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In response, the Agency acknowledges that an ecological risk assessment was completed in 

absence of these data. However, the Agency clearly identified uncertainty in this risk assessment 

due to the lack of sediment toxicity data. Specifically, the registrant submitted only one 

sediment toxicity study (28-d midge chronic toxicity; MRID 48250425) which was classified as 

supplemental because it only evaluated organism emergence and development rate (and not 

reproduction). The Agency further noted in its ecological risk assessment (D408705) chronic 

sediment toxicity data were lacking for two other species that are typically required (1 freshwater 

and 1 estuarine/marine amphipod). 

To further characterize and address this uncertainty for the purposes of this action, the Agency 

has applied toxicity extrapolation methods based on the chronic toxicity of tolfenpyrad to 

freshwater and estuarine/marine invertebrates exposed in the water column. The results of this 

analysis, in addition to results using the aforementioned sediment toxicity study, are shown in 

Table 1 below for the proposed use with the highest EECs in pore water (GA Peach).

Table 1. Estimated Risk Quotients for Benthic Invertebrates with the Proposed New Uses 

of Tolfenpyrad

21-d Pore 

Water EEC (μg 

a.i./L) (1)

Invertebrate 

Chronic NOAEC 

(μg a.i./L)

Toxicity Basis Species/MRID

Chronic 

Benthic 

Invertebrate 

RQ

0.14 0.0288 Sediment pore 

water

Chironomus 

riparius

(48250425)

4.8 (2)

0.14 2.3 Water column Americamysis 

bahia

(48250420)

0.06

0.14 0.244 Water column Daphnia magna 

(48250418)

0.6

(1)EEC in sediment pore water based on PRZM/EXAMS modeling for GA Pecan crop scenario (see Table 3.5 of 

D408705)

(2) Exceeds chronic risk level of concern of 1.0. The chronic NOAEC from this study does not include measurement 

of reproductive effects.

The results of this analysis indicate that the proposed uses of tolfenpyrad have the potential for 

chronic risk to benthic invertebrates, based on a chronic RQ of 4.8 for C. riparius. There is 

uncertainty associated with this RQ because effects on reproduction was not assessed in the 

applicable toxicity study. If effects of tolfenpyrad on C. riparius reproduction occur at lower 

concentrations than those on development rate and emergence, the chronic risk quotient will be 

greater than 4.8. On the other hand, the NOAEC from the C. riparius study represents the 

highest concentration tested (i.e., a LOAEC was not achieved in this study). Therefore, it is also 

possible that the RQ may be lower than 4.8 had higher concentrations been tested. For the mysid 

(A. bahia) and the daphnid (D. magna), chronic risks based on pore water exposure do not 

exceed the chronic risk level of concern (1.0). Uncertainty associated with these RQ values
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relate to the possibility that freshwater and estuarine/marine amphipods used in sediment toxicity

testing may be more or less sensitive to tolfenpyrad compared to daphnids and mysids.

Based on this analysis of risk to benthic invertebrates, EFED believes that sufficient information

exist from which to assess risks to benthic invertebrates for the proposed uses of tolfenpyrad.

However, in order to address the aforementioned uncertainties, EFED strongly recommends that

additional sediment toxicity data be submitted to the Agency for any new uses of tolfenpyrad in

the future.