Environmental Fate and Ecological Risk 

Assessment Preliminary Problem 

Formulation in Support of 

Registration Review of Pyrethrins 

DP Barcode D391619 

PC Code 069001 

Case No. 2580 

November 30, 2011 

Environmental Fate and Effects Division 

Office of Pesticide Programs 

U.S. Environmental Protection Agency 
 Prepared by: 

 Amanda Solliday, Biologist 

 José L. Meléndez, Chemist 

 Secondary Review: 

 Keith Sappington, Senior Advisor 

 Mah T. Shamim, Ph.D., Chief 

 Environmental Risk Branch V

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Table of Contents 

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

2. Problem Formulation .............................................................................................................. 5 

2.1 Nature of Regulatory Action ................................................................................................ 5 

2.2. Previous Risk Assessments .................................................................................................. 6 

3. Stressor Source and Distribution ............................................................................................ 9 

3.1. Mechanism of Action ........................................................................................................ 16 

3.2. Overview of Pesticide Usage ............................................................................................ 17 

3.3. Environmental Fate and Transport .................................................................................... 30 

4. Receptors............................................................................................................................... 35 

4.1. Aquatic and Terrestrial Effects ......................................................................................... 35 

4.2. Incident Database Review................................................................................................. 43 

4.3. Ecosystems Potentially at Risk ......................................................................................... 45 

5. Assessment Endpoints .......................................................................................................... 35 

6. Conceptual Model .............................................................................................................. 46 

6.1. Risk Hypothesis ............................................................................................................... 46 

6.2. Conceptual Diagram ........................................................................................................ 47 

7. Analysis Plan ..................................................................................................................... 52 

7.1. Stressors of Concern ......................................................................................................... 53 

7.2. Measures of Exposure ....................................................................................................... 53 

7.3. Measures of Effect ............................................................................................................ 58 

7.4. Integration of Exposure and Effects ................................................................................. 59 

7.5. Deterministic and Probabilistic Assessment Methods ...................................................... 59 

7.6. Endangered Species Assessments ..................................................................................... 59 

7.7. Drinking Water Assessment ............................................................................................. 60 

7.8 Endocrine Disruption Screening Program ........................................................................ 60 

7.9. Preliminary Identification of Data Gaps ........................................................................... 61 

7.9.1. Fate ............................................................................................................................. 61 

7.9.2 Effects ......................................................................................................................... 65 

8. References ................................................................................................................................ 70 

9. Bibliography ............................................................................................................................ 70 

Appendix A. PRD Data Request Justification Tables ................................................................ 80 

Appendix B. Pyrethrins Down-the-Drain Risk Assessment ....................................................... 84 
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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 pyrethrin. 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 risk (USEPA, 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 pyrethrin. 

Pyrethrin (also refered to in this document as pyrethrins; PC Code 069001) is a broad-spectrum 

insecticide used in four major sectors: agricultural settings, commercial/industrial/institutional/ 

food & non-food/mosquito abatement, domestic home and garden, and pet care. The pyrethrins 

are a mixture of naturally occurring insecticides derived from the flowers of Chrysanthemum 

cinerariaefolium and Chrysanthemum cineum. The six individual pyrethrins are pyrethrin 1, 

pyrethrin 2, cinerin 1, cinerin 2, jasmolin 1, and jasmolin 2. The technical grade active ingredient 

(FEK-99) is commonly referred to as pyrethrum extract, which is the sum of pyrethrins I (the 

esters of chrysanthemic acid - pyrethrin 1, cinerin 1 and jasmolin 1) and pyrethrins II (the esters 

of pyrethric acid - pyrethrin 2, cinerin 2, and jasmolin 2), and this mixture constitutes 45 to 55% 

of pyrethrum extract. In addition to pyrethrins, the extract contains “23-25% other phytochemical 

extracts containing triglyceride oils, terpenoids, and carotinoid plant colours. The extracts usually 

contain 20-25% light isoparaffins and 3-5% butylated hydroxytoluene, which may be added 

during and after processing, respectively, for extraction or as antioxidants” (Solecky 1999). All 

six pyrethrins have the same backbone molecular structure with different substituents at two sites. 

Since all the structures at the two sites are similar, they are expected to have similar 

environmental fate properties. The product PYRENONE® Crop Spray, a formulation that 

contains pyrethrins (6.0%), piperonyl butoxide (60.0%) and inert ingredients (34.0%), was used 

as a test material in many of the ecological effects laboratory studies. For the structure of the 

individual pyrethrins and further identification information, refer to Figure 3-2 and Table 3.1. 

There are many other formulation types, such as aerosol, combustible coil, dust, emulsifiable 

concentrate, ready to use liquid, shampoo, and wettable powder. According to the Chemical 

Profile for pyrethrins written by the Biological and Economic Analysis Division, “Application 

methods in agricultural and non-agricultural uses (based on the Reregistration Eligibility Decision 

[RED]) are diverse, and include: aerosol can, mist blower, metered release devices, total release 

aerosol, fixed wing aircraft, helicopter, truck-mounted ultra low volume (ULV) equipment, cold 

aerosol generator, hand held sprayers (high or low pressure handwands), thermal/cold/ULV 

fogging equipment, conventional dusting equipment (e.g., power duster, bulb duster, shaker can), 

outdoor misting systems, and irrigation systems (USEPA 2011). 

Of these, power dusting was banned by the RED due to inability to assess risk scenarios. 

However, dust applications to carpets are allowed as spot treatments only. All other application 

methods are still label uses. However, due to human health risk concerns, several risk mitigation 

measures (such as limits on the number of applications per year or individual area treated) were 

imposed by the RED for three general application methods: broadcast dusts applied to carpets, 
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indoor metered release devices, and outdoor residential misting systems. 

As stated in BEAD’s Chemical Profile for Pyrethrins, “[T]he Insecticide Resistance Action 

Committee (IRAC), comprised of technical personnel from various large agrochemical and public 

health companies, classifies pyrethrin as a member of the Mode of Action Group 3 (subgroup 

3A). This group of insecticides acts as sodium channel modulators, thus causing disruption of 

nerve impulses in the target insects (USEPA 2011). 

Like other compounds derived from the chemical structure of pyrethrum, it is most toxic to the 

target pest on contact, and has a quick “knockdown” effect (Doull 1976). Pyrethrin is sometimes 

formulated with a synergist compound, usually piperonyl butoxide, also known as PBO, or MGK264, to extend its active life and increase its toxic effect on target insects (Jones 1998).” 

For agriculture uses, maximum seasonal rates are 0.50 lb a.i./A, and for all crops, the maximum 

number of pyrethrin applications per season is 10 at the maximum single application rate of 0.050 

lb a.i./A (from the pyrethrins Master Label). Pyrethrin may be applied year-round; thus, in some 

regions of the United States more than one season per year are possible. Because target species 

could develop resistance to pyrethrins, it appears that multiple seasons at the maximum seasonal 

rate are unlikely. According to BEAD’s Chemical Profile for pyrethrin, “Based on private market 

pesticide usage data from 1998-2010, the annual total agricultural usage averaged approximately 

2,000 pounds active ingredient for 123,000 acres (GfKynetic, 1998-2010).” Furthermore, the 

usage data indicates that the consumer indoor use ranged from 53,000 to 113,000 lbs active 

ingredient from 2000-2005, which indicates that non-agricultural use exceeds that of use on 

agricultural crops. Pyrethrin may be used in a wide variety of crop and non-crop sites, 

ornamentals, lawns, etc. The chemical also has other FIFRA uses, such as applications to 

livestock (cattle, pigs, goats, horses and various others), pets (birds, dogs, cats, guinea pigs and 

various others) and in commercial animal housing sites (such as pet stores and zoos). Pyrethrin 

can also be used on human clothing (for insect and mold/ mildew control), including clothing, 

outerwear clothing, in storage clothing and woolens. 

2. Problem Formulation 

 2.1. Nature of Regulatory Action 

This report is the Environmental Fate and Effects Division’s (EFED) Problem Formulation for the 

Registration Review of pyrethrins. Previous risk assessments were completed for the use of this 

chemical, which serve as the basis for this document. 

The Food Quality Protection Act (FQPA) of 1996 mandated the EPA to implement registration 

review (http://www.epa.gov/oppsrrd1/registration_review/). All pesticides distributed or sold in 

the United States generally must be registered by the 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. In addition, it must not be expected to cause unreasonable adverse effects to 

human health through the dietary and residential routes of exposure under the Federal Food Drug 
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and Cosmetic Act (FFDCA). 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 unreasonable adverse effects to human health and 

the environment. Changes in science, public policy, and pesticide use practices will occur over 

time. Through the 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 Registration Review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is conducting an 

evaluation to determine whether pyrethrin 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. Previous Risk Assessments and Scientific Advisory Panels 

The most recent review performed for the pyrethrins was the national-level EFED chapter of the 

Reregistration Eligibility Decision Document (EFED RED, dated April 4th 2007; DP Barcode: 

D338495, USEPA 2007). The review indicated risk concerns for freshwater and estuarine/ 

marine organisms, including benthic organsims. For the agricultural uses, model generated 

exposure values suggested that maximum rates can result in acute risk to fish and aquatic 

invertebrates (freshwater and estuarine/ marine) with triggers that included restrictive use and 

endangered species concern. Although concern for estuarine/ marine endangered invertebrate was 

triggered, EFED noted there were no listed species under this category. However, it appears that 

at the present time there are listed estuarine/ marine species. Evaluating chronic risk from this 

exposure scenario showed that the LOC triggers were exceeded for estuarine/ marine 

invertebrates, while fish (freshwater and estuarine/ marine) and freshwater invertebrates were 

found not to be at chronic risk from pyrethrin exposure in the water column. Evaluation of four 

crop scenarios using the TGAI (ID potatoes, PA tomatoes, CA onions, OR snap beans) suggested 

that LOCs for freshwater and estuarine/marine fish and invertebrates should not be exceeded if 

the typical application rate is used. 

