Hazardous chemicals in laboratories, manufacturing, and other workplace environments pose a clear and present danger. To communicate the precise chemical compositions and the risk they pose to workers, the Chemical Abstracts Service (CAS) — a division of the American Chemical Society — began collecting, evaluating, and assigning a “CAS number.”

The organization’s first published abstracts included less than 12,000 substances. Today, its registry contains upwards of 250 million, and newcomers to chemical safety in the workplace usually ask the following questions about it. What is a CAS number? And why is the CAS number important? The answers, combined with proactive chemical safety measures, can prevent workplace injury or fatality.

What is the CAS registry?

The CAS Registry is a resource that stores information regarding unique organic and inorganic substances. The registry continues to add and update thousands of chemical abstracts concerning alloys, minerals, polymers, salts, and compounds on a daily basis.

A vast treasure trove of information, it remains the most extensive chemical database in the world. Widely recognized as the single most authoritative resource of its kind, scientists, safety professionals, and others who encounter sometimes obscure chemicals can refer to the registry for definitive information.

What Agency Represents CAS?

The Chemical Abstracts Service is not a standalone organization. It is a division of the American Chemical Society, the leading agency in related research and scientific advancement. Perhaps the most important facet the agency handles, in terms of safety, involves the CAS registry and the comprehensive abstracts it publishes.

Chemical abstracts date back to MIT Prof. Arthur A. Noye, who founded the “Review of American Chemical Research” in 1895. The Review published abstracts out of a sense that American scientists were not getting credited for their work overseas. In 1906, the American Chemical Society was persuaded to launch the “Chemical Abstracts” publication. By 1939, the number of published chemical abstracts soared from 12,000 to 1 million.

Although it took another 18 years to add a second million abstracts, the year 2006 saw 1 million published in a single year. What started as a fledgling publication designed to ensure professional integrity became the definitive global resource.

What is a CAS number?

The notion of starting a Chemical Registry System (CAS Registry) emerged in the 1950s as the number of chemical abstracts became unmanageable. The sheer volume of abstracts and comparable compounds led to chemicals receiving the same or very similar names. To put an end to this confusion, scientists sought a precise categorization solution that would uniquely and unmistakably identify each compound.

During the early 1960s, Harry Morgan created an algorithm that served as the foundation of the CAS Registry. After testing a trial database, the CAS Registry was fully operational by 1965. Rather than relying on chemical and drug names that sometimes spanned 70 characters, a CAS number streamlined it to 10 or fewer digits.

Significance of CAS Number System

The simplicity of the CAS number system may be the primary reason for its widespread growth as a go-to resource. Eliminating lengthy and confusing ways to identify hundreds of millions of substances, a CAS Registry number typically involves no more than 10 digits that are divided into three sections, set apart by hyphens.

The format is a lot like a 9-digit Social Security number used by employers and the Internal Revenue Service. And like SS numbers, the digit or digits are used to ensure uniqueness. These rank among the reasons why the CAS number system is critical for chemical identification and workplace safety.

Benefits of the CAS number system include:

  • Exclusivity: When handling, storing, or maintaining chemicals in close proximity, the CAS Number assigns an accurate and unique identifier. This is crucial because compounds can carry a variety of repetitive and similar industry names. The accuracy of the CAS number provides safety administrators with the information they require to ensure proper personal protective equipment and disposable clothing products are available.
  • Knowledge: When scientists or pharmaceutical company workers have concerns about a given substance, they can use the number to retrieve an abstract from the CAS database. The information housed in the database generally includes structural elements, properties, references to accompanying literature, and safety information.
  • Standardization: It’s important to note the CAS Registry is not just an American resource. The global scientific community recognizes the database as the most comprehensive and authoritative of its kind. That means laboratories and industrial environments that use hazardous substances around the world are on the same page. The CAS Registry is currently published in more than 50 languages.
  • Compliance: Governmental agencies have benefited from the CAS system. Rather than try to decipher what a product or substance is comprised of, organizations such as the Environmental Protection Agency (EPA) use the unique number to retrieve abstracts and information. Environmental and workplace safety officials can then apply the information in real-world settings. Access to this resource helps agencies ensure companies meet regulatory standards, address safety risks, and implement controls such as maintaining an inventory of PPE and disposable protective clothing.

How Does CAS Assign Registry Numbers?

Anytime a scientist or researcher creates, modifies, or discovers a new compound, its critical information is relayed to the Chemical Abstracts Service. Experienced experts at the CAS — not the person who discovered the chemical compound — analyze and authenticate the submitted information.

An evaluation process of its structure is undertaken in the context of current literature and research related to similar substances. Once the assessment and vetting process has been completed, CAS assigns a unique three-part number that only applies to the substance. The CAS Registry contains types of compounds that include the following.

  • Organic Compounds
  • Inorganic Compounds
  • Metals, Alloys, and Organometallics
  • Minerals
  • Coordination Compounds
  • Elements and Isotopes
  • Nuclear Particles
  • Proteins and Nucleic Acids
  • Polymers

In terms of safety and regulatory compliance, it’s important to keep in mind that CAS numbers do not necessarily apply to mixed compounds. In an industrial or laboratory setting, substances may be combined to create a product or further research. This limitation can present a challenge for safety administrators and oversight agencies.

Another issue for agency officials and workplace safety managers involves the constant updating of the CAS Registry. With thousands of entries being made on any given day, those tasked with regulatory oversight and workplace safety must routinely check for newly introduced substances as well as compounds used regularly.

What Industries Typically Rely on CAS Numbers?

The CAS Registry is open to wide-reaching industries, companies, non-profits, and government agencies that have a vested interest in the use of compounds and safety. The information included in an abstract helps safety professionals and researchers better understand the nature of the element, its potential applications, and necessary handling and storage precautions.

Following the adoption of the agreed-upon Globally Harmonized System of Classification and Labeling of Chemicals (GHS) system by the United Nations in 2003, CAS numbers were eventually mandated in all Safety Data Sheets. The consistent use of CAS numbers resolved significant confusion over misspelled chemical names and subpar safeguards implemented by people without a working knowledge of a given chemical agent or substance.

Fortunately, looking up a substance in the CAS Registry offers in-depth information and provides users with additional references. These generally include items such as patent numbers, reaction databases, chemical libraries, and a variety of easily accessible online resources. Having reliable and diverse resources helps safety professionals make informed decisions about personal protective equipment, disposable clothing inventories, and best practices.