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NTP — Anthraquinone Abstract: HHS Response to Rfc

March 19, 2003.

Mr. Jerry Cook 
Technical Director 
Chemical Products Corporation 
Cartersville, Georgia 30120

Dear Mr. Cook:

I am writing to you in response to your recent filing of a Submission for Information Quality Request for Correction of the Abstract for Draft National Toxicology Program (NTP) Technical Report TR-494. Given there is a process for handling comments regarding Draft NTP Technical Reports, we are responding to your request consistent with that process. Our process includes compiling all comments received on Draft NTP Technical Reports and making them available to key NTP staff and to the NTP Board of Scientific Counselors Technical Reports Review Subcommittee as part of the information that the Subcommittee considers in its formal peer review of the findings and conclusions of these reports. The peer reviews are held approximately twice each year in a public forum, and there is opportunity at each meeting for the public to make oral comments to the Subcommittee on any report being reviewed in addition to submitting written comments.

The basis for your request is the presence of a 0.1% 9-nitroanthracene contaminant in the sample of anthraquinone used in the NTP two-year carcinogenicity study and your contention that the presence of this mutagenic contaminant compromised the study. I appreciate your communicating your concerns regarding this abstract and would like to let you know the steps we are taking to update the public about our progress on studies of anthraquinone. Given the passage of time since the peer review of Draft NTP Technical Report TR-494 and our follow-up studies on anthraquinone described below, the current abstract for draft TR-494 is incomplete. We plan to put the following additional information on the NTP web site with the abstract within approximately one month.

  • A statement that the anthraquinone sample used in our two-year study and in the Salmonella mutagencity test giving positive results contained 0.1% contamination by 9-nitroanthracene.
  • A description of our follow-up mutagenicity and metabolism studies. The findings from those studies will be added to the web site after they are finalized. We anticipate that this will occur within a year . (A brief description of these studies is enclosed.)

As you know, we have been actively investigating what potential impact the 9-nitroanthracene contaminant might have had on the results of the anthraquinone two-year carcinogenicity study. As part of this investigation, we obtained highly purified samples of anthraquinone, 9-nitoranthracene, 2-nitroanthracene, 1-nitroanthracene, and the two anthraquinone metabolites, 1-hydroxyanthraquinone and 2-hydroxyanthraquinone. This investigation has been quite time-consuming due to the difficulties associated with synthesizing and purifying the anthraquinone metabolites and the anthracenes. We evaluated the mutagenicity of these samples in Ames mutagenicity assays using several strains of S. typhimirium. The results indicate that highly purified anthraquinone itself is not a mutagen. Thus, our initial findings agree with information you submitted to us previously. However, we did find in our most recent preliminary studies that 2-hydroxyanthraquinone, the major urinary metabolite of anthraquinone, is a strong mutagen and is approximately 10-fold more potent than 9-nitroanthracene. We are currently confirming this finding in a repeat study.

We also have underway a study to quantitate the amount of 2-hydroxyanthraquinone formed by rats administered anthraquinone from the original bioassay sample as well as anthraquinone prepared by both the Friedel-Crafts and Diels-Alder reactions. This will allow us to compare the amounts of 2-hydroxyanthraquinone and 9-nitroanthracene that the animals were exposed to during the anthraquinone carcinogenicity study. It will also provide data about the amount of 2-hydroxyanthraquinone formed from anthraquinone when prepared by the Friedel-Crafts and Diels-Alder methods. From this information we can better determine what impact, if any, the 9-nitroanthracene contaminant might have had on the results of our carcinogenicity study. Presently we do not have conclusive data to resolve this issue.

Once completed, the information from our follow-up studies of anthraquinone will be used to prepare a revised Draft NTP Technical Report TR-494. Consistent with our process for review of these reports, the revised Draft TR-494 will be made available for public comment and will be peer reviewed by our NTP Board of Scientific Counselors Technical Reports Review Subcommittee at a public meeting. The Subcommittee will evaluate the findings and conclusions of our follow-up studies and using this information re-examine the carcinogenicity findings from our two-year studies. The Subcommittee will make a recommendation to us regarding the carcinogenicity of anthraquinone in those studies.

I would like to let you know that you may appeal our agency's decision either in writing or electronically within 30 days of receiving this response. Your request should state the reasons for your appeal. It does not need to reference a tracking number. The request may be sent electronically to or in hard copy to the Associate Director for Communications, Office of the Director, National Institutes of Health, Building 1, Room 344, 9000 Rockville Pike, Bethesda, MD 20892. If the appeal is sent in hard copy, please clearly mark the appeal and outside envelope with the phrase "Information Quality Appeal."

We appreciate your comments and hope the information provided helps clarify the status of our work on anthraquinone and our efforts to communicate it to the public.

Sincerely yours,

Christopher J. Portier, Ph.D. 
Director, Environmental Toxicology Program 


Dr. Kenneth Olden, Director, NTP 
Mutagenicity Studies

We have obtained highly purified samples of anthraquinone, 1-hydroxyanthraquinone, 2-hydroxyanthraquinone, 1-nitroanthracene, 2-nitroanthracene, and 9-nitroanthracene. The mutagenicity of these purified samples is being evaluated in S. typhimirium TA98 and TA100 following standard NTP protocols.

Metabolism Studies

We are conducting a study to examine the major urinary metabolites of anthraquinone in F344 rats. The rats will be administered anthraquinone in the diet at a concentration of 3750 ppm, for one week. On the last day of the study, urine will be collected from each rat and subsequently analyzed for anthraquinone metabolites.

Last Revised:  April, 2004