EFED also addressed potential aquatic risk from the PBO formulation at the maximum and 

typical rates for a pyrethrin. In this case, the Agency only evaluated acute exposure to aquatic 

organisms. Risk quotients were calculated using the technical grade active ingredient for the 

agricultural uses and formulated product (PYRENONE® Crop Spray, EPA Reg. No. 432-1033) 

for the mosquito abatement uses. However, EFED also calculated potential risk from PBO 

formulation use on agricultural crops, which showed that acute risk to freshwater and 

estuarine/marine fish and invertebrates could increase by 2-7x for freshwater and estuarine/ 

marine fish and 10x for estuarine/marine invertebrates based on the enhanced toxicity of 

pyrethrins in the presence of the synergist PBO. However, the results obtained using the typical 

end use product with the synergist at the typical application rate resulted in reduction of the risk to 

aquatic organisms (freshwater and estuarine/ marine fish and freshwater invertebrates), but this 

reduction in exposure still presented the potential for acute high, acute restrictive, and chronic risk 
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to estuarine/marine invertebrates species. 

Evaluation of the mosquito abatement applications, at the maximum rate showed that there did 

not appear to be the potential for acute risk to freshwater fish and invertebrates or esrtuarine/ 

marine fish but there was the potential for acute LOCs being exceeded for estuarine/ marine 

invertebrates. However, this risk to estuarine/marine invertebrates appeared to be eliminated if 

the boom height is set at 150 ft and a Dv0.5 droplet size at 40 μm (a Dv0.5 value is the droplet size 

over which half of the volume of the droplets is above that value and half of the volume of the 

droplets is below that value). The Agency also evaluated the typical rate and found that potential 

acute risk to estuarine/marine invertebrates could be eliminated with a boom height of 75ft and a 

Dv0.5 50 μm droplet size. 

The Agency also evaluated the pharmacological uses of pyrethrin using the “Down-the-Drain” 

module of the Exposure and Fate Assessment Screening Tool (E-FAST) model and found that 

aquatic LOCs were not exceeded for freshwater or estuarine/marine organisms. 

In the RED risk assessment, the Agency did not find acute and chronic risks to listed or non-listed 

mammalian and avian species. Chronic avian data was not available, and risks were estimated 

using the results from a sub-acute dietary study. Although the Agency did not conduct a 

quantitative risk assessment for beneficial insects at the time, toxicity studies with honey bees 

show that pyrethrins are highly toxic on an acute contact basis. This suggests that pyrethrins are 

toxic to nontarget beneficial insects, as well as listed insect species. 

2009 Scientific Advisory Panel

OPP presented a “Proposed Common Mechanism Grouping for the Pyrethrins and Synthetic 

Pyrethroids” to a FIFRA SAP in June 2009. OPP proposed two subgroups based on Type I or 

Type II effects related to sodium current tails and neurobehavioral impact, with esfenvalerate and 

fenpropathrin showing symptoms of both types. The panel agreed with OPP and indicated that 

substances with mixed characteristics could be included in both groups (see p. 18 of SAP minutes, 

USEPA 2009). The natural pyrethrins are Type I pyrethroid insecticides, with no cyanosubstitution in the alpha-position. This mechanism of action assessment was performed by 

HED/OPP and presented to the SAP to determine if a cumulative assessment is required for the 

synthetic pyrethroids. Information on the SAP is available in the docket (with non-copyright 

material available at http://www.regulations.gov) under EPA-HQ-OPP-2008-0489. 

EFED does not currently conduct cumulative ecological risk assessments for several reasons. 

Specifically, the Division does not currently have the methodology to conduct similar cumulative 

risk assessments for all of the (non-human) biological entities for which EFED has responsibility. 

In addition to addressing the toxicological aspects of the cumulative effects of multiple 

pyrethroids to multiple biological entities, a cumulative ecological risk assessment would likely 

require consideration of exposure at a watershed scale in order to incorporate spatial and temporal 

variability in pyrethroid applications into cumulative exposure assessment. EFED does not have 

the modeling tools developed for conducting this type of assessment. However, EFED will 

consider open literature, currently available models and other lines-of-evidence (e.g., monitoring 
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data) as available, to address the potential for cumulative effects of pyrethroids and pyrethrins in 

the risk description of the ecological risk assessment for pyrethrin. 

National Water Quality Assessment (NAWQA)

The pyrethrins are not among the constituents monitored by the National Water Quality 

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

Aquatic Life Criteria and Aquatic Life Benchmarks 

The Clean Water Act requires the Agency to publish water quality criteria that accurately reflect 

the latest scientific knowledge on the kind and extent of all identifiable effects on health and 

welfare which might be expected from the presence of pollutants in any body of water, including 

ground water. While these recommended criteria do not, in themselves, impose any requirements, 

states and authorized tribes can use them to develop water quality standards. US EPA Aquatic 

Life Ambient Water Quality Criteria document has not been published for pyrethrin (at 

http://www.epa.gov/waterscience/criteria/ accessed 05/09/11). 

For pyrethrin, OPP has not published aquatic life benchmarks for freshwater species, based on the 

most sensitive species from the most recent risk assessments (refer to the following site 

http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm#benchmarks accessed 

05/09/11). 

Impaired Water Bodies 

Pyrethrin is not individually identified as a cause of impairment for any water bodies listed as 

impaired under section 303(d) of the Clean Water Act, based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

(accessed 10/24/11). However, the pyrethroids (which are pyrethrin-like compounds, and could 

involve natural pyrethrins) as a group have been identified as a cause for impairment for three 

water bodies in Central Valley, California: Del Puerto Creek, Ingram Creek Site (from confluence 

with Hospital Creek to Highway 33 crossing) and second Ingram Creek Site (from confluence 

with San Joaquin River to confluence with Hospital Creek). Additional bodies of water were 

evaluated and included into the list of impaired bodies of water by October 2011 (see 

http://www.waterboards.ca.gov/water_issues/programs/tmdl/integrated2010.shtml , 

http://www.swrcb.ca.gov/rwqcb5/water_issues/tmdl/impaired_waters_list/303d_list.shtml and 

http://www.epa.gov/region9/water/tmdl/303d-pdf/Final-DecisLtrEnclosResponsSumCA2008-10-

303d.pdf accessed 10/24/11). The 2010 303(d) list for California contains 10 additional streams 

due to pyrethroids in the sediments. EFED will include relevant information on 303(d) listings in 

the final ecological risk assessment as appropriate. 

No Total Maximum Daily Load (TMDL) criteria have been developed specifically for pyrethrin, 

based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=

885&p_pollutant_group_name=PESTICIDES (accessed 10/24/11). It appears that a TMDL was 

established for pyrethroids and specifically for bifenthrin (Rio de Santa Clara/Oxnard Drain No. 

3). More information on impaired water bodies and TMDLs can be found at 

http://www.epa.gov/owow/tmdl/. The Agency invites submission of water quality data for this 

pesticide. To the extent possible, data should conform to the quality standards in Appendix A of 
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the OPP Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water 

Quality Data in OPP’s Registration Review Risk Assessment and Management Process (at

http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm), in order to ensure they 

can be used quantitatively or qualitatively in pesticide risk assessments. 

3. Stressor Source and Distribution

Pyrethrins are nonvolatile hydrocarbons produced by certain species of the chrysanthemum plant 

(genus Chrysanthemum) and have been used as insecticides since the 1800s. The plant species 

with the most toxic content that can be efficiently used for industrial purposes are C. 

cinerariaefolium and C. coccineum, which are grown mainly in Australia and East Africa. The 

active insecticidal components are collectively known as pyrethrins and consist of six esters. 

Although the ground flowers can be used as a dust, a more concentrated and efficacious pyrethrin 

product is possible through solvent extraction. Pyrethrin-containing dusts and extracts usually 

have an active ingredient content of about 30%. However, after filtration and reextraction the 

concentration can reach 90-100% (Matsumura1985). These compounds are contact poisons 

which can quickly penetrate the neural system. Although the pyrethrins have an effective 

“knockdown” action (induction of temporary paralysis) they do not necessarily have high killing 

properties by themselves. These compounds are moderately persistent under certain 

environmental conditions but are quickly metabolized under other conditions such as in the 

presence of sunlight (photolysis). In order to delay the metabolic action (inhibition of microsomal 

enzymes) so that a lethal dose is assured, organophosphates, carbamates, or synergists (such as 

piperonyl butoxide) may be added to the pyrethrins (Ecobichon and Donald, 1991). Pyrethrin 

compounds have been used primarily to control human lice, mosquitoes, cockroaches, beetles, 

and flies. Some pyrethrin compounds used to control insects in horticultural crops, are only 0.3% 

to 0.5% pyrethrins, and are used at rates of up to 50 lb/A. Other pyrethrin compounds may be 

used in grain storage and in poultry pens and on dogs and cats to control lice and fleas. 

Natural pyrethrins have their limitations for use on a large scale for agricultural purposes because 

of their cost and instability in sunlight. Therefore, in recent decades, many man-made pyrethrinlike compounds were developed and are referred to as synthetic pyrethroids. These compounds 

are more stable in sunlight (due to lower reactivity of side-chains) and are generally effective 

against most agricultural insect pests when used at very low rates. 

The formulated products of pyrethrins usually contain a synergist, such as piperonyl butoxide, or 

MGK-264. These compounds enhance the insecticidal activity of pyrethrin. The Agency does 

not routinely include, in its screening risk assessments, an evaluation of more than one active 

ingredient. In the case of product formulations of active ingredients, each active ingredient is 

subject to an individual risk assessment for regulatory decision. It is noted, however, that some 

formulations of pyrethrin contain up to 60% PBO, with only about 5 to 6% pyrethrins. Table 3.1

provides some identification information for pyrethrins, also, refer to its general structure in 

Figures 3-1 and 3-2. 

 
Figure 3-1. The general structure and stereochemistry of the pyrethrins

R = -CH4 (for cinerin), -CH3CH4 (for jasmolin) or -CH=CH2 (for pyrethrin) 

R’= -CH3 (for pyrethrins I) -CO2CH4 (for the pyrethins II) 

The six individual pyrethrins are pyrethrin 1, pyrethrin 2, cinerin 1, cinerin 2, jasmolin 1, and 

jasmolin 2. These compounds are esters of two carboxylic acids (chrysanthemic acid and 

pyrethric acid) and three cyclopentenolones (pyrethrolone, cinerolone, and jasmolone). The 

technical grade active ingredient (FEK-99) is commonly referred to as pyrethrum extract, which is 

the sum of pyrethrins I (the esters of chrysanthemic acid - pyrethrin 1, cinerin 1, and jasmolin 1) 

and pyrethrins II (the esters of pyrethric acid - pyrethrin 2, cinerin 2, and jasmolin 2), also called 

"the pyrethrins", and this mixture constitutes 45 to 55% of pyrethrum extract. In the United 

States, the pyrethrum extract is standardized as 45-55% w/w total pyrethrins. The typical 

proportion of Pyrethrins I to II is 1:14, while the ratio of pyrethrins: cynerins: jasmolins is 71:21:7 

(Tomlin 1997). 

