2

Comments Related to the Environmental Fate Data Requirements

AMVAC Comment: Dissociation Constants in Water (OCSPP 830.7370), for all of NAA 

compounds except naphthalene acetic acid: AMVAC indicated that the dissociation of NAA 

and its different salts will be determined by the proton affinity of the carboxylic acid substituent 

and the pH of the surrounding aqueous solution. In the environment, the pH will be determined 

predominantly by the ions and their complexes in the water and equilibria with the surrounding 

soil, rather than by the much lower concentration counter ions (sodium, potassium, or 

ammonium) associated with the initial NAA salt.

The pKa of the sodium salt was determined to be 4.1 (Greenwood, 2005)1. In the literature, the 

pKa for NAA is reported at the comparable value of 4.2 (TOXNET). These values demonstrate 

that NAA and its associated salts will be more than 99% dissociated in ponds, lakes, and rivers, 

which typically have pHs in the range of 6.5‐8.5. The molecular species of NAA and all of its

associated salts in the environment will be the same dissociated organic anion. The 

environmental fate of NAA and its salts relate to that of the dissociated anionic species. On this 

basis, AMVAC finds it appropriate to apply the dissociation constant determined for the NAA 

sodium salt to NAA and its other salts.

Concerning the ethyl ester and acetamide of NAA, they are distinct chemical entities but, due to 

structural considerations, do not participate in acid/base equilibrium. Therefore, these two NAA

based compounds do not have a meaningful dissociation constant and are fully associated under 

environmental conditions.

AMVAC requested a waiver for any new studies to measure dissociation constant.

EFED Response: The purpose of the requests for physicochemical data for NAA related 

compounds is to confirm certain values derived from modeling (e.g., EPISUITE) and/or available 

from external sources. The Division has a study that indicated that the pKa of NAA acid is 3.5 

(MRID 40522903). This value also indicates a high tendency for the acid to be dissociated under 

typical environmental conditions. Based on this pKa, it appears that the salts will also be 

typically dissociated in the environment, and this is also supported by the study cited by AMVAC 

for the sodium salt, for which the pKa was 4.1 (Greenwood, 2005). However, the Division 

inspected the cited study (cited in the comments under MRID 40523003) and found that the pKa 

in this citation was for the NAA (acid) instead of the sodium salt, which is 3.5. Further, the study 

was performed by a different author and year (Feiler, 1987). EFED would like to confirm the 

pKa of 4.1 for the sodium salt cited above, and requests the registrant to submit the study or 

provide the correct MRID citation. Based on the data to be provided by the registrant, EFED may

assume that the acid form of NAA and its salts are fully dissociated in the environment and that 

the results of studies conducted on the acid and the sodium salt are representative of other salts. 

Regarding the ethyl ester and acetamide of NAA, the registrant indicated that these species do not 

 1 Greenwood, J.; Liney, P. (2005) 1‐Naphthaleneacetic acid sodium salt (purified): physicochemical properties, 

Covance Laboratories, Ltd., Study Report 1708/040‐D2149, AMVAC Report 400‐PCH‐037 (cited under MRID 

40522903).
3

have structural moieties participating in acid/base equilibrium and do not have a meaningful 

dissociation constant.

EFED requests the registrant to submit the study for the sodium salt or provide the correct MRID 

citation for Greenwood and Liney (2005). Once the study is submitted, EFED will consider using 

the pKa for the sodium salt in place of the potassium and ammonium salts.

Additionally, EFED recommends to remove the Dissociation Constant data requirement for the 

ethyl ester and acetamide forms of NAA.

AMVAC Comment: Water Solubility (OCSPP 830.7840/ 830.7860) for naphthalene 

acetamide and naphthalene acetic acid, potassium and ammonium salts: AMVAC said it will

provide EPA with an existing water solubility study for the NAA acetamide (Jentoft 1996, 

AMVAC Report 400‐PCH‐049). 

For NAA, the solubility of this carboxylic acid is pH dependent. However, at environmental pHs 

(i.e., 6‐8), the compound will be in its dissociated form and exist as a salt complex with the 

counter‐cations that are available in solution. All of the salts of NAA are predicted to be highly 

water soluble. For example, EPA has a study on the sodium salt that determined a water 

solubility of 295.5 g/L at 20.1°C (Greenwood, 2005). The potassium and ammonium salts are 

expected to have similar solubility and the concentration of these salts within their respective 

formulated aqueous products demonstrates this contention. K‐Salt Fruit Fix 800 (Registration No. 

5481‐413) is 24.2% potassium salt by weight and Fruit Fix Concentrate 800 (5481‐130) is more 

than 22.8% by weight. These products contain no adjuvants and are prepared by simply 

combining either potassium hydroxide or ammonia to NAA in water to make the respective salts.

Due to the high solubility associated with these products, it should be appropriate to simply list 

both the potassium and ammonium salts as having water solubility greater than 20% by weight 

(i.e., >200,000 ppm). This value should also be applied to NAA in consideration of its solubility 

at an environmental pH. Further, NAA is not sold in its acid form as a product. On this basis, 

AMVAC is seeking waivers for water solubility studies for NAA, the potassium salt, and the 

ammonium salt.

