UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF PREVENTION,

PESTICIDES AND 

TOXIC SUBSTANCES

MEMORANDUM

SUBJECT: Section 3 New Crop Use Registration of Hydramethylnon on Pineapples in Hawaii 

for Control of Bigheaded Ants (PC Code Number: 118401, DP Barcode: 

D249596)

TO: Richard Keigwin, Branch Chief

Richard Gebken, PM Team Reviewer

Registration Division (7505C)

FROM: Santhini Ramasamy, Environmental Scientist

Lewis Ross Brown, III, Biologist

Pat Jennings, RAPL

Sid Abel, Branch Chief

Environmental Fate and Effects Division (7507C)
Hydramethylnon

PC Code: 118401
Table of Contents

I. ENVIRONMENTAL RISK CONCLUSIONS................................................................ 3

II. INTRODUCTION....................................................................................................... 4

III. INTEGRATED ENVIRONMENTAL RISK CHARACTERIZATION............................ 6

IV. ENVIRONMENTAL FATE AND TRANSPORT ASSESSMENT............................... 9

V. DRINKING WATER ASSESSMENT. .................................................................... 10

VI. AQUATIC EXPOSURE AND RISK ASSESSMENT............................................... 13

VII. TERRESTRIAL EXPOSURE AND RISK ASSESSMENT..................................... 15

APPENDIX I: Summary of Environmental Fate and Transport Properties .................. 18

APPENDIX II : Drinking Water and Aquatic Exposure Model Outputs ........................ 24

APPENDIX III: Ecotoxicity Studies.............................................................................. 26

APPENDIX IV: Risk Assessment ................................................................................ 32

APPENDIX V: Data Requirements.............................................................................. 34
3

I. ENVIRONMENTAL RISK CONCLUSIONS

Although several studies are lacking, based on the available data EFED concludes the following 

concerning the potential environmental risk from the use of hydramethylnon:

Hydramethylnon is an organic trifluoromethyl aminohydrazone insecticide used in baits to control 

fire ants, leafcutter ants, and cockroaches in both indoor and outdoor applications. Using the 

proposed application rate on the label of 3.0 lbs a.i./A in granular formulation, hydramethylnon 

may pose acute risk to terrestrial organisms. The estimated risk quotients for the proposed 

pineapple uses of hydramethylnon for 20-g body weight small birds exceeded the levels of concern 

for acute, acute restricted use and endangered species risk presumption categories (RQ = 0.85). 

Acute risk quotients were below levels of concern for 180-g and 1000-g birds exposed to 

hydramethylnon. Acute levels of concern were exceeded at the acute risk, endangered species, 

and restricted use risk presumption categories for small to medium, 15-35 g, mammals (15-g 

mammals RQ = 2.54 and 35-g mammals RQ = 1.09). No acute levels of concern were exceeded 

for 1000-g mammals exposed to hydramethylnon. Chronic risk quotients for birds and 

mammals at all of the above body weights were not determined because there is presently no 

standard method for estimating chronic risk to terrestrial organisms for granular-type 

formulations.

In the absence of acute toxicity endpoints for terrestrial and semiaquatic plants, a quantitative 

assessment of acute risks was not possible. Based on proposed maximum label application rates 

and GENEEC 2.0 modeling, acute levels of concern for freshwater fish were exceeded for the 

acute restricted use and endangered species risk presumption categories (RQ = 0.11-0.18). No 

acute levels of concern were exceeded for freshwater invertebrates. Due to an absence of data on 

acute toxicity endpoints, estimating risk to estuarine/marine organisms (fish and invertebrates) 

from exposure to hydramethylnon was not possible. Based on the potential location and pattern 

of hydramethylnon use on pineapples these data are required and are listed as data gaps.

Based on hydramethylnon’s relative persistence and immobility in the environment, the major 

route of dissipation appears to be photodegradation, with a half-life of about 1 hr in aqueous 

systems and 21 to 25 days in soil. Because hydramethylnon is very strongly sorbed by soil 

particles (i.e., Kd = 1039-1725), it is practically immobile in most soils. At the soil surface, there 

is the potential for photodegradation of hydramethylnon. Due to limited sunlight below soil 

surfaces, the bound residues of hydramethylnon would not be susceptible to photodegradation. 

Based on laboratory aerobic and anaerobic soil metabolism studies, hydramethylnon is very 

persistent, with a half-life of more than a year for each process. Contamination of surface water is 

possible by movement of soil particles bound to hydramethylnon after rainfall events. 

Contamination of surface water from drift is negligible since the proposed use product for 

pineapples is granular. Based on strong binding to soil and low leaching potential (i.e., no 

residues recovered below 0-6 inches below the soil surface), it is unlikely that hydramethylnon 

would contaminate groundwater. It appears that hydramethylnon has a strong tendency to 

bioaccumulate and depuration is very slow. 

Based on a search of the National Water-Quality Assessment (NAWQA) Program, no monitoring 
4

data were found for hydramethylnon. Based on Tier -1 modeling (i.e., FIRST), the acute 

concentrations are not likely to exceed a peak concentration of 76.09 ppb which is recommended 

for estimating acute risks from exposure of humans to hydramethylnon in drinking water from 

surface water sources. The predicted annual daily average concentration is not likely to exceed

1.45 ppb which is recommended for estimating chronic risks from exposure of humans to 

hydramethylnon in drinking water from surface water sources. Hydramethylnon does not appear 

to substantially leach into soils, based on its high affinity to bind to soil (i.e., Kd = 1039-1725). 

Based on SCI-GROW modeling, the estimated concentrations in ground water for the 

proposed pineapple uses are not likely to exceed 0.035 ppb. This concentration is 

appropriate for estimating the potential for acute and chronic risks from exposure of 

humans to hydramethylnon in drinking water from ground water sources.

II. INTRODUCTION

Hydramethylnon is an organic trifluoromethyl aminohydrazone insecticide belonging to a 

chemical class of compounds known specifically as trifluoromethyl aminohydrazone 

compounds. Its mode of action is that of an electron transport inhibitor.

Physical and Chemical Properties

Common Name: Hydramethylnon

Chemical Name:

Tetrahydro-5,5-dimethyl-2(1H)-pyrimidinone[3-[4-(trifluoromethyl)phenyl]-1-[2-[4-t

rifluoromethyl)phenyl]ethenyl]-2-propenylidene]hydrazone

Chemical Family: amidinohydrazone

Empirical Formula: C25H24F6N4

Trade and Other Names: Amdro, Combat, Maxforce, Sensible, Siege

Molecular Weight: 494.50

CAS Registry No.: 67485-29-4

P.C. Code: 118401

Physical Appearance: Yellow to tan crystalline solid

Solubility in Water1: 0.88 ppm

Melting Point: 189-191 °C

Vapor Pressure1: 6 x 10 -8 mm of Hg at 25 °C

Henry’s Law Constant: 2.6x10 -7 atm.m3/mol (Calculated)

Octanol/Water Partition Coefficient (Kow)1: 27,965 at 25 °C (Log Kow = 4.45 ) -------------------------------------

1

MRID 41612502
5

Structure:

Approach to Risk Assessment

Hydramethylnon is proposed to be used on pineapples at a maximum rate per application of 

3.0 lbs a.i./A. The proposed maximum annual application rate is 6.0 lbs a.i./A. The 

proposed frequency of application is not listed on the label. Based on the proposed 

maximum annual rate and maximum rate per event, 2 applications per year were assumed. 

As proposed in the label, the application interval of 4 months is used in the exposure 

modeling. However, it is not clear whether it refers to minimum or maximum interval 

between applications. 

Toxicity testing reported in this document does not represent all species of bird, mammal, or 

aquatic organisms. Only two surrogate species for both freshwater fish and birds are used to 

represent all freshwater fish (2000+) and bird (680+) species in the United States. For mammals, 

acute toxicity studies are usually limited to laboratory rats and mice. Neither reptiles nor 

amphibians are tested. In assessing risk and/or hazard, it is assumed that avian and reptilian

toxicities are similar. Also, hazard and risk are assumed to be similar for fish and amphibians. 

Generally, the most toxic endpoints for the technical grade active ingredient (TGAI) are used in 

the assessment to represent each group of aquatic and terrestrial organisms.