 

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Figure 3-2. Specific structures of each of the pyrethrins

Table 3.1. Identification information for pyrethrins 

PARAMETER VALUE(s) SOURCES

Nomenclature of 

Pyrethrins 

(IUPAC Names) 

pyrethrin 1: 

(Z)-(S)-2-methyl-4-oxo-3-(penta-2,4-dienyl)cyclopent-2-

enyl (1R,3R)-2,2dimethyl-3-(2-methylprop-1-enyl) 

cyclopropanecarboxylate 

pyrethrin 2: 

(Z)-(S)-2-methyl-4-oxo-3-(penta-2,4-dienyl)cyclopent-2-

enyl (E)-(1R,3R)-3-(2methoxycarbonylprop-1-enyl)-2,2-

dimethylcyclopropanecarboxylate 

cinerin 1: 

(Z)-(S)-3-(but-2-enyl)-2-methyl-4-oxocyclopent-2-enyl 

(1R,3R)-2,2-dimethyl-3(2-methylprop-1-enyl) 

cyclopropanecarboxylate 

cinerin 2: 

(Z)-(S)-3-(but-2-enyl)-2-methyl-4-oxocyclopent-2-enyl 

(E)-(1R,3R)-3-(2methoxycarbonylprop-1-enyl)-2,2-

USEPA 2006b 

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Table 3.1. Identification information for pyrethrins 

PARAMETER VALUE(s) SOURCES

dimethylcyclopropanecarboxylate 

jasmolin 1: 

(Z)-(S)-2-methyl-4-oxo-3-(pent-2-enyl)cyclopent-2-enyl 

(1R,3R)-2,2-dimethyl-3(2-methylprop-1-

enyl)cyclopropanecarboxylate 

jasmolin 2: 

(Z)-(S)-2-methyl-4-oxo-3-(pent-2-enyl)cyclopent-2-enyl 

(E)-(1R,3R)-3-(2methoxycarbonylprop-1-enyl)-2,2-

dimethylcyclopropanecarboxylate 

Nomenclature of 

Pyrethrins 

(CAS Names) 

pyrethrin 1: 

(1S)-2-methyl-4-oxo-3-(2Z)-2,4-pentadienylcyclopenten1-yl (1R,3R)-2,2dimethyl-3-(2-methyl-1-propenyl) 

cyclopropanecarboxylate 

pyrethrin 2: 

(1S)-2-methyl-4-oxo-3-(2Z)-2,4-pentadienyl-2-

cyclopenten-1-yl (1R,3R)-3-[(1E)3-methoxy-2-methyl-3-

oxo-1-propenyl]-2,2-dimethylcyclopropanecarboxylate 

cinerin 1: 

(1S)-3-(2Z)-2-butenyl-2-methyl-4-oxo-2-cyclopenten-1-yl 

(1R,3R)-2,2-dimethyl3-(2-methyl-1-propenyl) 

cyclopropanecarboxylate 

cinerin 2: 

(1S)-3-(2Z)-2-butenyl-2-methyl-4-oxo-2-cyclopenten-1-yl 

(1R,3R)-3-[(1E)-3methoxy-2-methyl-3-oxo-1-propenyl]-

2,2-dimethylcyclopropanecarboxylate 

jasmolin 1: 

(1S)-2-methyl-4-oxo-3-(2Z)-2-pentenyl-2-cyclopenten-1-

yl (1R,3R)-2,2-dimethyl3-(2-methyl-1-

propenyl)cyclopropanecarboxylate 

jasmolin 2: 

(1S)-2-methyl-4-oxo-3-(2Z)-2-pentenyl-2-cyclopenten-1-

yl (1R,3R)-3-[(1E)-3methoxy-2-methyl-3-oxo-1-

propenyl]-2,2-dimethylcyclopropanecarboxylate 

USEPA 2006b 

PC Code 069001 USEPA 2006b 

Case Number 2580 USEPA 2006b 

CAS Reg. Nos. 

8003-34-7 Pyrethrum, 

121-21-1 pyrethrin 1, 

121-29-9 pyrethrin 2, 

25402-06-6 cinerin 1, 

121-20-0 cinerin 2, 

4466-14-2 jasmolin 1, 

1172-63-0 jasmolin 2 

USEPA 2006b 

Molecular Formulas 

Various as follows: 

C21H25O3, C21H25O5, C20H25O3, 

C22H30O5, C21H28O3, C22H28O5

USEPA 2006b 

Molecular Weights 

328.4 g/mol pyrethrin 1 

372.4 g/mol pyrethrin 2 

316.4 g/mol cinerin 1 

360.4 g/mol cinerin 2 

330.5 g/mol jasmolin 1 

357.7 g/mol jasmolin 2 

USEPA 2006b 

The structures of pyrethrins from the chemical’s data sheet accessed 05/10/2011 and available at 

http://www.alanwood.net/pesticides/pyrethrins.html . 

The laboratory environmental fate studies conducted for the pyrethrins were based on the data 
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obtained for pyrethrin 1, which was chosen as a surrogate for all the six pyrethrins. This selection 

appears to be appropriate since pyrethrin 1 is the pyrethrin with the highest abundance in the 

pyrethrum extract (e.g., see Essig and Zhao 2001). The following conclusions were derived for 

these compounds: Pyrethrins are considered to be persistent in certain environments and short 

lived in other environments. Hydrolysis under alkaline conditions is an important route of 

dissipation for pyrethrins in water (half-life at pH 9 range 14-17 days); however, this reaction 

appears to be relatively slow under neutral or acidic conditions (pH 5 and 7). Pyrethrins quickly 

photodegrade in shallow clear water. Pyrethrins adsorb strongly to soil surfaces and are generally 

considered to have a relatively low mobility in soils (mean KF = 301.5 L/kg); therefore, the 

potential to leach into groundwater is considered low. They could reach surface water via spray 

drift or runoff events accompanied by erosion where they quickly adsorb to suspended solids in 

the water column, and partition into the sediment. Sediments are likely to be an environmental 

sink for any non-degraded pyrethrins since they appear to persist under anaerobic conditions. 

Biodegradation under aerobic conditions occurs fairly rapidly with half-lives of a few days. 

Volatilization is not expected to be an important transport process since pyrethrins tend to have 

relatively low vapor pressure and Henry’s Law constant. 

Pyrethrins 1 and 2 have a range of water solubilities of 0.2-9.0 mg/L, and its hydrophobic nature 

leads to strong soil adsorption and a tendency to partition to sediment in aquatic systems. The 

reported value of log octanol/ water partition coefficients of 4.3-5.9 suggest that pyrethrins have a 

potential to bioaccumulate in aquatic organisms, assuming that chemical metabolism is negligible. 

However, the measured bioconcentration factor in fish (471x whole fish; depuration was rapid: by 

day 1, 77% of the accumulated [14C]-residues were eliminated, see Table 3.10) is much lower 

than that expected based on KOW alone, which suggests that pyrethrins metabolism by fish is 

substantial. Pyrethrins have a high molecular weight of ≥324 g/mol. With a vapor pressure of 

~2.0 x 10-5 to 4.0 x 10-7 torr, and due to its solubility limit range, its calculated Henry’s Law 

Constant is relatively low (e.g., 7.73 x 10-7 atm-m3/mol for pyrethrins 1). Pyrethrin 1’s air/water 

partition coefficient (KAW) is ~3.14 x 10-5 (unitless), which classifies it as ‘slightly volatile from a 

water surface’ (USEPA 2008), and the Cwater+soil/Cair = ~9.58 x 106, which classifies the chemical 

as ‘non-volatile from moist soil’ (USEPA 2008). Based on these properties, pyrethrin 1 would 

have a slight potential to volatilize from wet surfaces, but not from moist soil. The slight 

potential to volatilize of pyrethrin 1 is attenuated by its tendency to bind to organic matter (e.g., 

soils, sediments, or organic matter and particulate in natural water). Table 3.2 lists various 

important physicochemical characteristics of the chemical. Table 3.10 lists available 

environmental fate characteristics of pyrethrin 1, along with information on the major and minor 

degradates detected in the submitted environmental fate and transport studies.

Table 3.2. Physicochemical Properties of Pyrethrins 

Property 

Pyrethrin 

Value MRID or Source 

Density/ 

Specific Gravity 

0.982 g/mL 

pyrethrin 1 1.5242 g/mL 

pyrethrin 2 1.5355 g/mL 

USEPA 2006 

Boiling Point (0C) 

146–148 °C at 2x10-3 torr for pyrethrin 1 

196–198 °C at 7x10-3 torr for pyrethrin 2 

136–138 °C at 8x10-3 torr for cinerin 1 

182–184 °C at 0.001 torr for cinerin 2 

USEPA 2006 
Table 3.2. Physicochemical Properties of Pyrethrins 

Pyrethrin 

Property Value MRID or Source 

Vapor Pressure (250C) 

pyrethrin 1: 2x10-5 torr 

pyrethrin 2: 4x10-7 torr 

cinerin 1: 1.1x10-6 torr(a)

cinerin 2: 4.6x10-7 torr(a)

jasmolin 1: 4.8x10-7 torr(a)

jasmolin 2: 1.9x10-7 torr(a)

USEPA 2006 

(a) Estimated value from 

EPISuite 

Water Solubility 

(ppm) 

pyrethrin 1: 0.2 ppm 

pyrethrin 2: 9.0 ppm USEPA 2006 

Henry’s Law Constant 

(atm-m3

/mole) 

pyrethrin 1: ~7.7x10-7 Atm-m3

/mol 

pyrethrin 2: ~2.2x10–8 Atm-m3

/mol 

‘Non-volatile under field conditions’

cinerin 1: 9.6x10-7 Atm-m3

/mol 

cinerin 2: 9.2x10-10 Atm-m3

/mol 

jasmolin 1: 1.3x10-6 Atm-m3

/mol 

jasmolin 2: 1.2x10–9 Atm-m3

/mol 

Calculated for pyrethrin 1 and 

pyrethrin 2 

Estimated for all the other 

chemicals using EPISuite 

Octanol – water 

partition coefficient 

(log KOW) (25o

C)

pyrethrin 1: 5.9 

pyrethrin 2: 4.3 USEPA 2006 

Air-water partition 

coefficient (KAW) 