EFED Response: The Division has a study conducted on the acid form of NAA that 

indicates that the solubility is 420 mg/kg at 26°C (MRID 40522903). As indicated by the 

registrant, the solubility of the acid is pH dependent; however, the pH of the solution in the 

available study is not stated. The registrant-cited study on the sodium salt (Greenwood 2005, 

under MRID 40523003) was located by the reviewer, but it was found that it was conducted in a 

different year and by a different author (Feiler, 1987) than the MRID citation provided. 

According to the submitted study (MRID 40523003), the solubility of the sodium salt of NAA is 

340 g/100 g or 3,400,000 mg/kg at 26°C. Finally, EFED has a study conducted with the ethyl 

ester of NAA that indicates that the solubility is 105 mg/L at 25oC (MRID 47505905).

EFED will consider using the very high solubility of the sodium salt in place of the ammonium 

and potassium salts of NAA. Furthermore, EFED looks forward to the submission of an existing 

solubility study for NAA acetamide.
4

AMVAC Comment: N‐Octanol/Water Partition Coefficient (OCSPP 830.7550/830.7560/

830.7570), for naphthalene acetic acid and naphthalene acetamide: AMVAC indicated it will 

provide a partitioning study for NAA acetamide. However, the testing of an organic acid such as 

NAA that would be highly dissociated in the environment should not be necessary as ionic 

species will exhibit minimal partitioning behavior in non‐polar solvents at environmental pHs. 

On this basis, AMVAC is seeking a waiver for conducting a partitioning study on NAA and only 

performing the partitioning study on the acetamide.

EFED Response: On the basis of a pKa ranging from 3.5 for naphthalene acetic acid (MRID 

40522903) to the sodium salt of 4.1 (Greenwood and Liney, 2005, a study to be submitted or 

citation provided by the registrant), the acid and its salts should exist in the dissociated form as 

naphthalene acetate and its counter cation at environmentally relevant pHs (~6-8). Therefore, the 

Octanol/Water Partition Coefficient data requirement conducted on the acid is not required. 

Furthermore, the Agency is looking forward for the study AMVAC committed to conduct on the 

acetamide.

AMVAC Comment: Vapor Pressure (OCSPP 830.7950) for all salts, ethyl ester, and 

amide: AMVAC said that organic salts have extremely low vapor pressures and measurements 

are typically obscured by low level impurities. Therefore, such measurements are not provided by 

chemical distributors on MSDSs for acetate salts. For these salts, low level impurities, including 

acetic acid or ammonia are known to impair the extremely low measurements required for 

determining the vapor pressure of the pure salts. For this reason, AMVAC is seeking waivers for 

vapor pressure testing of any of the NAA salts; but commits to conducting a study on the ethyl 

ester. AMVAC has already performed a study on the acetamide (Lorence 1996, AMVAC Report 

400‐PCH‐054), and will provide it to the Agency.

EFED Response: The vapor pressure for the acid is 0.3 torr at 26°C (MRID 40522903). 

EFED will use this data in place of the Vapor Pressure data requirement for the NAA sodium, 

potassium and ammonium salts, since salts are not expected to volatilize substantially. Further, 

EFED welcomes the submission of the already available study on the acetamide, and a new study 

that the registrant committed to perform on the ethyl ester.

AMVAC Comment: Aerobic Soil Metabolism (OCSPP 835.4100) for naphthalene acetic 

acid and naphthalene acetamide: AMVAC proposes to address the study requirements for both 

NAA and the acetamide by conducting the required studies for the acetamide and using those 

studies to determine the kinetics of both the acetamide and NAA. Because the first step in the 

degradation of the acetamide is anticipated to be conversion to the acid, appropriate scheduling of 

sampling in the protocol will permit the determination of the formation and degradation constants 

of NAA.

EFED Response: EFED believes that a study conducted on the acetamide may provide 

suitable information about the degradation pattern of both the acetamide and the acid, as proposed 
5

by AMVAC, assuming that NAA acid is the primary degradate of the acetamide. The registrant 

is advised that all the transformation products of both chemicals >10% AR must be identified and 

the patterns of formation and decline clearly established. The degradation pathways for NAA 

acetamide and for NAA acid should be provided. The study should be conducted in four soils. 

Note that previously the Preliminary Problem Formulation requested two soils for the acid and 

two soils for the acetamide.

AMVAC Comment: Aerobic Aquatic Metabolism (OCSPP 835.4300) for naphthalene 

acetic acid and naphthalene acetamide: AMVAC believes that by experimentally determining 

the aerobic soil metabolism half‐life for NAA and NAA acetamide, a more definitive assessment 

of the potential for microbial degradation would be determined. EPA has traditionally applied a 

factor of 2X to the aerobic soil metabolism half‐life in estimating chemical degradation kinetics in 

a water phase associated with the sediment.

AMVAC contracted Stone Environmental for conducting a sensitivity analysis for the aerobic 

aquatic metabolism parameter on surface water exposure. This assessment utilized the QSAR 

modeled KOC and aerobic soil metabolism half‐life value previously determined by EPA and 

reported in the recent Problem Formulation. The sensitivity analysis assessed the extent to which 

surface water concentrations would change by modifying the aerobic aquatic metabolism half‐life. 