The EECs used for determining terrestrial risk quotients were derived using granular EEC 

calculations. The following formula was used to predict the granular EEC for birds and 

mammals at three different body weights (i.e., birds: 20 g, 180 g, 1000 g; mammals: 15 g, 35 

g, and 1000 g):

EEC lbs/ft2 = application rate (lbs a.i./A)* (453,590 mg/lbs/43,560 ft2

/A)

RQ = application rate (lbs a.i./A)*(453,590 mg/lbs/43,560 ft2

/A)

 LD50 mg/kg *BW (g)/(1000 g/Kg)
6

The EECs used for modeling acute and chronic aquatic exposures were determined through 

GENEEC 2.0 modeling. GENEEC 2.0 uses basic environmental fate data and pesticide 

label application information to estimate the EECs in a one-hectare, two-meter deep pond

adjacent to10 hectares of treated field.

III. INTEGRATED ENVIRONMENTAL RISK CHARACTERIZATION

Hydramethylnon is an insecticide and belongs to a class of chemical compounds known as 

trifluoromethyl aminohydrazone compounds. Hydramethylnon may pose acute risks to 

terrestrial organisms should the compound enter into terrestrial habitats. Intake of 

hydramethylnon residues from food items is the only route of exposure considered in this risk 

assessment. Risk quotients for 20-g birds and 15- to 35-g mammals exceed acute risk, restricted 

use, and endangered species risk presumption categories (see Appendix IV for details).

A search in the endangered species database (Danger 97) identified the following perching birds in 

two counties in Hawaii, with body weight around 20g , for which RQs exceeded levels of concern: 

Hawaii `akepa, `Akia pola`au, Palila, `O`u (Honey Creeper), `Akia loa, Nuku pu`u (Kauai), Kauai 

`O`o, small Kauai thrush, large Kauai thrush (Table 1). Based on consultation with Larry Turner 

of the Field and External Affairs Division (FEAD) of the Office of Pesticide Programs (OPP) of 

EPA, these song birds are not at risk from hydramethylnon uses on pineapples because many of 

these small birds inhabit elevated forests instead of lower tropical forests where pineapples are 

usually grown. Even the ground-dwelling birds (e.g., small Kauai thrush) live only in the dense, 

wet forests of Alkai swamp at 4000 feet on Kauai. Also, many of these species are extremely 

rare. For example, Akia loa was last seen in 1965 and is thought to be extinct (World Wildlife 

Fund Guide to Endangered Species, 1990). Therefore, the potential endangered risk posed by 

hydramethylnon uses on pineapples to small birds is minimal. Table 1 lists other endangered 

birds identified in two counties in Hawaii using the Danger 97 database. Since the other 

endangered birds are either duck-like birds (i.e., Hawaiian goose, Hawaiian duck) or sea birds (i.e., 

Hawaiian dark-rumped petrel and Hawaiian stilt) and are well above 20-g body weight and RQs 

did not exceed levels of concern for acute endangered species for larger birds, these birds are not 

expected to be impacted by hydramethylnon uses.

Among the mammals up to 30-g body weight, the Hawaiian Hoary bat was the only endangered 

species identified in Hawaii and Kauai counties. Based on consultation with Larry Turner, the 

bats are not believed to be at risk from hydramethylnon uses on pineapples as the bats mainly eat 

flying insects which are not expected to be exposed as a result of application of hydramethylnon. 

Although the listed endangered birds and mammals are not at risk for hydramethylnon uses on 

pineapples in Hawaii, the estimation of risk to endangered species would be revisited for other 

uses proposed in the future. 
7

Table 1: List of Endangered Avian Species Identified in Hawaii for Pineapple Uses 

Species Scientific Name County(ies)

Hawaii `Akepa Loxops coccineus coccineus Hawaii

Akia Pola`au Hemignathus munroi Hawaii

Hawaiian Coot (Alae keo keo) Fulica americana alai Hawaii, Kauai

Hawaii Creeper Oreomystis mana Hawaii

Hawaiian Crow (`Alala) Corvus hawaiiensis Hawaii

Hawaiian Duck (Koloa) Anas wyvilliana Hawaii, Kauai

Hawaiian Goose Nesochen sandvicensis Hawaii, Kauai

Hawaiian Hawk (Io) Buteo solitarius Hawaii

`O`u (Honey Creeper) Psittirostra psittacea Hawaii, Kauai

Palila Loxioides (=Psittirostra) bailleui Hawaii

Hawaiian Dark-rumped petrel Pterodroma phaeopygia sandwichensis Hawaii, Kauai

Newell’s Townsend’s Shearwater Puffinus auricularis newelii Hawaii, Kauai

Hawaiian Stilt Himantopus himantopus knudseni Hawaii, Kauai

`Akia Loa Hemignathus proceruhemignathus 

procerus

Kauai

Hawaiian Common Moorhen Gallinula chloropus sandvicensis Kauai

Nuku pu`u (Kauai) Hemignathus lucidus Kauai

Kauai `O`o Moho braccatus Kauai

Large Kauai Thrush Myadestes myadestinus Kauai

Small Kauai Thrush Myadestes palmeri Kauai

Although the results of this risk assessment indicate that hydramethylnon is not expected to pose 

acute risks to freshwater fish and invertebrates, levels of concern for freshwater fish for acute 

restricted use and acute endangered species risk presumption categories are exceeded (i.e., RQ = 

0.11-0.18). A search of the endangered species database, Danger 97, did not identify any 

endangered freshwater fish in ponds near the expected use area, so exposure and acute risk to 

endangered freshwater fish is not expected. Since no chronic ecotoxicity studies for 

freshwater organisms were submitted, chronic toxicity endpoints have not been determined. 

Therefore, potential chronic risks to freshwater organisms (i.e., fish and invertebrates) from 

proposed hydramethylnon uses are unknown. Since no acute or chronic ecotoxicity studies 

were submitted for estuarine/marine organisms (i.e., fish and invertebrates), acute and 

chronic toxicity endpoints for estuarine/marine organisms have not been determined. 

Therefore, potential acute and chronic risks to these organisms from proposed 
8

hydramethylnon uses are unknown.

Based on strong soil binding affinity of hydramethylnon and relatively fast photolytic degradation, 

it appears unlikely that surface water concentrations will be contaminated significantly from the 

proposed uses of hydramethylnon. However, under limited sunlight conditions, the high annual 

application rate of 6.0 lbs a.i./A may contaminate surface water with residues of hydramethylnon. 

It is expected that hydramethylnon reaches the surface water bound to soil particles due to strong 

soil binding properties. From the lab soil metabolism studies, hydramethylnon is considered to be 

persistent (half-life more than a year) in the environment. However, under field conditions, 

hydramethylnon appeared to dissipate at a faster rate with a half-life of 3 to 55 days. There is a 

difference of 1 to 2 orders of magnitude in half-lives between the laboratory soil metabolism study 

and the terrestrial field dissipation study. The laboratory half-life which is longer than the field 

half-life was used to estimate drinking and aquatic exposures. Environmental and drinking water 

concentrations would be lower if the actual half-life of hydramethylnon is closer to that 

determined from the terrestrial field dissipation study. 

It should be noted that the predicted EECs from Tier I models-(FIRST, GENEEC and SCIGROW) 

are not refined as they are mainly influenced by annual application rate and application method 

and do not account for location-specific hydrogeologic and climatic characteristics. 

Concentrations in the environment may be lower or higher than the Tier I predicted EECs 

depending upon the use scenarios and weather conditions. 

SCI-GROW was developed using Koc values ranging from 32-180 L/Kg. Given the high Koc for 

hydramethylnon (median Koc 205,570), there is uncertainty in the estimated ground water levels 

due to extrapolation beyond the range of Koc values used to develop the standard regression. It is 

possible that the volcanic Hawaii regions where the pineapples are grown are susceptible 

to ground water contamination due to the porous nature of the soil. Therefore, the 

ground water concentrations are still modeled using SCI-GROW. If concerns are raised 

by exposures of less than 0.0345 ppb, a prospective ground-water study would be 

recommended.

Environmental fate data are sufficient for predicting the parent concentrations in drinking water. 

