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Federal Register / Vol. 86, No. 165 / Monday, August 30, 2021 / Rules and Regulations below the Agencys level of concern.
Ref. 9 at 38. The residential postapplication LOC for children is 40, and the lowest risk estimate for children 11
to less than 16 years old was 1,200; the residential post-application LOC for adults is 100, and the MOE is 1,000.
Because the calculated MOEs are above the Agencys level of concern, there are no risks of concern from residential exposures.

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C. Risks From Drinking Water As noted above, the Agency aggregated exposures to chlorpyrifos from food and residential exposures and calculated the DWLOC, i.e., the amount of drinking water exposures that would be considered safe. The Agency calculated acute and steady state DWLOCs for infants less than 1 year old; children 1 to 2 years old; youths 612 years old, and adults females 1349 years old, which would be protective of other subpopulations. The most sensitive acute DWLOC was 23
ppb chlorpyrifos oxon, and the most sensitive steady state DWLOC was 4
ppb.
As indicated above in Unit VII.B.2., the Agency estimated drinking water contributions from registered uses of chlorpyrifos in its 2016 DWA. That document indicated that EDWCs exceed the DWLOC of 4.0 ppb on a national level and in every region of the United States. Ref. 28.
While the 2020 DWA produced estimated drinking water concentrations that were below the DWLOC of 4.0 ppb, those EDWCs were contingent upon a limited subset of chlorpyrifos use. When assessing different combinations of only those 11 uses in specific geographic regions, the modeling assumed that chlorpyrifos would not be labeled for use on any other crops and would not otherwise be used in those geographic regions. At this time, however, the currently registered chlorpyrifos uses go well beyond the 11 uses in the specific regions assessed in the 2020 DWA.
Because the Agency is required to assess aggregate exposure from all anticipated dietary, including food and drinking water, as well as residential exposures, the Agency cannot rely on the 2020
DWA to support currently labeled uses.
When one assesses the potential of all currently registered uses nationwide and in specific geographical areas, as was done in the 2016 DWA, the estimates of drinking water concentrations exceed the DWLOC of 4.0 ppb, in certain vulnerable watersheds across the United States.

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D. Aggregate Exposure and Determination Concerning Safety As noted above, in accordance with FFDCA section 408b2, EPA must, when establishing or leaving in effect tolerances for residues of a pesticide chemical, determine that the tolerances are safe. That is, EPA must determine that there is a reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue, including all anticipated dietary exposures and all other exposures for which there is reliable information. 21 U.S.C. 346ab2.
As discussed earlier in this Unit, exposures from food and nonoccupational exposures individually or together do not exceed EPAs levels of concern. The Agency determined that risks from exposures to chlorpyrifos residues in food comprised 3.2% of the aPAD for females 1349 years old and 9.7% of the ssPAD for children 12
years old, the highest exposed subpopulations. Combining those exposures with relevant residential exposures, the Agency calculated the allowable levels of drinking water concentrations. Based on the Agencys assessment of drinking water concentrations based on the currently registered uses, however, drinking water exposures significantly add to those risks. When considering the drinking water contribution from currently registered uses, the Agencys levels of concern are exceeded when combined with food and residential exposures.
As indicated above, the Agency calculated acute and steady-state DWLOCs, and the lowest DWLOC is for steady-state exposures to infants at 4.0
ppb; therefore, any EDWCs of chlorpyrifos oxon exceeding 4.0 ppb indicate that aggregate exposures of chlorpyrifos would be unsafe. The Agencys 2016 DWA demonstrates that DWLOC will be exceeded for some people whose drinking water is derived from certain vulnerable watersheds throughout the United States, which means that drinking water contributions will result in aggregate exposures that exceed the Agencys determined safe level of exposure. When taking into consideration aggregate exposures based on current labeled uses, the EDWCs exceed the DWLOC of 4.0 ppb. For example, as noted above in Unit VII.B.2., the 2016 DWA presented EDWCs for uses of chlorpyrifos, including concentrations based on use on golf courses and agricultural crops.
For those uses alone, the Agency estimated concentrations exceeding 4.0
ppb in every region in the country; See Table 25 of the 2016 DWA. Ref. 28 at
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7374. Comparing the calculated EDWCs from the 2016 DWA with the DWLOC calculated in the 2020 HHRA
shows that drinking water concentrations from chlorpyrifos uses will exceed the safe allowable level for contributions from drinking water. This means that aggregate exposure food, drinking water, and residential exposures exceeds the Agencys safe level for chlorpyrifos exposure. Because the FFDCA requires EPA to aggregate all dietary and non-occupational exposure, EPA cannot conclude that there is a reasonable certainty that no harm will result from aggregate exposure to chlorpyrifos residues when taking into consideration all labeled uses.
It is worth noting that the Agencys Proposed Interim Registration Review Decision PID recognized that there might be limited combinations of uses in certain geographic areas that could be considered safe, if the assessment only includes those specific uses in those areas. The PID noted that when considering all currently registered agricultural and non-agricultural uses of chlorpyrifos, aggregate exposures are of concern. If considering only the uses that result in DWLOCs below the EDWCs, aggregate exposures are not of concern. Ref. 32 at 19. The PID
proposed limiting chlorpyrifos applications to specific crops in certain regions where the EDWCs for those uses were calculated to be lower than the DWLOC. Id. at 40. The Agencys ability to make the safety finding for any remaining uses would be contingent upon significant changes to the existing registrations, including use cancellations, geographical limitations, and other label changes.
Consequently, while the 2020 PID
suggested that there may be limited combinations of uses that could be safe, FFDCA section 408b2 requires EPA
to aggregate all dietary and nonoccupational exposures to chlorpyrifos in making a safety finding. Without effective mitigation upon which to base a reduced aggregate exposure calculation, the products as currently registered present risks above the Agencys levels of concern. Based on the data available at this time and the aggregate exposures expected from currently registered uses, the Agency cannot, at this time, determine that aggregate exposures to residues of chlorpyrifos, including all anticipated dietary exposures and all other nonoccupational exposures for which there is reliable information, are safe.
Accordingly, as directed by the statute and in compliance with the Courts order, EPA is revoking all chlorpyrifos tolerances.

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