The half‐life was modified over a range of values that included the likely aerobic soil metabolism 

half‐life of 10 days as calculated by EPA using EPISUITE and a half‐life as long as 164 days. The

assessment was conducted on the product use pattern for the FL citrus scenario.

According to AMVAC, the sensitivity analysis demonstrates that by conducting an aerobic 

aquatic metabolism study and refining EPA’s default 2X the aerobic soil metabolism half‐life 

approach, there would be no significant change in the modeled calculation of surface water 

concentrations. In the determination of the acute surface water concentration, refining the aerobic 

aquatic metabolism half‐life would yield a negligible change on the peak surface water 

concentration over a wide range of aerobic aquatic half‐lives. Also, this refinement would only 

yield a minor change in the average surface water concentration of 1.5X.

Further, AMVAC said that there is information within the literature indicating that the 

metabolism of NAA in aquatic systems would likely be comparable to that associated with 

terrestrial environments. Information concerning the degradation of certain surrogate compounds 

provides insight into this issue. As NAA is a polycyclic aromatic compound, one would expect 

microorganisms capable of degrading these commonly occurring chemicals to be abundant in 

both terrestrial and aquatic environments. Previous studies have demonstrated that naphthalene is 

efficiently mineralized in diverse aquatic environments (Heitkamp 1987)2

. Such metabolism 

entails initial oxidation of the aromatic ring system through the formation of cis‐1,2‐dihydroxy‐

 2 Heitkamp, M. A.; Freeman, J. P.; Cerniglia, C. E. (1987) Naphthalene biodegradation in environmental 

microcosms: estimates of degradation rates and characterization of metabolites, Appl. Environ. Microbiol. 53 (1), 

129‐136.
6

1,2‐dihydronaphthalene by bacteria (Heitkamp 1987, Alquati 2005, Madhumita 2012)3 and of the 

trans-isomer by fungi (Cerniglia 1978)4. NAA, which contains the naphthalene structure within 

its core would be predicted to serve as a reasonably good substrate to these same organisms, 

especially given the fact that current data suggests that NAA itself would not likely display any 

significant toxicity to microorganisms [no source or evidence for this statement provided]. NAA 

would also be predicted to degrade through formation and degradation of CoA‐thioesters 

catalyzed by ubiquitous phenylacetyl‐CoA ligases found in the environment (Magdy 2000, 

Navarro‐Llorens 2005, Shrivastava 2011)5

.

On the basis of the above information, AMVAC is seeking a waiver from conducting aerobic 

aquatic metabolism studies for both NAA and NAA acetamide. AMVAC proposes that the 2X 

factor be applied to the aerobic soil metabolism half-life value that will be determined by 

AMVAC in an upcoming study.

EFED Response: At this time, the registrant has not submitted for review any information 

about the aerobic soil or aerobic aquatic metabolism of NAA acid or the acetamide, or their 

degradation pathways. An European Union study yielded DT50’s for the total system in two 

sediments are 6.2 and 9.5 days, suggesting that NAA acid degrades faster than previously 

assumed in modeling. No degradates were identified (source: public Draft Assessment Report, or 

DAR, Volume 3, Annex B, part 5, B.8, pp. 576-582, dated August 2008). EFED believes that an 

aerobic aquatic metabolism study is highly desirable for NAA (acid) and the acetamide, especially

in the absence of any other degradation information about these chemicals to date. Nonetheless, 

in the absence of an aerobic aquatic metabolism study, EFED will use a 2X factor (i.e., twice the 

aerobic soil metabolism input value), per the current Input Parameter Guidance, v.2.16.

AMVAC Comment: Adsorption/Desorption (Batch Equilibrium) (OCSPP 835.1230), for 

naphthalene acetic acid and naphthalene acetamide: AMVAC reviewed EPA’s information 

concerning the calculation of a KOC value using EPISUITE v.4.1 and believes that the determined 

value is appropriate for use in groundwater and surface water modeling assessments. The review 

by Wang (2015)7 provides data demonstrating that quantitative structure‐activity relationship 

 3 Alquati, C.; Papachini, M.; Riccardi, C., Spicaglia, S., Bestetti, G. (2005) Diversity of naphthalene‐degrading 

bacteria from a petroleum contaminated soil. Ann. Microbiol. 55 (4), 237‐242.

Madhumita, R.; Khara, P.; Dutta, T. K. (2012) meta‐Cleavage of hydroxynaphthoic acids in the degradation of 

phenathrene by Sphingobium sp. Strain PNB. Microbiol. 158, 685‐695. 4 Cerniglia, C. E.; Gibson, D. T. (1978) Metabolism of naphthalene by cell extracts of Cunninghamella elegans. 

Arch. Biochem. Biophys. 186, 121‐127. 5 Magdy, E‐S. M. (2000) Biochemical and molecular characterization of Phenylacetate‐Coenzyme A Ligase, an 

enzyme catalyzing the first step in aerobic metabolism of phenylacetic acid in Azoarcus evansii. J. Bacteriol. 182 (2), 

286‐294.

Navarro‐Llorens, J. M.; Patrauchan, M. A.; Stewart, G. R.; Davies, J. E.; Eltis, L. D.; Mohn, W. W. (2005) 

Phenylacetate catabolism in Rhodococcus sp. Strain RHA1: a central pathway for degradation of aromatic 

compounds. J. Bacteriol. 187 (13) 4497‐4504.