KAW = Cair/Cwater = HLC/RT 

= 3.14 x 10-5 (unitless) for pyrethrin 1 

‘Slightly volatile from a water surface’ 

Temperature assumed to be 

250C, calculated value; 

USEPA, 2008 

Octanol-air partition 

coefficient (KOA) KOA = KOW/KAW = 2.53 x 1010 for pyrethrin 1 Calculated Value 

Cwater/Cair 

⎟

⎠

⎞ ⎜

⎝

⎛

××

××× = 6

air

water

10GMW P

760RT S

C

C = RT/HLC 

= 1/KAW = 31,757 (unitless) for pyrethrin 1 

‘Slightly volatile from a water surface’ 

Calculated 

USEPA, 2008 

Volatilisation Flux ≤0.002 μg/cm2

·hour MRID 43096604 

Cwater+soil/Cair

Cwater+soil/Cair = (1/KAW) (1/r + Kd) = 

9.58 x 106

‘Non-volatile from moist soil’ 

Calculated Value, using the 

mean KF (assumed to be the 

same than Kd) 

USEPA, 2008 

For pyrethrin 1, log KOA> 5, log KOW> 2 and therefore is preliminarily identified as having a 

potential to biomagnify in terrestrial food chains.1

 However, its rate of biotransformation is 

moderate in the environment, and it appears to be moderately rapid in fish. Specifically, the 

bioconcentration factor is 471x for whole fish, which is much lower than would be expected if 

biotransformation was minimal. Furthermore, it is depurated rapidly in fish (depuration half life 

<1 day). Therefore, the potential of pyrethrins to biomagnify in terrestrial food chains appears to 

be low because it should be similarly biotransformed by terrestrial organisms. 

Even though various degradates were observed in the laboratory studies (e.g. chrysanthemic acid, 

pyrethric acid and chrysanthemum dicarboxilic acid), it was found that all of them were the result 

 

14

1

 This preliminary conclusion is based on the following presumption: If log KOA > 5, log KOW > 2 and the rate of 

chemical transformation is low, the chemical may biomagnify in terrestrial food chain. Gobas et al. 2003 and 

Armitage & Gobas, 2007 support this presumption, which is utilized here only as a broad reference to determine the 

potential for biomagnification. 
15

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. 

Figure 3.3 shows the chemical structures of pyrethrins’ major potential degradation products. All 

of them are expected to be more soluble and mobile than their respective parent compounds, 

especially the acids. Based on the information from pyrethrin 1, chrysanthemic acid appeared to 

be short lived and pyrethric acid and chrysanthemum dicarboxylic acid would be expected to 

behave similarly. The E-isomer of pyrethrin 1 (not shown in the figure) was observed in the 

photolysis on soil study to be short lived as well, therefore, it is of low concern. 

No registrant-submitted data are available that examine the ecotoxicity of pyrethrins degradates. 

At this time, the degradates will not be considered stressors of concern in the forthcoming 

environmental fate and ecological risk assessment. These conclusions are in agreement with 

EPA’s Health Effects Division’s (HED) approach of considering only the parent as the residue of 

concern for purposes of tolerance expression and risk assessment (HED chapter of the 

Reregistration Eligibility Decision Document (RED) for pyrethrins, dated April 1st 2009; DP 

Barcode D357566, see Appendix I). 

 
Figure 3.3. Structures of Potential Degradation Products of the Pyrethrins

Nomenclature of Pyrethrin Breakdown Products

Common Name Chemical Name 

Chrysanthemic acid 2-(1-isobutenyl-3,3-dimethylcyclopropanecarboxylic acid or 

3-isobutenyl-2,2-dimethylcyclopopanecarboxylic acid 

CDA or Chrysanthemum 

Dicarboxylic Acid 2,2-dimethyl-1,3-cyclopropanedicarboxylic acid 

3.1. Mechanism of Action 

Pyrethrins and pyrethroids share similar modes of action, resembling that of DDT, and are 

considered axonic poisons that affect both the peripheral and central nervous system. It is now 

well established that severe neurological symptoms of poisoning with pyrethroids and DDT in 

mammals and insects are the result of modification of Na+

 channel activity (cellular pores through 

which sodium ions are permitted to enter the axon to cause excitation) (Matsumura,1985). 

Advanced electrophysiological experiments using voltage clamp and patch clamp, together with 

ligand-binding and ionic flux experiments, have unveiled unique actions of pyrethroids of keeping 

the Na+

 channel in the open state for an extremely long period, sometimes as long as several 

seconds. This modification of Na+ channel properties leads to hyperactivity of the nervous 

system. Pyrethroids have also been shown to suppress GABA and glutamate receptor-channel 

complexes and voltage-activated Ca2+ channels, but the toxicological significance of these actions 

is uncertain. Relative to physiological responses, researchers have designated two types of 

pyrethroids, Type I (e.g., pyrethrins, S-bioallethrin, resmethrin, permethrin) and Type II (e.g., 

cypermethrin, deltamethrin, fenvalerate). Type I pyrethroids’ action is mainly associated with 

compounds that cause nerve excitation symptoms typified by the appearance of repetitive firing of 

16
17

axons in the peripheral nervous system and a negatively correlated temperature reversible 

knockdown property (similar to DDT) (Clark and Matsumura, 1987). Pyrethrins are nonsystemic insecticides that work by physical contact to the insect or by ingestion, and they have a 

slight repellent effect. 

The paralyzing effects caused by pyrethrins usually cannot occur without a synergist. For 

example, the synergist compound in PYRENONE® Crop Spray (e.g., EPA Reg. No. 432-1050) 

is piperonyl butoxide, and it blocks the metabolic pathway that would breakdown pyrethrin 

before the toxic effect occurs. Products that contain pyrethrins are primarily used as a knockdown agent on the insects and the addition of a synergist does contribute to the killing efficiency 

of a formulation (Casida and Quistad, 1995). 

3.2. Overview of Pesticide Usage

The use information presented in this problem formulation was obtained from the tables in 

Appendix A-1 and Appendix A-2 dated 03/22/2010 (and further revised 05/12/2011), from the 

Pyrethrins BEAD’s Chemical Profile for Registration Review (USEPA 2011), from various 

evaluated labels, and from the June 2006 Reregistration Eligibility Decision Document for 

Pyrethrins. There are around 640 pyrethrin-containing products. Use reported for pyrethrins 

appears to be based on a subset of the universe of labels available for the chemical, as shown in 

the 05/12/2011 revision of the Appendix A-1 and Appendix A-2. 

The pyrethrins have numerous uses. A summary of agricultural use patterns for pyrethrin is 

shown Table 3.3. Note that for all the uses, the maximum single and seasonal application rate, 

the maximum number of applications at the maximum rate, and the minimum retreatment 

interval are the same. Of the numerous crops mentioned, rice is worth mentioning separately 

because it will be assessed in a different way than other agricultural uses (see crop under Crop 

Group 15). This crop will be assessed using the tier 1 Rice Paddy Model (or further characterized 

using the PFAM model, see below). In all instances, there is a 1 day retreatment interval for 

high pest pressure, compared to a 3 day retreatment interval for normal pest pressure. 

Table 3.3. Summary of Agricultural Use Information for the Pyrethrins 

Maximum Applic. 

Rate (all crops) 

Maximum Seasonal 

Rate (all crops) 

Maximum Number of 

Applications (all crops) 

Minimum Retreatment Interval (all 

crops) 

0.050 lb a.i./A 0.50 lb a.i./A 10 1 day (extreme pest pressure) 

3 days (normal pest pressure) 

Pre-harvest interval (PHI) 0 days for all crops, except for cotton seed, for which it is 14 days. 

Application to hydroponically grown crops 10 applications at 0.10 ppm in water. 

Surface application to greenhouse grown crop 10 applications at 0.0012 lb a.i./1,000 sq. ft or 0.050 lb a.i./A. 

Space application to greenhouse grown crop 10 applications at 0.00014 lb a.i./1,000 cu ft. 

Other restrictions: Do not harvest until spray has dried. Do not wet foliage to point of runoff or drip. 

Crop Group 1: Root and Tuber Vegetables [including Arracacha; Arrowroot; Artichoke, Chinese; Artichoke, Jerusalem; Beet, garden, 

Beet, sugar; Burdock, edible; Canna edible; Carrot; Cassava; Celeriac; Chayote; Chervil, turnip-rooted; Chicory; Chufa; Dandelion; 

Dasheen; Ginger; Ginseng; Horseradish; Leren; Parsley, turnip-rooted; Parsnip; Potato; Radish; Radish, Oriental; Rutabaga; Salsify; 

Salsify, black; Salsify, Spanish; Skirret; Sweet Potato; Tanier; Taro; Turmeric; Turnip; Yam bean; and Yam, true] 

Crop Group 2: Leaves of Root and Tuber Vegetables [including Beet, garden; Beet, sugar; Burdock, edible; Carrot; Cassava; Chervil, 

turnip-rooted; Chicory; Dasheen; Parsnip; Radish; Radish, Oriental; Rutabaga; Salsify, black; Tanier; Taro; Turnip; and Yam, true] 

Crop Group 3: Bulb Vegetables [including Garlic; Garlic, great headed; Leek; Onion, dry bulb; Onion, green; Onion, potato; Onion, 

tree; Onion, welsh; and Shallot] 
Table 3.3. Summary of Agricultural Use Information for the Pyrethrins 

Crop Group 4: Leafy Vegetables (Except Brassica Vegetables) [including Amaranth, leafy; Arugula; Cardoon; Celery; Celery, 

Chinese; Celtuce; Chervil; Chrysanthemum, edible-leaved; Chrysanthemum, garland; Corn salad; Cress, garden; Cress, upland; 

Dandelion; Dock; Endive; Fennel, Florence; Kale, sea; Lettuce, head; Lettuce, leaf; Orach; Parsley; Purslane, garden; Purslane, winter; 

Radicchio; Rhubarb; Spinach; Spinach, Chinese; Spinach, New Zealand; Spinach, vine; Swiss chard; and Tampala] 

Crop Group 5: Brassica (Cole) Leafy Vegetables [including Broccoli; Broccoli, Chinese; Broccoli raab; Brussels sprouts; Cabbage; 

Cabbage, Chinese, Bok choy; Cabbage, Chinese, mustard; Cabbage, Chinese, napa; Cauliflower; Collards; Kale; Kohlrabi; Mustard 

greens; Mustard spinach; and Rape greens] 

