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MEMORANDUM i CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3000 Sacramento, CA 95827-3098 CALNET: 8-494-3000 TO: Thomas Pinkos FROM: Alexander MacDonald Assistant Executive Officer Senior Water Resource Control Engin r DATE: 28 August 1996 SIGNATURE: a- SUBJECT: DEPARTMENT OF TOXIC SUBSTANCES CONTROL (DTSC) MEMORANDUM DATED 19 JULY 1996 REGARDING 1,4-DIOXANE Ms. Barbara Cofer, Chief of the Statewide Cleanup Operations Division for DTSC issued the subject memorandum to DTSC staff in the Site Mitigation Section of DTSC. Her memorandum included memoranda from Dr. Stephen DiZio of the Office of Scientific Affairs for DTSC and Ms. Barbara Renzi, and associate toxicologist with the Office of Scientific Affairs. Ms. Coler states that sampling for 1,4-Dioxane ,shall not occur unless a known release of 1,4-dioxane has occurred. In addition, 1,4- dioxane is not to be considered a chemical of concern unless there has been a release of 1,4-dioxane, and only if the concentration exceeds the lower end of the 20-120 mg/I "no effect" range. Ms. Coler bases her declaration on the two memoranda from the toxicologists from the Office of Scientific Affairs. One of those memoranda provides a synopsis of the current California and Federal criteria for 1,4-dioxane and concludes that the 1 x10'6 incremental cancer risk level should be 2.5 W. The Proposition 65 established level is 15 µg/I (1 x 10' incremental cancer risk level). The second memoranda asserts that there is a large degree of uncertainty in the studies and development of the risk numbers for 1,4-dioxane. Furthermore, the memoranda states that 1,4- dioxane by itself does not cause cancer tumors, but is a cancer promoter. Simply put, it can cause damage to cells which may then be susceptible to cancer tumors when in the presence of a cancer- causing substance. 1,4-Dioxane Background Concentrations of 1,4-dioxane have been found in the ground water at Aerojet, Southern Pacific Transportation Company's Sacramento Yard, and McClellan AFB in the Sacramento area. 1,4- Dioxane is used as a stabilizer in some chlorinated solvents (primarily TCE and 1,1,1-TCA) and those solvents were widely used and discharged to the ground at all three of the Sacramento sites. Not all TCE and 1,1,1-TCA contain 1,4-dioxane, and its presence depends on the manufacturer of the solvent and purity required. 1,4-Dioxane is highly soluble in water, is not removed from water by either air-stripping or carbon adsorption, and analysis for it must be specifically requested. The analysis can be made using standard EPA Methods such as Method 8260 or 8270, only a reference standard needs to obtained. Sampling for 1,4-Dioxane Without sampling for 1,4-dioxane, it can not be ascertained if it might have been released during a spill or discharge of a particular solvent. Using the logic supplied by the DTSC memorandum and