Shrivastava R.; Purohit H.; Phale P. S. (2011) Metabolism and preferential utilization of phenylacetic acid and 4‐

hydroxyphenylacetic Acid in Pseudomonas putida CSV86. J Bioremed Biodegrad 2, 120‐130. 6 Available at http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm (accessed 03/27/2015). 7 Wang, Y.; Chen, J.; Yang, X.: Lyakurwa, F.; Li, X.; Qiao, X. (2015) In silico model for predicting soil organic 

carbon normalized (KOC) of organic chemicals, Chemosphere 119, 438‐444.
7

(QSAR) assessments [including EPA’s PCKOCWIN (MCI) and PCKOCWIN (Log KOW)] are 

accurate predictors of KOC for carboxylic acid compounds such as NAA. Only in one case (i.e., 

endothal) was the predicted KOC value not accurately determined. In this case, the actual value 

was higher; thus the modeling exaggerated the leaching potential for this compound. [EFED 

note: When KOC is higher, the leaching potential is smaller, not higher.]

The KOC value determined for NAA by EPA using EPISUITE v. 4.1 is 24.82 mL/gOC, which 

appears to be reflective of the low soil binding potential of an ionized species. AMVAC believes 

that this value is sufficiently conservative for the EPA to continue to rely on this value in its 

modeling assessment of environmental concentrations in water.

AMVAC worked with Stone Environmental who performed a sensitivity analysis on the KOC of 

NAA. AMVAC’s comments provide results of acute and chronic estimated drinking water 

concentrations (EDWCs), for groundwater and surface water that were used for assessing the 

sensitivity of the KOC parameter on predicted concentrations in water. The KOC evaluation was 

conducted for the FL citrus scenario. A 2X increase in the modeled QSAR KOC value is the 

maximum increase expected for a highly water soluble compound that would be ionized in the 

environment. Because the aerobic soil metabolism half‐life has not yet been firmly established, 

several different aerobic soil metabolism half‐lives ranging from 10 – 132 days were explored in 

the sensitivity assessment.

For surface water, sensitivity analysis demonstrates that the change in acute NAA concentration 

associated with a 2X increase in the KOC would yield a concentration reduction of 1.0 – 1.1X. 

This change would also yield a reduction in the chronic (average) surface water concentration of 

1.1X. These reductions are clearly insignificant. The sensitivity analysis determined that the 

change in peak NAA groundwater concentration associated with a 2X increase in the QSAR KOC

would yield only a 1.3 – 3X reduction. This KOC change would also yield a reduction in the post‐

breakthrough average groundwater concentration of 1.2 – 2.6X. These reductions are relatively 

insignificant compared with reductions associated with changes for other environmental 

parameters. For example, a change in the aerobic soil half‐life from 10 to 30 days would yield a 

reduction of 4.9X for the peak ground water concentration and of 6.2X for the post breakthrough 

average concentration, assuming the QSAR KOC of 24.82 mL/gOC.

As the EPA has stated in its recent Problem Formulation assessment that, “In the absence of data, 

conservative assumptions will be made for NAA and its derivative compounds”, AMVAC

believes that utilization of the current KOC values provides a sufficient and satisfactory means for 

conservatively assessing groundwater and surface water concentrations associated with product 

use. Further, as NAA is applied at a higher concentration than NAA acetamide and is more 

mobile, it represents a worse case assessment for the chemical group. Due to the lack of 

sensitivity of this parameter on predicting groundwater and surface water concentrations, the 

QSAR KOC value determined for NAA would provide a sufficient and satisfactory means for 

conservatively assessing groundwater and surface water concentrations associated with product 

use.

On this basis, AMVAC is seeking a waiver from conducting adsorption/desorption studies for 

both NAA and the acetamide and is proposing to use the QSAR model‐based KOC value 

determined by the Agency for all NAA based assessments.
8

EFED Response: It was noted that the sensitivity analysis did not explore the possibility that 

the KOC would be lower than predicted by EPISUITE. Chemicals with lower KOCs may 

contaminate surface waters mostly dissolved in runoff waters, in events occurring shortly after 

application or groundwater by leaching, depending on their persistence. However, it is noted that 

the European Union study shows KOC values ranging from 68.5 – 138 cm3

/gOC and the KFOC were 

43.5 – 88.5 cm3

/gOC (with 1/n range of 0.815 – 0.866), for three soils tested. These values 

compare favorably with EPISUITE v. 4.1 result of 24.82 mL/gOC for NAA acid (source: public 

Draft Assessment Report, or DAR, Volume 3, Annex B, part 5, B.8, pp. 556-559, dated August 

2008). If the registrant submits the EU study, and it is found to be acceptable or supplemental, 

the Agency may rely on that study in conducting the drinking water exposure and ecological risk 

assessments. Note that the study cited in the DAR is for NAA, while there are no studies 

submitted on the acetamide. Therefore, a study on NAA acetamide is also required.

AMVAC Comment: Environmental Chemistry Method/Independent Laboratory Validation 

(ECM/ILV, OCSPP 850.6100), for naphthalene acetic acid and naphthalene acetamide: AMVAC 

said that it intends to conduct this study in accordance with EPA’s requirement.