However, the fate studies are insufficient to identify and characterize degradates. Since 

hydramethylnon is relatively stable in soil metabolism studies, it is expected that photolytic 

degradation is the major route of dissipation under field conditions (21 to 25 days in the field 

versus more than 1 year in the laboratory). Although there is fast dissipation in the field studies, 

there is insufficient information on the potential photolytic degradates in the fate studies. 

Specifically, the two field studies for hydramethylnon do not include any information on the two

major photo transformation products, 4H-pyrimido 

[2-1,c]as-triazio-4-one-1,6,7,8-tetrahydro-7,7-dimethyl-3-[p-(trifluoromethyl)-styryl] and 1,5-bis 

(alpha, alpha, alpha-tri-fluoro-p-tolyl)-1,4-pentadien-3-one. Further, the lab aquatic photolysis 

study did not identify and characterize the two unknown major metabolites (Unknown 3 and 4). 

Finally, there are limited data on the mobility of hydramethylnon degradation products at this time. 
9

Based on the available data, EFED is unable to ascertain the potential contamination of surface and 

ground water sources with hydramethylnon degradates. If degradates were determined to be of 

toxicological concern, it is recommended that additional information needs to be submitted for any 

future uses of hydramethylnon. 

IV. ENVIRONMENTAL FATE AND TRANSPORT ASSESSMENT

Summary

Hydramethylnon is relatively persistent and non-mobile in the environment. The major route of 

dissipation for hydramethylnon appears to be photodegradation. Although the laboratory soil 

metabolism studies indicate that the compound is stable in the aerobic and anaerobic conditions, 

hydramethylnon degraded relatively fast in the field studies conducted in Florida and Texas. The 

rapid degradation in the field could not be adequately explained due to photodegradation alone, 

unless there is an offsite movement of pesticides. It is possible the granular product is moved 

from the field by ants or other species that mistake granules for food sources. Additional 

information is needed from the registrant to explain the discrepancy between the laboratory and 

field studies with regard to persistence of the chemical. Due to the high soil binding affinity (Kd 

= 1039-1725), the chemical is likely to partition into the soil and sediments. Hydramethylnon has 

a tendency to bioaccumulate and the depuration is slow. 

Environmental Fate Assessment

Hydramethylnon is moderately persistent and is classified as immobile according to McCall’s 

classification scheme (1980). Based on laboratory studies, hydramethylnon is stable to 

hydrolysis with a half-life greater than 30 days and stable to soil metabolism under aerobic and 

anaerobic conditions, with a half-life longer than one year for each. On soil surfaces under ample 

sunlight conditions, hydramethylnon could be photolysed rapidly and could be less persistent. 

The laboratory aqueous photolysis half-life is less than one hour and soil photolysis half-life 

ranges from 21to 25 days under continuous irradiation conditions. The aqueous photolysis study 

identified certain major degradates: a photodegradate, 4H-pyrimido 

[2-1,c]as-triazio-4-one-1,6,7,8-tetrahydro-7,7-dimethyl-3-[p-(trifluoromethyl)-styryl], 

representing 25.2 to 30.5% of the radioactivity and a second degradate, 1,5-bis(alpha, alpha, 

alpha-trifluoro-p-tolyl)-1,4-pentadien-3-one, representing 28.0% of the radioactivity. In addition, 

two other major degradates were noted but were not identified or characterized (i.e., Unknown 3 

and Unknown 4). Degradates were also observed in the soil photolysis study (hydramethylnon 

epoxide and ketone compounds) but these degradates were not considered major degradates. 

Hydramethylnon adsorbs strongly to most of the soils from loamy sand to silty loam (Kd = 

1039-1725). The calculated Koc values were: 358276 (loamy sand), 287759 (sandy loam), 

123381 (loam), and 95389 (silt loam). These high Koc values indicate hydramethylnon is very 

immobile in most soils in the environment. Under field conditions, in Texas and Florida, 

hydramethylnon appears less persistent with reported half-lives of 3 to 55 days. No degradate 

information was reported in the field studies. Hydramethylnon showed some tendency to 

accumulate in fish tissues with reported bioconcentration factors of 1300X in whole fish, 780X in 
10

fillet, and 1900X in viscera. Depuration was slow with 48 to 63% of residues decreased after a 

14-day clearance period.

The detailed fate summary and the structures of hydramethylnon and degradates can be found in 

Appendix I. 

V. DRINKING WATER ASSESSMENT

The laboratory studies submitted are fairly complete for modeling the parent compound for the 

drinking water assessment. Based on a search of the National Water-Quality Assessment 

(NAWQA) Program database, no monitoring data were found for hydramethylnon. No 

Maximum Contamination Limit (MCL) or Health Advisory (HA) has been established for 

hydramethylnon residues in drinking water. Based on the available information in the 

fate studies and on the toxicity of potential degradates, MARC (Metabolism Assessment 

Review Committee) recommended to examine parent, but not degradates for assessing 

drinking water exposures.

Surface Water

Contamination of surface water is possible by runoff of hydramethylnon bound to soil 

particles after rain events. Contamination from drift is negligible since the formulation for 

the proposed pineapple uses is granular. The Tier I model, FIRST (FQPA Index Reservoir 

Screening Tool, version 1.0, Aug 1, 2001) was used to estimate drinking water 

concentrations of hydramethylnon in surface water from a drinking water reservoir 

adjacent to a field to which pesticide has been applied. This model assumes the 

transport of pesticides from a 172.8-hectare field adjacent to a 5.3-hectare, 2.74-meter 

deep drinking water reservoir. In addition to fate and mobility characteristics of the 

pesticide, this model assumes reductions in the water concentrations of hydramethylnon 

due to the percentage of the watershed which is cropped (i.e., PCA, percent cropped 

area). There is no assigned PCA for pineapple uses, and therefore, the default value of 

0.87 is used. This model predicts the peak and annual daily average concentrations of 

the pesticide in drinking water from surface water sources. The peak concentration is 

used to estimate acute risks from exposure of humans to hydramethylnon in drinking 

water from surface water sources. The annual daily average concentration is used to 

estimate chronic risks from exposure of humans to hydramethylnon in drinking water from 

surface water sources. 

The input parameters for FIRST modeling are provided in the Table 2.

Table 2. FIRST Input Parameters

Model Input Parameter Input Value Source

Chemical Name Hydramethylnon AMDRO label (EPA Reg 

No: 241- 322)

AMDRO label (EPA Reg 
11

Table 2. FIRST Input Parameters

Crop Name Pineapples No: 241- 322)

Application Rate 3.0 lbs a.i./A AMDRO label (EPA Reg 

No: 241- 322)

Maximum. Number of 

Applications per Season

2* AMDRO label (EPA Reg 

No: 241- 322)

Interval Between 

Applications

120 days AMDRO label (EPA Reg 

No: 241- 322)

Percent Crop Area (PCA) 0.87 (default value) FIRST Users Manual 

(August 1, 2001)

Kd 1669 (Lowest non-sand value) MRID No. 41888302

Aerobic Soil Metabolism t1/2 = 407.6 days

(90 th upper percentile of the mean for the 

following half-lives: 375, 391 days)

MRID No. 42320801

Pesticide Wetted-in No AMDRO label (EPA Reg 

No: 241- 322)

Method of Application/Type 

of Droplet Size

Aerial, coarse granules AMDRO label (EPA Reg 

No: 241- 322)

Incorporation Depth 0.0 in AMDRO label (EPA Reg 

No: 241- 322)

Water Solubility 0.88 ppm Product Chemistry (MRID 

No. 41612502 )

Aerobic Aquatic Metabolism t1/2 = 815.2 days

(2 x 407.6 days)

Twice the aerobic soil 

metabolism input value

Hydrolysis t1/2 = stable MRID No. 42194701

Aqueous Photolysis t1/2 = 0.04 day MRID Nos. 42238201 and 

42473301

*

The proposed frequency of application is not explicit on the label. Derived based on the proposed maximum annual rate of 6.0 lbs a.i./A 

and maximum rate per event of 3.0 lbs a.i./A.

Based on Tier -1 modeling (i.e., FIRST), the acute concentrations are not likely to exceed 

a peak concentration of 76.09 ppb which is recommended for estimating acute risks from 

exposure of humans to hydramethylnon in drinking water from surface water sources. 

