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Questions for Session 3: DDVP (Dichlorvos) Risk Issues

The Agency poses the following questions to the SAP regarding DDVP (Dichlorvos) Risk Issues.

  1. Application of FQPA Safety Factor

    The standard Subdivision F Guideline developmental and reproductive toxicity studies submitted to the Agency showed no indication of increased susceptibility of rats, mice, or rabbits to in utero and/or postnatal exposure to dichlorvos. However, based on experimental results reported in the open literature, the OPP HED Hazard Identification Assessment Review Committee has requested a prenatal developmental toxicity study in guinea pigs to assess the findings reported in the open literature concerning the effect (decreased brain weight) of dichlorvos on the developing guinea pig brain. While there are no data gaps with respect to the standard Subdivision F Guideline requirements, these guideline requirements do not require measurement of fetal or neonatal brain weight.

    An FQPA safety factor of 3x has been recommended for the acute and chronic dietary risk assessments, and to the residential exposure assessment for the general population including infants and children primarily due to uncertainties surrounding the results described in the literature study.

    - Can the Panel comment on the appropriateness of using guinea pigs as a representative test species for assessing the likelihood of chemical-induced developmental effects in humans?

    - In view of the above, does the Panel consider it appropriate to retain an FQPA safety factor? If so, of what magnitude (i.e., 3x or 10x)?

  2. Resin Strip Residential Exposure Scenarios

    Estimates of residential post-application inhalation exposure from use of dichlorvos-impregnated resin strips have been calculated in several ways. Air monitoring data from a published literature study have been used to permit comparison among the following approaches:

    1. time weighted average for chronic exposures;
    2. percentile of time spent in proximity of resin strips;
    3. time weighted average for descriptors of various heating, ventilation, air conditioning (HVAC);
    4. an indoor air Multi-Chamber Concentration and Exposure Model (MCCEM);

    - Does the Panel have any preference(s) among the above approaches? If so, why?

Scientific Advisory Panel (SAP) July 1998 Meeting

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