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Federal Register / Vol. 86, No. 165 / Monday, August 30, 2021 / Rules and Regulations after the tolerance is established, modified, or left in effect, demonstrating that the levels in food are not above the levels anticipated. For the present action, EPA will issue such data call-ins as are required by FFDCA section 408b2E and authorized under FFDCA section 408f1. Data will be required to be submitted no later than 5 years from the date of issuance of these tolerances.
EPA did not use PCT estimates in the dietary assessment for thiabendazole;
100 PCT was assumed for all food commodities.
2. Dietary exposure from drinking water. The Agency used screening-level water exposure models in the dietary exposure analysis and risk assessment for thiabendazole in drinking water.
Further information regarding EPA
drinking water models used in pesticide exposure assessment can be found at http www2.epa.gov/pesticide-scienceand-assessing-pesticide-risks/aboutwater-exposure-models-used-pesticide.
Based on the FQPA Index Reservoir Screening Tool FIRST; surface water model and the Pesticide Root Zone Model for Ground Water PRZMGW;
groundwater, EPA used an estimated drinking water concentration EDWC of 3.80 ppb for the acute dietary risk assessment and a value of 0.47 ppb for the chronic dietary risk assessment.
3. From non-dietary exposure. The term residential exposure is used in this document to refer to nonoccupational, non-dietary exposure e.g., for lawn and garden pest control, indoor pest control, termiticides, and flea and tick control on pets.
Thiabendazole is currently registered for uses that may result in residential handler and post-application exposures, including use in paints and textiles. As an initial matter in assessing aggregate risk of the pesticide chemical residues, the Agency takes into consideration those residential exposure scenarios that provide the most conservative estimate of residential exposures, including handler exposure and post-application exposure or both.
The residential handler exposure scenario used in the aggregate assessment is for adult handler inhalation exposures from applying thiabendazole-treated paint using airless sprayers. For this scenario, the Aggregate Risk Index ARI approach was used since the PODs/endpoints were similar, but the levels of concern LOCs were different. An ARI greater than or equal to 1 is not of concern.
The residential exposure scenario used for the post-application assessment is incidental oral exposures from children 1 to <2 years old mouthing
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preserved textiles clothing treated with thiabendazole.
Further information regarding EPA
standard assumptions and generic inputs for residential exposures may be found at http www2.epa.gov/pesticidescience-and-assessing-pesticide-risks/
standard-operating-proceduresresidential-pesticide.
4. Cumulative effects from substances with a common mechanism of toxicity.
Section 408b2Dv of FFDCA
requires that, when considering whether to establish, modify, or revoke a tolerance, the Agency consider available information concerning the cumulative effects of a particular pesticides residues and other substances that have a common mechanism of toxicity.
Unlike other pesticides for which EPA
has followed a cumulative risk approach based on a common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as to thiabendazole and any other substances and thiabendazole does not appear to produce a toxic metabolite produced by other substances. For the purposes of this tolerance action, therefore, EPA has not assumed that thiabendazole has a common mechanism of toxicity with other substances.
D. Safety Factor for Infants and Children 1. In general. Section 408b2C of FFDCA provides that EPA shall apply an additional tenfold 10X margin of safety for infants and children in the case of threshold effects to account for prenatal and postnatal toxicity and the completeness of the database on toxicity and exposure unless EPA determines based on reliable data that a different margin of safety will be safe for infants and children. This additional margin of safety is commonly referred to as the FQPA Safety Factor SF. In applying this provision, EPA either retains the default value of 10X, or uses a different additional safety factor when reliable data available to EPA support the choice of a different factor.
2. Prenatal and postnatal sensitivity.
The data submitted to the Agency, as well as those from published literature, demonstrated increased quantitative susceptibility in the rat and rabbit developmental toxicity studies, in which developmental effects decreased fetal weights in rat and rabbit pups were observed while maternal toxicity was not observed up to the highest doses tested. No increased susceptibility was observed in mice in utero and/or to rats following early postnatal exposure to thiabendazole.

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3. Conclusion. EPA has determined there is reliable data to support a conclusion that a FQPA Safety Factor SF of 1X will be protective for infants and children for all scenarios, with the exception of the assessment of inhalation exposure. The default FQPA
10X SF remains in place for assessing the non-occupational inhalation exposure due to the lack of a subchronic inhalation study with thyroid measurements. That decision is based on the following findings:
i. The toxicology database for thiabendazole is complete with the exception of a subchronic inhalation toxicity study with thyroid measurements. Based on a weight of evidence approach considering all the available hazard and exposure information for thiabendazole, the Agency determined that a developmental thyroid toxicity study is not required at this time. Acceptable studies are available for developmental, reproduction, chronic, subchronic, subchronic neurotoxicity and immunotoxicity.
ii. In an acute neurotoxicity rat study ACN, reduced locomotor activity in males and females at time of peak effect approximately 3 hours post-dose were seen without morphological or histopathological effects on the brain.
Thiabendazole was not neurotoxic in rats in a subchronic neurotoxicity study at the highest dose tested 1,500 ppm equivalent to 95 mg/kg/day.
iii. As noted above, there is some evidence of increased susceptibility in the developmental fetus from exposure to thiabendazole. Nevertheless, the Agency has sufficient data to understand and protect against the potential developmental effects. The data indicating the potential for developmental toxicity presented welldefined NOAELs and LOAELs, which the Agency took into account when identifying endpoints. The selected points of departure for regulating exposure are protective of both the potential for neurotoxicity and the increased susceptibility of infants and children. There is no residual uncertainty concerning the potential for prenatal or post-natal toxicity that precludes the reduction of the FPQA
10X SF.
iv. There are no residual uncertainties in the exposure database. The dietary risk assessment is conservative and will not underestimate dietary and/or nondietary occupational exposure to thiabendazole. The acute and chronic dietary assessments conducted were slightly refined analyses. The assessments utilized tolerance-level residues, maximum residue or average
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