The predicted annual daily average concentration is not likely to exceed 1.45 ppb which 

is recommended for estimating chronic risks from exposure of humans to hydramethylnon 

in drinking water from surface water sources. The output from FIRST modeling is 

presented in the Appendix II. Currently, EFED does not have a scenario for pineapple 
12

uses to proceed with Tier 2 modeling. Should there be any drinking water concerns 

with Tier I modeling values, monitoring studies must be considered. 

Ground Water

Ground water contamination is expected to be low due to high binding affinity of 

hydramethylnon to the soil. For any potential ground water contamination from the 

proposed use of hydramethylnon on pineapples, SCI-GROW (version 2.2, Nov 1, 2001) 

modeling was performed. The model estimates the upper bound ground water 

concentrations of pesticides likely to occur when the pesticide is used at the maximum 

allowable rate in areas where ground water table is shallow particularly vulnerable to 

contamination. The SCI-GROW model is based on the fate properties of the pesticide, 

the application rate, and the number of applications. The input parameters are provided 

in Table 3. The estimated concentration in ground water for the proposed 

pineapple uses is 0.035 ppb. This value is appropriate for estimating acute and chronic 

risks for the human health dietary risk assessment. The actual output from SCI-GROW 

is presented in Appendix II.

Table 3. SCI-GROW Input Parameters 

MODEL INPUT VARIABLE INPUT VALUE SOURCE

Chemical Name Hydramethylnon AMDRO label (EPA Reg No: 241-

322)

Aerobic Soil Metabolism t1/2 = 383 (Median Value for the 

following half-lives: 375, 391 days)

MRID No. 42320801

Koc 205570 (Median for the following Koc 

values : 358276, 287759, 123381, 

95389)

MRID No. 41888302

Application Rate 3.0 lbs a.i./A AMDRO label 

Max. Number of 

Applications/Year

2 AMDRO label

SCI-GROW was developed using Koc values ranging from 32-180 L/Kg. Since Koc 

values for hydramethylnon (Koc 205570) are outside the range of values for which 

SCI-GROW was developed, there is uncertainty in the estimation of ground water 

concentrations. It is possible that the volcanic Hawaii regions where the pineapples are 

grown are susceptible to ground water contamination due to the porous nature of the soil. 

Therefore, the ground water concentrations are still modeled using SCI-GROW. If 

concerns are raised by exposures of less than 0.0345 ppb, a prospective ground-water 

study would be recommended.
13

VI. AQUATIC EXPOSURE AND RISK ASSESSMENT

Based on ecological effects data, the aquatic toxicity endpoints used in the current assessment can 

be characterized as follows:

 Very highly to moderately toxic in freshwater fish (rainbow trout, LC50= 150 ppb; channel 

catfish, LC50= 90 ppb; bluegill sunfish, LC50=1700 ppb)

 Moderately toxic to freshwater invertebrates (water flea LC50=1140 ppb).

 Data supporting the chronic reproductive effects of hydramethylnon to freshwater fish 

using the fathead minnow as the test species were not available for use in this risk 

assessment. Therefore, the chronic reproductive effects hydramethylnon may pose to 

freshwater fish are not known at this time.

 Data supporting the chronic reproductive effects to freshwater invertebrates using the 

Daphnia magna, water-flea, as the test species were not available for use in this 

assessment. Therefore, the chronic reproductive effects hydramethylnon may pose to 

freshwater invertebrates are not known at this time.

 Data supporting the acute ecotoxicity effects hydramethylnon may pose to 

estuarine/marine fish and invertebrates were not available for use in this assessment. 

Therefore, the acute ecotoxicological effects hydramethylnon may pose to 

estuarine/marine fishes and invertebrates are unknown at this time.

 Data supporting the chronic ecotoxicity effects hydramethylnon may pose to 

estuarine/marine fishes and invertebrates were not available for use in this assessment. 

Thus, the chronic ecotoxicological effects hydramethylnon may pose to estuarine/marine 

fishes and invertebrates can not be determined at this time.

Details of the aquatic toxicological studies are presented in Appendix III. The Agency’s LOCs 

for aquatic organisms are presented in Appendix 1V. 

Aquatic Exposure

The EECs needed for determining the acute and chronic risk quotients for aquatic organisms are 

modeled using GENEEC 2.0 (version 2.0, Aug 1, 2001). GENEEC 2.0 uses basic environmental 

fate data and application information from the pesticide label to estimate EECs in a one-hectare, 

two-meter deep pond adjacent to10 hectares of treated field. The environmental fate parameters 

used in the model are the same as those used for FIRST modeling. Unlike FIRST, the percent 

cropped area is not accounted for in the GENEEC 2.0 model. For details on input parameters for 

the GENEEC 2.0 model, refer to the input parameters in Table 2.
14

The proposed label for pineapple uses recommends a maximum rate per application of 3.0 lbs ai/A 

with no more than 6.0 lbs a.i./A per year, indicating two applications for the whole year. Since 

the application interval was not indicated on the label, a 30-day minimum preharvest interval 

specified on the label was assumed to be the interval between applications. The estimated surface 

water concentrations to which aquatic life are exposed are presented in Table 4. The peak 

exposure concentrations are used for estimating the acute risk for fish, aquatic invertebrates and 

aquatic plants. 

Table 4-GENEEC 2.0 Modeling 

Peak

(ppb)

21-day Average

(ppb)

60-day Average

(ppb)

90-day Average

(ppb)

15.9 2.85 1.00 0.67

Freshwater Fish 

Acute risk quotients for freshwater fish are presented in Table 5. Using the proposed 

application rate of 3.0 lbs a.i./A applied in granular formulation, levels of concern were 

exceeded for the endangered freshwater fish when the end points for rainbow trout (RQ = 

0.11) and channel catfish were used (RQ = 0.18). The results indicate that the acute 

risk posed to freshwater non-endangered fish from granular use of hydramethylnon on 

pineapples in Hawaii is expected to be minimal. 

Table 5--Freshwater Fish Acute Risk Quotients Using Hydramethylnon

Species Toxicity Value

(ppb)

Peak EEC

(ppb)

60-Day Average 

EEC

(ppb)

Acute

Risk Quotient

Chronic

Risk Quotient

Rainbow trout

(Oncorhynchus 

mykiss) 150 15.9 1.0 0.11 N/A

Bluegill sunfish

(Lepomis 

macrochirus) 1700 15.9 1.0 <<0.01 N/A

Channel catfish

(Ictalurus 

punctatus) 90 15.9 1.0 0.18 N/A

Chronic levels of concern were not quantified for freshwater fish due to a lack of available 

data for the Early-Life Stage using the fathead minnow. Without an endpoint value the 

chronic risk hydramethylnon may pose to freshwater fish cannot be determined.
15

Freshwater Invertebrates

Acute risk quotients for freshwater invertebrates are presented in Table 6. Based on 

proposed maximum application rates on the label, levels of concern were not exceeded 

for freshwater invertebrates exposed to the granular formulation of hydramethylnon.

Table 6-Freshwater Invertebrate Acute Risk Quotients Using Hydramethylnon

Species Toxicity Value

(ppb)

Peak EEC

(ppb)

21-Day Average 

EEC

(ppb)

Acute

Risk Quotient

Chronic

Risk Quotient

Daphnia magna

(waterflea) 1140 15.9 2.82 0.01 N/A

Estuarine/Marine Organisms

Acute and chronic risks to estuarine/marine fish and invertebrates cannot be quantified at 

this time due to a lack of appropriate ecotoxicological endpoints. 

Exposure and Risk to Plants

Acute risks to terrestrial and semi-aquatic plants cannot be quantified at this time due to a 

lack of appropriate ecotoxicity endpoints.

Aquatic Ecological Incident Data

No aquatic ecological incidents for hydramethylnon were identified in EFED’s Ecological 

Incident database.

