Environmental Fate and Ecological Risk 

Assessment Problem Formulation in 

Support of Registration Review for 

Deltamethrin 

March 23, 2010 

Environmental Fate and Effects Division 

Office of Pesticide Programs 

US Environmental Protection Agency 
2

Prepared by: 

Amanda Solliday, Biologist 

José L. Meléndez, Chemist 

Reviewed by: 

Keith Sappington, Senior Scientist 

Mah Shamim, Ph.D., Branch Chief 

Approved by: 

Mah Shamim, Ph.D., Branch Chief 

Environmental Risk Branch V 
3

Table of Contents 

1. Purpose.................................................................................................................................... 4 

2. Problem Formulation .............................................................................................................. 4 

2.1 Nature of Regulatory Action................................................................................................ 4 

2.2. Previous Risk Assessments.................................................................................................. 5 

3. Stressor Source and Distribution ............................................................................................ 7 

3.1. Mechanism of Action.......................................................................................................... 5 

3.2. Overview of Pesticide Usage............................................................................................ 10

3.3. Environmental Fate and Transport.................................................................................... 14 

4. Receptors............................................................................................................................... 22 

4.1. Aquatic and Terrestrial Effects ......................................................................................... 22 

4.2. Incident Database Review................................................................................................. 25

4.3. Ecosystems Potentially at Risk ......................................................................................... 27

6. Conceptual Model.............................................................................................................. 29 

6.1. Risk Hypothesis ............................................................................................................... 29 

6.2. Conceptual Diagram ........................................................................................................ 29 

7. Analysis Plan ..................................................................................................................... 31 

7.1. Stressors of Concern ......................................................................................................... 32 

7.2. Measures of Exposure....................................................................................................... 32 

7.3. Measures of Effect ............................................................................................................ 34 

7.4. Integration of Exposure and Effects ................................................................................. 35 

7.5. Deterministic and Probabilistic Assessment Methods...................................................... 35 

7.6. Endangered Species Assessments..................................................................................... 35 

7.7. Drinking Water Assessment ............................................................................................. 36 

7.8. Preliminary Identification of Data Gaps........................................................................... 36 

7.8.1. Fate............................................................................................................................. 36 

7.8.2 Effects ......................................................................................................................... 39 

8. References................................................................................................................................ 44 

Appendix A. SRRD data request justification tables.................................................................. 47 
4

1. Purpose 

The purpose of this problem formulation is to provide the foundation for the ecological 

risk assessment being conducted for the registered uses of deltamethrin. As such, it 

articulates the purpose and objectives of the risk assessment, evaluates the nature of the 

problem, and provides a plan for analyzing the data and characterizing the ecological risk 

(EPA, 1998). Additionally, this problem formulation is intended to identify data gaps, 

uncertainties and potential assumptions needed to address those uncertainties in 

characterizing the ecological risk associated with the registered uses of deltamethrin. 

Deltamethrin is a synthetic pyrethroid insecticide that is registered for a variety of 

agricultural and residential uses, including (but not limited to) globe artichokes, canola, 

crambe, rapeseed, field corn, popcorn, sweet corn, cotton, cucurbits, eggplant, groundcherry, pepinos, peppers, tomatillo, tomato, garlic, leeks, onion, shallots, apple, 

crabapple, loquat, mayhaw, pear, oriental pear, quince, carrot, celeriac, turnip-rooted 

chervil , chicory, edible burdock, garden beet, ginseng, horseradish, parsley (turniprooted), parsnip, radish, oriental radish, rutabaga, salsify, black salsify, Spanish salsify, 

skirret, turnip, potato, sweet potato, arracacha, arrowroot, Chinese artichoke, Jerusalem 

artichoke, edible canna, bitter and sweet cassava, chayote (root), chufa, dasheen, ginger, 

leren, tanier, tumeric, yam bean, true yam, sorghum, soybeans, sunflowers, tree nuts 

domestic dwellings, ornamental lawns and turf, ornamental woody shrubs and vines, 

paths/patios, paved areas (private roads/sidewalks), pet living/sleeping quarters, garbage 

cans, residential lawns, bathroom premises, cadavers, caskets (and also morgues and 

mortuaries), carpets, commercial transportation facilities, commercial/ institutional/ 

industrial premises (indoors), diaries and cheese processing plant premises, dogs/ canines 

(collars) (and also pet living quarters), drainage systems, eating establishments, feed 

mills/ feed processing plants, food processing plant premises, food stores/ markets/ 

supermarket premises, greenhouses, hospital/ medical institutions premises, household/ 

domestic dwellings, human bedding/ mattresses, public building/ structures, sewage 

systems, ships and boats, and zoos. 

2. Problem Formulation 

 2.1. Nature of Regulatory Action 

The Food Quality Protection Act of 1996 mandated the EPA to implement a new 

program, i.e., registration review (http://www.epa.gov/oppsrrd1/registration_review/). All 

pesticides distributed or sold in the United States generally must be registered by EPA. 

The decision to register a pesticide is based on the consideration of scientific data and 

other factors showing that it will not cause unreasonable risks to human health, workers, 

or the environment when used as directed on product labeling. The registration review 

program is intended to ensure that, as the ability to assess risk evolves and as policies and 

practices change, all registered pesticides continue to meet the statutory standard of no 
5

unreasonable adverse effects to human health and the environment. Changes in science, 

public policy, and pesticide use practices will occur over time. Through the new 

registration review program, the Agency periodically reevaluates pesticides to make sure 

that as change occurs, products in the marketplace can be used safely. 

As part of the implementation of the new Registration Review program pursuant to 

Section 3(g) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the 

Agency is beginning its evaluation to determine whether deltamethrin continues to meet 

the FIFRA standard for registration. This problem formulation for the environmental fate 

and ecological risk assessment chapter in support of the registration review is intended 

for the initial docket opening the public phase of the review process. 

2.2. Mechanism of Action 

Deltamethrin is classified as a Type II pyrethroid, with a cyano group at the alpha-carbon 

position, or the alcohol moiety. The primary biological effects of deltamethrin, and other 

pyrethroids, on insects and vertebrates reflect an inhibition of the correct firing of 

neurotransmitter deliver signals from one cell to another via nerve membrane inhibition 

of the voltage-gated Ca2+ channels (calcium ion channels) coupled with a stimulatory 

effect on the voltage-gated Na+ channels (sodium ion channels). The insecticidal effect 

of pyrethroids is characterized by a rapid “knock down,” or paralysis, of insects. In 

insects, the type II pyrethroids predominantly cause ataxia and uncoordinated movement. 

All pyrethroids act as axonic poisons, affecting both the peripheral and central nervous 

systems, and share similar modes of action. Pyrethroids, including deltamethrin, 

stimulate repetitive action in the nervous system by binding to voltage-gated Na+

channels, prolonging the Na+ ion permeability during the excitatory phase of the action 

potential. This action leads to spontaneous depolarizations, augmented neurotransmitter 

secretion rate and neuromuscular block, which ultimately results in paralysis of the 

insect. 

2.3. Previous Risk Assessments 

The previous risk assessments conducted on deltamethrin indicated risk concerns for 

organisms living in fresh and estuarine/ marine bodies of water. In addition, there were 

risk concerns for aquatic organisms living in the benthos. 

In 2007, EFED conducted an environmental fate and ecological risk assessment for 

deltamethrin use on flax, and concluded that the chemical is highly toxic to exposed 

aquatic organisms and to nontarget beneficial insects. Also, the assessment concluded 

that proposed use patterns prescribed for deltamethrin on flax have the potential for 

chronic exposure and harm to fish and aquatic invertebrates, including those living in or 

near the benthos, since deltamethrin is accumulated in the sediment. It was indicated that 

many use areas are expected to be located adjacent to some types of aquatic habitats, and 
6

that drift may be harmful to both beneficial insects and aquatic organisms. Based on the 

environmental fate properties for deltamethrin it appeared to be immobile, relatively 

persistent in the environment, stable to hydrolysis and photolysis, and very lipophilic. 

Prior to the 2007 assessment on flax, an risk assessment was issued in 2002 for the use of 

the chemical on field corn, sorghum, soybeans, sunflowers, bulb vegetables, cucurbit 

vegetables, leafy vegetables, fruiting vegetables, carrots, potatoes, radishes, artichokes, 

cauliflower, broccoli, cabbage, mustard greens, tree nuts, stone fruits and pome fruits. 

Findings from the 2002 ecological risk assessment were similar to those described above 

for flax. In 1994, EFED issued an assessment for the use of the chemical on cotton. The 

conclusions were as follows: 

“Based on the available information EEB concludes that the proposed use poses 

serious risk to exposed, aquatic organisms or nontarget beneficial insects. Many 

cotton production sites are expected to be located adjacent to some type of 

aquatic habitat. Without further precautions against drift contamination (such as 

application only when/wind direction is away from nontarget aquatic habitats), 

EEB cannot dismiss the possibility of hazard to aquatic species located in waters 

adjacent to application sites. The effects of drift to populations of pollinating 

beneficial insects may also be extreme unless applications are made at times of 

low activity (foraging) for these species. Endangered species concerns must be 

addressed on a site by site basis in relation to the ecological risk factor involved 

with that particular site location (i.e. proximity to critical habitat).” 

1999 Scientific Advisory Panel on Sediment Toxicity and Fate of Synthetic Pyrethroids

A Scientific Advisory Panel (SAP) in 1999 examined the sediment toxicity and fate of 

synthetic pyrethroids. In response to a question regarding whether sediment toxicity data 

on one pyrethroid (cypermethrin) could be used to predict sediment toxicity to all 

pyrethroids, the panel generally supported the method of using data from a few 

pyrethroids to extrapolate information on toxicity to other pyrethroids. The panel 

recommended testing cypermethrin, “bifenthrin (relatively non-toxic to freshwater 

aquatic organisms, very insoluble in water, large bioconcentration factor) and possibly 

trefluthrin (highly toxic to freshwater aquatic organisms, stable in water, intermediate 

solubility in water to cypermethrin and bifenthrin)” (USEPA, 1999). Although this 

agreement was made in 1999, the new CFR Part 158 requirements include sediment 

toxicity tests and these studies are considered particularly important for ecological risk 

assessment of deltamethrin. 

The SAP commented on the use of Kd or KOC to estimate concentrations of synthetic 

pyrethroids in sediments, recommending that the Agency reconsider KOC as a measure of 

the binding potential of synthetic pyrethroids to sediment and soil because the use of Kd

alone limits extrapolation to experimental conditions while KOC “allows one to estimate 

partitioning across a wide variety of soil/sediment types” (USEPA, 1999). The Panel 

expressed concern that standard methods used to measure sorption may not be applicable 

to highly hydrophobic compounds due to high solids to water ratio, consideration of the 
7

character of the organic matter, presence of dissolved organic carbon, use of nonrepresentative soils and sediments as sorbents, and improper methods used to measure 

organic carbon. 

While the biota-sediment-accumulation-factor is a widely accepted method of assessment 

of bioaccumulation in sediments, the Panel indicated that the bioconcentration data for 

Daphnia and Hyalella should be sufficient to predict bioconcentration of pyrethroids. 

Finally, the Panel indicated that use of a solid phase microextraction (SMPE) method to 

determine the dissolved concentration in water could be used to account for sorption of 

pyrethroids to organic carbon and colloids present in the water column in the 

measurement of bioconcentration factors. 

In 2003 and in response to the comments from the SAP on pyrethroids, EFED requested 

the following studies on esfenvalerate, cypermethrin, bifenthrin and cyfluthrin (Rexrode 

and Melendez, 2003). 

850.1735: Acute Sediment (freshwater)

- Test organism: Hyalella azteca and Chironomus tentans

- Duration: 10 days, endpoint is survival. 

EPA/600/R01/020: Chronic Estuarine/Marine Sediment Testing

- 28 day test on Leptocheirus plumulosus, 

- Percentage of neonates that survive as adults. 

- Growth rate. 

- Reproduction (#eggs/female, etc.). 

- Behavior. 

A chronic 65-day freshwater test was also requested for cypermethrin only. 

EPA/600/R-991064: Chronic Freshwater Sediment Testing 

- 65 day test on Chironomus tentans 

- Survival. 

- Growth rate. 

- Reproduction (# eggsffemale, time to oviposition, proportion of females 

ovipositing, % hatch).

3. Stressor Source and Distribution

Deltamethrin is a synthetic pyrethroid insecticide. Its structure has three rings, two 

phenyl rings attached to each other by an oxygen atom, and a cyclopropyl ring. It is 

cyano-substituted in the alpha position. The chemistry of deltamethrin may be dictated 

by its ester moiety; this is substantiated by the hydrolysis study, in which the chemical is 

labile at the highest pH of 9. The structure of the molecule has three chiral centers that 

could result in a total of 8 stereoisomers. Chemically, it is the [1R, cis; alpha S]-isomer 
8

[alternatively (1S)-alcohol (1R)-cis-acid] out of eight stereoisomeric esters of the 

dibromo analogue of chrysanthemic acid. Deltamethrin has a 2,2-dibromoethenyl 

substitution in the cyclopropyl ring. 

A summary of physicochemical properties of deltamethrin is included in Table 3.1. 

Table 3.1. Summary of physicochemical properties of deltamethrin.

PARAMETER VALUE(S) (units) SOURCE

CAS Chemical Name (S)-cyano (3-phenoxyphenyl) methyl (1R,3R)-3-(2,2-

dibromoethenyl)-2,2-dimethylcyclopropanecarboxylate 

IUPAC Chemical Name 

(S)-α-cyano-3-phenoxybenzyl (1R,3R)-3-(2,2-

dibromovinyl)-2,2-dimethylcyclopropanecarboxylate 

or 

(S)-α-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-

dibromovinyl)-2,2-dimethylcyclopropanecarboxylate 

Deltamethrin data sheet: 

http://www.alanwood.net/pe

sticides/deltamethrin.html 

accessed 06/23/09 

PC Code 097805 OPP Databases 

Chemical Structure 

(from chemical’s data 

sheet) 

CAS Reg. No. 52918-63-5 Deltamethrin data sheet 

Molecular Weight 505.2 Laskowski, 2002 

Solubility (20oC) 0.000200 mg/L or 2.00x10-4 ppm or 0.200 ppb Laskowski, 2002 

Vapor Pressure (25oC) 9.32 x 10-11 mmHg Laskowski, 2002 

Henry’s Law Constant 3.1 x 10-7 atm-m3

/mol (from vapor pressure and water 

solubility) Laskowski, 2002 

Octanol-Water Partition 

Coefficient (20oC) 

(log KOW and KOW) 

4.53 and 3.42 x 104 Laskowski, 2002 

Octanol-Air Partition 

Coefficient 

(log KOA and KOA) 

9.89 and 7.76 x 109

 EPISuite v.4.0 Estimate 

Biomagnification 

Potential 

Presumption*: If log KOA > 5, log KOW >2 and the rate of 

chemical transformation is low, the chemical may 

biomagnify in terrestrial food chains.* 

For deltamethrin, log KOA=9.89, log KOW=4.53 & rate of 

transformation is relatively low; it appears that 

deltamethrin has a potential to biomagnify in terrestrial 

food chains. 

*Gobas et al. 2003 and 

Armitage & Gobas, 2007 

support this presumption 

utilized here only as a broad 

reference to determine the 

potential for 

biomagnification. 

Deltamethrin has a very high molecular weight of 505.2 g/mol. With a very small 

solubility (only 0.200 ppb) and a high octanol/ water partition coefficient (KOW = 34,200), 
9

it appears that deltamethrin has the potential to bioaccumulate/ bioconcentrate. With a 

small vapor pressure (9.32 x 10-11 mmHg), a relatively small Henry’s Law Constant (3.1 

x 10-7 atm-m3/mol), and despite its low solubility, deltamethrin does not appear to 

volatilize substantially from wet surfaces. 

For deltamethrin, the log KOA is 9.89 and the log KOW is 4.53. For chemicals that are not 

readily metabolized in vivo, a log KOA and log KOW in this range (KOA > 5, log KOW >2) 

have been associated with biomagnification in terrestrial-based food webs based on 

information presented in articles by Gobas et al. and Armitage & Gobas (2003 and 2007, 

respectively). However, pyrethroids, such as deltamethrin, undergo substantial 

biotransformation in vivo. Even though the EFED has not adopted an official reference to 

distinguish chemicals that biomagnify, their presumption was utilized here as a general or 

broad reference to detect the biomagnification potential in terrestrial food chains. 

Even though various degradates were observed in the laboratory studies (e.g. 3-PBA and 

tetramethrinic acid), it was found that they were the result of the rupture of the ester bond 

of the parent molecule. It is believed that the resulting molecules are not as toxic as the 

parent because they presumably have lost the neurotoxic mode of action. Table 3.2

shows the chemical structures of deltamethrin’s major degradation products. At this 

time, except for alpha-R-deltamethrin, they are not considered stressors. 

