalTrials.gov and dossiers submitted to agencies such as Food and Drug Administration. Environmental scientists referencing datasets from National Oceanic and Atmospheric Administration and United States Geological Survey use the identifiers to harmonize chemical monitoring records across databases managed by European Environment Agency and United Nations Environment Programme.

Criticism and Limitations

Critiques have come from academics at Princeton University, University of Oxford, and policy researchers at Brookings Institution regarding proprietary access models, potential barriers to open science advocated by groups like Creative Commons, and limits in covering newly synthesized complex mixtures reported in patents at European Patent Office. Other concerns involve mapping ambiguities for polymers noted by researchers at MIT and stereochemical resolution issues discussed in symposia convened by IUPAC. Legal scholars at Yale Law School and Harvard Law School have debated the implications of relying on a centralized registry for public-interest research, while standards bodies such as International Organization for Standardization have engaged in dialogue about interoperability.

Legal and Regulatory Role

Regulatory agencies including Environmental Protection Agency, European Chemicals Agency, Food and Drug Administration, and Health Canada reference numeric identifiers in hazard communication, chemical inventory reporting, and submission dossiers for market authorization of pharmaceuticals and agrochemicals overseen in part by Organisation for Economic Co-operation and Development working groups. Patent offices such as United States Patent and Trademark Office and European Patent Office use registry mappings when prior-art searching for chemical claims, and customs authorities collaborate with trade organizations like World Trade Organization and International Chamber of Commerce to classify substances for tariff and safety compliance.