VII. TERRESTRIAL EXPOSURE AND RISK ASSESSMENT

Based on ecological effects data, the toxicity endpoints used in the current terrestrial assessment 

can be characterized as follows:

 Slightly toxic to practically non-toxic on an oral acute toxicity basis (Northern 

Bobwhite Quail, LD50=1828 mg/kg; Mallard Duck, LD50=2510 mg/kg)

 Slightly toxic on a subacute oral basis (Northern Bobwhite Quail, LC50=1136 ppm; 

Mallard Duck, LC50=4355 ppm)

 Chronic reproductive effects observed in mallard duck (NOAEC=28.5 ppm, based 

on weight of 14-day old survivors)

 Slightly toxic to small mammals on an acute basis (LD50= 817 for males and 

LD50=1502 for females)
16

 Chronic reproductive effects in smalls mammals (Norway rat NOAEL=50 ppm , 

male infertility was noted at 100 ppm).

 Practically non-toxic to non-targeted terrestrial insects (Honeybee LD50 =68 

μg/bee).

Details of the avian and mammalian toxicological studies are presented in Appendix III. The 

Agency’s LOCs for risk presumption categories for terrestrial organisms are presented in 

Appendix 1V. 

Avian Acute and Chronic Risk

Avian acute risk quotients for hydramethylnon granular broadcast applications were determined 

using the following formula:

RQ = Application rate(lbs/acre) *(453590 mg/lbs/43560 ft2

/acre)

 LD50 mg/kg BW/day*Weight of bird (g)/1000 g/Kg

Acute risk quotients for 20, 180, and 1000 g birds are shown in Table 7.

Table 7-Acute Risk Quotients For Avian Organisms Following Broadcast Granular Applications Of 

Hydramethylnon

Body Weight

(kg)

LD50

(mg/kg)1 mg ai/ft2 Acute RQ2(LD50/ft2

)

Risk Presumption

Categories 

Exceeded

0.020 36.6 31.24 0.85 Acute, Restricted Use, 

and Endangered 

Species 

0.180 329.04 31.24 0.09 None

1.0 1828 31.24 0.01 None

1. LD

50

per animal = LD

50

mg/kg BW/day*Weight of animal (g)/1000 g/Kg

2. RQ= Application rate(lbs/acre) *(453590 mg/lbs/43560 ft2/acre)

 LD

50

mg/kg BW/day*Weight of animal (g)/1000 g/Kg

Based on estimated risk quotient of 0.85, acute levels of concern were exceeded for 

acute risk, restricted use, and endangered species risk presumption categories for 20-g 

birds exposed to granular broadcast applications of hydramethylnon on pineapples. 

Acute risk levels of concern were not exceeded for 180-1000 g birds exposed to granular 

broadcast applications.

At present, EFED has no method to estimate chronic risk to birds exposed to granular 

formulations.
17

Mammalian Acute and Chronic Risk

For small mammals, acute risk quotients were calculated using the following formula:

RQ = Application rate(lbs/acre) *(453590 mg/lbs/43560 ft2/acre)

 LD50 mg/kg BW/day*Weight of animal (g)/1000 g/Kg

Acute risk quotients for smalls mammals are tabulated in Table 8.

Table 8-Acute Risk Quotients For Mammals Exposed to Broadcast Granular Applications of Hydramethylnon

Body Weight

(kg)

LD50

(mg/mammal)1

mg ai/ft2 Acute RQ2

(LD50/ft2

Risk Presumption

Categories Exceeded

Small mammal

0.015

12.3 31.24 2.54 Acute, Restricted Use, 

and Endangered 

Species 

Medium mammal

0.035

28.6 31.24 1.09 Acute, Restricted Use, 

and Endangered 

Species 

Large mammal

1.0

817 31.24 0.04 None

1. LD

50

per animal = LD

50

mg/kg BW/day*Weight of animal (g)/1000 g/Kg

2. RQ= Application rate(lbs/acre) *(453590 mg/lbs/43560 ft2/acre)

 LD

50

mg/kg BW/day*Weight of animal (g)/1000 g/Kg

Levels of concern were exceeded for 15 to 35 g mammals exposed to broadcast granular 

applications of hydramethylnon at the maximum application rate proposed on the label 

for acute risk, acute restricted use, and acute endangered species risk presumption 

categories. The risk quotient for 15-g mammals was determined to be 2.54 while that for 

35-g mammals was determined to be 1.09. No acute levels of concern were exceeded 

for 1000-g mammals.

At present, EFED has no method to estimate chronic risks to mammals exposed to 

granular formulations.

Terrestrial Insects

EFED has no method for quantifying risks to non-target terrestrial insects. Since 

hydramethylnon is categorized as practically non-toxic to non-target terrestrial insects, 

risk is expected to be low.

Terrestrial Ecological Incident Data

Currently, there are no terrestrial ecological incidents in the EFED database for 

hydramethylnon.
18

Appendix I

Summary of Environmental Fate and Transport Properties

(1) Degradation

Hydrolysis (MRID 42194701, §161-1)

Hydramethylnon is stable to hydrolysis at pH 5, pH 7, and pH 9. The half-lives are 

reported as >30 days at all pH values. In addition, the stability of hydramethylnon does 

not appear to be affected by type or concentration of buffer at pH 7. This study is 

classified as Acceptable.

Photodegradation in Water (MRIDs 42238201 and 42473301, §161-2)

The photodegradation in water data indicate that hydramethylnon rapidly photodegrades 

in pH 7 buffer solutions (half-life of 1 hour). Hydramethylnon was stable in the dark control 

treatment. A major photodegradate, 4H-pyrimido 

[2-1,c]as-triazio-4-one-1,6,7,8-tetrahydro-7,7-dimethyl-3-[p-(trifluoromethyl)-styryl], 

represented 25.2% and 30.5% of the recovered 14C-phenyl and 14C-pyrimidine 

radioactivity, respectively. A second major degradate, 1,5-bis(alpha, alpha, 

alpha-trifluoro-p-tolyl)-1,4-pentadien-3-one, represented 28.0% of recovered phenyl 

labeled material. In addition, five unidentified compounds (Unknowns 1, 2, 3, 4, and 5) 

were discernible in test samples. Unknowns 1, 3, and 4 were detected in the pyrimidine 

radiolabeled samples and reached concentrations of 9.5, 29.6, and 7.7% of recovered 

radioactivity, respectively. Unknowns 2 and 4 were detected in the phenyl radiolabeled 

samples and reached concentrations of 7.6 and 15.6% of recovered radioactivity, 

respectively. Unknown 2 did not appear in the HPLC analyses of the confirmatory 

samples, but was observed in the rates of formation and decline analyses. Attempts to 

identify these unknowns by LC/MS are inconclusive.

The status of the photodegradation in water data is Supplemental because the major 

degradates, Unknowns 3 and 4, present at concentrations of 29.6% and 15.6% of 

recovered radioactivity, respectively, were not identified and characterized. 

Photodegradation on Soil (MRID 42113401, §161-3)

Photodegradation of hydramethylnon was studied using loam soil. First order linear 

degradation of the data collected under continuous irradiation provided the half-life of 25 

and 21 days for phenyl and pyrimidyl labels of the parent compound. Under natural 

sunlight conditions, the respective half-lives corresponded to 43 and 37 days. Two 

unidentified peaks (Unknown A and B possibly representing hydramethylnon epoxide and 

ketone compounds), both of which comprised 10% of the applied radioactivity, were 

determined to be a mixture of compounds. The soil photolytic degradation is longer than 

the aqueous photolysis. The difference may be due to the rapid adsorption of 
19

hydramethylnon to the soil and the reduced availability of 
20

hydramethylnon to photolytic degradation. Hydramethylnon was stable in the dark 

control treatment. This study is classified as Acceptable. 

Aerobic Soil Metabolism (MRID 42320801, §162-1)

One guideline aerobic soil metabolism study was submitted to the Agency. 

Hydramethylnon appears to degrade relatively slowly under aerobic conditions when 

applied to sandy loam soil at the application rate (~0.095 ppm). After 1 year of aerobic 

incubation, first-order half-lives of 375 and 391 days were reported for the 14C-phenyl and 

14C-pyrimidine labeled hydramethylnon, respectively. One unidentified degradate, which 

HPLC analysis indicated to contain both labels and be more polar than the parent 

compound, was detected at concentrations of 15.6 and 16.8% of applied radioactivity in 

the 14C-phenyl and 14C-pyrimidine labeled samples, respectively. The study author 

believes that formation of this degradate was partially due to the soil extraction and 

analytical methodology of the extracts and that it is unstable. Further attempts to identify 

this degradate by LS/MS were unsuccessful. In addition, up to 18 minor degradates, all at 

concentrations <0.004 ppm, were discernible in the soil extracts. Additional information 

on the identities of the 18 minor degradates is not needed at present because of the low 

rate of occurrence of these compounds in the study. This study is classified as 

Acceptable. 

