On May 2, 2019, California’s Office of Environmental Health Hazard Assessment (OEHHA) published a definition of nickel (soluble compounds) for the purposes of Proposition 65 (Prop 65). Under the notice, nickel (soluble compounds) are defined to be compounds of nickel with solubility in water of greater than 0.1 moles per liter (mol/L) at 20oC. OEHHA states that this definition is consistent both with the discussion by the Developmental and Reproductive Toxicant Identification Committee (DARTIC) that led to the listing of nickel (soluble compounds) and OEHHA’s prior definition of soluble nickel compounds in the 2012 document, “Nickel Reference Exposure Levels: Nickel and Nickel Compounds. Nickel Oxide. Reference Exposure Levels (RELs).”

As reported in our October 29, 2018, memorandum, “California Lists Nickel (Soluble Compounds) on Prop 65 as Known to Cause Reproductive Toxicity,” OEHHA added nickel (soluble compounds) to the Prop 65 list of chemicals known to the state to cause reproductive toxicity on October 26, 2018. At that time, it did not define “soluble.” The listing of nickel (soluble compounds) means that warning requirements will apply in one year, or as of October 26, 2019.


OEHHA announced on July 27, 2018, the availability for public review of the hazard identification document entitled “Evidence on the Developmental and Reproductive Toxicity of Nickel and Nickel Compounds.” DARTIC considered this document in making its listing decision at its October 11, 2018, meeting. In preparing the hazard identification document, OEHHA issued a request for information relevant to the assessment of the evidence of developmental and male and female reproductive toxicity for nickel and nickel compounds. The data call-in (DCI) period for nickel and nickel compounds opened on February 19, 2016, and closed on April 4, 2016. OEHHA considered information received from the DCI in preparing the hazard identification document. After completing the hazard identification document, OEHHA sent additional studies to DARTIC members. Comments on the hazard identification document that were timely filed were provided to DARTIC in advance of the meeting. The September 11, 2018, comments submitted by NiPERA, Inc. seem to align with OEHHA’s decision. According to the comments, “the Prop 65 listing of soluble nickel compounds based on rodent developmental effects is warranted, with the most sensitive effect being perinatal mortality.” Soluble nickel compounds reflect the highest bioavailability.


Prior to listing nickel (soluble compounds), OEHHA had several distinct listings for nickel: nickel (metallic), nickel acetate, nickel carbonate, nickel carbonyl, nickel compounds, nickel hydroxide, nickelocene, nickel oxide, nickel refinery dust from the pyrometallurgical process, and nickel subsulfide Almost immediately following the listing of nickel (soluble compounds), industry sought guidance from OEHHA as to the exact compounds that would be affected by this new listing, given the ubiquity of nickel in a wide range of products and the variability of solubility. OEHHA’s definition does not provide a specific list of compounds or identifiers such as Chemical Abstracts Service Registry Numbers that stakeholders may have preferred. The definition is quite specific, however, and should assist industry in clarifying the scope of the listing.