Crop Group 6: Legume Vegetables (Succulent or Dried) [including Bean (adzuki, broad, dry, kidney, lablab, lima, moth, mung, navy, 

pink, pinto, rice, runner, snap, tepary, urd, wax, yardlong); Catjang; Chickpea; Cowpea; Guar; Gum, edible; Jackbean; Lentil; Lupin, 

grain; Pea (blackeyed, crowder, dry, dwarf, edible-pod, English, field, garden, green, pigeon, snow, southern, succulent, sugar snap); 

Soybean; and Swordbean] 

Crop Group 7: Foliage of Legume Vegetables [including Bean (dry, lima, snap); cowpea; Lupin, grain; Pea (field and pigeon); 

Soybean] 

Crop Group 8: Fruiting Vegetables (Except Cucurbits) [including Chili; Eggplant; Groundcherry; Pepino; Pepper (bell, nonbell, 

nonbell sweet); Tomatillo; Tomato] 

Crop Group 9: Cucurbit Vegetables [including Balsam apple; Balsam pear; Cantaloupe; Chayote; Cucumber; Cucumber, Chinese; 

Gherkin, West Indian; Gourd, edible; Melon; Melon, citron; Muskmelon; Pumpkin; Squash; Squash, summer; Squash, winter; 

Watermelon; Waxgourd, Chinese] 

Crop Group 10: Citrus Fruits (Citrus spp., Fortunella spp.) [including Calamondin; Citron, citrus; Citrus; Citrus hybrids; Grapefruit; 

Kumquat; Lemon; Lime; Mandarin, satsuma; Orange, sour; Orange, sweet; Pummelo; Tangelo; Tangerine] 

Crop Group 11: Pome Fruits [including Apple; Crabapple; Loquat; Mayhaw; Pear; Oriental Pear; and Quince] 

Crop Group 12: Stone Fruits [including Apricot; Cherry, sweet; Cherry, tart; Nectarine; Peach; Plum; Plum, chickasaw; Plum, damson; 

Plum, Japanese; and Plum, prune] 

Crop Group 13: Berries [including Blackberry, Blueberry; Currant; Elderberry; Gooseberry; Huckleberry; Loganberry; and Raspberry 

(black and red)] 

Crop Group 14: Tree Nuts [including Almond; Beech nut; Brazil nut; Butternut; Cashew; Chestnut; Chinquapin; Filbert; Hickory nut; 

Macadamia nut; Pecan; Pistachio; Walnut, black; and Walnut, English] 

Crop Group 15: Cereal Grains [including Barley; Buckwheat; Corn (field, pod, pop, and sweet); Millet; Millet, pearl; Millet, proso; 

Oat; Rice; Rice, wild; Rye; Sorghum, grain; Teosinte; Triticale; Wheat; Wheat, vavilovi; Wheat, wild einkorn; and Wheat, wild emmer] 

Crop Group 16: Forage, Fodder, and Straw of Cereal Grains [including Barley; Corn (field, pod, pop, and sweet); Millet; Millet, 

pearl; Millet, proso; Oat; Rice; Rice, wild; Rye; Sorghum (forage and grain); Teosinte; Triticale; Wheat; Wheat, vavilovi; Wheat, wild 

einkorn; and Wheat, wild emmer] 

Crop Group 17: Grass Forage, Fodder, and Hay [including Alkali sacaton; Alkaligrass; Arizona cottontop; Bahiagrass; Beachgrass; 

Bentgrass; Bentgrass, spike; Bermudagrass; Blowoutgrass; Bluegrass; Bluegrass, silky; Bluestem australian; Bluestem, big; Bluestem, 

Caucasian; Bluestem, Diaz; Bluestem, little; Bluestem, sand; Bluestem, silver; Bluestem, south African; Bluestem, yellow; Bristlegrass, 

plains; Bromegrass; Broomsedge; Buffalograss; Buffelgrass; Canarygrass, annual; Canarygrass, reed; Caribgrass; Carpetgrass; 

Carpetgrass, broadleaf; Centipedegrass; Cordgrass, marsh hay; Crabgrass; Curly mesquite; Dallisgrass; Dropseed, pine; Dropseed, sand; 

Dropseed, tall; Fescue; Fingergrass, feather; Foxtail, creeping; Foxtail, meadow; Gamagrass, eastern; Grass; Grass, galleta; Grass, gama; 

Grass, muhly; Grass, pasture; Grass, St. Augustine; Grass, wildrye; Grass, zoysia; Hairgrass tufted; Hardinggrass; Indiangrass; Junegrass; 

Limpograss; Lovegrass; Maidencane; Mannagrass; Millet, foxtail; Millet, Japanese; Molassesgrass; Napiergrass; Needlegrass; Oat, sand; 

Oat, slender; Oat, wild; Oatgrass; Oatgrass, tall; Oniongrass; Orchardgrass; Pangolagrass; Panicgrass; Paspalum; Polargrass; Quackgrass; 

Redtop; Reedgrass; Rhodesgrass; Rhodesgrass, multiflower false; Ricegrass, indian; Ryegrass, Italian; Ryegrass, perennial; Sandreed, 

prairie; Sixweeks threeawn; Sloughgrass; Smilograss; Sorghum, forage; Spikeoat; Sprangletop, green; Squirreltail; Sudangrass; 

Sunolgrass; Tanglehead; Timothy; Timothy, alpine; Trisetum, spike; Vaseygrass; Veldtgrass, perennial; Velvetgrass; Wheatgrass; 

Wheatgrass, bluebunch; Wheatgrass, crested; Wheatgrass, fairway; Wheatgrass, intermediate; Wheatgrass, pubescent; Wheatgrass, 

Siberian; Wheatgrass, slender; Wheatgrass, streambank; Wheatgrass, tall; Wheatgrass, thickspike; Wheatgrass, western; and 

Windmillgrass, hooded] 

Crop Group 18: Nongrass Animal Feeds (Forage, Hay, Straw, and Hay) [including Alfalfa; Arrowleaf balsamroot; Burclover; 

Clover; Clover, alsike; Clover, alyce; Clover, arrowleaf; Clover, ball; Clover, berseem; Clover, bigflower; Clover, crimson; Clover, hop; 

Clover, lappa; Clover, persian; Clover, red; Clover, rose; Clover, seaside; Clover, strawberry; Clover, striate; Clover, sub; Clover, sweet; 

Clover, true; Clover, white; Clover, whitetip; Crownvetch; Kudzu (note: kudzu is a generally considered a noxious weed and not a crop in 

the United States); Lespedeza; Lupine; Lupine, forage; Lupine, sweet; Mustard; Sainfoin; Trefoil; Velvetbean; Vetch; and Vetch, milk] 

Crop Group 19: Herbs and Spices [Including Allspice; Angelica; Anise; Anise hyssop (mint); Anise, star; Annatto; Balm; Basil; 

Borage; Burnet; Camomile; Caper; Caraway; Caraway, black; Cardamom; Cardamon amomum; Cassia; Catnip; Celery, seed; Chervil; 

Chive; Chive, Chinese; Cinnamon; Clary; Clove; Coriander; Costmary; Cilantro (False coriander); Cumin; Curry; Dill; Dillweed; Fennel; 

Fennel, florence; Fenugreek; Grains of paradise; Horehound; Juniper berry; Lavender; Lemongrass; Lovage; Mace; Marigold, pot; 

Marjoram (Oregano); Mustard; Nasturtium; Nutmeg; Parsley; Pennyroyal; Pepper, black; Pepper, white; Poppy; Rosemary; Rue; Saffron; 

Sage; Savory, summer; Savory, winter; Sweet bay; Tansy; Tarragon; Thyme; Vanilla; Wintergreen; Woodruff; and Wormwood] 

 18
Table 3.3. Summary of Agricultural Use Information for the Pyrethrins 

Miscellaneous Fruit, Subtropical/Tropical [including Acerola; Atemoya, Avocado; Banana; Carob bean; Cherimoya; Date; Durian; 

Feijoa; Fig; Guava; Kiwifruit; Lychee; Mango; Papaya; Passionfruit; Persimmon; Pineapple; Pomegranate; Rambutan; and Starfruit 

(Carambola) ] 

Vegetable, Oriental [including Artichoke, Chinese; Balsam pear (bitter melon); Bean, mung; Bean, yardlong; Broccoli, Chinese; 

Cabbage, Chinese, bok choy; Cabbage, Chinese, mustard; Cabbage, Chinese, napa; Coriander (Cilantro); Dasheen; Ginger; Ginseng; 

Melon, citron; Radish, oriental; Spinach, Chinese; and Waxgourd, Chinese] 

(Note: Individual crops listed above belong to various crop groups previously listed.)

Miscellaneous Commodities: Asparagus; Coffee; Cotton; Cranberry; Grape; Jojoba; Okra; Safflower; Strawberry; Sugarcane; 

Sunflower; and Tea 

All data were based Appendices A-1 and A-2, updated 05/12/2011. 

For agricultural products, application methods include aerial, air blast, or ground spray (foliar). 

As per requirements from the Reregistration Eligibility Decision (USEPA 2006), the following 

label requirements should be incorporated, to avoid spray drift. However, inspection of a 

representative label (EVERGREEN® Crop Protection EC 60-6; McLaughlin Gormley King 

Company or MGK®, containing 6.00% pyrethrins and 60.00% PBO, EPA Reg. No. 1021-1770), 

indicated that the label does not have the below mentioned requirements. The Pesticide 

Reevaluation Division (PRD) has confirmed that at the present time, these changes are being 

made for all pyrethrins labels. 

SPRAY DRIFT MANAGEMENT for AGRICULTURAL CROPS

• Avoiding spray drift at the application site is the responsibility of the applicator and the 

grower. The interactions of many equipment and weather-related factors determine the 

potential for spray drift. The applicator and the grower are responsible for considering all 

these factors when making decisions. 

• Do not apply at wind speeds greater than 10 mph at the application site. 

• Do not make any type of application into temperature inversions. 

• Apply as a medium or coarser spray (ASABE standard 572). 

• Additional requirements for aerial applications: a) Do not release spray at a height 

greater than 10 feet above the ground or crop canopy. b) The boom length must not 

exceed 75% of the wingspan or 90% of the rotor blade diameter. c) Aerial applicators 

must consider flight speed and nozzle orientation in determining droplet size. d) When 

applications are made with a cross-wind, the swath will be displaced downwind. The 

applicator must compensate for this displacement at the downwind edge of the 

application area by adjusting the path of the aircraft upwind. 

