UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                                                   "' '''
                      WASHINGTON, D,C-  20460

                         NOVEMBER 23, 19S3
                                                         OFFICE OP
                                                      THE
Mr. William D. Ruckelshaus
Administrator
U.S. Environmental Protection Agency
401 H Street, S.W*
Washington, D,C.  20460

Dear Mr. luckelshaus;

     The Environmental Health Committee of the Science Advisory
Board has completed  its review of revised drafts of  the
Health Assessment Document for 1,1,l-*Trichloroethane  (Methyl
Chloroform) prepared by the Agency's Office of Research
and Development.  The major conclusions of the document state
that in tests conducted to date, there is no adequate scientific
basis for determining the carcinogenicity of Methyl  Chloroform
CMC},  Recent information available on the biologic  effects
of MC and its role in contributing to an increased incidence
of skin cancer as a  result of ozone depletion also downplays
the potential role of this chemical.  As a result, a definitive
evaluation of MC and its contribution to health hazards in
the workplace or as  the result of ambient exposures  is not
possible at the present time.

     Drafts of the Health Assessment Document for Methyl
Chloroform have been formally reviewed by the Committee on
September 28-29, 1982 and December 8, 1982.  In addition, a
revised draft dated  May 1983 has been discussed with the
Committee at a public meeting on June 10, 1983.  The Committee
understands that the May 1983 draft will be further  changed
to reflect the most  current status of the National Toxicology
Program (NTP) 1983 rat study.

     Agency staff have adequately responded to Committee
advice for revising  the document in terras of the discussion
of the carcinogenicity issue as well as other issues.  The
Committee is satisfied that the revisions to the November 1982
and May 1983 documents present a thorough and balanced
treatment of the existing scientific literature concerning
this pollutant.

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     Committee comments and recommendations on these successive
drafts of the document ar© summarized in the attached report.
A full record of the Committee's review of Methyl Chloroform
is contained in 'the transcripts on file at the Science Advisory
Board*  With the understanding that the final document will
incorporate the further changes discussed with Agency staff,
the Committee unanimously concludes that the assessment
document is scientifically adequate.
                              Sincerely,
                              Herschel E, Grifl
                              Chairman
                              Environmental Health Committee
                              Science Advisory Board
Attachment

ccs  Mr* Alvin Aim
     Mr. Joseph Cannon
     Dr. Bernard Goldstein
     Dr. Lester Grant
     Dr. Terry Yosie

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   Environmental Health Committee Key Findings, Conclusions
       and Recommendations on the Revised Draft Health
        Assessment Document for l,lrl-Trichloroethane
                 (Methyl Chloroform) (May 1983)


     1.  The Summary and Conclusions chapter has been revised

in response to recommendations made by the Committee,  In the

Committee's view these revisions have enhanced the quality of

this chapter by;

          * expanding the discussion of directly-induced

     health effects to delineate No-Observed Effects Level

     (NOEL) estimates from Lowest-Observed Effects Level (LOEL)

     numbers for Methyl Chloroform,  These estimates have in

     turn been contrasted with 'the generally much lower level

     ambient Methyl Chloroform exposures.

          * clarifying the role of Methyl Chloroform as a

     contributing factor to ozone layer depletion and to a

     consequent rise in the incidence of skin cancer.  Recent

     evaluations of this issue by the world Meterological

     Organization and the National Research Council suggest

     that the potential role for MC is smaller than indicated

     in previous drafts of this document.

     2.  The document and EPA staff discussion of the issue

of the carcinogenicity of Methyl Chloroform is more straight-

forward in presenting and assessing the current state of

knowledge*  Staff have indicated that there is no adequate

basis at the present time for evaluating the carcinogenicity

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of this chemical.  Acknowledgment is given to previous



assessments of MC carcinogenic!ty and why those assessments



have proven inconclusive.



     The Cancer Assessment Group's (CAG) evaluation of the



carcinogenicity of MC will not include a discussion in the



document of the results of the lifetime animal bioassay



carried out under the auspices of the National Toxicology



Program (NTP),  CAG staff have informed the Committee they



will evaluate the results of this study when they are finalized



and available from NTP. In the meantime, they and their



colleagues in the Office of Research and Development plan to



finalize the Health Assessment Document for Methyl Chloroform



and to incorporate information on the current status of the



NTP work.  The need to modify or issue an addendum to the



document to incorporate NTP results will be determined by



EPA staff at the time of final issuance of the NTP results.



The Environmental Health Committee concurs with the judgment



reached by Agency staff on these matters.



     3. The discussion of the biotransformation of Methyl



Chloroform to reactive intermediate metabolites overstates



the case*  There is insufficient scientific evidence to



support the EPA position as stated in the document.  The final



document should incorporate a revised statement that indicates



that this issue has not been resolved.  EPA staff have



concurred with this recommendation.

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     4,  Information has been added in several of the chapters



that strengthen the document.  This includes:  updating of



information on sources, emissions and ambient concentrations



of MC (chapter 3); and including recent studies on metabolism



and pharmacokineties (chapter 4)f and neurotoxicology,



behavioral toxicology and mutagenicity (chapter 5).



     5.  As part of the overall assessment of Methyl Chloroform,



major information gaps or research needs should be briefly



identified.



     The Committee made additional suggestions for improving



the final document which are included in the transcripts of



the Committee's meetings.  With the understanding that these



and other changes identified in this report will be incorporated



in the final Health Assessment Document for Methyl Chloroform



the Environmental Health Committee unanimously concludes that



the document is scientifically adequate.

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