Public Comment Period and Workshops on the Draft Reference Exposure Levels for Hexamethylene Diisocyanate and Toluene

The Office of Environmental Health Hazard Assessment (OEHHA) is releasing two draft documents for public review, summarizing the toxicity and derivation of proposed Reference Exposure Levels (RELs) for Hexamethylene Diisocyanate (HDI) and toluene.   RELs are airborne concentrations of a chemical that are not anticipated to result in adverse non–cancer health effects for specified exposure durations in the general population, including sensitive subpopulations.

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 develops RELs and inhalation cancer unit risk factors for many air pollutants.  The proposed HDI and toluene RELs were developed using the most recent “Air Toxics Hot Spots Program Technical Support Document for the Derivation of Noncancer Reference Exposure Levels,” finalized by OEHHA in 2008. 

The draft HDI and toluene REL documents are available starting today on the OEHHA website.  The posting of the document will commence a 60-day public review period that will end on January 30, 2018

Public workshops will be held in Northern and Southern California at the following locations and times:

Northern California                                      Southern California

January 8, 2018                                              January 10, 2018
1:30 PM - 4:30 PM                                          9:00 AM - 12:00 PM
Training Room 1 East                                     Room CC-2
Cal/EPA Building                                            South Coast Air Quality Management District
1001 I Street,                                                  21865 E. Copley Drive
Sacramento, CA 95812                                  Diamond Bar, CA 91765

After the close of the public comment period, the documents will be revised as appropriate by OEHHA, and peer reviewed by the state’s Scientific Review Panel on Toxic Air Contaminants. 

Please direct your comments on the documents, in writing or by e–mail, and any inquiries concerning technical matters or availability of the documents to:

Dr. John Budroe
Chief, Air Toxicology and Risk Assessment Section
Air, Community, and Environmental Research Branch
Office of Environmental Health Hazard Assessment
1515 Clay Street, 16th Floor
Oakland, CA, 94612
Telephone: (510) 622-3145

Information about dates and agenda for meetings of the Scientific Review Panel can be obtained from the California Air Resources Board website at