Another potential source of deltamethrin is tralomethrin. Tralomethrin is another 

synthetic pyrethroid that, upon degradation, yields deltamethrin as its major 

transformation product. In the risk assessment, the exposure to deltamethrin due to the 

use of tralomethrin will be addressed qualitatively. (For additional information about 

tralomethrin, please, refer to DP Barcode 365550.) 

Table 3.2. Major Transformation Products of Deltamethrin 

Common 

Name Chemical Name Structure 

alpha-Rdeltamethrin 

(R)-α-cyano-3-phenoxybenzyl 

(1R,3R)-3-(2,2-dibromovinyl)-2,2-

dimethylcyclopropane-carboxylate 

(R)-alcohol (1R)-cis acid of deltamethrin 

(structure not provided) 

m-PBA or 

mPBAc or 

3-PBA 

(CAS No. 

3739-38-6) 

3-phenoxybenzoic acid 

O

OH

O

3-

PBAldehyde 

(CAS No. 

39515-51-0) 

3-phenoxybenzaldehyde 

O

H

O
10

Table 3.2. Major Transformation Products of Deltamethrin 

Common 

Name Chemical Name Structure 

Decamethrinic 

Acid or cisBr2CA (CAS 

No. 53179-78-

5) 

(lR-cis)-3(2,2-dibromoethyl)-2,2-

dimethylcyclopropanecarboxylic acid 

Br

Br

OH

O

 

3.1. Overview of Pesticide Usage

A summary of all agricultural use patterns for deltamethrin is shown in Table 3.3. 

Table 3.3. Summary use information for deltamethrin, based on LUIS Report Table A2, 

dated 06/24/09, and evaluation of two labels (EPA Reg. Nos. 264-1007 and 264-1011). 

USE 

SINGLE APP. 

RATE (lb. 

a.i./A) 

NUMBER 

OF APPS.

SEASONAL 

APP. RATE 

(lb. a.i./A) 

INTERVAL 

BETWEEN 

APPS. (days) APP. METHOD PHI (days) 

Globe artichoke 0.028 5 0.14 3 Aerial, 

Ground Spray 

or Dust 

3 

Canola, crambe, rapeseed 0.009 2 0.018 7 Aerial or 

Ground Spray 

7 

Corn, field 0.022 5 0.095 21 Aerial or 

Ground Spray 

21 

Corn, pop 0.022 5 0.095 21 Aerial, 

Ground Spray 

or Dust 

21 

Corn, sweet 0.028 16 0.45 1 Aerial, 

Ground Spray 

or Dust 

1 

Cotton 0.030 10 0.3 5 Aerial or 

Ground Spray 

21 

Cucurbit crop group 9

(cantaloupe, chayote, Chinese 

waxgourd, citron melon, 

cucumber, gherkin, gourds, 

Momordica species, 

muskmelon, pumpkin, squash, 

watermelon) 

0.028 6 0.168 3 Aerial, 

Ground Spray 

or Dust 

3 

Fruiting vegetables crop 

group 8 (eggplant, groundcherry, pepinos, peppers, 

tomatillo, tomato) 

0.028 6 0.168 5 Aerial, 

Ground Spray 

or Dust 

1 
11

Table 3.3. Summary use information for deltamethrin, based on LUIS Report Table A2, 

dated 06/24/09, and evaluation of two labels (EPA Reg. Nos. 264-1007 and 264-1011). 

USE 

SINGLE APP. 

RATE (lb. 

a.i./A) 

NUMBER 

OF APPS.

SEASONAL 

APP. RATE 

(lb. a.i./A) 

INTERVAL 

BETWEEN 

APPS. (days) APP. METHOD PHI (days) 

Tomato 0.011 NS NS 7 Dust, 

Shaker Can 

NS 

Bulb vegetables crop 

group 3 (garlic, leeks, onion, 

shallots) 

0.028 4 0.112 5 Aerial, 

Ground Spray 

or Dust 

1 

Pome fruits crop group 11

(apple, crabapple, loquat, 

mayhaw, pear, oriental pear, 

quince) 

0.022 1-2 0.042 7 Aerial or 

Ground Spray 

21 

Root vegetables crop 

subgroup 1B (except 

sugarbeet) (carrot, celeriac, 

turnip-rooted chervil , chicory, 

edible burdock, garden beet, 

ginseng, horseradish, parsley 

(turnip-rooted), parsnip, radish, 

oriental radish, rutabaga, salsify, 

black salsify, Spanish salsify, 

skirret, turnip) 

0.028 5 0.14 3 Aerial, 

Ground Spray 

or Dust 

3 

Tuberous and corm 

vegetables crop subgroup 

1C (potato, sweet potato, 

arracacha, arrowroot, Chinese 

artichoke, Jerusalem artichoke, 

edible canna, bitter and sweet 

cassava, chayote (root), chufa, 

dasheen, ginger, leren, tanier, 

tumeric, yam bean, true yam) 

0.028 5 0.14 3 Aerial, 

Ground Spray 

or Dust 

3 

Sorghum 0.022 2 0.045 Not 

Specified 

Aerial or 

Ground Spray 

14 

Soybeans 0.028 4-5 0.1 Not 

specified 

Aerial or 

Ground Spray 

21 

Sunflowers 0.018 2-3 0.045 Not 

specified 

Aerial or 

Ground Spray 

21 

Tree nuts crop group 14

(almond, beech nut, Brazil nut, 

butternut, cashew, chestnut, 

chinquapin, filbert, hickory nut, 

macadamia nut, pecan, 

pistachio, walnut) 

0.033 5 0.165 7 Aerial or 

Ground Spray 

(foliar or 

dormant)

21 

The Label Use Information System (LUIS report) & Usage/Label Use Reports for 

Deltamethrin (provided by BEAD) was based on a partial listing of labels, due to the 

large number of labels available for review; use data is not based on an exhaustive review 

of the entire population of labels. Section 3 labels or major producers labels, along with 
12

all State and Local Needs (SLNs) labels, are included in the LUIS report. These data 

represent the major uses of this chemical. 

Potential application methods include ground and aerial spray, chemigation spray, 

sprinkler irrigation (apparently no ULV), and dust application. 

The labels for deltamethrin require a buffer zone of 10 ft around certain bodies of water, 

such as lakes, reservoirs, rivers, permanent streams, marshes or natural ponds, estuaries 

and commercial fish farm ponds, so as to allow growth of a maintained vegetative filter 

strip. The agricultural products should not be applied by ground equipment within 25 ft 

or by aerial equipment within 150 ft of freshwater or estuarine/ marine bodies of water. 

Inspection of the use information for tralomethrin and deltamethrin found one product 

that contains both active ingredients. Deltamethrin is the major degradate of tralomethrin 

in the environment. The product, HR 20900 (EPA Reg. No. 34147-10), is for use on 

cotton via ground or aerial applications (no ULV). The product contains 1 lb a.i./gallon 

(0.5 lb of tralomethrin and 0.5 lb of deltamethrin/gallon) and the maximum seasonal total 

application rate is 0.20 lb a.i./A/growing season. 

Available toxicity data for environmental mixtures of deltamethrin with other pesticides 

will be presented as part of the ecological risk assessment. It is expected that the toxic 

effect of deltamethrin, in combination with other pesticides used in the environment, is 

likely to be a function of many factors including but not necessarily limited to: (1) the 

exposed species, (2) the co-contaminants in the mixture, (3) the ratio of deltamethrin and 

co-contaminant concentrations, (4) differences in the pattern and duration of exposure 

among contaminants, and (5) the differential effects of other physical/chemical 

characteristics of the receiving waters (e.g. organic matter present in sediment and 

suspended water). Quantitatively predicting the combined effects of all these variables 

on mixture toxicity to any given taxa with confidence is beyond the capabilities of the 

available data and methodologies. However, a qualitative discussion of implications of 

the available pesticide mixture effects data regarding the confidence of risk assessment 

conclusions will be addressed as part of the uncertainty analysis. 

Piperonyl butoxide and MGK are commonly used in formulations with pyrethroids. For 

deltamethrin, one active product registration exists for a ready-to-use solution (Reg. # 

73049-389). Another currently active registration exists for the formulation intermediate 

of the ready-to-use solution (Reg. # 73049-210). Piperonyl butoxide acts as a potentiator 

in both mammals and insects because the pyrethroid is not metabolized and excreted as 

quickly (Barile, 2004; Hodgson and Smart, 2001). Exposure to pyrethroids along with 

piperonyl butoxicide increases the toxicity of the pyrethroids (Weston & Lydy, 2010). 

MGK-264, another potentiator/synergist used with pyrethroids, has similar effects as 

those observed for piperonyl butoxide (Hodgson and Smart, 2001). No current 

deltamethrin registrations exist for a product with MGK-264. 

The Agency routinely assesses potential exposure to formulations by examining acute 

exposure to spray drift. Acute toxicity data on the formulation is compared to potential 
13

exposure to spray drift. The sole active deltamethrin registration that contains piperonyl 

butoxide is a residential spray can use. The spray drift associated with this use will be 

minimal. Therefore, a quantitative assessment of the potential aquatic exposure to the 

formulation containing piperonyl butoxide is not necessary. However, piperonyl butoxide 

and/or MGK from other pyrethroid applications could interact with tralomethrin in the 

environment or the additives could be applied co-currently as a tank mix. Therefore, 

potential interactions will be discussed qualitatively in the risk assessment. 

A summary from the Screening Level Usage Analysis (SLUA) for deltamethrin is 

provided in Table 3.4. 

Table 3.4. Summary of Screening-Level Estimates of Agricultural Uses of 

Deltamethrin (SLUA, dated 03/16/09). 

Percent (%) Crop Treated 

Crop lb a.i. Average Maximum 

Almonds <500 <1 <2.5 

Apples <500 <1 <2.5 

Artichokes <500 15 20 

Corn <500 <1 <2.5 

Cotton 6,000 <2.5 <2.5 

Onions <500 <1 <2.5 

Pears <500 5 5 

Potatoes <500 <1 <2.5 

Sorghum 1,000 <1 <2.5 

Soybeans <500 <1 <2.5 

Sunflowers <500 <1 <2.5 

Sweet Corn <500 <1 <2.5 

Walnuts <500 <1 <2.5 

All numbers are rounded. '<500' indicates less than 500 pounds of active ingredient. '<2.5' indicates less 

than 2.5 percent of crop is treated. '<1' indicates less than 1 percent of crop is treated. 

The sources of the SLUA include the USDA-NASS, Private Pesticide Market Research, the National 

Pesticide Use Database (NPUD 2002) of the CropLife America Foundation and California Department of 

Pesticide Regulation (CDPR) data. The information reflects amalgamated data developed by the Agency 

and are in a releasable format. 

The U.S. Geological Survey (USGS) pesticide use maps (Fig. 3.1) show regional scale 

patterns in use intensity within the United States. The USGS pesticide maps are based on 

State level estimates of pesticide use rates for individual crops, which have been 

compiled by the National Center for Food and Agricultural Policy (NCFAP) for 1999 

through 2004, and on the 2002 Census of Agriculture for county crop acreage crop. 

The only use for deltamethrin included in the map at the time (through 2002) was cotton, 

constituting 100% of the use and with 9,448 lb applied mostly through a belt including 

the states of VA, NC, SC and GA. Multiple uses have been added to the chemical as 

indicated above. 
14

Fig. 3.1. Estimated Use of Deltamethrin in 2002

Note of Caution: The pesticide use maps available from the web 

(http://water.usgs.gov/nawqa/pnsp/usage/maps/compound_listing.php?year=02 ) show the average annual pesticide use intensity expressed as 

average weight (in pounds) of a pesticide applied to each square mile of agricultural land in a county. The area of each map is based on statelevel estimates of pesticide use rates for individual crops that were compiled by the CropLife Foundation, Crop Protection Research Institute 

during based on information collected during 1999 through 2004 and on 2002 Census of Agriculture county crop acreage. The maps do not 

represent a specific year, but rather show typical use patterns over the five year period 1999 through 2004. Use intensity rates are expressed as 

the pounds applied per square mile of mapped agricultural land in a county. The area of mapped agricultural land for each county was obtained 

from an enhanced version of the 1992 USGS National Land Cover Data (NLCD). The key limitations of the data used to produce these maps 

include the following: (1) state use coefficients represent an average for the entire state and consequently do not reflect the local variability of 

pesticide management practices found within states and counties, (2) pesticide use estimates are not for a specific year, but represent typical use 

patterns for the five year period, (3) state pesticide use coefficients may not have been available for all states where a pesticide may have been 

applied to agricultural land, and therefore, are not displayed on the maps, (4) the county crop acreage is based on the 2002 Census of 

Agriculture and may not represent all crop acreage because of Census nondisclosure rules, and (5) agricultural land area used to calculate the 

pesticide use intensity and display the data was derived from 30-meter satellite remote sensing data that may over estimate or underestimate the 

actual agricultural land area. The maps are not intended for making local-scale estimates of pesticide use, such as estimates at the county level. 

Please refer to Method for Estimating Pesticide Use for a detailed discussion of how the pesticide use data were developed. 

In addition to the classical agricultural use sites, deltamethrin has multiple other uses. 

These uses include food/feed use sites and non-food/ non-feed use sites. Deltamethrin 

may be used in multiple urban environments. Many of these uses are classified as 

outdoor residential such as household/ domestic dwellings, ornamental lawns and turf, 

ornamental woody shrubs and vines, paths/patios, paved areas (private roads/sidewalks), 
15

pet living/sleeping quarters, garbage cans, and residential lawns. Table 3.5 provides a 

summary of the terrestrial nonagricultural use sites for deltamethrin. Uses such as spot 

treatment or crack and crevice are included, and application methods vary. Many of 

these uses could involve substantive exposure to wildlife, specifically, aquatic organisms, 

and they will be assessed accordingly (e.g., turf, golf course turf, household premises, 

rights of way, ornamentals/ shade trees, recreational areas, urban areas and residential 

lawns). 

Table 3.5. Uses Classified as Terrestrial Nonagricultural for Deltamethrin 

Use 

Max. App. Rate/ 

units

Max. No. 

Apps./ Year 

Max. App. 

Rate per 

Year 

Min. App. 

Int./ days 

animal kennels/sleeping quarters (commercial) 1 application NS NS 7, 14, 30, NS 

automobiles, taxis, limousines, recreational vehicles, & tires 1 application NS NS 7, 14, 30, NS 

barley 5.0x10-5 lb cwt NS NS NS 

barns/barnyards/auction barns 2 sec NS NS NS 

commercial storages/warehouses premises 1 application NS NS 7, 14, 30, NS 

commercial/industrial lawns 0.131 lb/A and others NS NS 7 

commercial/institutional/industrial premises/equipment (outdoor) 1 application NS NS 30, NS 

compost/compost piles 1 application NS NS NS 

corn (unspecified) and corn, pop 2.8x10-5 lb cwt NS NS NS 

eating establishments 1 application NS NS 7, NS 

fencerows/hedgerows 1 application NS NS NS 

golf course turf 

0.131 lb/A, 0.0034 lb 

1K sq.ft, 0.0097 

lb/mound NS NS 7 

household/domestic dwellings outdoor premises Various NS NS 

7, 21, 28, 30, 

AN, NS 

industrial areas (outdoor) 1 application NS NS 30 

nonagricultural outdoor buildings/structures 0.0034 lb 1K sq.ft and 

others NS NS 7, NS 

nonagricultural rights-of-way/fencerows/hedgerows 0.0026 lb 1K sq.ft, 

0.0039 lb/mound NS NS 7, NS 

oats 2.6x10-5 lb cwt NS NS NS 

ornamental and/or shade trees 

0.0050 lb 1K sq.ft and 

others NS NS 7, 21, NS 

ornamental grasses 0.0016 lb 1K sq ft NS NS 7, NS 

ornamental herbaceous plants 

0.0050 lb 1K sq.ft and 

others NS NS 

7, 21, 28, NS, 

AN 

ornamental lawns and turf 

0.131 lb/A, 0.0034 lb 

1K sq.ft and others NS NS 7, 21, 28, NS 

ornamental nonflowering plants 

0.0050 lb 1K sq.ft and 

others NS NS 7, 21, 28, NS 

ornamental sod farm (turf) 

0.131 lb/A, 0.0034 lb 

1K sq.ft, 0.0097 

lb/mound & others NS NS 7 

ornamental woody shrubs and vines 

0.0050 lb 1K sq.ft, 

2.6x10-5 lb/mound & 

others NS NS 7, 21, 28, NS 

paths/patios 

0.0050 lb 1K sq.ft, 

0.0050 lb/mound, 

6.2x10-4 lb/sq ft NS NS 

7, 21, 28, 30, 

AN, NS 

paved areas (private roads/sidewalks) 

0.0026 lb 1K sq.ft, 

0.0039 lb/mound NS NS 7, 30, NS 

pet living/sleeping quarters 

0.0050 lb 1K sq.ft and 

others NS NS 

7, 14, 21, 30, 

NS 

recreation area lawns 

0.131 lb/A, 0.0034 lb 

1K sq.ft, 0.0097 

lb/mound NS NS 7 

recreational areas 1 application NS NS 7, 30, NS 

refuse/solid waste containers (garbage cans) 

0.0026 lb 1K sq ft, 

others NS NS 7, 14, 30, NS 

refuse/solid waste sites (outdoor) 0.0050 lb 1K sq.ft, NS NS 7, 21, 30, NS 
16

Table 3.5. Uses Classified as Terrestrial Nonagricultural for Deltamethrin 

Use 

Max. App. Rate/ 

units

Max. No. 

