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• 835.4300: Aerobic aquatic metabolism

• 835.4400: Anaerobic aquatic metabolism

• 850.1300: Aquatic invertebrate life cycle (freshwater)

• 850.1400: Fish Early-Life Stage (saltwater)

• 850.2300: Avian Reproduction (bobwhite quail)

• 850.3030: Honey bee toxicity of residues on foliage

• 850.4100: Seedling emergence

• 850.4150: Vegetative vigor

• 850.6200: Analytical method in water and sediment 

• Special study: Acute oral honey bee adult toxicity

EFED Response: The environmental fate data has been received and is undergoing review. 

EFED will review the ecotoxicity data when they are submitted.

Syngenta Comment 2: RQs for Aquatic Organisms

The risk quotients for non-target aquatic organisms calculated in the last assessment are highly 

conservative because much of the environmental fate data were from older studies that no longer 

meet acceptability criteria. Therefore the modeling assumed abamectin to be stable in the 

environment. Syngenta has submitted new environmental fate studies which will allow for 

refinement to the aquatic exposure modeling.

EFED Response: EFED will review the submitted environmental fate data and will use them 

for modeling in the registration review risk assessment if they are found to be suitable for 

quantitative use. 

Syngenta Comment 3: Adsorption/Desorption Data

A more recent adsorption/desorption study was submitted (MRID 49071002) and the results 

from this study should be included in the risk assessment. 

EFED Response: The adsorption/desorption study has been received and is undergoing 

review. If the data are found to be useful, they will be considered for use in the registration 

review risk assessment.

Syngenta Comment 4: Mysid Shrimp NOAEC

The NOAEC value for the mysid shrimp should be 0.0035 μg ai/L rather than 0.00035 μg ai/L.

EFED Response: The stated NOAEC of 0.00035 μg ai/L was based on reproduction when 

compared to the negative control. The NOAEC of 0.0035 μg ai/L was based on survival. The 

study was originally classified as supplemental. However, while reviewing the data for these 

comments, a new evaluation of the study was conducted and it was determined that the 

survival data were acceptable but the reproduction data were invalid. A solvent effect on 

reproduction was noted that may have confounded the results. 

As stated in the study report, there was a statistically significant difference between 

reproductive success (offspring/female/reproductive day) in the negative control and solvent 

control (p=0.038). The solvent used in the study was acetone at a concentration of 5.7 μL/L.

Reproductive success in the solvent control was reduced by 30% compared to the negative 
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control. As a result of this difference, the reviewer could not determine whether effects on 

reproductive success observed were due solely to exposure to the test substance. Compared 

to the solvent control, decreases in reproductive success were apparent at some test 

concentrations but these differences were not statistically significant. Compared to the 

negative control, statistically significant effects on reproductive success were observed at two 

test concentrations, 0.00076 μg/L and 0.0035 μg/L (p<0.05). If the negative control is used 

as the comparison group, the NOAEC for reproductive success in the study is 0.00035 μg/L.

The apparent solvent effect on reproductive success makes this endpoint unreliable for use in 

quantitative risk assessment.

In contrast, survival was not affected by the solvent. The NOAEC based on survival, as 

stated in the original DER, is 0.0035 μg/L.

Syngenta Comment 5: Earthworm LC50

The 28-d LC50 for earthworms should be 28 ppm rather than 18 ppm. 

EFED Response: The stated 28-d LC50 of 18 ppm, calculated using probit regression, is 

accurate. The calculations are detailed in the DER.

Syngenta Comment 6: Use Table

Syngenta has submitted a document to the registration review docket summarizing abamectin 

food/feed uses from multiple registrants.

EFED Response: EFED will refer to this document when constructing maximum use 

scenarios for the registration review risk assessment.

Syngenta Comment 7: Endangered Species Assessment Methods

Syngenta has submitted a document to the registration review docket summarizing the types of 

refinements that should be considered for an endangered species assessment.

EFED Response: EFED has received the document and will take Syngenta’s 

recommendations under advisement when conducting the endangered species assessment.