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CAS vs TSCA – Personal Care 101

Do I need a CAS number? My ingredient has a CAS number, why isn’t it registered on the TSCA Inventory? I don’t have a CAS number; can I register my substance on the TSCA Inventory? Required regulatory registrations can be confusing when it comes to cosmetics and personal care product ingredients. However, the regulations governing cosmetics in the U.S. – and other countries – have a common goal: to protect the consumer by ensuring safe ingredients and finished products. Here’s a quick lesson on the what, why, and when of registering cosmetic ingredients on the CAS Registry® and the TSCA Inventory.

What is a CAS number?

CAS Registry Numbers®, commonly referred to as CAS numbers, are numerical identifiers assigned to chemicals by the Chemicals Abstract Service (A Division of The American Chemical Society). CAS numbers provide a simple, consistent, and reliable way of identifying chemical substances. Chemicals and their assigned CAS numbers are part of a centralized collection known as the CAS Registry®. The CAS Registry® is internationally recognized as an authoritative database of disclosed chemical substances.

Why do we need CAS numbers?

Chemical compounds can often be described in different ways, such as by molecular formula, shipping name, proprietary or trade name, etc. Because CAS numbers are generally unique and specific to individual substances, they provide an unmistakable way of identifying chemicals no matter how they might be described. CAS numbers are a valuable tool that quickly show users reliable and accurate information about a chemical. Referencing a CAS number also helps reduce the confusion caused by differences in chemical nomenclature conventions or by chemical names being inadvertently misspelled or mispronounced.

When is a CAS number required?

As of December 2015, CAS numbers are required to be included in all Safety Data Sheets (SDS). Including CAS numbers on an SDS, provides an extra form of identification for the chemical. A CAS number may also be required to register a chemical on a National Chemical Inventory, such as the TSCA Inventory in the United States or DSL in Canada. Governmental agencies rely on CAS numbers for substance identification in regulatory applications because they are unique, easily validated, and internationally recognized.

What is TSCA?

TSCA – Toxic Substances Control Act – requires the EPA (Environmental Protection Agency) to keep a current list (TSCA Chemical Substance Inventory) of all existing chemical substances manufactured, processed, or imported in the United States that do not qualify for an exemption or exclusion under TSCA.

Why aren't all chemicals listed on the TSCA Inventory?

Chemicals on the TSCA Inventory are considered an ‘existing’ chemical substance in U.S. commerce. In addition, the TSCA Inventory contains information on existing chemical substances that are subject to manufacturing or use restrictions.

Chemical substances not on the TSCA Inventory are those with uses not regulated under TSCA. The use of these chemical substances is governed by other U.S. statutes. For example, cosmetics are regulated by the FDA under the Federal Food, Drug and Cosmetic Act (FD&C Act).

When is being on the TSCA Inventory required?

While cosmetics are not regulated by the EPA and are not required to be listed on the TSCA Inventory in the United States, other countries require cosmetic ingredients to be registered on the National Chemical Inventory, or a country’s equivalent. In addition, different countries employ different measures to ensure the safety of cosmetic products marketed within their borders: what defines a cosmetic, who is responsible for safety – manufacturer or governmental agency – and banned or restricted ingredients.


In summary, a substance with a CAS number is not necessarily registered on the TSCA Inventory, but a substance registered on the TSCA Inventory must have a CAS number. A CAS number is generally a unique identifier used to provide distinguishing information about a substance and not required unless the substance is to be registered on the TSCA Inventory in the U.S., or the equivalent in another country. In the U.S., cosmetic ingredients are regulated by the FDA and not required to be registered on the TSCA Inventory. Remember, registrations and listings are in place to promote the protection of the consumer and support cosmetic and personal care products manufacturers as they work to create and market safe products throughout the world.

Ethox is your partner for all things Personal Care.

The Ethox Personal Care team has the experience and expertise to support all your personal care needs – technology and regulatory registrations. Contact us to learn more about how we can be your trusted partner in Personal Care.

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