A substance identified primarily by an EC or list number may be linked with more than one CAS number, or with CAS numbers that have been deleted. The CAS number is the substance numerical identifier assigned by the Chemical Abstracts Service, a division of the American Chemical Society, to substances registered in the CAS registry database. CAS (Chemical Abstract Service) registry number The EC or list number is the primary substance identifier used by ECHA. If the substance was not covered by the EC Inventory, ECHA attributes a list number in the same format, starting with the numbers 6, 7, 8 or 9. More information about the EC Inventory can be found here. The EC Inventory is a combination of three independent European lists of substances from the previous EU chemicals regulatory frameworks (EINECS, ELINCS and the NLP-list). The EC Number is the numerical identifier for substances in the EC Inventory. Some substance identifiers may have been claimed confidential, or may not have been provided, and therefore not be displayed. The substance identifiers displayed in the InfoCard are the best available substance name, EC number, CAS number and/or the molecular and structural formulas. Learn more about the peer-reviewed research on Cr(VI).The ‘Substance identity’ section is calculated from substance identification information from all ECHA databases.

This draft IRIS assessment for hexavalent chromium is at odds with the findings of over 30 peer-reviewed studies, which support a threshold for effects and a non-linear, dose-dependent response. The IRIS program, however, has a troubling history of being out of step with the best available science and methods, lacking transparency, and being unresponsive to peer review and stakeholder recommendations.

The EPA’s IRIS program identifies human health hazards associated with a substance. In October 2022, the EPA released a draft Cr(VI) Integrated Risk Information System (IRIS) assessment of oral and inhalation exposure for public comment. The EPA’s IRIS Assessment for Hexavalent Chromium See what various regulatory agencies have to say about hexavalent chromium here. The EPA, for example, has a drinking water standard of 100 parts per billion (ppb) for total chromium. The human body naturally detoxifies low levels of Cr(VI) into non-toxic Cr(III), no matter the source. Cr(III), also known as trivalent chromium, can also be naturally present in drinking water and is a micronutrient that is essential for metabolism. National and international regulatory agencies have set drinking water standards to protect the public from all forms of chromium (Cr(VI) and Cr(III)) in drinking water. drinking water supplies contain naturally occurring chromium. There are two potential sources of hexavalent chromium in drinking water – natural sources such as rocks, minerals, and other geology, and localized industrial runoff. Hexavalent chromium (Cr(VI)) is a form of the element chromium, which is one of the most abundant chemical elements found in the earth’s crust.