EFED Response: The Division is looking forward to the submission of the above mentioned 

ECM/ILV reports.

Comments Related to the Ecological Effects Data Requirements

AMVAC Comment:

850.1010. Acute toxicity to freshwater invertebrates TGAI, naphthalene acetamide

850.1035. Acute toxicity to estuarine/marine invertebrate (mysid) TGAI, naphthalene acetamide

850.1075 Acute toxicity to estuarine/marine fish TGAI, naphthalene acetamide

850.1300 Chronic Toxicity to Freshwater Invertebrates TGAI, naphthalene acetamide

AMVAC indicated that if the freshwater fish chronic study (850.1400) on NAA acetamide were 

to demonstrate toxicity that would yield a risk at an unacceptable level of concern, it would 

conduct these studies. On this basis, AMVAC proposes that these studies be listed as reserved 

until the results of the pending chronic fish study are reviewed. 

EFED Response: EFED noted in its Problem Formulation document that no aquatic animal 

toxicity data exists for the amide form of NAA, but that QSAR estimates of toxicity suggest that 

it may be of similar chronic toxicity as the ester form with respect to fish. Due to uncertainty 

associated with QSAR estimates of toxicity for pesticides, EFED does not rely on QSAR 

estimates as the basis of its ecological risk assessments. However, EFED noted that in the 

absence of data, EFED would rely on measured toxicity data for similarly structured compounds 

with the same mode of action (e.g., Quinclorac and Quinmerac), however, these ecological 

toxicity data gaps would remain. EFED notes that submission of a chronic early life stage fish 

test for NAA acetamide would be useful in its future ecological risk assessment, but that given the 

high degree of variability in sensitivity between fish and invertebrate taxa, a single study for fish 
9

would not fulfill data gaps for invertebrate taxa. EFED would encourage the registrant to 

consider conducting a chronic toxicity test with Daphnia magna, since this would help to resolve 

uncertainties regarding the sensitivity of aquatic invertebrates to NAA acetamide. Once a Data 

Call-In is issued for these data, EFED will respond in detail to the registrant’s proposal when 

submitted as a formal waiver request for 850.1010, 850.1035, and 850.1300.

AMVAC Comment: AMVAC has already provided an acute 48‐hour study for NAA on 

Daphnia magna (MRID 00082526) that EPA has determined to be acceptable. EPA concluded in 

their Problem Formulation assessment that the 48‐h EC50 of 180 mg/L is indicative of a chemical 

that is practically non‐toxic. This is because the EC50 is orders of magnitude higher than the 

predicted environmental concentrations (PECs) of NAA in groundwater and surface water. It is 

highly unlikely that EC50 for the acetamide would be significantly different as EPA’s QSAR 48‐

h EC50 initial estimate for NAA of 540 mg/L was not significantly different from the measured 

value of 180 mg/L. EPA then applied a correction factor to the QSAR 48‐h EC50 for the NAA 

acetamide and determined a 48‐h EC50 of 147 mg/L, which is quite comparable to the NAA 

toxicity value. Even if the estimate for NAA acetamide was somewhat in error, it is highly 

unlikely to result in any level of concern for the chronic risk to this species. 

However, AMVAC recognizes that there is no aquatic animal data at the moment for NAA 

acetamide; thus we propose conducting a chronic toxicity study on freshwater fish, which has 

been determined to be the most sensitive aquatic animal species to NAA and also according to 

EPA’s QSAR assessment. Assuming that this study were to yield an EC50 value that 

approximates the QSAR value of 0.15 mg/L, this value would be more than an order of 

magnitude greater than the average surface water PEC and approximately an order of magnitude 

greater than the maximum surface water PEC. This would be clear evidence that the acute and 

chronic risk for fish and other aquatic animal species would not be of concern.

EFED Response: See EFED’s previous response to the first comment above. 

AMVAC Comment: 850.2300 Avian Reproduction TGAI, naphthalene acetamide.

AMVAC’s intention is to bridge to similar mode of action studies and will contact the appropriate 

data submitters.

EFED Response: At this time there is no chronic avian data available for any of the NAA 

related active ingredients. As indicated in its Problem Formulation document, in absence of data, 

EFED will evaluate the structural similarity of any proposed chemicals for satisfaction of bridging 

to satisfy avian reproduction studies for NAA and related active ingredients. AMVAC has not 

indicated which chemicals will be proposed and whether data from these chemicals will be 

available for their use. EFED recommends a formal waiver request be submitted with a detailed 

rationale for bridging avian reproduction data for NAA and related active ingredients, 

AMVAC Comment: 850.3020 Honey Bee Adult Acute Contact Toxicity TGAI, naphthalene 

acetic acid.
10

AMVAC has a guideline contact study on honey bees made available by our business partner 

Agro‐Kanesho and we will provide this study to the EPA (Sidermann 2004)8. The study was 

conducted in accordance with OECD Guideline 214 and should address study needs as defined by 

EPA Guideline 850.3020 per the Agency’s requirement as indicated in its Preliminary Work Plan. 

The completed study clearly demonstrates the safety of honey bees to contact exposure by NAA.

EFED Response: EFED will make every effort to quickly review the honeybee acute contact 

study mentioned above upon submission by the registrant. Until this study is submitted and 

reviewed, the data gap for the acute contact toxicity with the honey bee will remain.