Apps./ Year 

Max. App. 

Rate per 

Year 

Min. App. 

Int./ days 

0.0050 lb/mound 

residential lawns 

0.131 lb/A, 0.0034 lb 

1K sq.ft, 0.0097 

lb/mound NS NS 7, NS 

rice, rye, sorghum 5.0x10-5 lb cwt NS NS NS 

specialized animals various NS NS 7, 14 

urban areas 

0.0050 lb 1K sq.ft, 

0.0050 lb/mound, 

others NS NS 21 

wheat 3.0E-5 lb bu NS NS NS 

wide area/general outdoor treatment (public health use) 1 application NS NS NS 

NS = Not Specified; AN = As Needed. Data obtained from LUIS Report, Table 1. 

In addition, there are numerous other indoor non-food use sites like for example, 

bathroom premises, cadavers, caskets (and also morgues and mortuaries), carpets, 

commercial transportation facilities, commercial/ institutional/ industrial premises 

(indoors), diaries and cheese processing plant premises, dogs/ canines (collars) (and also 

pet living quarters), drainage systems, eating establishments, feed mills/ feed processing 

plants, food processing plant premises, food stores/ markets/ supermarket premises, 

greenhouses, hospital/ medical institutions premises, household/ domestic dwellings, 

human bedding/ mattresses, public building/ structures, sewage systems, ships and boats, 

and zoos. These labeled uses will be assessed only qualitatively in the ecological risk 

assessment, as they present minimal chance for exposure to nontarget organisms in 

aquatic or terrestrial environments. 

In a recent study (Stout II, et al. 2009), conducted by the US Department of Housing and 

Urban Development, in collaboration with the Agency, several chemicals were surveyed 

on floors of occupied homes. The survey included several synthetic pyrethroids like 

deltamethrin. Deltamethrin was detected with a frequency of 27%, illustrating that this 

chemical is commonly applied in homes. Weston et al. 2005, studied the presence of 

synthetic pyrethroids in Roseville, CA, selected as a typical suburban development. 

Sediments from creeks that drain subdivisions of single-family homes were found to be 

toxic to Hyalella azteca. The synthetic pyrethroids were considered to be the primary 

cause of the toxicity. Amweg et al. 2006 also studied synthetic pyrethroids in urban 

areas of CA and TN. Deltamethrin was found to be a contributor to the toxicity of 

sediments sampled. These are just a few examples that illustrate the high use of synthetic 

pyrethroids in urban settings and potential ecological repercussions. 

Deltamethrin is not among the constituents monitored by the National Water Quality 

Assessment (NAWQA), maintained by the U.S. Geological Survey. However, multiple 

articles from the literature document the presence of synthetic pyrethroids in both urban 

and agricultural sediments. For example, Weston et al. 2005 (see also above), reported 

that there were detectable amounts of deltamethrin at up to 46 ng/g in sediments of creeks 

and tributaries in Roseville, CA (Placer County). Out of 24 sampling sites, deltamethrin 

was detected in 14 sites (reporting limit <1 ng/g). Generally bifenthrin was the synthetic 

pyrethroid most detected and at highest concentrations. The authors indicate that the 

presence of synthetic pyrethroids was not likely to be due to agricultural uses. In Placer 
17

County, the use of synthetic pyrethroids for agricultural purposes was reported to amount 

to around 1%, with no agricultural use of the chemical deltamethrin. Budd et al. 2007 

sampled sediments in mixed land (urban and agricultural) in the San Diego Creek in 

Newport Bay Watershed in southern California. Bifenthrin and fenpropathrin were 

among the most frequently detected synthetic pyrethroids. The researchers found that the 

concentration of synthetic pyrethroids was generally lower in residential or commercial 

areas as opposed to agricultural sites. Also, the frequency of detections of pyrethroids 

was higher during the wet season (e.g. for deltamethrin 28% during the wet season vs.

11% during the dry season). Trimble et al. 2009 screened a previously referenced 

database of 24 pesticides and 94 urban sediment samples (with minimal agricultural or 

industrial contribution) collected from creeks and streams throughout central and 

northern California. The synthetic pyrethroids and chlorpyrifos were the pesticides 

detected more frequently. After normalizing the chemical concentrations for organic 

carbon “to provide better estimates of the biologically available chemical fractions,” all 

the seven pyrethroids monitored had levels exceeding the established level of interest, 

LOI (defined as 0.005 toxic units, TU) for at least one sample. Deltamethrin exceeded 

0.5TU in greater than 5% of the samples (so did bifenthrin, cypermethrin, cyfluthrin and 

lambda-cyhalothrin). Deltamethrin’s frequency of occurrence was 49%. It was detected 

in a large number of samples, but it decreased in relevance when the level of exceedance 

was established at 0.5TU. Therefore, it was considered of “moderate concern” because it 

did not contribute frequently or substantially to the overall TU values in the samples. In 

a study by Weston et al. 2009, bifenthrin was the most frequently detected pyrethroid 

from runoff waters from Roseville and Elk Grove urban sites. Cyfluthrin and permethrin 

were also frequently detected. Deltamethrin was observed only on occasion and at 

relatively low concentrations (<3 ng/L); however, one sample from Elk Grove, obtained 

during a November rainfall, had the highest concentration of deltamethrin of any 

pyrethroid (with 252 ng/L). During the dry season, deltamethrin was not detected in 

either site, while during the wet season, it was found with a frequency of detection of 

25% (in both sites). Amweg et al. 2004 found that the average sediment 10-day LC50 for 

deltamethrin was 0.79 μg/gOC. 

Weston 2007 says that, “Contrary to popular perception, non-agricultural use of pyrethroids 

far exceeds agricultural use, at least in California, one of the few areas where data are 

available. A similar situation is likely elsewhere where there is substantial urban 

development. Whereas agricultural use of pyrethroids in California is about 300,000 lb/yr, 

non-agricultural commercial use (mostly applications done by professional pest control 

firms) is currently about 700,000 lb/yr. Retail sales to homeowners are not included in this 

non-agricultural figure, but are probably about another 100,000 lb/yr. Some of the major 

urban uses of pyrethroids include cypermethrin and permethrin for termite control, 

permethrin to maintain landscaping, and bifenthrin and cyfluthrin for a variety of pests 

around homes.” 

Another potential source of deltamethrin is tralomethrin. Tralomethrin is another synthetic 

pyrethroid that, upon degradation, yields deltamethrin as its major transformation product. In 

the risk assessment, the exposure to deltamethrin due to the use of tralomethrin will be dealt 

with qualitatively.
18

3.2. Environmental Fate and Transport 

A summary of environmental fate/transport properties of deltamethrin is included in 

Table 3.6. 

Table 3.6. Summary of Environmental Fate and Transport Properties of Deltamethrin

PARAMETER VALUE(S) (units) SOURCE

Hydrolysis Half-life 

 pH 5, 7, 9; (25oC) 

Stable at pH 5 and 7. Half-life of 2.5 days at pH 9. 

BR2CA and m-PB Aldehyde 

MRID 41651038, 

Supplemental 

Aqueous Photolysis - Halflife (pH 5) 

64 and 84 days for benzyl and gem labels, respectively or 

considered relatively stable. cis-BR2CA 

MRID 42114818, 

Acceptable 

Soil Photolysis - Half-life The half life was 9 days, but, at the end of the 30 day study, 

both the irradiated and dark control samples had around the 

same amount of parent material. Considered relatively 

stable to photodegradation on soil. 

MRID 42114819, 

Acceptable 

Aerobic Soil Metabolism 

Half-life 

Dubbs fine SL and Memphis SiL (soil pHs 5.8-5.9) were 

tested at two application rates and with two radiolabels, first 

order half-lives as follows (half-lives provided for cyano and 

phenoxy labels, respectively: SL: at 0.02 lb/A: 52.5, 54.6 

days, at 0.20 lb/A 50.2, 55.0 days; for the SiL: at 0.02 lb/A 

46.2, 50.2 days, at 0.20 lb/A 45.6, 52.5 days. It appeared 

that the application rate did not affect the rate of reaction. 

Additional study conducted with Dubbs fine SL at 10-40oC, 

the half-lives obtained at 25oC were 19.7 and 24.6 days for 

the cyano and vinyl labels, respectively. 

Alkaline Arizona SL (pH 8.1) half-lives 22 and 26 days 

MRID 41677404, 41677405, 

42114820 

Acceptable 

Anaerobic Soil 

Metabolism - Half-life 

Alkaline SL half-lives 32, 36 days for the benzyl and gem 

labels, respectively. BR2CA max. 52%. 

[Additional study performed with deltamethrin: SL system – 

In the study deltamethrin was a major degradate, with halflives of 42.9-46.7 days. Also 3-PBA (20.6%) and BR2CA 

(40.6-57.0%)] 

MRID 42114821 

Acceptable 

 [Additional study performed 

on deltamethrin: 44814505] 

Anaerobic Aquatic 

Metabolism - Half-life 

Not Available Not Available 

Aerobic Aquatic 

Metabolism - Half-life 

Both systems from the Netherlands: System I, L: 25.9 days; 

System II, SL: 120 days – half-lives include deltamethrin 

plus α-R-deltamethrin. 

Major – α-R-deltamethrin (21-24% at 7-14 d) and 

unidentified volatiles (possibly CO2) – minor 3-PB Acid 

(≤7%) & RU 53605. Systems from the Netherlands. Halflives based on the sum of deltamethrin plus the alpha-Risomer of deltamethrin. 

MRID 44977005 

Supplemental 

Organic Carbon Partition 

Coefficient for Parent 

(KOC) 

392000, 577000, 204000, 460000 mL/gOC, 

for AK SiL, GA SiL, TX SL, and MS SiClL.

Immobile (FAO 2000) 

Soil Partition Coefficient 

for Parent (Kd) 

3000, 4750, 960, 3740 mL/g, 

for AK SiL, GA SiL, TX SL, and MS SiClL 

MRID 41651039, 42976501 

Acceptable, Partial (the 

additional mobility 

information is provided in 

Table 3.8). 
19

Table 3.6. Summary of Environmental Fate and Transport Properties of Deltamethrin

PARAMETER VALUE(S) (units) SOURCE

Terrestrial Field 

Dissipation 

 Half-life 

Louisiana cotton 231 days, long half-life observed, both for 

the bareground and the cropped plot; this soil had a lower 

organic matter content and it was postulated that it was the 

reason for the longer half-lives. California cotton 37 d for 

bareground plot, and 40 d for cropped plot. Minnesota corn 

69 d for bareground plot, and 14 days for the cropped plot. 

Studies provide limited information about the degradates. 

MRID 42137505, 42773903, 

42114822 

Acceptable 

Biaccumulation in Fish 

(BCF) 

698X whole body, 189X edible portion, depuration was 

moderately slow (50% between 3-7 days, and 70-75% after 2 

weeks) 

MRID 41651040, 43072701, 

43072702 

Acceptable 

When applied to the field, deltamethrin is likely to partition to the soil and organic matter in 

the crops; deltamethrin appears to bind strongly to soil and organic matter, though binding is 

not instantaneous or immediate (KOW = 34,200 and KOC»100,000; immobile, FAO 2000). It 

is not expected to leach into subsurfaces. It may reach aquatic environments via spray drift 

or in runoff events accompanied by erosion. Deltamethrin appears to be moderately to 

highly persistent in terrestrial environments (aerobic soil metabolism 20-55 days; terrestrial 

field dissipation 14-231 days). It has the potential to persist in aquatic environments, where 

it may partition with the sediment and has the potential to affect benthic and epibenthic 

organisms (aerobic aquatic metabolism 26-120 days; anaerobic soil metabolism 32-47 

days). Due to its low vapor pressure (9.32 x 10-11 mmHg) and Henry’s Law Constant 

(3.1x10-7 atm-m3/mol), deltamethrin is unlikely to volatilize substantially. 

Deltamethrin is relatively stable at pH 5 and 7. However, it rapidly degraded (half-life of 

2.5 days) at an alkaline pH of 9 to form (lR-cis)-3-(2,2-dibromoethyl)-2,2-dimethylcyclopropanecarboxylic acid (Br2CA, <0.l5 μg/L) and 3-phenoxybenzaldehyde (3-

PBaldehyde, 3.42 μg/L). It does not appear to photodegrade substantially in aqueous 

solutions (half-lives 64 & 84 days). Although the soil photolysis study gave a half-life of 9 

days, considerable degradation was occurring in the dark controls as well. 

Based on acceptable aerobic soil metabolism data, deltamethrin in Dubbs fine sandy loam 

and Memphis silt loam soil, tested at two application rates and with two radiolabels, 

degraded at moderate rates (first order half-lives 19.7-55.0 days) to form DBVA (or Br2CA) 

(<10%) and CO2. Over the l28 day incubation period, 62-77% and 52-60% of the 14Ccyano- and the 14C-phenoxy-labelled parent evolved as 14CO2. The proposed routes of 

degradation are ester hydrolysis and microbial-mediated mineralization to CO2. An 

additional aerobic soil metabolism study was submitted for an alkaline Arizona sandy loam 

(pH 8.l), which yielded somewhat lower half-lives of 22 and 26 days. For the gem label 

study, Br2CA was formed, which peaked at 23-26% on day 30 and 14, respectively. Given 

the fact that the pH of the latter study was higher, the half-lives were lower, which is what 

was expected from the hydrolysis study. 

 

In an anaerobic soil metabolism study, deltamethrin degraded in an Arizona sandy loam (pH 

8.l) with a half-life of 32-36 days for the benzyl and gem labels, respectively. For the gem 

label experiment, only l metabolite, Br2CA or decamethrinic acid, was found at 49% of the 
20

applied radioactivity by day 30 and remained at about this level on days 59 (52%) and 90 

(48%). For the benzyl label, the only metabolite identified was m-PB Acid, which was only 

detected in a day 30 sample, accounting for only 3% of the applied radioactivity. This study 

is not representative of a neutral or acidic pH soil, which is expected to yield higher halflives. 

In aerobic aquatic metabolism study, consisting of a loam or a sandy loam test systems from 

the Netherlands, the half lives for the whole systems were 26 and 120 days, respectively. 

The major transformation product was the α-R-isomer of deltamethrin, at up to 24% in the 

SL. A new anaerobic aquatic metabolism study should provide additional valuable 

information on a test system that is completely aerobic. No anaerobic aquatic 

metabolism study is available for review. 

In batch equilibrium studies, deltamethrin was found to be immobile (KOC>100,000, FAO 

classification, FAO 2000) and had Freundlich Kd's of 3,790 for a Mississippi SiClL, 3000 

for an Arkansas SiL, 4750 for a Georgia SiL, and 960 for a Texas SL. KOC's ranged from 

204000 to 577000. Although deltamethrin is tightly bound, adsorption was not immediate, 

because equilibrium times were 4-24 hours. 

In three terrestrial field dissipation studies parent appeared not to be mobile in soil and 

degraded in l-2 months, except the Louisiana study, where the half-life was almost 8 

months. The longer half-life could fall within the range of normal field variability and the 

Louisiana soil was the lowest in organic matter, which could result in the lowest amount of 

soil binding and soil microbial degradation. No clear pattern of degradate formation and 

decline was seen, possibly because the low application rate and 6" sampling intervals 

resulted in soil dilution, so degradates were not detected. 

In fish bioconcentration study, deltamethrin had bioconcentration factors of 189x and 3630x 

in edible and visceral fish tissues, respectively. The whole body BCF of 698x was 

calculated from edible and visceral fish tissue results (as opposed to a direct measurement of 

whole body). The majority of the radioactive residue found in fish was parent, accounting 

for 78 and 83% of the total radioactive residue in edible and visceral fish tissues, 

respectively. No depuration study was done; however, the depuration rate (about 50% 

between days 3-7 and 70-75% after 2 weeks of depuration) from a previously submitted 

study was considered (MRID#416510-40, similar BCF's). 

