Notice of Public Comment/Workshops for Proposed Revised Reference Exposure Levels for Toluene Diisocyanate and Methylene Diphenyl Diisocyanate

The Office of Environmental Health Hazard Assessment (OEHHA) is releasing two documents for public review, one summarizing the toxicity and derivation of Reference Exposure Levels (RELs) for Toluene Diisocyanate (TDI) and the other summarizing the toxicity and derivation of RELs for Methylene Diphenyl Diisocyanate (MDI).  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 for many air pollutants.  The MDI and TDI 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 distribution of the document will commence a 60-day public review period that will end on September 2, 2014 September 16, 2014.  Public workshops will be held in Northern and Southern California at the following locations and times:

August 5, 2014, 9:00 am- 12:00 pm                   
South Coast Air Quality Management District
21865 E. Copley Dr,                                           
Diamond Bar, CA 91765                                    

August 13th, 2014, 9:00 am-12:00pm
Room 550
Cal/EPA Building
1001 I Street,
Sacramento, CA.

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 in late 2014. 

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

E–mail: (link sends e-mail)

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 web page at