The Office of Environmental Health Hazard Assessment (OEHHA) is adopting revised acute, 8-hour and chronic Reference Exposure Levels (RELs) for nickel and nickel compounds. The values of the RELs are listed in the table below. These values and the supporting document will be added to the appendices of the Technical Support Document for the Derivation of Noncancer Reference Exposure Levels. Further, OEHHA, following the analysis presented in the document, hereby adds nickel and nickel compounds to the list of Toxic Air Contaminants that may cause infants and children to be especially susceptible to illness, pursuant to Health and Safety Code Section 39669.5(b)(2).
Acute, 8-hour, and Chronic Reference Exposure Levels for Nickel and Nickel Compounds.
Acute Toxicity (for a 1-hour exposure)
Inhalation reference exposure level
0.2 μg Ni/m³
8-Hour REL (for repeated 8-hour exposures)
0.06 μg Ni/m3
Chronic REL Nickel and Nickel Compounds (except NiO)
0.014 μg Ni/m3
Chronic REL Nickel Oxide
0.02 μg Ni/m3
Chronic Oral REL Nickel and Nickel Compounds
Oral Reference exposure level
0.011 mg Ni/kg-day
The Office of Environmental Health Hazard Assessment (OEHHA) is required to develop guidelines for conducting health risk assessments under the Air Toxics Hot Spots Program (Health and Safety Code Section 44360(b)(2)). In response to this statutory requirement, OEHHA has developed revised Reference Exposure Levels (RELs) for nickel and nickel compounds. (A REL is an airborne level of a chemical at or below which non-cancer health effects are not anticipated for specified exposure durations.) These were developed using the most recent “Air Toxics Hot Spots Program Technical Support Document for the Derivation of Noncancer Reference Exposure Levels” (OEHHA, 2008), and replace existing values which were developed using previous guidance. This method allows for the estimation of acute, 8-hour and chronic RELs for use in Air Toxics Hot Spots program risk assessments. The new guidance reflects current scientific knowledge and techniques, and in particular explicitly includes consideration of possible differential effects on the health of infants and children, in accordance with the mandate of the Children’s Environmental Health Protection Act (Health and Safety Code sections 39669.5 et seq.).
A draft of the nickel RELs was released on June 4, 2010 to solicit public comment, and was discussed at public workshops in Oakland and Diamond Bar, CA in July 2010. The document was then revised to reflect public comments, and peer reviewed by the State’s Scientific Review Panel on Toxic Air Contaminants (SRP). It was initially presented to the SRP on May 3, 2011. A revised version of the document reflecting comments of the SRP was discussed at a second meeting held on October 31, 2011. At the latter meeting, the SRP approved the document describing the RELs and their derivation, subject to some additional editorial changes which have been incorporated into the final version.