• Additional requirements for ground applications: Do not release spray at a height greater 

than 4 feet above the ground or crop canopy. 

• Additional requirements for airblast applications: a) Direct sprays into the canopy. b) 

Turn off outward pointing nozzles at row ends and when spraying outer rows. 

The pyrethrins are toxic to fish, aquatic invertebrates and beneficial insects. The following 

Environmental Hazards statements are required for products labeled for outdoor uses other than 

mosquito adulticide (USEPA 2006): 

 

 19
ENVIRONMENTAL HAZARD STATEMENTS 

• This product is toxic to aquatic organisms, including fish and invertebrates. Drift and 

runoff may be hazardous to aquatic organisms in water adjacent to treated areas. This 

product may contaminate water through runoff. This product has a potential for runoff for 

several weeks after application. Poorly draining soils and soils with shallow water tables 

are more prone to produce runoff that contains this product. 

• This product is highly toxic to bees exposed to direct treatment on blooming crops or 

weeds. Do not apply this product or allow it to drift to blooming crops or weeds while 

bees are actively visiting the treatment area. 

• Do not apply directly to water, to areas where surface water is present or to intertidal 

areas below the mean high water mark. Do not contaminate water when disposing of 

equipment wash-waters or rinsate. 

The pyrethrins also have multiple non-agricultural uses, as described in Table 3.4. They include 

among others, garden crops and ornamentals, and lawn. 

Table 3.4. Summary of Non-Agricultural Crops for the Pyrethrins

Use Single App. Rate 

Number 

of Apps. 

Seasonal 

App. Rate 

(lb a.i./A) 

Interval Between 

Apps. (days) 

Preharvest Application to Garden Crops 

Residential applications to garden crops. 0.050 lb a.i./A 10 0.50 lb a.i./A 1 (extreme pressure), 

3 (normal pressure) Residential application to hydroponically grown 

crops 0.10 ppm in water 10 NS 

Non-food Crops in Greenhouse: Ornamental, Flowering and Foliage Plants 

Surface applications 0.15 lb ai/A NS NS 1 

Space spray 0.00042 lb/ 1,000 cu ft NS NS 1 

Non-food Crops Grown Outside: Ornamentals, Flowering and Foliage Plants, and Lawn 

Surface applications 

(including fire ants and turf diagnostic aid) 

Residential: 

0.10 lb ai/A) 

Non-residential 

0.0075 lb/ 1,000 sq ft 

NS NS 1 

Crack/crevice or spot surface applications 

(including fire ants and turf diagnostic aid) 0.002 lb ai/1,000 sq ft NS NS 1 

Crack/crevice or spot surface applications 

(including fire ants and turf diagnostic aid) 

.002 lb ai/ 

1,000 sq ft NS NS 1 

NS = Not specified 

Furthermore, the pyrethrins have mosquito control uses. Applications are usually using very 

small droplet sizes (i.e., Ultra-Low Volume or ULV). For these uses, the master label says two 

application rates, both of which are much smaller than for typical agricultural applications 

(Table 3.5). 

Table 3.5. Adulticide Uses for the Pyrethrins 

Use Max. App. Rate/ units Max. App. Rate per Year 

Agricultural Crops/Soils: Groups of Agricultural Crops Which Cross Established Crop Groupings (Croplands); Agricultural 

Uncultivated Areas: Fallow lands, Pastures, and Rangelands; Intermittently Flooded Areas/Water; Irrigation Systems 

Thermal fog 0.0025 lb ai/A Do not apply more than 0.2 lbs ai/acre/year in any treated 

 20
Table 3.5. Adulticide Uses for the Pyrethrins 

Use Max. App. Rate/ units Max. App. Rate per Year 

Non-thermal fog 

ULV 0.008 lb ai/A area. 

Various restrictions for the adulticide uses required during the RED process (USEPA 2006) are 

as follows: 

SPRAY DRIFT MANAGEMENT for WIDE AREA MOSQUITO ABATEMENT

A variety of factors including weather conditions (e.g., wind direction, wind speed, temperature, 

relative humidity) and method of application (e.g., ground, aerial, airblast, chemigation) can 

influence pesticide drift. The applicator must evaluate all factors and make appropriate 

adjustments when applying this product. 

WIND SPEED: 

Apply only when wind speed is greater than or equal to 1 mph. 

Ground-based wide area mosquito abatement application: 

• Spray equipment must be adjusted so that the volume median diameter is less than 30 

microns (Dv0.5 < 30 μm) and that 90% of the spray is contained in droplets smaller than 

50 microns (Dv0.9 < 50 μm). Directions from the equipment manufacturer or vendor, 

pesticide registrant or a test facility using a laxer-based measurement instrument must be 

used to adjust equipment to produce acceptable droplet size spectra. Application 

equipment must be tested at least annually to confirm that pressure at the nozzle and 

nozzle flow rate(s) are properly calibrated. 

Aerial wide area mosquito abatement application: 

• Spray equipment must be adjusted so that the volume median diameter produced is less 

than 60 microns (Dv0.5 < 60 μm) and that 90% of the spray is contained in droplets 

smaller than 80 microns (Dv0.9 < 80 μm). The effects of flight speed, and for non-rotary 

nozzles, nozzle angle on the droplet size spectrum must be considered. Directions from 

the equipment manufacturer or vendor, pesticide registrant or a test facility using a wind 

tunnel and laser-based measurement instrument must be used to adjust equipment to 

produce acceptable droplet size spectra. Application equipment must be tested at least 

annually to confirm that pressure at the nozzle and nozzle flow rate(s) are properly 

calibrated. 

RELEASE HEIGHT: 

Fixed wing: 

• Apply using a nozzle height of no less than 100 feet above the ground or canopy. 

Rotary wing: 

• Apply using a nozzle height of no less than 75 feet above the ground or canopy.

 21
The agricultural usage of pyrethrin, from the Screening Level Usage Analysis (SLUA) is 

provided in Table 3.6. The table is arranged by crop in alphabetical order. According to the 

table, the major agricultural use for pyrethrin is wheat, with 2000 lb a.i. Numerous crops are 

provided in the table, for which the pounds of active ingredient applied is <500. The crop with 

the highest percent crop treated is spinach (average 5%, maximum 20%). Various other crops 

have moderate percent crop treated (i.e., 5-15%); however, for most of the crops, the percent 

crop treated is small (i.e., <1 or <2.5%). 

Table 3.6. Screening-Level Estimates of Agricultural Uses of Pyrethrin 

(SLUA)2

Crop Lb. A.I. 

Percent Crop Treated 

Avg. Max. 

Alfalfa <500 <1 <2.5 

Almonds <500 <1 <2.5 

Apples <500 <1 <2.5 

Artichokes <500 5 15 

Beans, Green <500 <1 <2.5 

Broccoli <500 <2.5 5 

Brussels Sprouts* <500 NC NC 

Cabbage <500 <1 <2.5 

Caneberries <500 5 10 

Cantaloupes <500 <1 <2.5 

Carrots <500 5 5 

Cauliflower <500 5 10 

Celery <500 <2.5 5 

Cherries <500 <1 <2.5 

Chicory* <500 NC NC 

Corn <500 <1 <2.5 

Cotton <500 <1 <2.5 

Cucumbers <500 <1 <2.5 

Dry Beans/Peas <500 <1 <2.5 

Figs* <500 NC NC 

Grapes <500 <1 <2.5 

Hazelnuts (Filberts) <500 <1 <2.5 

Lemons <500 5 5 

Lettuce <500 5 10 

Nectarines* <500 NC NC 

Olives* <500 NC NC 

Onions <500 <1 <2.5 

Oranges <500 <1 <2.5 

 

2

 Dated 01/21/2011 

 22
Table 3.6. Screening-Level Estimates of Agricultural Uses of Pyrethrin 

(SLUA)2

Percent Crop Treated 

Crop Lb. A.I. Avg. Max. 

Peaches <500 <1 <2.5 

Pears <500 <1 <2.5 

Peas, Green <500 <1 <2.5 

Pecans <500 <1 <2.5 

Peppers <500 <2.5 5 

Pistachios <500 <1 <2.5 

Pomegranates* <500 NC NC 

Potatoes <500 <1 <2.5 

Prunes <500 <1 <2.5 

Pumpkins <500 <1 <2.5 

Sorghum <500 <1 <2.5 

Soybeans <500 <1 <2.5 

Spinach <500 5 20 

Squash <500 <2.5 5 

Strawberries <500 5 15 

Sugarcane <500 <1 <2.5 

Sunflowers <500 <1 <2.5 

Sweet Corn <500 <1 <2.5 

Tomatoes <500 <1 <2.5 

Walnuts <500 <1 <2.5 

Watermelons <500 <1 <2.5 

Wheat 2,000 <1 <2.5 

Sorted alphabetically. All numbers rounded. 

<500 Less than 500 pounds of active ingredient 

<2.5 Less than 2.5 percent of crop treated 

<1 Less than 1 percent of crop treated 

N/C Only Lbs. A.I. available 

* CA data only (95% or more of U.S. acres in California) 

SLUA data sources include: 

USDA-NASS (United States Department of Agriculture's National Agricultural Statistics Service) 

(pesticide usage data from 2001 to 2008) 

Private Pesticide Market Research (pesticide usage data from 2001 to 2008) 

 California DPR (Department of Pesticide Regulation) (data for 2000 to 2008) 

These results reflect amalgamated data developed by the Agency and are releasable to the public. 

BEAD provided agricultural information by states in its Pyrethrins Chemical Profile for 

Registration Review (USEPA 2011): “On average, the states with the most agricultural usage in 

terms of pounds a.i. applied are California (52%), Oklahoma (16%), and Arizona (6%).” 

 23
Table 3.7 provides a summary of several nonagricultural (terrestrial/ outdoor) or non-crop uses 

for pyrethrin. The uses are classified by broad categories as follows: commercial animal 

housing, outdoor agricultural premises, residential sites – outdoors, and outdoor eating 

establishments. For various uses, the maximum application rate is expressed in units other than 

“lb a.i./A” and in some instances it is expressed in units of percent pyrethrins. Many of the uses 

may well involve substantive exposure to wildlife, especially aquatic organisms, and they will be 

assessed accordingly (e.g., surface applications). 

Table 3.7. Non-Crop Outdoor Uses for Pyrethrins 

Use Max. App. Rate/ units

Max. No. 

Applications/ 

Year 

Max. App. 