AMVAC Comment: OECD 213 Honey Bee Adult Acute oral Toxicity TGAI, naphthalene 

acetic acid.

AMVAC has a guideline oral study on honey bees made available by our business partner Agro‐

Kanesho and we will provide this study to the EPA (Sidermann 2004)9. The study was conducted 

in accordance with OECD Guideline 213 and EPPO Guideline No. 170 per EPA’s requirement as 

indicated in its Preliminary Work Plan. The completed study clearly demonstrates the safety of 

honey bees to oral exposure by NAA.

EFED Response: EFED will make every effort to quickly review the honeybee acute oral 

toxicity study mentioned above upon submission by the registrant. Until this study is submitted 

and reviewed, the data gap for the acute contact toxicity with the honey bee will remain.

AMVAC Comment: Non-Guideline Honey Bee 10 Day Adult Chronic Toxicity TGAI, 

naphthalene acetic acid.

AMVAC has a guideline contact study on a different species of larval insect, the Ladybird beetle, 

made available by our business partner Agro‐Kanesho and we will provide this study to the EPA 

(Tsukidate, 2004)10. The study evaluated dermal exposure to the post‐molting, 2nd instar larvae 

by dipping the larvae into a 400 mg ai/L solution and observing for 10 days in accordance with 

JMAFF Guideline for toxicity studies on natural enemy insects (2‐8‐3) in 13 Seisan 3986, “Of 

applying ‘annex guidelines for preparation of study results submitted when applying for

registration of agricultural chemicals’”.

The study showed no mortality or abnormal behavior in the test organisms that completed 

pupation within the 10‐day study window. Given the lack of an effect under these extreme dosing 

 8 Sidermann, A. B.; Porch, J. R.; Kruger, H. O. (2004) NAA‐NA: An acute contact toxicity study with the honey bee

(OECD Guideline 850.3020), Unpublished study performed by Wildlife International LTD.

9 Sidermann, A. B.; Porch, J. R.; Kruger, H. O. (2004) NAA‐NA: An Acute Oral Toxicity Study with the Honey Bee

(OECD Guideline 213 and 170), Unpublished study performed by Wildlife International LTD, Project Number 283‐

117, AMVAC Study No. 400‐NON‐014. 10 Tsukidate, Y. (2004) A laboratory study to evaluate the toxicity of AKD‐8147 technical against the ladybird beetle 

Coccinella septempunctata bruckii Mulsant, Unpublished study performed for Agro‐Kanesho Company, Ltd. By 

Eco‐Science Corporation, Project No. AMVAC Study No. 400‐EFF‐009.
11

conditions, it is reasonable to assume that there would also not be any effects of concern on honey 

bee larvae. 

Also, the fact that the structural elements of NAA are able to efficiently mimic the ubiquitous 

plant auxin 3‐indole acetic acid (3‐IAA) indicates that NAA would not be toxic to bees as 3‐IAA 

is ubiquitous to plants to which honey bees would be exposed. The important synergy between 

plants and honey bees requires that 3‐IAA not be toxic to the adults or their larvae. Although 3‐

IAA is primarily synthesized in the vascular tissue of the stem, protein regulation of 3‐IAA also 

occurs within the pollen (Dal Bosco 2012)11; thus insect and larval exposure to this auxin is 

imminent. Due to the structural similarity of NAA to 3‐IAA, toxicity of NAA to honey bees at 

larval or adult stages would not be expected to be significantly different. In fact, the lack of 

toxicity of NAA and NAA acetamide to three different adult species of bees has recently been 

established for both NAA and NAA acetamide (Kim 2014)12. 

Further, given the longstanding use of NAA in the field, if there were problems related to hive 

performance, reports should have become evident. To our knowledge that is not the case. On the 

basis of this information, the available Ladybird beetle larval study should be sufficient to address 

the Agency’s concern regarding the potential toxicity of NAA to honey bee larvae and on that 

basis the substitution of the Ladybird beetle study is proposed in lieu of the required honey bee 

larvae study. 

EFED Response: EFED will review the chronic exposure toxicity study with ladybird 

beetle mentioned above upon submission by the registrant. However, this non-guideline test with 

a different non-pollinator species of insect may not be adequate to satisfy the honeybee chronic 

toxicity data requirement as related to current OPP policy requirements for pollinator protection. 

EFED will also consider the arguments regarding similarity to 3-indole acetic acid and it’s 

structural resemblance to NAA, however bridging another chemical’s toxicity information is not 

currently addressed in our pollinator protection guidance. Once the Data Call-In is issued, the 

registrant may provide additional information during the waiver request process for the nonconductance of honeybee chronic toxicity guideline for NAA.

AMVAC Comment:

Non‐guideline (OECD 234) Honey Bee Larval Acute Toxicity TGAI, naphthalene acetic acid 

Non‐guideline Honey Bee Larval Chronic Toxicity TGAI, naphthalene acetic acid

The previously mentioned chronic contact study on the Ladybird beetle will provide data that 

demonstrates that there is no acute toxicity to Ladybird beetle larvae at high doses. This 

information can then be interpreted to provide a finding that the product will have very low or no 

toxicity to honey bee larvae. 