Table 3.7 provides a summary of the various degradation products formed by each 

process in the studies reviewed for deltamethrin. 

Table 3.7. Summary of degradate formation from degradation of deltamethrin. 

DEGRADATE and MAXIMUM CONCENTRATION 

STUDY TYPE 

cis-Br2CA 

(% applied)

Deltamethrin Isomers 

(% applied)

m-PBAc or m-PBald 

(% applied) SOURCE 

Hydrolysis <0.15 μg/L (vs. app. 

rate 10.0 μg/L) 

_ m-PBald: 3.37 μg/L at 

30 days (vs. app. rate 

10.0 μg/L) 

MRID 41651038 
21

Table 3.7. Summary of degradate formation from degradation of deltamethrin. 

DEGRADATE and MAXIMUM CONCENTRATION 

STUDY TYPE 

cis-Br2CA 

(% applied)

Deltamethrin Isomers 

(% applied)

m-PBAc or m-PBald 

(% applied) SOURCE 

Aqueous Photolysis 3% at day 21 m-PBAc 11% at day 

21 

MRID 42114818 

Soil Photolysis 40% at 21 days 

(samples contained 

more cis- than transBr2CA; it was 

present also in dark 

control) 

R-S epimerization 

was reported, but no 

trans-deltamethrin 

observed 

m-PBAc 11% at 14 

days in preliminary 

study 

MRID 42114819 

Aerobic Soil Metabolism 23-26% at 14-30 

days 

_ _ MRID 41677404, 

41677407, 

42114820 

Anaerobic Soil Metabolism 49% by day 30, and 

remained at that 

level through day 90 

(48-52% during the 

period) 

_ m-PBAc 3% at 30 

days 

MRID 42114821 

Aerobic Aquatic 

Metabolism 

_ 24% at day 14 m-PBAc (≤7%) MRID 44977005 

Terrestrial Field 

Dissipation 

Detected in one 

study. 

2-4 ppb detected 

sporadically. transdeltamethrin 

detected in one 

study. 

Not monitored MRID 42114822, 

42137505, 

42773903 

It appears that m-PB-Acid and m-PB-aldehyde are not very persistent in the environment. 

However, Br2CA appears to persist much more than the former compounds. It was 

observed in laboratory studies and in the field. These degradates are the result of the ester 

rupture in the parent molecule. Another transformation product that was monitored in 

various of the studies (soil photolysis and aerobic aquatic metabolism) was the α-Rdeltamethrin, an isomer of deltamethrin. It appears that it was not measured or could not be 

distinguished from the parent in other laboratory studies. 

Table 3.8 provides a summary of batch equilibrium data for 3-PB-acid and decamethrinic 

acid (cis-Br2CA). 

 Table 3.8. Summary of mobility data for deltamethrin degradates 

PARAMETER VALUE(S) (units) SOURCE

Organic Carbon Partition 

Coefficient, 3-PB-Ac (KOC) 

288, 190, 105, 50.7 mL/gOC 

(for Cl, SiClL, SL & ClL) 

Soil Partition Coefficient, 

3-PB-Ac (Kd) 

0.668, 1.54, 2.68, 1.34 

mL/g (for Cl, SiClL, SL & ClL) 

MRID 44977006, 

Acceptable, Partial 

(additional mobility 

information in Table 3.6) 

(m-Phenoxybenzoic Acid, 

m-PBA or 3-PBA) 
22

 Table 3.8. Summary of mobility data for deltamethrin degradates 

PARAMETER VALUE(S) (units) SOURCE

Organic Carbon Partition 

Coefficient, cis-Br2CA, (KOC) 

38.2, 46.8, 43.7, 23.0, 10.1 mL/gOC

for AZ SL#2, AZ SL#3, SiClL, SL, ClL 

Soil Partition Coefficient, 

cis-Br2CA (Kd) 

0.09, 0.11, 0.36, 0.59, 0.27 mL/g 

for AZ SL#2, AZ SL#3, SiClL, SL, ClL 

MRID 42475908, 

Acceptable, Partial 

(Decamethrinic acid, 

RU 23441 or cis-Br2CA) 

A major degradate of deltamethrin, cis-Br2CA or decamethrinic acid, appeared to be mobile 

in 5 soils (Freundlich Kds <l, and KOC‘s=10.1-46.8, FAO mobility classification, FAO 

2000). In addition, for the degradate m-PB-Acid, Kd’s were in the range of 0.7-2.7 while the 

KOC’s were in the range of 51-288 (mobile to moderately mobile according to FAO mobility 

classification, FAO 2000). Of these degradates, Br2CA has the potential to leach to 

subsurfaces, or to reach adjacent bodies of water via runoff events, most likely dissolved in 

the water.

 

4. Receptors 

4.1. Aquatic and Terrestrial Effects 

The receptor is the biological entity that is exposed to the stressor (EPA, 1998). Due to 

the outdoor uses of deltamethrin, the types of receptors that may be exposed include both 

aquatic and terrestrial receptors, such as birds, reptiles, mammals, amphibians, freshwater 

and estuarine/ marine fish, non-target terrestrial & aquatic invertebrates and terrestrial & 

aquatic plants. This list may not be comprehensive. Spray drift and runoff exposures are 

expected for both ground and aerial applications of deltamethrin. Consistent with the 

process described in the Overview Document (EPA, 2004), this risk assessment uses a 

surrogate species approach in its evaluation of deltamethrin. Toxicological data 

generated from surrogate test species, which are intended to be representative of broad 

taxonomic groups, are used to extrapolate to potential effects on a variety of species 

(receptors) included under these taxonomic groupings. 

Tables 4.1 and 4.2 provide a summary of the taxonomic groups and the surrogate species 

tested to help understand potential acute ecological effects of pesticides to these nontarget taxonomic groups. In addition, the tables provide a preliminary overview of the 

potential acute toxicity of deltamethrin by providing the acute toxicity classifications. 

Terrestrial Species 

The available toxicity data suggests that deltamethrin appears to be practically nontoxic 

on an acute basis to avian species based on a bobwhite quail (Colinus virginianus) single 

dose LD50 > 2250 mg/kg bw (MRID 00158273) and an 8-day dietary LC50 > 4640 mg/kg 

diet for the mallard duck (Anas platyrynchos) (MRID 00060723). Deltamethrin showed 

no adverse effects to reproduction at the highest concentration tested (NOAEC = 450 

mg/kg diet) in the two one-generation chronic studies conducted on the bobwhite quail 

and mallard duck (MRIDs 42114808 and 42114809). 
23

For mammalian toxicity, EFED will coordinate with HED to determine the most sensitive 

endpoints for acute and chronic studies. 

As expected for a registered insecticide, deltamethrin is highly toxic to nontarget 

terrestrial invertebrates. An acute contact study on honeybees (Apis mellifera) for 

deltamethrin technical produced an LD50 = 0.0015 μg/bee (MRID 42114815). In a foliage 

residual study conducted with deltamethrin EC (2.5% a.i.), 100% mortality occurred in 

honey bees exposed to direct contact at 0.01 – 0.015 lbs EC/A (0.00025 lbs a.i./A – 

0.000375 lbs a.i./A) and significant adverse effects (78% mortality) were still occurring 

when bees were exposed to alfalfa foliage 34 hours after treatment at the 0.015 lbs EC/A 

level (0.000375 lbs a.i./A) (MRID 42475905). In another foliage residual test, the RT25 at 

0.02 lbs a.i./A was estimated to be somewhere between 2 and 8 hours after treatment 

(MRID 42773902). 

Table 4.1 Summary of most sensitive endpoints from submitted terrestrial toxicity studies for deltamethrin. 

Species 

(common 

name)

Taxa 

Represented

Endpoint Mean Concentration

Test 

Substance 

(% a.i.) 

Citation 

MRID 

Acute 

Toxicity 

Classification 

Colinus 

virginianus 

(Bobwhite 

quail) 

LD50 > 2250 mg/kg bw 99.3 00158273 Practically 

nontoxic 

Anas 

platyrynchos 

(Mallard duck) 

LC50 > 4640 mg/kg diet 98 00060723 

NOAEC 450 mg/kg diet Colinus 

virginianus 

(Bobwhite 

quail) 

and 

Anas 

platyrynchos 

(Mallard duck)

Birds, terrestrialphase 

amphibians, and 

reptiles 

LOAEC NA 

99.4% 42114808 and 

42114809 

Practically 

nontoxic 

Apis mellifera

(Honey bee) 

Terrestrial 

invertebrates LD50 0.0015 μg/bee 99.7 42114815 Highly toxic 

1

Based on percent of normal hatchlings from three-week embryos. 

Aquatic Species 

 

Freshwater
24

Deltamethrin technical is very highly toxic to freshwater fish, with a 96-hour LC50 = 0.58 

μg a.i./L in the most sensitive acute test conducted on Lepomis gibbosus (Pumpkinseed 

sunfish) (MRID 00060721). In other tests with deltamethrin technical, the 96-hour LC50

= 0.91 μg a.i./L for coldwater rainbow trout (Oncorhynchus mykiss) and the 96-hour LC50

= 0.91 μg a.i./L for warmwater bluegill sunfish (Lepomis macrochirus) (MRIDs 

00158274 and 00158275). Deltamethrin EC is also considered to be highly toxic to the 

rainbow trout (Oncorhynchus mykiss) on an acute basis, with an LC50 = 0.25 μg a.i./L 

(MRID 41651013). A chronic freshwater life cycle fish study for deltamethrin technical 

resulted in a 28-day NOAEC=0.017 μg a.i./L and LOAEC = 0.035 μg a.i./L for fathead 

minnow (Pimephales promelas) based on reduced growth of females (MRID 42786802. 

An early life stage study with fathead minnow resulted in a NOAEC=0.022 μg a.i./L and 

a LOEC = 0.036 μg a.i./L for a 36-day test with larval growth as the most sensitive 

endpoint effected (MRID 42114814). 

Daphnia magna is used as the test species for freshwater invertebrates for both acute and 

chronic effects. Acute toxicity values for daphnids suggest that deltamethrin technical is 

highly toxic to freshwater invertebrates, with a 48-hour EC50 range from 0.57 μg a.i./L to 

3.5 μg a.i./L (MRIDs 44928701 and 00158276). In an acute toxicity test with 

deltamethrin EC (2.54% a.i.), the 48-hour EC50 = 0.11 μg a.i./L (MRID 41651014). 

Chronic toxicity to invertebrates is represented through Daphnia magna life cycle 

studies. In a daphnid chronic life-cycle test with deltamethrin, the NOAEC = 0.0041 μg/L 

and the LOAEC = 0.0089 μg/L based on adverse effects to growth and reproductive 

success at mean-measured concentrations (MRID 42114813). 

Estuarine/Marine

Estuarine/marine fish are represented by the sheepshead minnow (Cyprinodon 

variegatues). Acute toxicity studies indicates that deltamethrin is highly toxic to 

estuarine/marine fish, with an LC50 = 0.58 μg a.i./L for the technical material and an LC50

= 0.36 μg a.i./L for the EC (25.4% a.i.) (MRIDs 41651015 and 42114811). 

Estuarine/marine aquatic invertebrates are represented by the mysid shrimp (Mysidopsis 

bahia) and eastern oyster (Crassostrea virginica) with toxicity studies indicating 

deltamethrin is very highly toxic to both. In an acute study with mysid shrimp, the 96-

hour LC50 = 0.0037 μg a.i./L for deltamethrin technical, based on mean-measured 

concentrations (MRID 42114810). For the deltamethrin formulated product, an acute 

toxicity study with the mysid shrimp resulted in 96-hour LC50 = 0.0017 μg a.i./L (MRID 

42114812). In studies with the eastern oyster, the 96-hour EC50 = 12.0 μg a.i./L for 

deltamethrin technical and the 96-hour EC50 = 17.9 μg a.i./L for deltamethrin EC (2.48% 

a.i.), based on effects to shell deposition (MRIDs 41651016 and 41651017). No chronic 

estuarine/marine study with estuarine/marine invertebrates has been submitted for 

deltamethrin. 

Aquatic Studies with Deltamethrin and Tralomethrin Co-formulation

Six studies were submitted for the tralomethrin/deltamethrin co-formulated product, 

HR2900 or Striker EC (12.4% a.i. of tralomethrin and deltamethrin in approximately 
25

equal proportions). For freshwater fish, this co-formulated product has a 96-hour 

LC50=1.5 μg a.i./L for bluegill sunfish (MRID 43073903) and a 96-hour LC50=0.39 μg 

a.i./L for rainbow trout (MRID 43073904). The tralomethrin/deltamethrin co-formulation 

has a 48-hour EC50 of 0.18 for freshwater invertebrates, represented by Daphnia magna

(MRID 43073905). For estuarine/marine fish represented by the sheepshead minnow, the 

acute 96-hour LC50=0.49 μg a.i./L (MRID 43073906). Acute estuarine/marine 

invertebrate toxicity tests with mysids resulted in an LC50=0.021 μg a.i./L (MRID 

43073908) and LC50<110 μg a.i./L for eastern oysters (no endpoint was established 

because greater than a 50% reduction occurred at the lowest dose tested) (MRID 

43073907). 

For these studies on the tralomethrin and deltamethrin co-formulation, some uncertainty 

exists regarding the degree of the effect that can be attributed to the formulation (inerts 

and ingredients other than the active) and which are a result of the combining the two 

active ingredients. It is important to note that these studies give lower acute toxicity 

endpoints than either technical active ingredient or single active ingredient formulation 

alone for freshwater fish. 

Table 4.2. Summary of most sensitive endpoints from submitted aquatic toxicity studies 

for deltamethrin. 

Species 

(common name) 

Taxa 

Represented 

Endpoint Duration 

(hours) 

 Mean 

concentration 

(μg a.i./L) 

Citation 

MRID 

Acute 

Toxicity 

Classification 

 Lepomis gibbosus

(Pumpkinseed 

sunfish) 

LC50 96 0.58 00060721 

NOAEC Pimephales 0.017 

promelas 

(Fathead Minnow)

Freshwater fish 

and aquaticphase 

amphibians

LOAEC 

28 (days) 0.035 42786802 

Very highly 

toxic 

EC50 48 0.11 41651014 

NOAEC 0.0041 Daphnia magna 

(Water Flea) 

Freshwater 

Invertebrates 

LOAEC 

 21 (days) 0.0089 42114813 

Very highly 

toxic 

Cyprinodon 

variegatus

(Sheepshead 

minnow) 

Estuarine/ 

Marine Fish LC50 96 0.36 42114811 Very highly 

toxic 

LC50 96 0.0017 42114812 Very highly 

toxic 

NOAEC NA Mysidopsis bahia 

(Mysid shrimp) 

Estuarine/ 

Marine 

Invertebrates 

LOAEC 

28 (days) NA NA NA 
26

Plants 

One study has been submitted for effects of deltamethrin on terrestrial plants. This study 

was conducted on 55 species of nursery plants, and does not satisfy any non-target plant 

phytotoxicity data requirements, as no endpoints were established. Deltamethrin was 

applied in dust form, with products containing 4.8% and 0.05% active ingredient. No 

treatment-related phytotoxic effects were observed (MRID 43519101). 

No aquatic plant data is available to the Agency for deltamethrin. 

Available open literature will be used to evaluate the potential direct effects of 

deltamethrin to the terrestrial receptors identified in this section. This includes toxicity 

data on the technical grade active ingredient, and when available, formulated products 

(e.g. “Six-Pack” studies). 

At this time, a full and complete ECOTOX search has not been performed, but will be 

conducted prior to issuance of any Data Call-in. The open literature studies will be 

identified through EPA’s ECOTOX database (http://cfpub.epa.gov/ecotox/), which 

employs a literature search engine for locating chemical toxicity data for aquatic life, 

terrestrial plants, and wildlife. The evaluation of data can also provide insight into the 

direct and indirect effects of deltamethrin on biotic communities from loss of species that 

are sensitive to the chemical and from changes in structure and functional characteristics 

of the affected communities. Open literature toxicity data for other ‘target’ insect species 

(not including bees, butterflies, beetles, and non-insect invertebrates including soil 

arthropods and worms), which include efficacy studies, are not currently considered in 

deriving the most sensitive endpoint for terrestrial insects. Efficacy studies do not 

typically provide endpoint values that are useful for risk assessment (e.g., NOAEC, 

EC50, etc.), but rather are intended to identify a dose that maximizes a particular effect 

(e.g., EC100). Therefore, efficacy data and non-efficacy toxicological target insect data 

will not be included in the ECOTOX open literature search. 