Anaerobic Aquatic Metabolism (MRID 43102701, §162-3)

Hydramethylnon appears to be relatively persistent under anaerobic conditions. First 

order linear degradation half-lives of 552 and 455 days were calculated for the phenyl and 

pyrimidine labeled hydramethylnon samples, respectively. The concentration of 

14

C-phenyl and 14C-pyrimidine hydramethylnon decreased from 90.7% and 82.6% to 

50.4% and 57.4%, respectively, of applied radioactivity by termination of testing period (1 

year). Two additional peaks besides parent hydramethylnon were discernible in test 

samples. Peak A was discernible at maximum concentrations of 15 to 8.8% at 9 and 12 

months post-treatment for phenyl and pyrimidine labeled samples, respectively. Peak A 

was determined by HPLC and Thin Layer Chromatography (TLC) to be mainly parent 

hydramethylnon. Peak B was determined to be a photolytic product formed during sample 

analysis. Since Peaks A and B generated multiple peaks during HPLC and liquid-liquid 

chromatography, they could not be identified. Peak B was reported to reach a maximum 

concentration of 12.7% and 9.2% of applied radioactivity at 3 and 4 months 

post-treatment samples in the phenyl and pyrimidine labeled test samples, respectively. 

The study is classified as Acceptable.

(2) Mobility (MRID 41888301, MRID 41888302 §163-1)

Two guideline mobility studies were submitted to the Agency. One of these is an unaged 

adsorption/desorption study, MRID 41888302, and the other is a TLC study, MRID 

41888301. 
21

In the batch equilibrium study (MRID 41888302), hydramethylnon appears to be relatively 

non-mobile (Kd values ranged from 1039-1782 mL/g). In addition, hydramethylnon was 

reported to be stable since only one major spot, which co-chromatographed with 

non-labeled hydramethylnon, was discernible on the normal phase assays. Although 

there is a poor correlation between the organic carbon content of the soil and the 

adsorption coefficients, for the purpose of modeling, the Koc vales were determined as 

358276 (loamy sand), 287759 (sandy loam), 123381 (loam), and 95389 (silt loam). 

The strong adsorption properties of hydramethylnon were also observed in soil TLC study 

(MRID 41888301). The results indicate that hydramethylnon is relatively non-mobile in 

loamy sand, sandy loam, loam, and clay loam soils.

Both studies are considered scientifically valid. However, the Agency does not accept 

soil TLC mobility data (MRID 41888301) towards mobility data requirement (§163-1) so 

this study is considered Supplemental. The unaged mobility study, MRID 41888302 is 

Acceptable. Because the current risk assessment is based on parent alone, no 

additional information on aged mobility is needed at this time. However, since photolysis 

appears to be a major route of degradation, aged mobility data for photodegradation 

products may be needed to support any additional uses of hydramethylnon.

(3) Bioaccumulation (MRID 00101611, §165-4)

Hydramethylnon showed some tendency to accumulate in fish tissues with reported 

bioconcentration factors of 1300X in whole fish, 780X in fillet, and 1900X in viscera. The 

depuration was slow with a decrease of approximately, 48 to 63% of residues after a 

14-day clearance period. This study is classified as Supplemental. 

(4) Terrestrial Field Dissipation (MRID 43293101 and MRID 43293102, §164-1)

Two studies using the formulation product AMDRO conducted in bare soil in Windermere, 

Florida (MRIDs 43293101) and in Pattison, Texas (MRID 43293102) were submitted to 

the Agency for guideline requirement §164-1. Hydramethylnon appeared to dissipate in 

Florida sand soil with a calculated first order half-life of 3 days. Average residues above 

the analytical detection limit (0.010 ppm) were not detected below the 0-6 inch soil depth 

level. Hydramethylnon residues ranged from 115 ppb at immediately after treatment (0.01 

day test interval) to <10 ppb at 14 days post-treatment. No attempt was made for the 

identification of degradation products during the entire testing period of 152 days. 

In Texas sandy loam soil, hydramethylnon appeared to dissipate with a first-order 

calculated half-life of 55 days. Average residues above the analytical detection limit 

(0.010 ppm) were not detected below the 0-6 inch soil depth level. Hydramethylnon 

residues ranged from 114 ppb at immediately after treatment (0.01 day test interval) to 

<10 ppb at 30 days post-treatment and thereafter, the residues remain close to the 

detection limit for the entire testing period of 148 
22

days. Similar to other field dissipation study in Florida, no attempt was made for the 

identification of degradation products during the entire testing period. 

Both field studies are classified as Supplemental.

(5) Spray Drift

American Cyanamid is a member of the Spray Drift Task Force and is able to cite those

data. Although there are aerial broadcast application uses, the granular formulation would 

not be expected to drift during typical application.
23

Structures of Hydramethylnon and its Degradates
24
25
26

Appendix II

Drinking Water and Aquatic Exposure Model Outputs

FIRST Output

 RUN No. 1 FOR Hydramethylnon ON Pineapples * INPUT VALUES *

 --------------------------------------------------------------------

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

 ONE(MULT) INTERVAL Kd (PPB ) (%DRIFT) AREA (IN)

 --------------------------------------------------------------------

3.000( 5.446) 2 120 1669.0 880.0 AERIAL(16.0) 87.0 .0

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

 --------------------------------------------------------------------

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.)

 --------------------------------------------------------------------

 407.60 2 N/A .04- 4.96 815.20 4.93

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.0 AUG 1, 2001

 --------------------------------------------------------------------

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

 CONCENTRATION CONCENTRATION

 --------------------------------------------------------------------

 76.086 1.447

Scigrow Output

 SCIGROW

 VERSION 2.2: NOVEMBER 1, 2001

RUN No. 1 FOR hydramethylnon ** INPUT VALUES **

--------------------------------------------------------

 APP RATE APPS/ TOTAL/ SOIL AEROBIC SOIL METAB

 (LBS/AC) YEAR SEASON KOC HALFLIFE (DAYS)

--------------------------------------------------------

 3.000 2 6.000 205570.0 383.00

GROUND-WATER SCREENING CONCENTRATION (IN UG/L - PPB)

--------------------------------------------------------

 .034447
27

--------------------------------------------------------
28

GENEEC Output

 

RUN No. 1 FOR Hydramethylnon ON Pineapples * INPUT VALUES *

 --------------------------------------------------------------------

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE NO-SPRAY INCORP

 ONE(MULT) INTERVAL Kd (PPB ) (%DRIFT) ZONE(FT) (IN)

 --------------------------------------------------------------------

3.000( 5.446) 2 120 1669.0 880.0 AERL_C( 9.2) .0 .0

 FIELD AND STANDARD POND HALFLIFE VALUES (DAYS)

 --------------------------------------------------------------------

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

 (FIELD) RAIN/RUNOFF (POND) (POND-EFF) (POND) (POND)

 --------------------------------------------------------------------

 407.60 2 N/A .04- 4.96 815.20 4.93

 GENERIC EECs (IN MICROGRAMS/LITER (PPB)) Version 2.0 Aug 1, 2001

 --------------------------------------------------------------------

 PEAK MAX 4 DAY MAX 21 DAY MAX 60 DAY MAX 90 DAY

 GEEC AVG GEEC AVG GEEC AVG GEEC AVG GEEC

 --------------------------------------------------------------------

 15.90 10.75 2.85 1.00 .67
29

Appendix III

Ecotoxicity Studies

Toxicity testing reported in this section does not represent all species of bird, mammal, or aquatic 

organism. Only two surrogate species for both freshwater fish and birds are used to represent all 

freshwater fish (2000+) and bird (680+) species in the United States. For mammals, acute studies 

are usually limited to laboratory rats or mice. Estuarine/marine testing is usually limited to a 

crustacean, a mollusk, and a fish. Also, neither reptiles nor amphibians are tested. The 

assessment of risk or hazard makes the assumption that avian and reptilian toxicities are similar. 

The same assumption is used for fish and amphibians. 