Rate per 

Year 

Min. App. 

Interval/ 

days 

Commercial Animal Housing 

Animal areas and quarters; Animal shelters; Catteries; Dog runs; Kennels; Pet grooming shops; Pet stores; Research animal 

quarters; Zoos. (Animals are not present during application) 

Surface – General 0.056 lb ai/1,000 ft2 NS NS 1 

Surface - Crack and crevice or spot 0.056 lb ai/1,000 ft2 NS NS 1 

Space – General 0.0033 lb ai/1,000 ft3 NS NS 

1 (restricted 

to 

commercial 

pet areas) 

Space - Metered release

0.000476 lb a.i./1000 ft3/ 

day NS NS NS 

Outdoor Agricultural Premises 

Empty Uncultivated Agricultural Areas: Corrals; Dairy areas; Farms; Goat holding areas; Hog operations; Rights-of-way; Sheep 

holding areas. 

Empty Cattle Feedlots: Beef cattle operations; Feedlots; Holding lots; Livestock lots; Swine lots and yards 

Surface - General 0.0075 lb a.i./1,000 ft2 NS NS 1 

Surface - Crack and crevice or spot 0.22 lb ai/1,000 ft2 NS NS 1 

Impregnated mat 1.0% pyrethrins NS NS 1 

Combustible coils 1.0 % pyrethrins NS NS 1 

Residential Sites – Outdoor 

Ant hills; Ant nests; Ant trails; Backyards; Doors; Driveways; Entranceways; Mud dauber, wasp, and yellow jacket nests; Outside

surfaces of buildings; Patio furniture; Picnic areas; Residential areas; Screens; Siding; Spigots; Storage areas; Tree holes; Under 

eaves; Under siding; Wall voids; Windows. 

Nonagricultural Outdoor Buildings/Structures: Atriums; Carports; Decks; Fences; Gazebos; Lanais; Porches; Sheds; Tree houses; 

Tunnels and cavities in wood; Verandas; Tents. 

Fencerows; Hedgerows; Nonagricultural Rights-of-way; Paths; Patios; Paved Areas: Private Roads; Sidewalks; Garbage bins; 

Dumpsters; Meter boxes; Electrical equipment; Electrical fittings; Manure; Compost piles. 

Surface – General 0.002 lb a.i./1,000 ft2 NS NS 

1 Surface - Crack and crevice or spot 0.056 lb a.i./1,000 ft2 NS NS 

Impregnated mat 1.0% pyrethrins NS NS 

Combustible coil 1.0% pyrethrins NS NS 

Outdoor Eating Establishments 

Eating Establishments Equipment/Utensils, Food Handling Areas, Food Serving Areas, Non-Food Areas of outdoor eating 

establishments and drive-in restaurants 

Surface applications 0.0075 lbs a.i./1000 ft2 NS NS 

1 Crack/crevice or spot surface 0.056 lbs a.i./1000 ft2 NS NS 

Impregnated mat 1.0% pyrethrins NS NS 

Combustible coil 1.0% pyrethrins NS NS 

Other uses are classified as indoor. They include several broad categories as follows: 

 24
postharvest applications to vegetables, fruit and nuts, bulk grain and seed, application to 

agricultural premises and equipment – indoor, residential – indoor, commercial/ industrial/ 

institutional establishments – indoor, eating establishments – indoor, food handling and 

processing establishments – indoor, retail and storage – indoor, transportation – indoor, and pet 

premise treatment. 

Table 3.8. Indoor Uses for Pyrethrins 

Use Max. App. Rate/ units

Max. No. 

Applications/ 

Year 

Max. App. 

Rate per 

Year 

Min. App. 

Interval/ 

days 

Postharvest Application to Vegetables, Fruit, and Nuts 

Food/Feed Storage Areas -Full: Postharvest Application to Apple, Blackberry, Blueberry, Boysenberry, Cherry, Crabapple, 

Currant, Dewberry, Fig, Gooseberry, Grape, Guava, Loganberry, Mango, Muskmelon, Orange, Peach, Pear, Pea, Pineapple, Plum, 

Potato, Raspberry, or Tomato in baskets, on trucks, in processing plants, in hampers, or in temporary storage areas (including raw 

stock stacked in yards) 

Copra (processed) in baskets, on trucks, in processing plants, in hampers, or in temporary storage areas (including raw stock stacked 

in the yard) 

Postharvest application to Almonds, Peanuts, and Walnuts (English/black) in bulk. 

Surface - General 0.01 lb a.i./ 1,000 ft2

10 

0.10 lb a.i./ 

1000 ft2

7 

Surface - Direct application to fruits or tomatoes in 

baskets or hampers 0.16 ppm NS 

Dip or spray 0.0004 lbs a.i./ gallon NS 

Space - Fruits, vegetables, and copra 0.001 lb a.i./ 1,000 ft3 0.010 lb a.i./ 

1000 ft3

Postharvest Direct Application to Bulk Grain and Seed

Bulk Grain and Seed 0.10 lb a.i./ 1,000 

bushels grain 

NS NS 30 

 - Barley 0.0033 oz/cwt NS NS 30 

 - Beans 0.0027 oz/cwt NS NS 30 

 - Beans, lima 0.0029 oz/cwt NS NS 30 

 - Birdseed 0.0032 oz/cwt NS NS 30 

 - Buckwheat 0.0033 oz/cwt NS NS 30 

 - Cocoa beans 0.0037 oz/cwt NS NS 30 

 - Corn 0.0029 oz/cwt NS NS 30 

 - Cottonseed 0.0057 oz/cwt NS NS 30 

 - Flax 0.0029 oz/cwt NS NS 30 

 - Grain sorghum 0.0029 oz/cwt NS NS 30 

 - Oats 0.0050 oz/cwt NS NS 30 

 - Pea (field) 0.0027 oz/cwt NS NS 30 

 - Rice 0.0036 oz/cwt NS NS 30 

 - Rye 0.0029 oz/cwt NS NS 30 

 - Wheat: club, common, durham 0.0027 oz/cwt NS NS 30 

 - Wheat: emmer, spelt 0.0040 oz/cwt NS NS 30 

 25
Table 3.8. Indoor Uses for Pyrethrins 

Use Max. App. Rate/ units

Max. No. 

Applications/ 

Year 

Max. App. Min. App. 

Rate per Interval/ 

Year days 

Application to Agricultural Premises and Equipment – Indoor 

Greenhouses (empty) 

Agricultural/Farm Structures/Buildings and Equipment: Animal houses; Calf hutches; Calving pens and parlors; Dairies; Dairy 

farms; Goat houses; Livestock housing structures; Loafing sheds; Poultry houses; Poultry operations; Rabbit houses; Rabbit 

hutches; Stables; Swine houses. 

Barns/Barnyards/Auction Barns: Barns (Beef, Cattle, Dairy, Horse, Hog, and Livestock) 

Dairy Farm Milking Stalls/Parlors: Milk houses; Milking parlors 

Dairy Farm Milk Storage Rooms/Houses/Sheds: Milk rooms 

Dairy Farm Milk Handling Facilities/Equipment: Milk handling equipment 

Dairy Farm Milking Equipment: Milking equipment 

Seed Houses/Stores/Storage Areas/Warehouses: Stored seed warehouses; Seed warehouse bins; Granaries; Seed storage sites; Seed 

bins; Stable bins; Stored seed warehouses 

Silos and Mushroom houses 

Surface – General 0.056 lb ai/1,000 ft2 NS NS 

Space – General 0.0008 lb ai/1,000 ft 1 3 NS NS 

Space - Metered release 0.000476 lbs a.i./ 

1000 ft3

/ day NS NS 

Residential – Indoor 

Household/Domestic Dwellings: Apartments; Cabins; Campers; Condominiums; Dwellings; Homes; Mobile homes; Recreational 

vehicles; Residences; Public housing; Sheds; Toolsheds; Townhouses. 

Household/Domestic Dwelling Contents: Beds (cracks, crevices, framework); Bedding; Bookcases; Box springs; Boxes; Cabinets; 

Carpet; Cooking equipment; Cut Flowers; Drawers; Dressers; Draperies; Dryers; Equipment; Fabrics; Flowering plants; Foliage 

plants; Formica; Furniture; Furniture bases; Furniture legs; Glass; Light fixtures; Linoleum; Machinery; Mattresses; Picture frames; 

Plastic fabric bags; Refrigerator; Rugs; Shelves; Shrubs; Sofas and Chairs; Sofa and Chair surfaces; Soffits; Stainless steel; Storage 

drawers; Stored items; Stoves; Tables; Tiles; Trees; Upholstered furniture; Upholstery; Vinyl tile; Washers. 

Household/Domestic Dwellings Indoor Food Handling Areas (food covered): Cupboards; Kitchens; Sinks; Underneath sinks; Food 

areas. 

Household/Domestic Dwellings Indoor Nonfood Handling Areas: Attics; Basements; Bedrooms; Closets; Closed porches; Crawl 

spaces; Dining rooms; Garages; Pantries; Porches; Solariums; Storage areas; Sun porches; Utility rooms; Bathrooms. 

Household Domestic Dwellings Indoor Premises: Baseboards; Closed void areas; Cracks and crevices; Dark corners; Doorframes; 

Door jambs; Doors; Door sills; Drains; Equipment voids; False ceilings; Floors; Foundations; Moldings; Moist places; Niches; 

Pipes; Screens; Soffits; Tunnels and cavities in wood; Walls; Windows; Window frames; Window sills; Weep holes; Woodwork; 

Voids in attics, walls, ceilings, and equipment. 

Electrical Supplies/Equipment: Meter boxes; Electrical equipment; Electrical fittings. 

Human Clothing (Insect and Mold/Mildew Control): Clothing; Clothing (outerwear); Clothing (in storage); Woolens. 

Garbage cans and Garbage/trash compactors. 

Commercial/Industrial/Institutional Establishments – Indoor 

Apartments; Auditoriums; Buildings; Churches; Commercial buildings; Correctional facilities; Communications centers; 

Courthouses; Day care centers; Dormitories; Drugstores; Elevators; Equipment voids; Factories; Fake ceilings; Florists; Food 

service storage and preparation areas; Gas stations; Hotels; Industrial buildings; Industrial installations; Institutions; Interiorscapes; 

Jails; Kitchens; Laboratories; Laundry areas; Lavatories; Libraries; Locker rooms; Lathhouses; Missions; Motels; Movie Theatres; 

Museums; Non-food areas of commercial buildings; Non-residential buildings; Offices and office buildings; Other commercial, 

industrial, and governmental sites; Parking garages; Prisons; Public buildings; Resorts; Schools; Shadehouses; Sheds; Stores; 

Textile mills & warehouses; Theaters; Universities; Utilities/utility rooms; Health care facilities; Hospices; Hospitals; Nursing 

homes; Veterinary clinics.

