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Federal Register / Vol. 86, No. 228 / Wednesday, December 1, 2021 / Rules and Regulations
proprietary market surveys, and California Department of Pesticide Regulation CalDPR Pesticide Use Reporting PUR for the chemical/crop combination for the most recent 10
years. EPA uses an average PCT for chronic dietary risk analysis and a maximum PCT for acute dietary risk analysis. The average PCT figure for each existing use is derived by combining available public and private market survey data for that use, averaging across all observations, and rounding to the nearest 5%, except for those situations in which the average PCT is less than 1% or less than 2.5%.
In those cases, the Agency would use less than 1% or less than 2.5% as the average PCT value, respectively. The maximum PCT figure is the highest observed maximum value reported within the most recent 10 years of available public and private market survey data for the existing use and rounded up to the nearest multiple of 5%, except where the maximum PCT is less than 2.5%, in which case, the Agency uses less than 2.5% as the maximum PCT.
The Agency believes that the three conditions discussed in Unit III.C.1.iv.
have been met. With respect to Condition a, PCT estimates are derived from Federal and private market survey data, which are reliable and have a valid basis. The Agency is reasonably certain that the percentage of the food treated is not likely to be an underestimation.
As to Conditions b and c, regional consumption information and consumption information for significant subpopulations are taken into account through EPAs computer-based model for evaluating the exposure of significant subpopulations including several regional groups. Use of consumption information in EPAs risk assessment process ensures that EPAs exposure estimate does not understate exposure for any significant subpopulation group and allows the Agency to be reasonably certain that no regional population is exposed to residue levels higher than those estimated by the Agency. Other than the data available through national food consumption surveys, EPA does not have available reliable information on the regional consumption of food to which bifenthrin may be applied in a particular area.
2. Dietary exposure from drinking water. The Agency used screening level water exposure models in the dietary exposure analysis and risk assessment for bifenthrin in drinking water. These simulation models take into account data on the physical, chemical, and fate/
transport characteristics of bifenthrin.

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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.
EPA used the limit of solubility as the drinking water input, i.e., the maximum possible residues that could occur in drinking water based on the chemical properties of the compound. EPA used the modeled EDWCs directly in the dietary exposure model to account for the contribution of bifenthrin residues in drinking water as follows: 0.014 ppb was used in the acute assessment and 0.014 ppb was used in the chronic 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. Bifenthrin is currently registered for the following uses that could result in residential exposures: Lawns/turf, indoor environments, gardens/trees, pets dog shampoo, termiticide and indoor/
outdoor surface treatment for various residential and commercial premises.
EPA assessed residential exposure using the following assumptions. There is the potential for residential handler and post-application exposures from the use of bifenthrin. These exposures were assessed using the 2012 Residential SOPs and submitted chemical-specific residue data bifenthrin-specific turf transferable residue TTR; liquid and granular and dislodgeable foliar residue DFR; liquid data are available. EPA
did not quantitatively assess the outdoor residential handler uses in/around home foundations, outdoor impervious surfaces, wood piles/structures and fence posts. Residential handler exposure assessments were performed for adult homeowners applying bifenthrin ready-to-use products aerosol, hose-end sprayers and dog shampoos; mixing/loading/applying liquid concentrates; loading/applying granular formulations and applying dust formulations. The application rates for these uses that were quantitatively assessed are equal to or higher than those outdoor uses and thus are protective of the outdoor uses. Dermal and inhalation risk estimates were combined in this assessment because the toxicological effects for these exposure routes were the same. A total aggregate risk index ARI was used because the levels of concern LOCs for dermal exposure 100 and inhalation exposure 30 are different. ARIs of less than 1 are risk estimates of concern. The
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ARIs were calculated as follows.
Aggregate Risk Index ARI = 1
Dermal LOC Dermal MOE +
Inhalation LOC Inhalation MOE. All exposures are short-term in nature.
There are no dermal or inhalation risk estimates of concern for residential handlers for the registered uses of bifenthrin.
Post-application exposure was assessed for broadcast applications to turf, gardens/trees, indoor environments carpets and hard floor and treated pets.
Residential post-application exposures are expected to be short-, intermediateor long-term in duration. Because the single dose and repeat dosing bifenthrin studies show that repeat exposures do not result in lower points of departure, the residential assessments are conducted as a series of acute exposures and the same endpoint is used regardless of duration. Therefore, the acute/single day residential postapplication assessments are protective of expected longer-term exposures.
Dermal and incidental oral risk estimates were combined because the toxicological effects for these exposure routes were similar combined Margin of Exposure MOE approach used since LOCs are the same.
There were some residential postapplication risk estimates of concern identified previously in Registration Review. Specifically, dermal postapplication risks were identified for a liquid formulation product with a maximum application rate of 2.3 lb ai/
A, and risks were identified for episodic ingestion of granules at application rates greater than 0.34 lb ai/A. As a result, during Registration Review, some bifenthrin labels were amended or canceled to address these risk concerns.
The product label for the liquid formulation with the high application rate of 2.3 lb ai/A, which was canceled as of July 2021 EPA Reg. 2793152, was never commercialized. Because that product was never sold or distributed, there are no exposures from that product for consideration in the aggregate risk assessment. In addition, 25 granular products were either canceled or amended to require watering in of the product after application when application rates were greater than 0.34 lb ai/A. Although these label changes reduce the risks from ingestion of granules, that use is not included in the aggregate assessment because it is considered an episodic event and not a routine behavior.
The following residential exposure scenarios were selected for aggregation and represent the worst-case risk estimates: Adults contacting treated gardens dermal exposure; children 1 to
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