Incident Database Review 

A preliminary review on August 11, 2009 of the Ecological Incident Information System 

(EIIS, version 2.1), which is maintained by the Agency’s Office of Pesticide Programs, 

and the Avian Monitoring Information System (AIMS), which is maintained by the 

American Bird Conservancy, indicates one reported ecological incident associated with 

the use of deltamethrin. These incidents are summarized in Table 4.3. This total excludes 

incidents classified as ‘unlikely’ and only includes those incidents with certainty 

categories of ‘highly probable’, and ‘probable’ and ‘possible’ (for EIIS) and ‘certain’, 

‘highly likely’, ‘likely’, ‘probable’, and ‘possible’ (for AIMS). In the EIIS and AIMS 

databases, the “unlikely” category is used when a chemical is not likely to be responsible 

for the incident. For example, an ‘unlikely’ classification might be applied in situations 

where a given chemical is practically nontoxic to the category of organism killed and/ or 

there is evidence that another pesticide or stressor likely caused the incident. Incidents 

classified as ‘unlikely’ for deltamethrin will not be included in this Problem Formulation 
27

or the ecological risk assessment conducted for Registration Review. 

In a single incident reported for deltamethrin (Deltaguard GC 5SC), two other chemicals 

were also involved, imidacloprid and thiophanate-methyl. These chemicals were applied 

to a golf course, and runoff caused a fish kill of approximately 350 bullhead fish 

(Ameirurus sp). Deltamethrin was considered the probable cause of the incident, as it is 

much more toxic to fish than either imidacloprid and thiophanate-methyl. Residues of 

deltamethrin were detected in water collected at the incident site at 0.13 ppb. This 

incident was classified as a misuse (EIIS I015407-001). See Table 4.3 for summary. 

Table 4.3. Wildlife Incidents Associated with Deltamethrin

Chemical 

Name 

Incident 

Number 

(Source) 

Taxa 

Involved Magnitude Year 

Location 

(County, 

State) 

Use Legality 

of Use 

Certainty 

Category1

Residue

s 

Other 

Chemicals 

Involved 

Deltamethrin 

EIIS 

I015407-

001 

Fish 

(Ameriuru

s sp.) 

350 

individuals 2004 Allen, OH Golf Course Misuse Probable 

0.13 ppb 

in 

affected 

water 

Imidacloprid 

and 

Thiophanate

-methyl 

1

Incidents classified as ‘unlikely’ are excluded. 

Although only a total of one incident for deltamethrin has been reported to the Agency, 

the absence of reported incidents should not be construed as the absence of incidents. 

Incident reports for non-target organisms typically provide information only on mortality 

events and plant damage incidents. Except for phytotoxic effects in terrestrial plants, 

sublethal effects for organisms such as reduced growth or impaired reproduction are 

rarely reported. EPA’s changes in the registrant reporting requirements for incidents in 

1998 may account for a reduced number of reported incidents. Registrants are now only 

required to submit detailed information on ‘major’ fish, wildlife, and plant incidents. 

Minor fish, wildlife, and plant incidents, as well as all other nontarget incidents, are 

generally reported aggregately and are not included in EIIS. In addition, there have been 

changes in state monitoring efforts due to lack of resources. 

In the risk assessment, the incident will be further evaluated to determine if it represents 

current patterns of use for deltamethrin. Examples of additional considerations are 

mitigation (e.g., reduced application rates), product cancellations, and changes in use 

patterns that have occurred since the date of the reported incidents. 

As it has been indicated earlier, deltamethrin is not among the constituents monitored by 

the National Water Quality Assessment Data Warehouse, (NAWQA) maintained by the 

U.S. Geological Survey; however, multiple articles from the literature document the 

presence of synthetic pyrethroids like deltamethrin in both urban and agricultural 

sediments (refer to Section 3.2). 

4.3. Ecosystems Potentially at Risk 
28

Deltamethrin may be applied on a variety of food crops, including corn, cotton, soybeans, 

cucurbits, fruiting vegetables, bulb vegetables, pome fruits, tuberous and corm vegetables 

and tree nuts. Thus, the ecosystems at risk may be extensive in scope, and as a result it 

may not be possible to identify specific ecosystems during the development of a baseline 

risk assessment. In general terms, terrestrial ecosystems potentially at risk due to the use 

of deltamethrin, could include the treated field and areas immediately adjacent to the 

treated field that may receive drift or runoff. Areas adjacent to the treated field could 

include cultivated fields, fencerows and hedgerows, meadows, fallow fields or 

grasslands, woodlands, riparian habitats and other uncultivated areas. Due to the 

persistence of deltamethrin, it is expected to drift and/ or runoff due to application to food 

crops, resulting in possible exposure to aquatic ecosystems. Aquatic ecosystems 

potentially at risk due to the use of deltamethrin include water bodies adjacent to, or 

down stream from, the treated field and might include impounded bodies such as ponds, 

lakes and reservoirs, or flowing waterways such as streams or rivers. For uses in coastal 

areas, aquatic habitat also includes marine ecosystems, including estuaries. 

5. Assessment Endpoints 

Assessment endpoints are defined as “explicit expressions of the actual environmental 

value that is to be protected.” Defining an assessment endpoint involves two steps: 1) 

identifying the valued attributes of the environment that are considered to be at risk; and 

2) operationally defining the assessment endpoint in terms of an ecological entity (i.e., a 

community of fish and aquatic invertebrates) and its attributes (i.e., survival and 

reproduction). Therefore, selection of the assessment endpoints is based on valued 

entities (i.e., ecological receptors), the ecosystems potentially at risk, the migration 

pathways of pesticides, and the routes by which ecological receptors are exposed to 

pesticide-related contamination. The selection of clearly defined assessment endpoints is 

important because they provide direction and boundaries in the risk assessment for 

addressing risk management issues of concern. Changes to assessment endpoints are 

typically estimated from the available toxicity studies, which are used as the measures of 

effects to characterize potential ecological risks associated with exposure to pesticides, 

such as deltamethrin. 

To estimate exposure concentrations, the ecological risk assessment considers a single 

application at the maximum application rate to fields that have vulnerable soils. The 

most sensitive toxicity endpoints are used from surrogate test species to estimate 

treatment-related direct effects on acute mortality and chronic reproductive, growth and 

survival assessment endpoints. Toxicity tests are intended to determine effects of 

pesticide exposure on birds, mammals, fish, terrestrial and aquatic invertebrates, and 

plants. These tests include short-term acute, sub-acute, and reproduction studies and are 

typically arranged in a hierarchical or tiered system that progresses from basic laboratory 

tests to applied field studies. The toxicity studies are used to evaluate the potential of a 

pesticide to cause adverse effects, to determine whether further testing is required, and to 

determine the need for precautionary label statements to minimize the potential adverse 

effects to non-target animals and plants. 
29

An open literature search will be conducted to determine any relevant endpoints. The 

search will focus on survival, growth and reproductive effects for aquatic and terrestrial 

effects of deltamethrin. More sensitive endpoints from acceptable open literature studies 

will be included in this risk assessment. 

 6. Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological receptors in 

biologically significant concentrations. An exposure pathway is the means by which a 

pesticide moves in the environment from a source to an ecological receptor. For an 

ecological pathway to be complete, it must have a source, a release mechanism, an 

environmental transport medium, a point of exposure for ecological receptors, and a 

feasible route of exposure. 

A conceptual model provides a written description and visual representation of the 

predicted relationships between deltamethrin, potential routes of exposure, and the 

predicted effects for the assessment endpoint. A conceptual model consists of two major 

components: risk hypothesis and a conceptual diagram (EPA, 1998). 

6.1. Risk Hypothesis 

Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in 

assessment endpoints) and may be based on theory and logic, empirical data, 

mathematical models, or probability models (EPA 1998). For this assessment, the risk is 

stressor-initiated, where the stressor is the release of deltamethrin into the environment. 

The following risk hypothesis is presumed for this screening-level assessment: 

Deltamethrin, when used in accordance with registered labels, will likely lead to 

off-site movement of the compound via runoff, spray drift, and eroded soil leading 

to exposure of nontarget plants and animals Based on information on 

environmental fate, mode of action, direct toxicity and potential indirect effects, 

EFED assumes that registered uses of deltamethrin have the potential to cause 

reduced survival, growth, and reproduction to non-target terrestrial and/or 

aquatic animals and plants.

Note that another potential source of deltamethrin is tralomethrin. Tralomethrin is 

another synthetic pyrethroid that, upon degradation, yields deltamethrin as its major 

transformation product. In the risk assessment, the exposure to deltamethrin due to the 

use of tralomethrin will be addressed qualitatively. 

The conceptual model is a generic graphic depiction of the risk hypothesis. It includes 

the potential pesticide or stressor (deltamethrin), the source of the pesticide and/or 

transport pathways, exposure media, exposure point, biological receptor types, and 

attribute changes. 

6.2. Conceptual Diagram
30

The conceptual site model is a generic graphic depiction of the risk hypothesis, and 

assumes that the insecticide deltamethrin, having outdoor uses, is capable of affecting 

aquatic and terrestrial animals provided that environmental concentrations are sufficiently 

elevated as a result of proposed label uses. Based on an examination of the physicochemical properties of deltamethrin, the fate and disposition in the environment, and 

mode of application, a conceptual model was developed that represents the possible 

relationships between the stressors, ecological receptors, and the assessment endpoints. 

Through a preliminary iterative process of examining available data, the conceptual 

model (i.e., the representation of the risk hypothesis) may be refined to reflect the likely 

exposure pathways and the organisms that are most relevant and applicable to this 

assessment (see Figure 6.1, below). It includes the potential pesticide or stressor 

(deltamethrin), the sources and/ or transport pathways, exposure media, exposure points, 

biological receptor types and attribute changes. The conceptual model depicted in Fig. 

6.1 is similarly applicable to the urban outdoor uses of deltamethrin. 

In order for a chemical to pose an ecological risk, it must reach ecological receptors in 

biologically significant concentrations. An exposure pathway is the means by which a 

pesticide moves in the environment from a source to an ecological receptor. For an 

ecological exposure pathway to be complete, it must have a source, a release mechanism, 

an environmental transport medium, a point of exposure for ecological receptors, and a 

feasible route of exposure. In addition, the potential mechanisms of degradation/ 

transformation (i.e., which degradation/ transformation products may form in the 

environment, in which media, and how much) must be understood, especially if for the 

chemical, its metabolites/ transformation products are of greater toxicological concern 

than the parent compound. The assessment of ecological exposure pathways, therefore, 

includes an examination of the source and potential migration pathways for constituents, 

and the determination of potential exposure routes. 

Under the possible uses of deltamethrin, the sources and mechanisms of release of the 

compound are from ground or aerial spray applications. Surface runoff from the areas of 

application is assumed to depend on factors such as topography, irrigation, and rainfall 

events. Direct deposition may result in contamination of food items that may be 

consumed by terrestrial organisms. Spray drift results in contaminated adjacent areas, 

including bodies of water. 

For aquatic receptors, the major point of exposure is through direct contact with the water 

column, sediment, and pore water (gill/ integument) contaminated with spray drift (from 

spray application) and/ or runoff from treated areas. Indirect effects to aquatic organisms 

(especially fish) can also occur through impact to various food chains and through 

bioaccumulation. The representative aquatic receptors are certain freshwater and 

estuarine/ marine fish, invertebrates, and, in certain cases, aquatic plants. The major 

point of exposure for terrestrial animals is consumption of food contaminated with 

residues such as grass, foliage, and small insects. For plants, the point of exposure is 

direct contact or root uptake. The representative terrestrial receptors are mammals, birds, 

and, in certain cases, terrestrial plants. The attribute changes used to assess risk to 

terrestrial receptors depend on the type of test (e.g., reduced survival, growth, or 
31

reproduction for animals and seedling emergence and vegetative vigor for plants). It 

should be noted, that these species do not cover all the possible species in the animal and 

plant kingdoms; certain taxa are considered as surrogates for other taxa. For example, 

fish are considered surrogates for aquatic phase amphibians. 

Note: This simplified conceptual model does not show details about biomagnification for 

a chemical (though it shows bioaccumulation). Deltamethrin has a very high KOW and 

according to its physicochemical and fate properties, there is a potential for 

bioaccumulation/ bioconcentration in aquatic organisms, and biomagnification in 

terrestrial organisms. The potential for bioaccumulation/ biomagnification is not stressed 

in this conceptual model, but will be examined in the risk assessment. See Section 7.2

Measures of Exposure. 

 

7. Analysis Plan 

In order to address the risk hypothesis, the potential for adverse effects on the 

environment is estimated. Usage, environmental fate and transport, and ecological 

effects of deltamethrin are characterized and integrated to assess the risks. This is 

accomplished using a risk quotient (ratio of exposure concentration to effects 

concentration) approach. Although risk is often defined as the likelihood and magnitude 
32

of adverse ecological effects, the risk quotient-based approach does not provide a 

quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as 

outlined in the Overview Document (USEPA 2004), the likelihood of effects to 

individual organisms from particular uses of a chemical is estimated using the probit 

dose-response slope and either the level of concern (discussed below) or the actual 

calculated risk quotient value. 

This analysis plan will be revisited and may be revised depending on the data available in 

the open literature and the information submitted by the public in response to the opening 

of the Registration Review docket. 

7.1. Stressors of Concern 

The focus of this assessment is on the parent material, deltamethrin. However, the 

Agency will review open literature to identify degradate(s) of potential toxicological 

concern. Various degradates of deltamethrin, such as m-phenoxybenzoic acid (3-PB Ac) 

and decamethrinic acid (or cis-Br2CA), exist; however, they are not structurally related to 

the parent since they have lost the backbone structure of the parent after ester cleavage. 

They are believed to be less toxic than the parent. Deltamethrin also undergoes 

epimerization under certain circumstances. The half-lives calculated for deltamethrin, are 

based on the sum of the parent and its isomers. 

Toxicity data for environmental mixtures of deltamethrin with other pesticides (those 

mixtures occurring in the environment following application), if available, may be 

presented as part of the ecological risk assessment. It is expected that the toxic effect of 

deltamethrin, in combination with other pesticides used in the environment (e.g.

tralomethrin, a source of deltamethrin), is likely to be a function of many factors 

including, but not necessarily limited to: (1) the exposed species, (2) the co-contaminants 

in the mixture, (3) the ratio of deltamethrin and co-contaminant concentrations, (4) 

differences in the pattern and duration of exposure among contaminants, and (5) the 

differential effects of other physical/ chemical characteristics of the receiving waters (e.g.

organic matter present in sediment and suspended water). Quantitatively predicting the 

combined effects of all these variables on mixture toxicity to any given taxa with 

confidence is beyond the capabilities of the available data and methodologies. However, 

a qualitative discussion of implications of the available pesticide mixture effects data on 

the confidence of risk assessment conclusions will be addressed as part of the uncertainty 

analysis. 

7.2. Measures of Exposure 

In order to estimate risks of deltamethrin exposures in aquatic and terrestrial 

environments, all exposure modeling and resulting risk conclusions will be made based 

on maximum application rates for the current use patterns. Measures of exposure are 

based on aquatic and terrestrial models that predict estimated environmental 

concentrations of deltamethrin using maximum labeled application rates and methods, as 
33

well as any mitigation measures specifically indicated on the label. The models used to 

predict aquatic EECs are the Pesticide Root Zone Model coupled with the Exposure 

Analysis Model System (PRZM/EXAMS). The model used to predict terrestrial 

exposure is T-REX. The model used to derive EECs relevant to terrestrial and wetland 

plants is TerrPlant. The potential for bioaccumulation for the chemical is assessed using 

the KABAM model, as well the results from BCF studies. These models are 

parameterized using relevant reviewed registrant-submitted environmental fate and 

transport data. 

PRZM (v.3.12.2, May 2005) and EXAMS (v.2.98.4.6, April 2005) are screening 

simulation models coupled with the input shell PE5.pl (August, 2007) to generate daily 

exposures and 1-in-10 year EECs of deltamethrin, that may occur from spray drift and 

runoff to surface water bodies adjacent to application sites. PRZM simulates pesticide 

application, movement and transformation on an agricultural field and the resultant 

pesticide loadings to a receiving water body via runoff, erosion and spray drift. The 

EXAMS model simulates the fate of the pesticide and resulting concentrations in the 

water body. The standard scenario used for ecological pesticide assessments assumes 

application to a 10-hectare agricultural field that drains into an adjacent 1-hectare water 

body that is 2 meters deep (20,000 m3

 volume) with no outlet. PRZM/ EXAMS is used 

to estimate screening-level exposure of aquatic organisms to deltamethrin and/ or its 

transformation products, should they be of concern. The measure of exposure for aquatic 

species is the 1-in-10 year return peak or rolling mean concentration. The 1-in-10 year 

peak is used for estimating acute exposures of direct effects to aquatic organisms. The 1-

in-10-year 60-day mean is used for assessing chronic exposure to fish and aquatic-phase 

amphibians. The 1-in-10-year 21-day mean is used for assessing aquatic invertebrate 

chronic exposure. 

