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Questions for the Panel on Hazard Characterization of DEET
Scientific Advisory Panel (SAP) June 1997 Meeting
The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) has completed its review of the Office of Pesticide Programs (OPP) hazard characterization of N,N-diethyl-meta-toluamide (DEET) and the decision not to establish toxicity endpoints for risk assessment use. The review was conducted in an open meeting held in Arlington, Virginia, on June 4, 1997. The meeting was chaired by Dr. Ernest E. McConnell. Other panel members present were: Dr. Janice E. Chambers (Mississippi State University); Dr. Amira T. Eldefrawi (University of Maryland); Dr. Ernest Hodgson (North Carolina State University); Dr. Harihara M. Mehendale (Northeast Louisiana University); Dr. Genevieve M. Matanoski (Johns Hopkins University); Dr. Stephen Saunders (Frito-Lay Corporation); Dr. Mary Anna Thrall (Colorado State University).
Public Notice of the meeting was published in the Federal Register on April 22, 1997.
Oral statements were received from:
Dr. Gerald Schoenig, Toxicology Regulatory Services
Written statements were received from:
Chemical Specialties Manufacturers Association
QUESTIONS FOR THE PANEL ON HAZARD CHARACTERIZATION OF DEET
1. Based on the currently available data on DEET, OPP requests that the members of the SAP comment on the OPP's hazard characterization of this chemical and the decision for not establishing the toxicity endpoints for risk assessment.
The Panel agrees with the Agency's hazard characterization and decision not to establish toxicity endpoints to be used for risk assessment, as exposure to DEET does not result in clearly characterized specific toxicological responses; to rationally choose toxicity endpoints that reflect a consistent response to DEET would be impossible. However, hazard characterization could be improved by the Agency's consideration of factors such as impact of multiple applications, inhalation or ingestion of DEET, site of dermal application, and amount of dermal absorption in children. Because of the potential exposure to aerosol-sprayed DEET via breathing, it was recommended that limited animal studies be conducted to compare data from exposure via inhalation to those available from ingestion and dermal exposure.
Panel Members were supplied as background reading the peer review reports from CAL-EPA and Health Canada and several Panel Members noted differences in these data and methodologies used by these two groups but the Agency did not elaborate on these differences at the meeting. For example, a spokesperson for Health Canada noted that they used an endpoint from a one year dog study for a chronic risk assessment. Several Panel Members recommended that the current Agency risk assessment be expanded to include much better exposure scenarios, chronic exposure being one of the recommended scenarios for which use of the one year dog study endpoint might be appropriate for a risk assessment.
2. What do you think about our approach to and methodology for the risk assessment and characterization?
In general, the Panel agrees with the Agency's approach to and methodology for risk assessment and characterization. While the assessment appears to be thorough, the Panel suggests that the Agency consider using several more realistic human exposure scenarios for risk assessment and characterization. Factors in these scenarios should include repeated applications, particularly around the face, smaller body weight of children (20 to 25 lb., rather than 55), and ranges of exposure situations including possible chronic exposure. Additionally chronic exposure studies of over one year may be warranted based on the number of people who are exposed occupationally.
3. What is your opinion of our interpretation of the incident information? (EPA believes that the reported incidences are inconclusive.)
The Panel agrees with the Agency's interpretation of the incident information (that the reported incidences are inconclusive). There is no compelling information that exposure to DEET is causing an appreciable number of seizures, and data from animal studies do not support or predict symptoms experienced by children exposed to DEET. However, a more complete description of the reports of children and adults who have had symptoms associated with DEET exposure should be included in the document, including serum concentration of DEET when that information is available. Animal experiments do suggest some synergism when DEET is used in conjunction with other toxicants, and such synergism may precipitate clinical signs in sensitive individuals. Moreover, physicians may not be recognizing seizures related to DEET exposure, since the product is considered to be safe. While several members of the Panel believed that appropriate warning labels should be adopted, it was recognized that seizures not actually related to DEET exposure might then be attributed to DEET. In summary, the panel recommends that the Agency continue to accumulate data from cases of suspicious DEET intoxications from pediatric neurologists, poison control centers, and the manufacturer. The continued maintenance and analyses of accurate incidence records is very important for DEET.
FOR THE CHAIRPERSON:
Certified as an accurate report of findings:
Larry C. Dorsey
Designated Federal Official
FIFRA/Scientific Advisory Panel