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Agenda for the August 2000 Meeting

FIFRA SAP WEB SITE https://www.epa.gov/scipoly/sap/
OPP Docket Telephone: (703)305-5805

(703) 243-9800

  • 10:30 AM BREAK
  • 10:45 AM Panel Discussion (continued)

    Question 2.3: The CARC considered the April 2000 PWG report for female Fischer 344 rat liver tumors to be valid and used these values in the cancer hazard assessment.

    2.3.1:The SAP agree that the female rat liver tumor PWG report (from April 2000) should be considered valid and that these values should be used in this hazard assessment for malathion? If yes, why? If not, why not?

    2.3.2: Does the SAP consider the statistically significant trend and pair-wise increases in liver tumors in female Fischer 344 rats at 12,000 ppm (adenomas - 5/38 compared to 0/41 in controls) to be related to malathion exposure? If not, why not? What weight should be placed on this data since there is evidence of excessive toxicity based on severe cholinesterase inhibition in all three compartments (RBC, plasma and brain) and mortality?

    Question 2.4: The Committee could not determine whether the nasal tumors in rats were due to treatment or random occurrence because: on the one hand: (1)there was no dose response over a wide range of doses (100/50 to 12,000 ppm); (2) there was no statistical significance; (3) there were only adenomas, one in each of two doses for females and only one at the high dose in males; (4) the high dose in both male and females were considered excessively toxic; and (5) these tumors occurred in section 5 where there was little to no evidence of non-neoplastic lesions in the nasal mucosa. On the other hand: (1) an adenoma of the respiratory epithelium was seen in one female at 6000 ppm (not an excessive dose); (2) spontaneous nasal tumors are very rare in rats, there were no nasal tumors in the concurrent controls and the incidences exceeded the historical control incidence of the testing laboratory and NTP. It should be noted that the biological significance of the olfactory epithelial tumor is unknown since it is from a different cell of origin and these types of tumor (esthesioneural epithelial neoplasms) should not be combined with other tumors of the respiratory nasal cavity. The biological significance of this in relation to tumors of the respiratory epithelium is unknown. It should be pointed out that there were 5 nasal sections per rat. Historical control studies usually have only 1 or 2 sections.

    2.4.1: Does the SAP agree that nasal respiratory epithelial tumors in Fischer 344 rats are rare tumors in light of the number of sections in the current study as compared to the historical control data base? Why or why not?
    Please be advised that agenda times are approximate. For further information, please contact the Designated Federal Officials for this meeting, Mr. Larry Dorsey and Mr. Paul Lewis, via telephone: (703) 305-5369; fax: (703) 605-0656; or email: dorsey.larry@epa.gov, lewis.paul@epa.gov.


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