 

Given the aquatic toxicity of deltamethrin and its likelihood to occur in sediment, the 

Agency will also consider the potential exposures resulting from benthic/ sediment 

concentrations (EECs). Pore water concentrations are commonly used to predict toxicity 

of non-ionic substances in sediments and characterize exposure to organisms that spend 

time in or near sediments (Di Toro et al. 1991; US EPA 2002). PRZM/ EXAMS 

estimates 1-in-10-year peak and 21-day mean EECs for pore water. 

Exposure estimates for terrestrial animals assumed to be in the target area are derived 

using the T-REX model (version 1.3.1, 12/07/2006). For pesticides such deltamethrin, 

which can be applied as a dust, this includes the amount of pesticide per square foot, used 

in LD50 per square foot risk assessment calculations. EECs for terrestrial plants 

inhabiting dry and wetland areas are derived using TerrPlant (version 1.2.2, 12/26/2006). 

This model uses estimates of pesticides in runoff and in spray drift (assumed to be 0% for 

granulars) to calculate EECs. EECs are based upon solubility, application rate and 

minimum incorporation depth. 

As indicated in Table 3.1, deltamethrin appears to have a potential to bioconcentrate/ 

biomagnify. The potential for bioaccumulation of deltamethrin will also be examined in 

the risk assessment. Because deltamethrin has a fairly high KOW (34,200) and the 
34

chemical is persistent in sediments, there is a potential for bioaccumulation. The 

depuration rate is moderately slow (about 50% between days 3-7 and 70-75% after 2 

weeks of depuration, MRID 41651040. Bioaccumulation will be assessed using the results 

from BCF studies, as well as the KABAM model (KOW (based) Aquatic BioAccumulation 

Model, version 1.0, 2009), adjusting for biotransformation rates. 

7.3. Measures of Effect 

Ecological effects data are used as measures of direct and indirect effects to biological 

receptors. Data are typically obtained from registrant-submitted studies or from literature 

studies identified by ECOTOX. The ECOTOX database provides more ecological effects 

data in an attempt to bridge existing data gaps. ECOTOX is a source for locating single 

chemical toxicity data and potential chemical mixture toxicity data for aquatic life, 

terrestrial plants, and wildlife. ECOTOX was created and is maintained by the USEPA, 

Office of Research and Development, and the National Health and Environmental Effects 

Research Laboratory's Mid-Continent Ecology Division. 

The acute measures of effect used for animals in this assessment are the LD50, LC50 and 

EC50. LD stands for "Lethal Dose", and LD50 is the amount of a material, given all at 

once, that is estimated to cause the death of 50% of the test organisms. LC stands for 

“Lethal Concentration” and LC50 is the concentration of a chemical that is estimated to 

kill 50% of the test organisms. EC stands for “Effective Concentration” and the EC50 is 

the concentration of a chemical that is estimated to produce a specific effect in 50% of 

the test organisms. Endpoints for chronic measures of exposure for listed and non-listed 

animals are the NOAEL/NOAEC and NOEC. NOAEL stands for “No ObservedAdverse-Effect-Level” and refers to the highest tested dose of a substance that has been 

reported to have no harmful (adverse) effects on test organisms. The NOAEC (i.e., “NoObserved-Adverse-Effect-Concentration”) is the highest test concentration at which none 

of the observed effects were statistically different from the control. The NOEC is the NoObserved-Effects-Concentration. For non-listed plants, only acute exposures are 

assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed plants 

either the NOAEC or EC05 is used. 

Information on the potential effects of deltamethrin on non-target animals is also 

collected from the Ecological Incident Information System (EIIS). The EIIS is a database 

containing adverse effect (typically mortality) reports on non-target organisms where 

such effects have been associated with the use of pesticides. Information on incidents 

involving avian species are also provided through the Avian Monitoring Information 

System (AIMS), which is maintained by the American Bird Conservancy. 

Where available, sub-lethal effects observed in both registrant-submitted and open 

literature studies will be evaluated qualitatively. Such effects may include behavioral 

changes (e.g., lethargy and changes in coloration). Quantitative assessments of risks, 

though, are limited to those endpoints that can be directly linked to the Agency’s 

assessment endpoints of impaired survival, growth and reproduction. Acute aquatic 
35

toxicity studies conducted with the Typical End-Use Product (TEP) may be used to 

assess effects as a result of exposure to spray drift only and only reflect potential effects 

from a brief exposure to the formulation. 

The assessment of risk for direct effects to non-target organisms makes the assumption 

that the toxicity of deltamethrin to birds is similar to terrestrial-phase amphibians and 

reptiles. The same assumption is made for fish data, which is used to infer toxicity to 

aquatic-phase amphibians. 

 

7.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterization 

to determine the potential ecological risk from the use of pesticides and the likelihood of 

direct and indirect effects to non-target organisms in aquatic and terrestrial habitats. The 

exposure and toxicity effects data are integrated in order to evaluate the risks of adverse 

ecological effects on non-target species. For the assessment of risks, the risk quotient 

(RQ) method is used to compare exposure and measured toxicity values. EECs are 

divided by acute and chronic toxicity values. The resulting RQs are then compared to the 

Agency’s Levels of Concern (LOCs) (USEPA 2004). These criteria will be used to 

indicate when deltamethrin’s uses, as directed on the label, have the potential to cause 

adverse direct or indirect effects to non-target organisms. In addition, incident data from 

the EIIS will be considered as part of the risk characterization. 

 

7.5. Deterministic and Probabilistic Assessment Methods 

The quantitative assessment of risk will primarily depend on the deterministic pointestimate based approach described in the risk assessment. An effort may also be made to 

further qualitatively describe risk using probabilistic tools that the Agency has developed. 

These tools have been reviewed by FIFRA Scientific Advisory Panels 

(http://www.epa.gov/scipoly/sap/index.htm) and have been deemed as appropriate means 

of refining assessments where deterministic approaches have identified risks. 

7.6. Endangered Species Assessments 

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), 

the Agency will evaluate risks to Federally-listed threatened and/or endangered (listed) 

species from registered uses of deltamethrin. This assessment will be conducted in 

accordance with the Overview Document (USEPA 2004), provisions of the ESA, and the 

Services’ Endangered Species Consultation Handbook (USFWS/NMFS, 1998). 

The assessment of effects associated with the registration of deltamethrin is based on an 

action area. The action area is considered to be the area directly or indirectly affected by 
36

the federal action, as indicated by the exceedance of Agency Levels of Concern (LOCs) 

used to evaluate direct or indirect effects. The Agency’s approach to defining the action 

area under the provisions of the Overview Document (USEPA 2004) considers the results 

of the risk assessment process to establish boundaries for that action area with the 

understanding that exposures below the Agency’s defined LOCs constitute a no-effect 

threshold. For the purposes of this assessment, attention will be focused on the footprint 

of the action (i.e., the area where deltamethrin application occurs), plus all areas where 

offsite transport may result in potential exposure that exceeds the Agency’s LOCs. 

Specific measures of ecological effect that define the action area for listed species include 

any direct and indirect effects and/ or potential modification of its critical habitat, 

including reduction in survival, growth, and reproduction as well as the full suite of sublethal effects available in the effects literature. Therefore, the action area extends to a 

point where environmental exposures are below any measured lethal or sub-lethal effect 

threshold for any biological entity at the whole organism, organ, tissue, and/ or cellular 

level of organization. In situations where it is not possible to determine the threshold for 

an observed effect, the action area is not spatially limited and is assumed to be the entire 

United States. 

7.7. Drinking Water Assessment 

A drinking water assessment will be conducted to support future human health risk 

assessments of deltamethrin should it be required by HED. The drinking water 

assessment will incorporate model estimates of deltamethrin in surface and ground 

waters. Concentrations in surface waters will be estimated using FQPA Index Reservoir 

Screening Tool (FIRST, v.1.1.1, 12/18/07) (or subsequently using PRZM/ EXAMS, with 

the Index Reservoir - see description above, if refinements are required). Ground water 

estimates of concentrations will be estimated using the Screening Concentration in 

Ground Water (SCI-GROW) model (v.2.3, July 2003). The drinking water assessment 

will also include a summary of available surface and ground water monitoring data. 

 

7.8. Preliminary Identification of Data Gaps 

7.8.1. Fate 

The environmental fate database for deltamethrin is largely complete. For registration 

review, the following are the data gaps for the chemical: 

835.4300. Aerobic Aquatic Metabolism – A study is required in one water/sediment 

system, which is preferably domestic since the supplemental data available is from two 

foreign water/ sediment systems (from the Neatherlands). The percent organic matter 

was very high in both sediments (3.0 and 12.4%), and furthermore, the pH of the water in 

both systems was above 8 (the range for two systems, measured at the initial and final 

intervals was 8.0 to 8.7). Deltamethrin is known to be susceptible to hydrolysis at higher 

pHs. The new test system should have a near neutral or slightly acidic pH. Also, other 

deficiencies included that the system was not completely aerobic or anaerobic, the 
37

analytical method could not distinguish deltamethrin from its primary α-R-isomer or 

trans-deltamethrin, there is an unexplained steady decline in the material balance to 80-

87% at the last test interval, and radioactive material may have been adhered to the walls 

of the vessels and the methodology could not account for that fact, as indicated in the 

study Data Evaluation Record (DER). 

835.4400. Anaerobic Aquatic Metabolism – No study has been submitted. The study is 

required. 

Environmental Chemistry Methods (ECMs), and Independent Laboratory 

Validations (ILVs), for Soil, Water and Sediment. ECMs associated with the 

Terrestrial Field Dissipation study (Field dissipation §158.1300; OPPTS guidelines 

835.6100, 835.6200, and 835.6300), along with successful confirmatory method trials 

(validation) by an independent laboratory (i.e. ILVs), are required. If there is risk 

concern for a given taxon, ECMs should be available for the environmental media in 

which organisms of the taxon reside. These ECMs should have limits of quantization for 

the residues of concern that are lower than the relevant toxicological levels of concern. 

All previous reviews on deltamethrin indicate that there is high concern for acute and 

chronic aquatic toxicity. Certain scenarios may have triggered acute and chronic levels 

of concern for freshwater and/ or estuarine/ marine aquatic invertebrates and/ or for fish. 

In addition, the latter risk assessments conducted on deltamethrin, indicated risk concerns 

for organisms living in the benthos. Therefore, ECMs for water and sediment are 

required in addition to the ECM for soil. The ECMs should include parent and those 

residues found in the laboratory studies that exceeded 10% of the applied. The following 

appear to be the residues of concern for each media: 

Soil – parent, its epimers, alpha-R-deltamethrin, trans-deltamethrin, Br2CA, 3-PBAc 

Water – parent, its epimers, alpha-R-deltamethrin, Br2CA, 3-PBAc, 3-PBAldehyde 

Sediment – parent, its epimers, alpha-R-deltamethrin Br2CA, 3-PBAc and 3-

PBAldehyde 

The registrant is encouraged to submit state-of-the-art environmental chemistry methods; 

further, multi-residue methods (MRMs) for soil, water and sediment are preferred. The 

registrant submitted one method for soil (MRID 42773903, LOQ 2 ppb, published in the 

Agency’s ECM website)1 is available, that could quantify deltamethrin, transdeltamethrin and decamethrinic acid (Br2CA) in soil; the method is not useful to quantify 

3-PBAc, which was up to 11% in the soil photodegradation study. A full description of 

the method validation procedures performed by an independent laboratory should be 

submitted. It should include the following information: (a) Recovery level(s) of the test 

compound(s) from the soil, water and sediment (substrates) at various relevant 

fortification level(s) using the residue analytical methodology; (b) a validated method 

sensitivity level; (c) results of the study and statistical test applied, including a stepwise 

presentation of the procedure for calculating percent recovery from the raw data; (d) all 

the data/ information necessary to independently verify the results; (e) summary of the 

results; and, (f) discussion and conclusions of the results. 

Table 7.1 lists the status of the environmental fate data requirements for deltamethrin. 

 

1 Available at url: http://www.epa.gov/oppbead1/methods/ecmindex.htm
38

Table 7.1. Summary of Environmental Fate Data Requirements for Deltamethrin

Study Identification 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This Requirement? 

Bibliographic 

Citation 

Must Additional 

Data Be Submitted 

Under FIFRA 

3(c)(2)(B)? 

§158.1300 ENVIRONMENTAL FATE

Degradation Studies-Lab:

 835.2120 Hydrolysis 1,2 Yes 41651038 No

 835.2240 Photodegradation in 

Water 

1,2 Yes 42114818 No 

 835.2410 Photodegradation 

on Soil 

1,2 Yes 42114819 No 

 835.2370 Photodegradation in 

Air 

1,2 No Not Available Waived2

Metabolism Studies-Lab:

 835.4100 Aerobic Soil 1,2 Yes 41677404, 

41677407, 

42114820 

No 

 835.4200 Anaerobic Soil 1,2 Yes 42114821, 

44814505

No 

 835.4400 Anaerobic Aquatic 1,2 No Not Available Yes 

 835.4300 Aerobic Aquatic 1,2 Partially 44977005 Yes3 

Mobility Studies:

 835.1230 Leaching – 

Adsorption/ Desorption 

1,2 Yes 41651039, 

42475908, 

42976501, 

44977006 

No 

 835.1410 Volatility (Lab) 1,2 No Not Available Waived2

 835.8100 Volatility (Field) 1,2 No Not Available Waived2

Dissipation Studies-Field:

 835.6100 Terrestrial Field 

Dissipation 

1,2 Yes 42114822, 

42137505, 

42773903 

No 

835.6200 Aquatic Field 

Dissipation 

1,2 No N/A Reserved 

835.6300 Forestry Dissipation 1,2 No N/A N/A 

Ground Water Monitoring Studies:
39

Table 7.1. Summary of Environmental Fate Data Requirements for Deltamethrin

Study Identification 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This Requirement? 

Bibliographic 

Citation 

Must Additional 

Data Be Submitted 

Under FIFRA 

3(c)(2)(B)? 

 835.7100 Ground Water 

Monitoring 

1,2 No NA Reserved 

§158.1100 SPRAY DRIFT

 201-1 Droplet Size Spectrum 1,2 No2 NA No4 

 202-1 Drift Field Evaluation 1,2 No2 NA No4

Other Studies: 

ECM and ILV 1,2 Partially 42773903 Yes5

1. Use Patterns: 1=Terrestrial/Food; 2=Terrestrial/Feed. 2. Deltamethrin has low vapor pressure and Henry’s Law 

Constant, data requirement was waived. 3. One study is required in only one water/sediment system. The system 

should be domestic, have a near neutral pH, and should address deficiencies listed in the previous study. 4. Data 

requirement covered by submission of the Spray Drift Task Force. 5. The registrant is encouraged to submit stateof-the-art environmental chemistry methods; further, multi-residue methods (MRMs) for soil, water and sediment are 

preferred. 

7.8.2 Effects

For registration review, the following studies are being requested to fulfill any data gaps: 

Guideline Number: 850-2100 

Study Title: Passerine Acute Avian Oral 

Although an acute avian oral study was received for the bobwhite quail, the Agency 

updated its data requirements in 40 CFR Part 158 (October 26, 2007) to include an acute 

oral toxicity study for both a passerine species and either a waterfowl or an upland game 

species. Prior to starting toxicity testing, a protocol will need to be provided for review. 

Many passerine species utilize agricultural fields, forests, residential areas and 

surrounding areas, and, therefore, have the potential to be exposed to pesticides used in 

agricultural, forest, and residential settings. It is likely that, for most pesticide use 

patterns, passerines are more likely to be exposed to pesticides than upland game species 

and waterfowl. Passerines are smaller and have faster metabolisms than the waterfowl 

and upland game bird species traditionally used in avian toxicity tests which could impact 

their sensitivity to chemicals. 

Guideline Number: 850.1400 

Study Title: Fish Early Life Stage (saltwater) 

Guideline Number: 850.1500 

Study Title: Fish Life Cycle (saltwater) 

Deltamethrin has the potential to enter estuarine/marine water bodies based on current 

usage patterns that include coastal areas. Exposure to aquatic organisms is also evidenced 

by studies from Weston et al (2005) and Amweg et al (2006). Furthermore, the acute 
40

LC50 = 0.36 μg a.i./L for estuarine/marine fish, indicating that deltamethrin is very highly 

toxic on an acute basis to sheepshead minnow and demonstrating potential chronic risk to 

this taxon (MRID 42114811). Available ecological studies also show that low-level 

chronic exposure to deltamethrin has the potential to cause adverse reproductive effects 

in freshwater fish (NOAEC = 0.017 μg a.i./L, MRID 42786802). Without this study, the 

Agency would have to presume chronic risk to listed and non-listed estuarine/marine fish, 

but would not be able to quantify the risk.