I Toxicity To Terrestrial Organisms

(1) Birds, Acute and Subacute

An acute oral toxicity study using the technical grade of the active ingredient (TGAI) was 

conducted to establish the toxicity of hydramethylnon to avian species. The preferred test 

species are the mallard duck (a waterfowl) and the bobwhite quail (an upland gamebird). The 

results of this study are tabulated below: 

Table 1-Avian Acute Oral Toxicity

Species %ai LD50

(mg/kg)

Toxicity

Category

MRID Number Study

Classification

Northern 

Bobwhite Quail

(Colinus 

virginianus) 92% 1828 Slightly toxic 00064576 Core

Mallard Duck

(Anas 

platyrhynchos) 92% 2510 Practically non-toxic

00064575 Core

Since the LD50 falls in the range of 1828-2510 mg/kg, hydramethylnon is slightly toxic to 

practically non-toxic to avian species on an acute oral basis. Both acute oral toxicity studies are 

classified as Core.

Two subacute dietary studies using the TGAI were conducted to establish the toxicity of 

hydramethylnon to birds. These studies were performed on the two preferred test species, the 

mallard duck and the bobwhite quail. The results of these tests are tabulated below:
30

Table 2-Avian Subacute Oral Toxicity

Species %ai LC50

(mg/kg)

Toxicity

Category

MRID Number Study

Classification

Northern 

Bobwhite Quail

(Colinus 

virginianus) 92% 1136 Slightly toxic 00064577 Core

Mallard Duck

(Anas 

platyrhynchos) 92% 4355 Slightly toxic 00085931 Core

1Test organisms observed an additional three days while on untreated feed

Since the LC50 falls in the range of 1136-4355 ppm, hydramethylnon is slightly toxic to 

avian species on a subacute dietary basis. Both acute dietary studies are classified as Core.

(2) Birds, Chronic

Avian reproduction studies are required when birds may be exposed repeatedly or continuously 

through persistence, bioaccumulation, or multiple applications. Avian reproduction studies are 

also required if mammalian reproduction tests indicate a reproductive hazard. The 

hydramethylnon label calls for multiple applications on pineapples, therefore, avian reproductive 

studies are required. The results of this test are tabulated below:

Table 3-Avian Reproduction Toxicity

Species %AI NOAEC

(ppm)

LOAEC

(ppm)

Endpoints

Affected

MRID Number Study 

Classification

Northern 

Bobwhite Quail

(Colinus 

virginianus)

97.8% >57.0 57.0 None 45449701 Supplemental1

Mallard Duck

(Anas 

platyrhynchos)

97.8% 28.5 57.0 weight of 

14-day old 

survivors

45449702 Core

1

 This toxicity study is scientifically sound, but only partially satisfies the guideline requirement for a 

bobwhite quail reproductive toxicity study because no reproductive toxicity was shown and, so, a NOAEC 

was not identified.

Although a NOAEC was not determined for the bobwhite quail study, no endpoints were 

affected and the study is classified as Supplemental. In the case of the mallard duck, the 

NOAEC was determined to be 28.5 ppm by which the weights of 14-day old survivors were 

affected. This study is classified as Core .
31

(3) Mammals, Acute and Chronic

In general, EFED utilizes acute and reproduction toxicity data submitted to HED on laboratory 

rodents and/or non-rodents in evaluating risk for wild mammals. The acute and chronic toxicity 

values obtained from rodents are tabulated below:

Table 4- Mammalian Toxicity ( Acute And Chronic)

Species %AI Test Type Toxicity Value Toxicity Value MRID Number

Norway Rat

(Rattus 

norvegicus)

95% LD50 817(m)

1502 (F)

Slightly Toxic 416125-03

Norway Rat

(Rattus 

norvegicus)

92% 3rd Generation 

Reproduction 

Toxicity test

NOAEL=50 ppm

LOAEL=100 ppm

Male infertility

was noted at 100 

ppm

35525

35526

101575

The results indicate that hydramethylnon is slightly toxic to small mammals on an acute oral basis. 

Reproductive effects(male infertility) occurred at 100 ppm (NOAEL= 50ppm)

In a three generation study (MRID 43741501), 98.2% hydramethylnon was administered to 

Sprague-Dawley rats. The reproductive NOAEL was determined to be 25 ppm and the 

reproductive LOAEL was determined to be 50 ppm based on histological findings in the testes and 

the epididymides. At 75 ppm, reproductive performance of the males was decreased. As noted 

above, these findings are suggestive of the potential for reproductive effects in other organisms 

including birds.

(4) Insects

A honey bee acute contact study using the TGAI was required for hydramethylnon because its 

outdoor use may result in honey bee and non-targeted insect exposure. Results of this test are 

tabulated below:

Table 5-Non-targeted Acute Contact Toxicity

Species %AI

LD50

(μg/bee) Toxicity

Category

MRID Number Study 

Classification

Honey bee

(Apis mellifera) 96.8 68.0

Practically 

non-toxic 416078-01 Core

The results indicate that hydramethylnon is practically non-toxic to bees on an acute contact basis. 

The study is classified as Core.
32

II. Toxicity To Aquatic Organisms

(1) Freshwater Fish, Acute

Two freshwater fish toxicity studies using the TGAI are required to establish the toxicity of 

hydramethylnon to freshwater fish. The two preferred species are the rainbow trout (a coldwater 

fish) and the bluegill sunfish (a warm water fish). Acute toxicity test using channel catfish was 

also submitted to the Agency. The results of these tests are tabulated below:

Table 6-Freshwater Fish Acute Toxicity

Species %AI 96-Hour LC50

(ppb)1

Toxicity 

Category

MRID Number Study

Classification

Rainbow trout

(Oncorhynchus 

mykiss) 92 150 Highly toxic 00052857 Core

Bluegill sunfish

(Lepomis 

macrochirus) 92 1700 Moderately toxic 00061708 Core

Channel catfish

(Ictalurus 

punctatus) 92 90 Very Highly Toxic 00061707 Core

1

Note: LC50 concentrations for bluegill sunfish exceed the water solubility of hydramethylnon. These concentrations were achieved through the use 

of dimethyl formalin as a co-solvent

Because the LC50 falls in the range of 90 to 1700 ppb, hydramethylnon is moderately to very 

highly toxic to freshwater fishes in an acute basis. Based on the results, catfish appears to be 

sensitive to toxic effects of hydramethylnon as compared to other species tested. All of the fish 

acute toxicity tests are classified Core. 

(2) Freshwater Fish, Chronic

A freshwater fish early life-stage test using the TGAI may be required for hydramethylnon 

because the end-use product may be transported to water from the intended use sites and 

conditions are met with regard to the chemical’s toxicity. The guideline requirement 72-4 is 

reserved for the hydramethylnon uses on pineapples. This test is expected to be submitted for 

future expansion of hydramethylnon uses. 

(3) Freshwater Invertebrates, Acute

A freshwater aquatic invertebrate toxicity test using the TGAI is required to establish the toxicity 

of hydramethylnon to aquatic invertebrates. Results of this test are tabulated below:
33

Table 7-Freshwater Invertebrate Acute Toxicity

Species %AI 48-Hour LC50

(ppb)

Toxicity

Category

MRID Number Study

Classification

Waterflea

(Daphnia magna) 92% 1140 Moderately toxic 00035877 Core

Since the LC50 is 1140 ppb, hydramethylnon is moderately toxic to aquatic invertebrates on an 

acute basis. The acute Daphnia test is classified Core.

(4) Freshwater Invertebrates, Chronic

A freshwater aquatic invertebrate life-cycle testing using the TGAI is required for 

hydramethylnon because the end-use product may be transported to water from the 

intended use sites. The guideline requirement 72-4 is reserved for the hydramethylnon uses on 

pineapples. This test is expected to be submitted for future expansion of hydramethylnon uses. 

(5) Estuarine/Marine Fish, Acute

Acute toxicity testing with estuarine/marine fishes using the TGAI of hydramethylnon is required 

because the end-use product is expected to reach estuarine/marine habitats. The preferred test 

species is the sheepshead minnow. This data has not been submitted for use in this risk 

assessment. Therefore, it is listed as a data gap until it is submitted and reviewed. 