 11 Dal Bosco, C.; Dovzhenko, A.; Liu, X.; Woerner, N.; Rensch, T.; Eismann, M.; Eimer, S.; Hegermann, J.; 

Paponov, I.A.; Rupert, B.; Heberle‐Bors, E.; Touraev, A.; Cohen, J. D.; Palme, K. (2012) The endoplasmic reticulum 

localized PIN8 is a pollen‐specific auxin carrier involved in intracellular auxin homeostasis. Plant J., 71 (5), 1365‐

1375.

12 Kim, D. (2014) Acute toxicity of six flower/fruit thinners to Apis mellifera, Bombus terrestris (Hymenoptera: 

Apidae) and Osmia cornifrons (Hymenoptera: Megachilidae) in laboratory bioassays. November 17th Meeting of the 

Entomological Society of America, https://esa.confex.com/esa/2014/webprogram/Paper88333.html
12

AMVAC will therefore seek to fulfill these requirements by providing the previously referenced 

chronic study on Lady beetle larvae (Tsukidate, 2004).

EFED Response: EFED will review the chronic exposure toxicity study with ladybird 

beetle mentioned above upon submission by the registrant. However, this non-guideline test with 

a different non-pollinator species of insect may not be adequate to satisfy the honeybee larval 

acute or chronic toxicity data requirement as related to current OPP policy requirements for 

pollinator protection. Once the Data Call-In is issued, the registrant may provide additional 

information during the waiver request process to justify the non-conductance of honeybee larval 

toxicity guideline for NAA.

AMVAC Comment:

850.4100 Terrestrial plant toxicity, seedling emergence TGAI, naphthalene acetamide

AMVAC indicated that previous seedling emergence studies have been conducted with the 

potassium and ammonium salts of NAA. For seedling emergence, AMVAC indicated that none 

of the crops were very sensitive to the potassium salt of NAA. Tomato was the most sensitive 

species with EC25s at 0.14, 0.029, and 0.033 lb. a.e./A for plant survival, height, and dry weight,

respectively. These rates are associated with chemical applications of greater than 10% of the 

labeled rate. Studies with ammonium salts, as predicted, produced results that were comparable 

to that of the potassium salts. The only significant difference was noted for carrots. The 

ammonium salt EC25 yielded 0.10 and 0.06 ppm for plant height and dry weight, respectively, 

while the potassium salt was 0.30 and 0.25 ppm, respectively. Still, all of these values represent 

chemical applications of greater than 10% of the labeled rate. 

Because the acetamide serves as a relatively inactive precursor to NAA and the relative lack of 

toxicity associated with the NAA salts on seedling germination and emergence, AMVAC believes 

that the studies herein cited should be sufficient for assessing the terrestrial phytotoxicity for 

NAA and its related products. On this basis, we are seeking a waiver for the requirement to 

conduct a seedling emergence study on NAA acetamide.

EFED Response: Once the Data Call-In is issued, EFED will review and consider the 

registrant’s suggestion that earlier studies with products containing ammonium and potassium 

salts of napthalene are adequate to characterize effects from the napthalene acetamide during an 

official waiver request process. Any additional information to support this claim will also be 

considered at this time.

AMVAC Comment:

850.4150 Terrestrial plant toxicity, vegetative vigor TGAI, naphthalene acetamide

Information concerning the vegetative vigor of NAA acetamide at rates greater than 22 ppm are 

not available; but even this concentration is sufficient to demonstrate that treatment with this 

chemical would not pose a risk to other terrestrial plant species. Also, it is generally accepted that 
13

the biological activity associated with the acetamide only comes about after hydrolysis and 

production of NAA. The European Commission stated within the Draft Assessment report (DAR) 

on the acetamide, “As 1‐NAA has significant biological activity as an auxin mimic (and has 

registered plant protection uses as such), it is therefore assumed that 1‐NAA is the active 

compound and 1‐NAD merely a precursor/variant”. Within the upcoming aerobic soil metabolism 

study that AMVAC has committed to performing, information will be developed that 

substantiates claims made in the literature that the acetamide is labile in the environment. This has 

been shown to be the case for other acetamides such as the acylanilide herbicides, where 

hydrolysis of the amide functionality is also necessary for activity. For example, propanil is 

rapidly converted by an aryl acylamidase to produce the active agent 3,4‐dichloroaniline (Grover 

1990).

The rapid degradation of NAA acetamide in the environment is also evident based on the results 

of an apple foliar study (Obrist 1994). Within the study, NAA had a half‐life of 34.2 hours and 

NAA acetamide had a half‐life of 131.6 hours. Therefore, considering the 14‐day interval 

associated with standard EPA guideline testing for vegetative vigor, most of the acetamide would 

be converted to NAA before the test was completed. Given the fact that the active form of the 

acetamide, NAA in the form of either the potassium or ammonium salt are relatively nontoxic to 

terrestrial plant species, AMVAC believes that the studies herein cited should be sufficient for 

assessing the terrestrial phytotoxicity for NAA and all of its related products.

Depicker, A. G.; Jacobs, A. M.; Van Montagu, M. C. (1988) A negative selection scheme for tobacco 

protoplastderived cells expressing T‐DNA gene 2. Plant Cell reports 7, 63‐66.