Guideline Number: 850.1350 

Study Title: Aquatic Invertebrate Life-Cycle (saltwater) 

The acute toxicity of deltamethrin to estuarine/marine invertebrates indicates the potential 

for chronic risk to animals in this taxon, and the potential for chronic exposure exists. 

Deltamethrin has the potential to enter estuarine/marine water bodies based on current 

usage patterns that include coastal areas. Without this study, the Agency would have to 

presume chronic risk to listed and non-listed estuarine/marine invertebrates, but would 

not be able to quantify the risk. The Agency had conditionally required aquatic 

invertebrate life-cycle studies (Guidelines 850.1300, 850.1350, and 850.1400) for 

terrestrial food and nonfood, aquatic food and nonfood, forestry, and domestic outdoor 

uses. 

Guideline Number: 850-1790 

Study Title: Whole sediment: chronic invertebrates freshwater and marine 

No chronic sediment toxicity tests for freshwater or marine invertebrates have been 

submitted to satisfy the Agency’s updated data requirements for outdoor uses in 40 CFR 

Part 158 (October 26, 2007). Benthic organisms inhabit sediment environments that may 

be exposed to run-off or spray drift from deltamethrin applications used in agricultural, 

forest, and residential settings. Previous studies have identified a potential adverse effect 

for freshwater and estuarine/marine aquatic organisms based on water column toxicity 

values. Therefore, there is uncertainty associated with that estimate that can be reduced 

using data from a toxicity test with benthic organisms. There is the potential for persistent 

exposure from deltamethrin in sediment indicated by the fate properties and open 

literature studies on pyrethroids (Stout II, et al. 2009, Weston et al. 2005, and Amweg et 

al. 2006). For sediment studies involving pyrethroids, tests on Hyalella azteca, 

Chironomus tentans, and Leptocheirus plumulosus are requested. Although both are 

freshwater species, Hyalella and Chironomus differ substantially in their ecological 

niche (i.e., epibenthic vs. infaunal species), physiology, and there is some evidence 

suggesting Hyalella is among the more sensitive invertebrates to some pyrethroids based 

on water column tests (Anderson et al. 2006). 

Guideline Numbers: 850.4150 and 850.4250 

Study Title: Vegetative vigor and Seedling emergence, Tier I/ Tier II 

No acceptable toxicity data are currently available to assess the risk of deltamethrin to 

non-target terrestrial plants. Since deltamethrin has residential outdoor uses, vegetative 

vigor and seedling emergence studies are required. These phytotoxicity data are needed 

to evaluate the level of pesticide exposure to non-target terrestrial and aquatic plants and 

to assess the impact of pesticides on endangered and threatened plants. 
41

Guideline Number: 850.4400 

Study Title: Aquatic Vascular Plant Growth-Lemna spp. Tiers I/II 

No acceptable studies for deltamethrin have been submitted for vascular aquatic plants. 

The Agency has finalized its update to the data requirements in 40 CFR Part 158. In 

these updated data requirements, which were promulgated on October 26, 2007, vascular 

plant testing is required for pesticides such as deltamethrin with outdoor uses. 

Guideline Number: 850.5400 

Study Title: Algal toxicity test, Tier I/II 

No toxicity data are currently available to assess the risk of deltamethrin to aquatic 

nonvascular plants. Since deltamethrin has residential outdoor uses, Tier I/II aquatic 

nonvascular plant studies are required. These phytotoxicity data are needed to evaluate 

the level of pesticide exposure to non-target aquatic plants and to assess the impact of 

pesticides on endangered and threatened plants. 

For mammalian toxicity, EFED will coordinate with HED to determine the most sensitive 

endpoints for acute and chronic studies. 

Testing on Typical end-use products (TEP) 

A Typical End-Use Product is defined in the Pesticide Assessment Guidelines 

Subdivision J Hazard Evaluation: Nontarget plants on Part 120-2(1) on Page 18 as “a 

pesticide product that is representative of a major formulation category (e.g., emulsifiable 

concentrate, granular product, wettable powder) and pesticide group (e.g., herbicide, 

fungicide, insecticide etc.) and contains the active ingredient of the applicant’s product.” 

(Holst and Ellwanger, 1982) 

Page 5 of the Pesticide Assessment Guidelines Subdivision J Hazard Evaluation: 

Nontarget plants provides additional information on what TEP data should be tested for 

toxicity testing in the following excerpt. 

“The Agency seeks to avoid imposing a burden of duplicative testing on 

applicants for registration. Therefore, where 40 CFR Part 158 specifies that the 

test substance should be a representative end-use product, testing may be 

performed using the formulation in question (end-use product being registered) or 

similar, yet representative, end-use product. It is not necessary to repeat the test 

using other similar products.” (Holst and Ellwanger, 1982). 

When TEP data are requested data should be submitted for the different formulations, 

e.g., wettable powder, emulsifiable concentrate, granular, along with a rationale as to why 

the TEP is representative of other similar end-use products. Acute aquatic toxicity studies 

conducted with the Typical End-Use Product (TEP) may be used to assess effects as a 

result of exposure to spray drift only and reflect potential effects from a brief exposure to 

the formulation. Therefore, appropriate TEPs should be selected from formulations that 

are registered for agricultural uses, not residential. 
42

Table 7.2 lists the status of the ecological effects data requirements for deltamethrin. 

Table 7.2. Ecological Effects Data Requirements for Deltamethrin

Data Requirement 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This 

Requirement? 

(Yes, No, or 

Partially) 

Bibliographic 

Citation 

Must 

Additional 

Data Be 

Submitted 

Under FIFRA 

3(c)(2)(B)? 

§158.490 TERRESTRIAL ORGANISMS

71-1(a) Acute Avian Oral, Quail/Duck 1,2 Partially 00158273 Yes2 

71-2(a) Acute Avian Diet, Quail 1,2 No NA Waived3 

71-2(b) Acute Avian Diet, Duck 1,2 Yes 00060723 No 

71-3 Wild Mammal Toxicity 1,2 NA 

71-4(a) Avian Reproduction Quail 1,2 Yes 42114808 No 

71-4(b) Avian Reproduction Duck 1,2 Yes 42114809 No 

71-5(a) Simulated Terrestrial Field Study 1,2 NA 

71-5(b) Actual Terrestrial Field Study 1,2 NA 

§158.630 AQUATIC ORGANISMS TESTING

72-1(a) Acute Fish Toxicity Bluegill 1,2 Yes 00158275 No 

72-1(b) Acute Fish Toxicity (TEP) 1,2 Yes 41651013 No4 

72-1(c) Acute Fish Toxicity Rainbow 

Trout 

1,2 Yes 00158274 No 

72-2(a) Acute Aquatic Invertebrate 1,2 Yes 44928701 No 

72-2(b) Acute Aquatic Invertebrate (TEP) 1,2 Yes 41651014 No 

72-3(a) Acute Est/Mar Toxicity Fish 1,2 Yes 41651015 No 

72-3(b) Acute Est/Mar Toxicity Mollusk 1,2 Yes 41651016 No 

72-3(c) Acute Est/Mar Toxicity Shrimp 1,2 Yes 42114810 No 

72-3(d) Acute Est/Mar Toxicity Fish (TEP) 1,2 Yes 42114811 No 

72-3(e) Acute Est/Mar Toxicity Mollusk 

(TEP) 

1,2 Yes 41651017 No 

72-3(f) Acute Est/Mar Toxicity Shrimp 

(TEP) 

1,2 Yes 42114812 No 

72-4(a) Early Life Stage Fish 1,2 Partially 42114814 Yes5 
43

Table 7.2. Ecological Effects Data Requirements for Deltamethrin

Data Requirement 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This 

Requirement? 

(Yes, No, or 

Partially) 

Bibliographic 

Citation 

Must 

Additional 

Data Be 

Submitted 

Under FIFRA 

3(c)(2)(B)? 

72-4(b) Life Cycle Aquatic Invertebrate 

(freshwater) 

1,2 Yes 42114813 No 

850.1350 Life Cycle Aquatic Invertebrate 

(saltwater) 

1,2 No NA Yes 

72-5 Life Cycle Fish 1,2 Partially 42786802 Yes5 

72-6 Aquatic Organism Accumulation 1,2 NA 

72-7(1) Simulated Aquatic Field Study 1,2 NA 

72-7(b) Actual Aquatic Field Study 1,2 NA 

 850.1730 Bioaccumulation in Fish 1,2 Yes 41651040, 43072701, 

43072702 

No 

850.1735 Whole sediment: acute freshwater 

invertebrates 

1, 2 No NA Waived 

850.1740 Whole sediment: acute marine 

invertebrates 

1, 2 No NA Waived 

Whole sediment: chronic invertebrates 

freshwater & marine 

1, 2 No NA Yes 

§158.540 PLANT PROTECTION

122-1(a) Seed Germ, Seedling Emergence 1,2 No NA Yes 

122-1(b) Vegetative Vigor 1,2 No NA Yes 

122-2 Aquatic Plant Growth 1,2 No NA Yes6 

123-1(a) Seed Germ./Seedling Emerg. 1,2 NA NA No7 

123-1(b) Vegetative Vigor 1,2 NA NA No7 

123-2 Aquatic Plant Growth 1,2 NA NA No8 

124-1 Terrestrial Field Study 1,2 NA 

124-2 Aquatic Field Study 1,2 NA 

§158.490 NONTARGET INSECT TESTING

141-1 Honey Bee Acute Contact 1,2 Yes 42114815 No 

141-2 Honey Bee Residue on Foliage 1,2 Yes 42475905 and 

42773902 

No 

141-5 Field Test for Pollinators 1,2 NA 
44

Table 7.2. Ecological Effects Data Requirements for Deltamethrin

Data Requirement 

Use 

Pattern1

Does EPA Have 

Data To Satisfy 

This 

Requirement? 

(Yes, No, or 

Partially) 

Bibliographic 

Citation 

Must 

Additional 

Data Be 

Submitted 

Under FIFRA 

3(c)(2)(B)? 

1

 Use Patterns: 1=Terrestrial/Food; 2=Terrestrial/Feed. 

2 Data are required for one passerine species and either on waterfowl or one upland game bird species. At this time, only an 

acute oral test for a game bird species has been submitted. 

3

 Because none of the previously submitted studies show any acute oral, dietary or chronic toxic effects to waterfowl and 

upland game bird species, no dietary study is required for the mallard duck. 

4 Part 158 data requirements state that the freshwater fish test species for the TEP testing should be the most sensitive of the 

species tested with the TGAI. The 96-hour LC50 = 0.91 μg a.i./L for coldwater rainbow trout (Oncorhynchus mykiss) and 

warmwater bluegill sunfish (Lepomis macrochirus) (MRIDs 00158274 and 00158275) were equivalent for deltamethrin 

technical. The most sensitive species tested for deltamethrin technical acute toxicity was Lepomis gibbosus (Pumpkinseed 

sunfish) (MRID 00060721). However Lepomis gibbosus is not a guideline species. Therefore, the rainbow trout acute 

toxicity test for the formulated product satisfies the guideline requirement. 

5

 Data are required for saltwater/marine fish species. With current registered use patterns, deltamethrin can potentially enter 

water bodies, based on the available environmental fate data. Exposure to aquatic organisms is also evidenced by studies 

from Weston et al (2005) and Amweg et al (2006). Furthermore, the acute LC50 = 0.36 μg a.i./L for estuarine/marine fish, 

indicating that deltamethrin is very highly toxic on an acute basis to sheepshead minnow (MRID 42114811). Available 

ecological studies also show that low-level chronic exposure to deltamethrin has the potential to cause adverse reproductive 

effects in freshwater fish (NOAEC = 0.017 μg a.i./L, MRID 42786802). 

6

 Aquatic toxicity tests are required for both algal and aquatic vascular species. 

7

 Required if a tested terrestrial species exhibits a 25 percent or greater detrimental effect in the Tier I study. 

8

 Required if a tested aquatic species exhibits a 50 percent or greater detrimental effect in a Tier I study. 

8. References 

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Sediment Toxicity in Urban Creeks from California and Tennessee. Environ. Sci. 

Technol., 2006, 40 (5), pp 1700–1706. 

Amweg, E.L., D.P. Weston and N.M. Ureda. 2004. Use and Toxicity of Pyrethroid 

Pesticides in the Central Valley, California, USA. Environ Toxicol & Chem, 24 (4), pp. 

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Armitage, J.M., & Gobas, F.A.P.C. 2007. A terrestrial food-chain bioaccumulation model 

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Budd, R, S. Bondarenko, D. Haver, J. Kabashima, and J. Gan. 2007. Occurrence and 

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http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm 

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(Accessed December 14, 2009). 

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and Effects Division. Office of Pesticide Programs, Washington, D.C. January 24, 2005. 

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service 

(NMFS). 1998. Endangered Species Consultation Handbook: Procedures for 

Conducting Consultation and Conference Activities Under Section 7 of the Endangered 

Species Act. Final Draft. March 1998. 

Weston, D.P., R.W. Holmes, J. You and M.J. Lydy. 2005. Aquatic Toxicity Due to 

Residential Use of Pyrethroid Insecticides. Environ. Sci. Technol., 2005, 39 (24), pp 

9778–9784. 

Weston, D. 2007. Impacts of Pyrethroid Pesticides on Water Quality from Urban and 

Agricultural Sectors. Conference Proceedings; California Plant and Soil Conference: 

Opportunities for California Agriculture. California Chapter of the American Society of 

Agronomy, pp. 35-37. 

Weston, D.P., R.W. Holmes, and M.J. Lydy. 2009. Residential runoff as a source of 

pyrethroid pesticides to urban creeks. Environmental Pollution 157, 287–294. 

Weston, D.P. and M.J. Lydy. 2010. Urban and Agricultural Sources of Pyrethroid 

Insecticides to the Sacramento-San Joaquin Delta of California. Environ. Sci. Technol. 

2010, 44, 1833–1840.
47

Appendix A. SRRD data request justification tables 

The following proposed Data Call-in tables include rationales for requiring the data 

requested in this problem formulation, explanations of the utility of the data, and 

explanations for how the data might impact risk assessment, following the format 

provided by SRRD. 

Guideline Number: 835.4300 

Study Title: Aerobic Aquatic Metabolism 

Guideline Number: 835.4400 

Study Title: Anaerobic Aquatic Metabolism

Rationale for Requiring the Data 

According to 40 CFR Part 158, Subpart N (Environmental Fate) §158.1300 (Environmental fate 

data requirements table), these data are required for all terrestrial use patterns. 

An aerobic aquatic metabolism study is required in one water/sediment system, which is 

preferably domestic since the supplemental data available is from two foreign water/ sediment 

systems. The percent organic matter was very high in both sediments (3.0 and 12.4%), and 

furthermore, the pH of the water in both systems was above 8 (range for two systems, measured 

at the initial and final intervals was pH of 8.0 to 8.7). Deltamethrin is known to be susceptible to 

hydrolysis at higher pHs. The new test system should have a near neutral pH. Also, other 

deficiencies listed in the study Data Evaluation Record (DER) should be addressed. 

There is no anaerobic aquatic metabolism study. 

Practical Utility of the Data 

How did the Agency make its registration decision without these data? 

The previous assessments were based on supplemental aerobic aquatic metabolism data and the 

anaerobic soil metabolism study. 

How will the data be used? 

Deltamethrin is a synthetic pyrethroid with high toxicity towards aquatic organisms, including 

those living in the benthos. Knowledge of its persistence in aquatic environments is important. 

The results of this study will be used in the environmental fate assessment, and later on, in the 

ecological risk characterization. 

In addition, the data will be used to derive the rate of reaction input parameter to be used in the 

aquatic models GENEEC2, PRZM/ EXAMS and FIRST. The results from these models are used 

for ecological risk estimation and in drinking water exposure assessments. 

How could the data impact the Agency’s future decision-making? 

Without these data, the Agency would have to make certain conservative assumptions (e.g. use a 

two times the aerobic soil metabolism half-life input for the aerobic aquatic metabolism or two 

times the anaerobic soil metabolism half-life for the anaerobic aquatic metabolism in the aquatic 

models). These conservative assumptions could lead to higher predicted concentrations (EECs), 

according to the models, and consequently, higher risk quotients. Also, there would be a higher 

degree of uncertainty in the environmental fate assessment. Knowledge of these dissipation 

pathways in detail is essential to perform a better and accurate environmental fate assessment and 

risk assessment. 
48

The lack of these data will limit the flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in use restrictions for deltamethrin 

that may be unnecessary. 
49

Guideline Number: None 

Study Title: Environmental Chemistry Methods (ECM) and Independent Laboratory 

Validation (ILV) for Soil, Water and Sediment

Rationale for Requiring the Data 

According to the data requirements in 40 CFR Part 158, ECMs are currently required along with 

successful confirmatory method trials (validation) by an independent laboratory (i.e. ILVs). In 

addition to the method for soil, at this time, methods are required for water and sediment. 