(6) Estuarine/Marine Fish, Chronic

The guideline requirement 72-4 is reserved for hydramethylnon uses on pineapples. This test is 

expected to be submitted for any future proposed uses of hydramethylnon. 

(7) Estuarine and Marine Invertebrates, Acute

Acute toxicity testing using estuarine/marine invertebrates using the TGAI of hydramethylnon is 

required because the end-use product is expected to reach estuarine/marine habitats. The 

preferred test species are the mysid shrimp (Americamysis bahia) and the eastern oyster 

(Crassostrea gigas). Since these studies were not submitted, it is listed a data gap until it is 

submitted and reviewed for use in future risk assessments.

(8) Estuarine and Marine Invertebrate, Chronic

The guideline requirement 72-4 is reserved for the hydramethylnon uses on pineapples. This test 

is expected to be submitted for any future proposed uses of hydramethylnon. 
34

III Toxicity to Plants

(1) Terrestrial

Currently, terrestrial plant testing is not required for pesticides other than herbicides except on a 

case-by-case basis (e.g., phytotoxicity observed based on incident data or literature). EFED has 

not requested studies supporting the ecotoxicological and phytotoxicological effects of 

hydramethylnon on terrestrial plants because the incident database did not show any evidence of 

phytotoxicity.

(2) Aquatic 

Semi-aquatic plant testing is required if the pesticide is expected to enter into aquatic habitats in 

significant quantities. Data supporting the ecotoxicological effects of hydramethylnon on 

semi-aquatic plants was not available for use in this risk assessment. The request for the aquatic 

plant toxicity data is reserved for the proposed uses.
35

Appendix IV

Risk Assessment

Risk assessment of a pesticide’s ecological effects integrates the results of exposure and toxicity

data to evaluate the likelihood of adverse ecological effects on a non-target species. The means of 

integrating these exposure factors is the risk quotient (RQ) method. Risk quotients are calculated 

by dividing estimated environmental concentrations (EECs) of the pesticide by acute and chronic 

toxicity values. EECs are based on the maximum application rates for that pesticide. 

Risk quotients are then compared to the Agency’s levels of concern (LOCs). These LOCs are 

used to analyze potential risk to non-target organisms and the need to consider regulatory action. 

The criteria are used to indicate when a pesticide used as directed has the potential to cause adverse 

effects on non-target organisms. LOCs currently address the following risk presumption 

categories: (1) acute : potential for acute risk for all nontarget organisms which may warrant 

regulatory action in addition to restricted use classification; (2) acute restricted use: potential for 

acute risk for all nontarget organisms, but may be mitigated through restricted use classification; 

(3) acute endangered species: endangered species may be adversely affected by use; and (4) 

chronic risk: potential for chronic risk may warrant regulatory action. Currently, the Agency does 

not assess chronic risk to plants, acute and chronic risks to non-target insects, or chronic risk from 

granular/bait formulations to birds or mammals. In addition, the Agency considers any incident 

data that is submitted concerning adverse effects on non-target species.
36

RQ Calculations, LOCs, and Risk Presumptions for Terrestrial Animals

Risk Presumption RQ LOC

Birds

Acute Risk

Acute Restricted Use

Acute Endangered Species

Chronic Risk

EEC1/LC50 , LD50/sq ft2 or LD50/day3

EEC/LC50 , LD50/sq ft or LD50/day (or LD50 < 50 mg/kg)

EEC/LC50 , LD50/sq ft or LD50/day 

EEC/NOAEC

0.5

0.2

0.1

1

Wild Mammals

Acute Risk

Acute Restricted Use

Acute Endangered Species

Chronic Risk 

EEC/LC50 , LD50/sq ft or LD50/day

EEC/LC50 , LD50/sq ft or LD50/day (or LD50 < 50 mg/kg)

EEC/LC50 , LD50/sq ft or LD50/day

EEC/NOAEC

0.5

0.2

0.1

1

1

 abbreviation for Estimated Environmental Concentration (ppm) on avian/mammalian food items 

2

 mg/ft2 3 mg of toxicant consumed/day

 LD50 * wt. of bird LD50 * wt. of bird 

RQ Calculations, LOCs, and Risk Presumptions for Aquatic Animals

Risk Presumption RQ LOC

Acute Risk

Acute Restricted Use

Acute Endangered Species

Chronic Risk

EEC/(LC50 or EC50)

EEC/(LC50 or EC50)

EEC/(LC50 or EC50)

EEC/(NOAEC)

0.5

0.1

0.05

1

RQ Calculations, LOCs, and Risk Presumptions for Plants

Risk Presumption RQ LOC

Terrestrial and Semi-Aquatic Plants 

Acute Risk

Acute Endangered Species

EEC1/EC25

EEC/EC05 or NOAEC

1

1

Aquatic Plants

Acute High Risk

Acute Endangered Species

EEC2/EC50

EEC/EC05 or NOAEC 

1

1

1

 EEC = lbs a.i./A 

2

 EEC = (ppb/ppm) in water 
37

Appendix V

Data Requirements

Table 1: Status of Environmental Fate Study Requirements for Hydramethylnon

Guideline # Data Requirement

Study 

Classificatio

n MRID #’s 

Is Guideline 

Requirement 

Satisfied? 

161-1 Hydrolysis Acceptable 42194701 Yes

161-2 Aquatic Photolysis

Supplementa

l 

42238201

42473301 No1

161-3 Soil Photolysis Acceptable

42113401

Yes

162-1 Aerobic Soil Metabolism Acceptable 42320801 Yes

162-3

Anaerobic Aquatic 

Metabolism Acceptable 43102701 Yes

162-4

Aerobic Aquatic 

Metabolism N/A N/A No2

163-1

Leaching-Adsorption/De

sorption

Acceptable 

Supplementa

l

41888302

41888301 Yes

164-1

Terrestrial Field 

Dissipation

Supplementa

l

43293101

43293102 No1

165-4 Accumulation in Fish Acceptable 00101611 Yes

1 Degradate information needed. Major degradates are not characterized.

2 Reserved for this registration action on pineapples
38

Table 2: Status of Ecological Study Requirements for Hydramethylnon

Study 

Guideline 

Data Requirement Study 

Classification

MRID # Is Guideline 

Requirement 

Satisfied

Birds

71-1a Avian acute oral

Bobwhite quail

Core 00064576 Yes

71-1b Avian acute oral

Mallard duck

Core 00064575 Yes

71-2a Avian subacute dietary

Bobwhite quail

Core 00064577 Yes

71-2b Avian subacute dietary

Mallard duck

Core 00085931 Yes

71-4a Avian reproduction

Bobwhite quail

Supplemental 45449701 No1

71-4b Avian reproduction 

Mallard duck

Core 45449702 Yes

Fish and Invertebrates

72-1a Freshwater fish acute

Bluegill sunfish

Catfish

Core

Core

00061708

00061707

Yes

72-1c Freshwater fish acute

Rainbow trout

Core 00052857 Yes

72-2 Freshwater acute 

invertebrate, Daphnia

Core 00035877 Yes

72-3a Estuarine/marine acute fish 

Sheepshead minnow

- None No

72-3b Estuarine/marine acute 

invertebrate, Eastern oyster

- None No

72-3c Estuarine/marine acute 

invertebrate, Mysid

- None No

72-4a Freshwater fish, early-life 

stage 

Fathead minnow

- None Reserved 2
39

Table 2: Status of Ecological Study Requirements for Hydramethylnon

Study 

Guideline 

Data Requirement Study 

Classification

MRID # Is Guideline 

Requirement 

Satisfied

72-4b Freshwater invertebrate life 

cycle, Daphnia

- None Reserved 2

72-4c Estuarine/marine fish early 

life-stage, Sheepshead 

minnow

- None Reserved 2

72-4d Estuarine/marine life cycle 

Mysid

- None Reserved2

Plants

122-1a Terrestrial plants 

Seedling emergence

- None Reserved3

122-1b Terrestrial plants 

Vegetative vigor

- None Reserved3

122-2 Aquatic plants - None Reserved2

Non-target Insects

141-1 Acute honey-bee contact Core 41607801 Yes

1 Partially satisfied as the NOAEC not established.

2 Reserved for pineapple uses.

3 Requested on a case by case basis for pesticides other than herbicides.