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a <br /> i. <br /> UNITED STATES ENVIRONMENTAL PROTEcT10N AGENCY <br /> t1EGIO14 Ix <br /> '"'°'`` 75 Hawthorne Street <br /> San Francisco, CA 94105.3901 <br /> September 1, 1995 <br /> Subject: LRIgion IX PW1iminS Remediation Goals PRGs Second Hatt 1995 <br /> From: Stanford J. Smucker, Ph.D, <br /> Regional Toxicologist (H-9.3) <br /> Technical Support Section <br /> To: PRG Table Mailing List <br /> Please find the update to the Region IX PRG table, The table has been revised to reflect the most <br /> current EPA toxicological and risk assessment information. Updates to EPA toxicity values were <br /> obtained from IRIS through July 1995 and HF-AST through November 1994. <br /> Although Region 9 risk-based PRGs are 'evergreen' and will change as new methodologies and <br /> parameters are developed, they have matured and are changing less than in the past. Meanwhile, the <br /> mailing list has increased exponentially and updating and distributing the table by mail has become a <br /> considerable burden. Upon reflection, we've decided to change from a semi-annual to annual <br /> distribution beginning in 1995. We think this change will allow us to keep publishing the PRG table, <br /> while having little effect on the table's usefulness. <br /> ft you are not currently on the PRG mailing list, but would like to be, please make the request through <br /> EPA's project manager working on your site. Or, for faster service, simply download the file <br /> (PAG21VD952IP) trom Callfomla Regional water Board's DBS 1(510) 286-4D404). Also, In the 1)0t- <br /> too-distant future, we antic'1p <br /> late that the PRG table will be available via intemet access. To determine <br /> whe`her the file is available through this delivery system, direct gopher client to 'gopher.epa.go� and <br /> 6eiect the following menus: EPA Offices and Regions; Region 9; Superfund Program. <br /> Defore relying heavily ort any number in the table, k is recommended that the user verity the numt>ers <br /> with a toxicologist or Regional risk assessor because the toxicity/exposure information in the table <br /> may contain errors or default assumptions thll need to be refined based &,� further evaluation_ It you <br /> ttnd an error please send me it note via tax at (415) 744-1916. <br /> This version of the table contairis now toxicity values for ars4nic, benzene, 1-chlora1,l•dlftuomethane <br /> (HCFC-142b), cobalt, danhol, hydrogen chloride, hydrogen auEfide, methyl mercury, and phosphine. <br /> The updated values are indicated in boldface print in the table. <br /> t.s.+rd&A Xfrvckd%syrr <br />