Acceptable ECMs for the residues of concern (parent and its transformation products) should 

have levels of quantization that are adequate to address risk concerns or that are at levels below 

the toxicological endpoints for the relevant aquatic organisms. The results of previous 

assessments indicate that there is risk for freshwater and estuarine/ marine fish, invertebrates and 

benthic organisms. Therefore, ECMs for water and sediment are required in addition to the ECM 

for soil. The ECMs should include parent and those residues found in the laboratory studies that 

exceeded 10% of the applied. The registrant is encouraged to submit state-of-the-art 

environmental chemistry methods; further, multi-residue methods (MRMs) for soil, water and 

sediment are preferred. 

Practical Utility of the Data 

How did the Agency make its registration decision without these data? 

Instead of monitoring data, models were utilized to calculate the exposure (i.e. Estimated 

Environmental Concentrations, EECs), using available environmental fate data. Currently, there 

is a published method for soils, but the method is not useful to quantify 3-PBAc, which was up to 

11% in the soil photodegradation study. 

How will the data be used? 

The data will be used to verify the suitability of the methods. Subsequently the methods could be 

used by states or other enforcement agencies, departments or entities, to monitor concentrations 

of the residues of concern. Validated analytical methods in environmental media (a.k.a., ECMs) 

are useful for conducting and evaluating submitted environmental fate and toxicity field and 

monitoring studies and for addressing potential risks to the environment posed by the use and/or 

accidental release of pesticides. 

How could the data impact the Agency’s future decision-making? 

If monitoring of the chemical is required or performed, the Agency could be able to determine if 

the chemical is present in the environment at concentrations that are threatening to wildlife (or to 

humans, in the case of drinking waters), according to the levels of concern (LOCs). If that is the 

case, measures to prevent these concentrations to occur could be taken. The data could also be 

used by enforcement entities like the states or government agencies or departments. Without 

these data, the potential for the determination of residues of deltamethrin and its epimers and 

degradates in soil, water and sediment is restricted. The lack of these data will limit the 

flexibility the Agency and registrants have in coming into compliance with the Endangered 

Species Act, and could result in use restrictions for deltamethrin which may otherwise be 

avoided, or which are unnecessarily severe. 
50

Guideline Number: 850-2100 

Study Title: Passerine Acute Avian Oral 

Rationale for Requiring the Data 

Although an acute avian oral study was received for the bobwhite quail, the Agency updated its 

data requirements in 40 CFR Part 158 (October 26, 2007) to include an acute oral toxicity study 

for both a passerine species and either a waterfowl or an upland game species. Prior to starting 

toxicity testing, a protocol will need to be provided for review. 

o Many passerine species utilize agricultural fields, forests, residential areas 

and surrounding areas, and, therefore, have the potential to be exposed to 

pesticides used in agricultural, forest, and residential settings 

 It is likely that, for most pesticide use patterns, passerines are more 

likely to be exposed to pesticides than upland game species and 

waterfowl 

o Passerines are smaller and have faster metabolisms than the waterfowl and 

upland game bird species traditionally used in avian toxicity tests which 

could impact their sensitivity to chemicals. 

Practical Utility of the Data 

How did the Agency make its registration decision without these data? 

Since this is a new requirement, EPA was using the results from the toxicity tests for the upland 

gamebird species (Note: A study on a waterfowl species was never submitted). 

How will the data be used? 

Data from passerine toxicity studies will be used to estimate potential risks to birds associated 

with uses of deltamethrin. The data will reduce uncertainties associated with the current risk 

assessment for passerine species and will improve our understanding of the potential effects of 

deltamethrin. 

How could the data impact the Agency’s future decision-making? 

Because birds significantly contribute to overall environmental quality, a solid understanding of 

the potential risks to birds, including passerine species, is essential for sound environmental 

management. Without acceptable data for deltamethrin, the Agency cannot determine the levels 

of deltamethrin that result in effects to passerine species. If the data indicates that registered 

tralomethrin usage may pose a risk of adverse effects to non-target birds above the Agency Level 

of Concern, the Agency may explore decision options to mitigate this risk. The lack of these data 

will limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act, and could result in use restrictions for deltamethrin which may 

otherwise be avoided, or which are unnecessarily severe. 
51

Guideline Number: 850.1400 

Study Title: Fish Early Life Stage (saltwater) 

Guideline Number: 850.1500 

Study Title: Fish Life Cycle (saltwater) 

Rationale for Requiring the Data 

Deltamethrin has the potential to enter estuarine/marine water bodies based on current usuage patterns that 

include coastal areas. Exposure to aquatic organisms is also evidenced by studies from Weston et al (2005) 

and Amweg et al (2006). Furthermore, the acute LC50 = 0.36 μg a.i./L for estuarine/marine fish, indicating 

that deltamethrin is very highly toxic on an acute basis to sheepshead minnow and demonstrating potential 

chronic risk to this taxon (MRID 42114811). Available ecological studies also show that low-level chronic 

exposure to deltamethrin has the potential to cause adverse reproductive effects in freshwater fish 

(NOAEC = 0.017 μg a.i./L, MRID 42786802). 

Practical Utility of the Data 

How did the Agency make its re-registration decision without this data? 

To address potential risks, the Agency imposed mitigation, as an interim measure, which included reduced 

use rates and application restrictions. 

How will the data be used? 

The estuarine/marine fish early life stage and fish life-cycle study would allow the Agency to analyze 

chronic effects, including effects on reproductive success and growth, to estuarine/marine fish. The effects 

data would be used to determine the likelihood that the chronic risks can potentially impact aquatic 

communities, either by direct effects on fish or by indirect effects via invertebrates by reducing their food 

sources. By refining the assessment, the Agency would be able to determine whether the mitigation 

imposed as part of the reregistration process was appropriate due to toxicity concerns with deltamethrin. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have to 

assume that deltamethrin "may affect" endangered invertebrates directly (and endangered species from 

other taxa indirectly), and use of deltamethrin might need to be restricted in areas where endangered 

species could be exposed. The lack of these data will limit the flexibility the Agency and registrants have 

in coming into compliance with the Endangered Species Act and could result in use restrictions for 

deltamethrin which are unnecessarily severe.
52

Guideline Number: 850.1350 

Study Title: Aquatic Invertebrate Life-Cycle (saltwater) 

Rationale for Requiring the Data 

The acute toxicity of deltamethrin to estuarine/marine invertebrates indicates the potential for chronic risk 

to animals in this taxon, and the potential for chronic exposure exists. Deltamethrin has the potential to 

enter estuarine/marine water bodies based on current usuage patterns that include coastal areas. The parent 

compound tralomethrin exhibits chronic toxicity effects to estuarine/marine invertebrates. Without this 

study, the Agency would have to presume chronic risk to listed and non-listed estuarine/marine 

invertebrates, but would not be able to quantify the risk. 

The Agency had conditionally required aquatic invertebrate life-cycle studies (Guidelines 850.1300, 

850.1350, and 850.1400) for terrestrial food and nonfood, aquatic food and nonfood, forestry, and 

domestic outdoor uses. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without this data? 

To address potential risks, the Agency imposed mitigation, as an interim measure, which included reduced 

use rates and application restrictions. 

How will the data be used? 

The aquatic invertebrate life-cycle study would allow the Agency to analyze chronic effects, including 

effects on reproductive success and growth, to saltwater invertebrates. The effects data would be used to 

determine the likelihood that the chronic risks can potentially impact aquatic communities, either by direct 

effects on invertebrates or by indirect effects on fish by reducing their food sources. By refining the 

assessment, the Agency would be able to determine whether the mitigation imposed as part of the 

reregistration process was appropriate due to toxicity concerns with deltamethrin. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the Agency would have to 

assume that deltamethrin "may affect" endangered invertebrates directly (and endangered species from 

other taxa indirectly), and use of deltamethrin might need to be restricted in areas where endangered 

species could be exposed. The lack of these data will limit the flexibility the Agency and registrants have 

in coming into compliance with the Endangered Species Act and could result in use restrictions for 

deltamethrin which are unnecessarily severe.
53

Guideline Number: None 

Study Title: Whole sediment: Chronic invertebrates freshwater and marine 

Rationale for Requiring the Data 

No chronic sediment toxicity tests for freshwater or marine invertebrates have been submitted to 

satisfy the Agency’s updated data requirements for outdoor uses in 40 CFR Part 158 (October 26, 

2007). For sediment studies involving pyrethroids, tests on Hyalella azteca, Chironomus tentans, 

and Leptocheirus plumulosus are requested. Although both are freshwater species, Hyalella and 

Chironomus differ substantially in their ecological niche (i.e., epibenthic vs. infaunal species), 

physiology, and there is some evidence suggesting Hyalella is among the more sensitive 

invertebrates to some pyrethroids based on water column tests (Anderson et al. 2006). 

o Benthic organisms inhabit sediment environments that may be exposed to 

run-off or spray drift from deltamethrin applications used in agricultural, 

forest, and residential settings 

o Previous studies have identified a potential adverse effect for freshwater 

and estuarine/marine aquatic organisms based on water column toxicity 

values. Therefore, there is uncertainty associated with that estimate that 

can be reduced using data from a toxicity test with benthic organisms. 

o There is the potential for persistent exposure from deltamethrin in 

sediment indicated by the fate properties and open literature studies on 

pyrethroids (Stout II, et al. 2009, Weston et al. 2005, and Amweg et al.

2006).

Practical Utility of the Data 

How did the Agency make its registration decision without these data?

Surface waters EECs were estimated, while the benthic zone of the bodies of water could not be 

estimated at the time. The possibility of accumulation of the chemical in sediments was stressed 

in all the reviews. It was noted that LOCs for aquatic organisms were exceeded using a variety of 

methods to calculate EECs. Recently, the Agency has used the pore water EECs, generated by 

PRZM/ EXAMS, for other synthetic pyrethroids with similar aquatic toxicity and level of binding 

to soils/ sediments than deltamethrin. Using the equilibrium partitioning theory (EqP), the RQs 

were estimated for other pyrethroids. It has been found that the RQs exceeded the LOCs for these 

chemicals. A similar finding is expected for deltamethrin. 

How will the data be used? 

Data from sediment toxicity studies will be used to estimate potential risks to benthic organisms 

associated with uses of deltamethrin. The data will reduce uncertainties associated with the 

current risk assessment for benthic species and will improve our understanding of the potential 

effects of deltamethrin. 

How could the data impact the Agency’s future decision-making? 

Although there was uncertainty in estimating the effect of deltamethrin on benthic organisms in 

the previous assessment, there was a potential risk associated with adverse effects identified for 

estuarine/marine acute and chronic organisms. Acceptable data for benthic organisms will reduce 

the uncertainty from the previous assessment If the data indicates that registered deltamethrin 

usage may pose a risk of adverse effects to non-target benthic organisms above the Agency Level 

of Concern, the Agency may explore decision options to mitigate this risk. The lack of these data 
54

will limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act, and could result in use restrictions for deltamethrin which may 

otherwise be avoided, or which are unnecessarily severe. 
55

Guideline Numbers: 850.4150 and 850.4250 

Study Title: Vegetative vigor and Seedling emergence, Tier I/ Tier II 

Rationale for Requiring the Data 

No acceptable toxicity data are currently available to assess the risk of deltamethrin to terrestrial 

plants. 

Since deltamethrin has residential outdoor uses, vegetative vigor and seedling emergence studies 

are required. These phytotoxicity data are needed to evaluate the level of pesticide exposure to 

non-target terrestrial and aquatic plants and to assess the impact of pesticides on endangered and 

threatened plants. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

Since EPA was unable to evaluate the potential risks to terrestrial plants associated with the 

proposed uses of deltamethrin, risks were not precluded for vegetative vigor and seedling 

emergence endpoints for terrestrial plants. 

How will the data be used? 

Data from terrestrial plant toxicity studies will be used to estimate potential risks to plants 

associated with uses of deltamethrin. The data will reduce uncertainties associated with the 

current risk assessment for terrestrial plants and will improve our understanding of the potential 

effects of deltamethrin on plants. 

How could the data impact the Agency’s future decision-making?

Because plants form the basis of most habitats and significantly contribute to overall 

environmental quality, a solid understanding of the potential risks to terrestrial plants is essential 

for sound environmental management. Without acceptable plant growth data for deltamethrin, the 

Agency cannot determine the levels of deltamethrin that result in effects to terrestrial plants. If the 

data indicates that registered deltamethrin usage may pose a risk of adverse effects to non-target 

terrestrial plants plants above the Agency Level of Concern, the Agency may explore decision 

options to mitigate this risk. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act, and could result in 

use restrictions for deltamethrin which may otherwise be avoided, or which are unnecessarily 

severe. 
56

Guideline Number: 850.4400 

Study Title: Aquatic Vascular Plant Growth-Lemna spp. Tiers I/II 

Rationale for Requiring the Data 

No acceptable studies for deltamethrin have been submitted for vascular aquatic plants. The 

Agency has finalized its update to the data requirements in 40 CFR Part 158. In these updated 

data requirements, which were promulgated on October 26, 2007, vascular plant testing is 

required for pesticides such as deltamethrin with outdoor uses. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

Since EPA was unable to evaluate the potential risks to aquatic vascular plants associated with 

the use of deltamethrin, risks were presumed for vascular aquatic plants. 

How will the data be used? 

Data from aquatic plant toxicity studies will be used to estimate potential risks to plants 

associated with uses of deltamethrin. The data will reduce uncertainties associated with the 

current risk assessment for aquatic plants and will improve our understanding of the potential 

effects of tralomethrin on vascular aquatic plants. 

How could the data change the Agency’s decision, or impact the Agency’s future decisionmaking? 

Because plants form the basis of most habitats and significantly contribute to overall 

environmental quality, a solid understanding of the potential risks to aquatic plants is essential 

for sound environmental management. Without plant growth data for deltamethrin, the Agency 

cannot determine the levels of deltamethrin that result in effects to vascular aquatic plants. If 

the data indicates that registered deltamethrin usage may pose a risk of adverse effects to nontarget aquatic vascular plants above the Agency Level of Concern, the Agency may explore 

decision options to mitigate this risk. 

If future endangered species risk assessments are performed without these data, the Agency 

would have to assume that deltamethrin "may affect" endangered plants and use of deltamethrin 

might need to be restricted in areas where endangered species could be exposed. The lack of 

these data will limit the flexibility the Agency and registrants have in coming into compliance 

with the Endangered Species Act and could result in use restrictions for deltamethrin that may 

be unnecessarily severe.
57

Guideline Number: 850.5400 

Study Title: Algal toxicity test, Tier I/II 

Rationale for Requiring the Data 

No toxicity data are currently available to assess the risk of tralomethrin and the degradate 

deltamethrin to aquatic nonvascular plants. Since tralomethrin has residential outdoor uses, Tier 

I/II aquatic nonvascular plant studies are required. These phytotoxicity data are needed to 

evaluate the level of pesticide exposure to non-target aquatic plants and to assess the impact of 

pesticides on endangered and threatened plants. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

Since EPA was unable to evaluate the potential risks to aquatic nonvascular plants associated with 

the proposed uses of tralomethrin, risks were presumed for aquatic plants. 

How will the data be used? 

Data from Tier I/II nonvascular aquatic plant toxicity studies will be used to estimate potential 

risks to plants associated with uses of tralomethrin. The data will reduce uncertainties associated 

with the current risk assessment for nonvascular aquatic plants and will improve our 

understanding of the potential effects of tralomethrin and the degradate deltamethrin. 

How could the data impact the Agency’s future decision-making?

Because plants form the basis of most habitats and significantly contribute to overall 

environmental quality, a solid understanding of the potential risks to nonvascular aquatic plants is 

essential for sound environmental management. Without plant growth data for tralomethrin and 

the degradate deltamethrin, the Agency cannot determine the levels of tralomethrin that result in 

effects to aquatic plants. If the data indicates that registered tralomethrin usage may pose a risk of 

adverse effects to non-target aquatic nonvascular plants above the Agency Level of Concern, the 

Agency may explore decision options to mitigate this risk. The lack of these data will limit the 

flexibility the Agency and registrants have in coming into compliance with the Endangered 

Species Act, and could result in use restrictions for tralomethrin which may otherwise be avoided, 

or which are unnecessarily severe.