Proposal for the Adoption of a Unit Risk Value for Naphthalene

Jan 23, 2004

The Office of Environmental Health Hazard Assessment (OEHHA) is releasing a draft document describing a unit risk factor for estimating cancer risk associated with inhalation of naphthalene, to solicit public comment. This draft document has been developed by OEHHA for use in implementing the programs for Toxic Air Contaminants (Health and Safety Code Section 39650 et seq.) and Air Toxics Hot Spots (Health and Safety Code Section 44300 et seq.).

Naphthalene, a widespread atmospheric contaminant, is a constituent of various fuels and other hydrocarbon mixtures, and is also emitted by various combustion processes. It is suspected of causing cancer and other adverse health impacts. Naphthalene is a toxic air contaminant (TAC) identified by the ARB in 1993 pursuant to Health and Safety Code Section 39657(b). In addition to its identification as a TAC as a single substance, it also meets the definition of Polycyclic Organic Material (POM), a category separately identified as a TAC by Health and Safety Code Section 39657(b).

OEHHA proposes a unit risk for use in estimating the lifetime cancer risk associated with inhalation exposures to naphthalene, based on the results of recent studies by the National Toxicology Program. A document has been prepared which describes toxicity data on naphthalene, and the derivation of the unit risk factor. This is in the form of a toxicity summary to be included as an addendum to the Air Toxics Hot Spots Program Risk Assessment Guideline, Part II: Technical Support Document for Describing Available Cancer Potency Factors, along with additional background and supporting material. We are seeking comments on this document, including its clarity, and the appropriateness of the methodology and data on which the unit risk is based. Following this public comment period, the document and any comments received, along with OEHHA’s response to these comments, will undergo review by the state’s Scientific Review Panel on Toxic Air Contaminants.

The draft document on naphthalene becomes available on the OEHHA Home Page at http://www.oehha.ca.gov on January 23, 2004. The availability of the document on this site will commence a 45-day public review period that will end on March 8, 2004.

A public workshop will be held at 10.00 am – 1.00 p.m. on Tuesday, February 17, 2004 in Oakland. Location information is as follows:
Rooms 2, 3, and 4
Elihu Harris Building
1515 Clay St., 2nd Floor
Oakland, CA 94612

Please direct any inquiries concerning technical matters or availability of this document to Dr. Andrew G. Salmon at (510) 622-3191 or e- mail to:Andy Salmon.

Please direct your comments, in writing, regarding the document to:
Dr. Andrew G. Salmon
Chief, Air Toxicology and Risk Assessment Unit
Office of Environmental Health Hazard Assessment
1515 Clay St., 16th Floor
Oakland, CA 94612.