Grover, R.; Cessna, A., (1990) Environmental Chemistry of Herbicides, CRC Press.

Harnish, W. (1992) K‐salt Fruit Fix 800 Tier I non‐target plant hazard evaluation‐terrestrial vegetative 

vigor. ID 22925B006, Unpublished report by Landis Int’l, Inc., AMVAC Report 400‐NON‐006.

Harnish, W. (1994a) Fruit Fix Super Concentrate 800 (NAA‐ammonium 21.4%): Tier I non‐target plant 

hazard evaluation‐terrestrial vegetative vigor. ID 22925B006, Unpublished report by Landis Int’l, Inc., 

AMVAC Report 400‐NON‐005, MRID 43141101.

Harnish, W. (1994b) K‐salt Fruit Fix 800 Tier II non‐target plant hazard evaluation‐terrestrial vegetative 

vigor. ID 22925B006, Unpublished report by Landis Int’l, Inc., AMVAC Report 400‐NON‐075, MRID 

43141101.

Harnish, W. (1997) The effect of Amcotone® on tomato under greenhouse conditions. ID 229078001, 

Unpublished report by Landis Int’l, Inc., AMVAC Report 400‐EFF‐006, MRID 4380321.

Obrist, J. J. (1994) NAA bridging study: determination of half‐life of naphthaleneacetic acid, (NAA),

naphthaleneacetamide, and naphthalene acid, ethyl ester on apple leaves. Report 94399, Unpublished 

report by Pan Agricultural Labs, Inc., AMVAC Report 400‐RES‐002, MRID 4380321.

Rappateur Member State France (2008) Draft Assessment report (DAR): – public version ‐ Initial risk 

assessment provided by the rappateur Member State France for the existing active substance 1‐

Naphthalenacetamide (1‐Naphthaleneacetamide) of the fourth stage of the review programme referred to in 

Article 8(2) of Council Directive 91/414/EEC, Vol. 3, Annex B, part 6, B.9, August, 2008.
14

Shah, J.; Tsui, F.; Klessig, D. F. (1997) Characterization of a salicylic acid‐insensitive mutant (sai1) of 

Arabidopsis thaliana, identified in a selective screen utilizing the SA‐inducible expression of the tms2 

gene. Molec. Pl.‐Mic. Inter. 10(1) 69‐78.

Sheldrake, A. R. (1973) The production of hormones in higher plants. Bio. Rev. 48, 509‐559.

Thomashow, L. S.; Reeves, S.; Thomashow, M. F. (1984) Crown gall oncogenesis: Evidence that a T‐

DNA gene from the Agrobacterium Ti plasmid pTiA6 encodes an enzyme that catalyzes synthesis of 

indoleacetic acid. Proc. Natl. Acad. Sci. USA, 81, 5071‐5075.

EFED Response: The AMVAC response discusses results from a number of submitted and 

non-submitted open literature studies (listed above) as justification for waiver of Vegetative Vigor 

testing with the acetamide. Once a Data Call-In is issued, EFED will review and consider the 

registrant’s suggestion that results from earlier studies with products containing ammonium and 

potassium salts of napthalene are adequate to characterize effects from the napthalene acetamide 

during an official waiver request process. Any additional information to support this claim will 

also be considered at this time.

AMVAC Comment:

850.4500 Aquatic Plant Toxicity Testing with Freshwater & Marine Diatom TGAI of naphthalene 

acetic acid and naphthalene acetamide.

850.4550 Aquatic Plant Toxicity Testing with Blue‐green algae TGAI of naphthalene acetic acid 

and naphthalene acetamide

Aquatic plant toxicity studies have been conducted with the green algae species, Selenastrum 

capricornutum. Both the potassium and ammonium salt demonstrated stimulatory and inhibitory 

effects versus control. The NOEC was observed at 6.44 and 6.47 mg/L (Hughes 1992a and b). 

These values are well above the predicted levels in surface water of 22.3 ppb associated with the 

0.33 lb. a.i./A use rate for olives. Although different sensitivity may exist for different unicellular 

aquatic plant species and cyanobacterial species that difference would not likely be extended the 

several orders of magnitude needed to yield an effect in the environment.

Because there is strong evidence that NAA is a growth stimulant with positive effects on algal 

and diatom systems, there is no reason to believe that exposure would be deleterious to these 

organisms. Also, the fact that NAA is only anticipated to occur at very low concentrations in the 

environment, exposure at concentrations that might cause any inhibitory effects is highly unlikely. 

Given the fact that NAA acetamide is a precursor to NAA, studies for this compound would not 

yield information of significant value. On this basis, AMVAC is requesting waivers for NAA and 

NAA acetamide for algal and diatom toxicity studies.

EFED Response: The AMVAC response discusses results from two submitted laboratory 

studies and several non-submitted open literature studies which discuss plant auxins as stimulants 

as justification for waiver of further aquatic plant studies. Currently the Agency has only 

reviewed two studies with end use products on a single species of algae. These end use product 
15

tests are inadequate to address hazard for all NAA actives despite arguments to the contrary as 

expressed in the AMVAC response. 

Despite this lack of data, EFED will consider additional information or submitted studies during 

the formal waiver request process once the Data Call-In is issued in order to support an exemption 

for aquatic plant studies on three species of algae using technical grade active ingredients.