Eating Establishments –Indoor 

Eating Establishments (Food Contact) [Equipment/Utensils; Food Handling Areas; Food Serving Areas]: Cafeterias; Restaurants; 

Mess halls

 26
Table 3.8. Indoor Uses for Pyrethrins 

Use Max. App. Rate/ units

Max. No. 

Applications/ 

Year 

Max. App. Min. App. 

Rate per Interval/ 

Year days 

Food Handling and Processing Establishments – Indoor 

Food Handling and Processing Plant Premises and Equipment (Food Contact): Bakeries; Bottling plants; Beverage plants; 

Canneries; Conveying Equipment; Dried fruit processing plants; Feed areas of commercial buildings; Food areas of commercial 

buildings; Food processing plants; Fruit packing sheds; Mushroom processing plants; Peanut processing plants; Processing areas of 

dried food products; Tobacco processing plants; Wineries 

Meat Processing Plant Premises and Equipment (Food Contact): Conveying equipment; Edible product areas of official 

establishments operating under the meat; poultry; shell egg grading and egg products inspection operations; Meat packing plants; 

Poultry processing plants; Rabbit processing plants; USDA inspected meat and poultry plants 

Dairies/Cheese Processing Plant Premises and Equipment (Food Contact): Dairies 

Egg Processing Plants 

Tobacco Processing Plants 

Feed Mills/Feed Processing Plants: Conveying equipment; Feed processing and handling sites; Flour mills; Grain mills; Mills; 

Milling operations; Roll housing and hoppers; Stored grain mills; Rice mills 

Feed/Food Treatment - Storage/Processing/Handling Equipment: Conveying equipment; Grain handling equipment

Retail and Storage – Indoor 

Commercial Storage/Warehouses Premises: Brandy storage warehouses; Dried fruit warehouses; Elevators; Food storage areas; 

Freight containers; Peanut storage warehouses; Spirit storage; Storage areas; Storage areas of dried food products; Stored seed

warehouses; Warehouses; Wine storage warehouses; Tobacco warehouses 

Food Stores/Markets/Supermarkets Premises and Equipment: Food marketing - storage- distribution; Grocery and convenience 

stores; Stores; Supermarkets; Conveying equipment; Freight containers; Stored product areas 

Food/Feed Storage Areas-Full: Stored product areas.

Transportation – Indoor 

Commercial Transportation Facilities: Airplanes; Boats; Box cars; Buses; Cabins and holds of aircraft; Commercial transportation 

centers; Freight containers; Ocean fright containers; Pallets; Passenger rail cars; Railroad cars; Recreational vehicles; Ships & ships’ 

holds; Trains; Trucks; Trailers; Truck trailers; Livestock hauling equipment; Horse trailers. 

Commercial Transportation Facilities – Empty: Grain transportation containers (truck beds; planes; box cars; cargo ship holds);

Pallets. 

Commercial Shipping Containers- Empty: Grain transportation containers (truck beds; planes; box cars; cargo ship holds); Pallets. 

Trunks of Automobiles, Taxis, Limousines.

Pet Premise Treatment 

Pet Living/Sleeping Quarters: Areas of floors & floor coverings where pets may be present; areas where female insects may crawl to 

lay eggs, and similar hiding places; Dog houses and other sleeping quarters; Dog runs; Pet bedding and premises; Pet premises; Pet 

resting areas; Kennels. 

The pyrethrins also have numerous uses on pets and other animals, as indicated in Table 3.9. 

Uses include cattle (beef/range/feeder and dairy), dairy goats (meat, dairy), dogs/ canines, cats, 

hogs/ pig/ swine treatments, horses, livestock, poultry, and sheep animal treatment, etc. 

Treatments include direct application to livestock and poultry (dust), direct application to 

livestock (liquid solution, towelette, spot-on and pour-on), and direct application to poultry 

(liquid solution). For cattle, the retreatment interval is 1 day while for pets, it is not specified. 

Applied amounts may vary depending on the formulation. Figure 3.3 shows the cattle and 

calves inventory as of 2007. Each dot represents 10,000 cattle and calves. Since exposure to 

water bodies due to treatment of cattle and various other animals is possible, these uses will be 

assessed in the ecological risk assessment to estimate potential pyrethrins exposure following 

application to livestock. 

 27
Figure 3.4 Cattle and Calves Inventory as of 20073

Table 3.9. Pet Care, Cattle and Various Other Animal Treatments of Pyrethrins 

Use 

Max. App. 

Rate/ units

Max. No. 

Applications/ 

Year 

Max. App. 

Rate per 

Year 

Min. App. 

Interval/ 

days 

Birds: Amazon parrots; Budgies; Canaries; Cockatiels; Finches; Love birds; Macaws; Ostrich; Parakeets; Parrots. 

Cats (including kittens), Dogs (including puppies), Monkeys, Ferrets, Rabbits. 

Chimpanzees; Chinchillas; Horses; Llamas; Lemurs; Minks; Ponies; Pot bellied pigs. 

Rodents: Gerbils; Guinea pigs; Hamsters; Mice; Rats.

Shampoos 0.3% a.i. 

NS NS NS 

Sprays 0.20 % ai 

Spot-on or Pour-on 1.0% a.i. 

Dust 1.0% a.i. 

Towelettes 0.2% a.i. 

 

3

Information obtained from the following website accessed 05/18/2011: 

http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Ag_Atlas_Maps/Livestock_and_Animals/Live

stock,_Poultry_and_Other_Animals/07-M134.asp 

 28
Table 3.9. Pet Care, Cattle and Various Other Animal Treatments of Pyrethrins 

Use 

Max. App. 

Rate/ units

Max. No. 

Applications/ 

Year 

Max. App. Min. App. 

Rate per Interval/ 

Year days 

Direct Application to Animals 

Cattle (Beef/Range/Feeder and Dairy); Hogs/Pig/Swine; Goats (Meat and Dairy); Kids; Sheep; Lamb; Rabbits; Game Animals 

(including Beefalo, Buffalo, Deer, Exotics such as European red deer, Llamas, Moose, Elk); Livestock (including Donkeys, Horses, 

Ponies, Mules); and Poultry 

Direct application to livestock and poultry - Dust 1.0% 

NS NS 1 

Direct application to livestock – Liquid Solution 0.035 lb ai/gal 

Direct application to livestock - Towelette 0.2% 

Direct application to livestock - Spot-on or Pour-on 1.0% 

Direct application to poultry – Liquid Solution 0.01% 

The Agency has limited use and usage information relevant to urban exposures and residential 

uses of pyrethrins. The Agency intends to use available non-agricultural use and usage data, 

such as the Kline database, the California Department of Pesticide Regulation’s (CDPR) 

Pesticide Use Reporting Data and Pest Control Operator’s usage survey, and the Residential 

Joint Venture Task Force homeowner survey data (2003), to inform reasonable assumptions 

regarding various applications and information related to urban/residential use. Due to the 

limited data available, exposure to the environment and uncertainties will be characterized. 

Detailed information on non-agricultural use and usage of pyrethrins products would be useful in 

order to reduce those uncertainties for the final environmental ecological risk assessment for 

pyrethrins. 

For indoor uses, the Division has conducted environmental risk assessments for a few chemicals 

for Reregistration Eligibility Decisions (e.g., resmethrin and permethrin). The pyrethrins were 

among the chemicals assessed. At the time, there were no exceedances of any of the LOCs. In 

one study (Weston and Lydy, 2010), several synthetic pyrethroids were observed in effluents 

after secondary treatment from POTWs in the Sacramento-San Joaquin Delta. In the study, 

bifenthrin was the most frequently detected pyrethroid from municipal wastewater treatment 

plant effluents (POTWs) tested in the Sacramento-San Joaquin Delta (18 samples tested), and it 

exceeded the Hyalella azteca EC50. Based on the above information, there is the potential for 

pyrethrins to reach surface waters via exposure from contaminated drains, even after treatment in 

wastewater plants (POTWs). Thus, EFED conducted a preliminary assessment of the indoor 

uses of pyrethrins using highly unrefined usage information and found no ecological risks of 

concern (i.e., all RQs were below the acute and chronic LOCs). The Division will evaluate the 

potential for exposure to aquatic organisms from the indoor uses of pyrethrins, using refined 

usage information and new endpoints (if any) developed by the registrant in the registration 

review ecological risk assessment (for further details see Section 6, Conceptual Model, Section 

7, Analysis Plan and Appendix C). 

Pyrethrins Use with Synergists 

Toxicity data on environmental mixtures of pyrethrins with other pesticides may be presented, if 

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

pyrethrins, 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 pyrethrins and co-contaminant concentrations, (4) 

 29
differences in the pattern and duration of exposure among contaminants, and (5) the differential 

effects of other physical/ chemical characteristics of the receiving waters, such as 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 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. EFED will consider open literature, currently 

available models and other lines-of-evidence (e.g., monitoring data), as available to address the 

potential for cumulative effects of pyrethrins and pyrethroids in the risk description of the 

ecological assessment for pyrethrins. 

Piperonyl butoxide (PBO) and MGK-264 are commonly used in formulations with pyrethrins 

and pyrethroids. PBO acts as a potentiator in both mammals and insects because the pyrethroid 

is not metabolized and excreted as quickly in its presence (Stewart 1998). MGK-264, another 

potentiator/synergist used with pyrethroids, has similar effects as those observed for piperonyl 

butoxide (US EPA 2006a). 

Currently, data on the extent to which the toxicity of pyrethrins and pyrethroids active 

ingredients are enhanced by varying concentrations of PBO are needed to address the ecological 

risk of products when co-applied with PBO. The Agency is currently evaluating a proposed 

study protocol that will quantify the enhancement of acute toxicity of pyrethroids to the 

freshwater amphipod, Hyalella azteca, by simultaneous exposure to PBO at varying 

PBO:pyrethroid ratios. It is expected that this comprehensive testing strategy, when augmented 

with similar acute toxicity data with freshwater fish and other selected pesticide active 

ingredients, will facilitate bridging of the synergist toxicity enhancement to other co-formulated 

or co-applied pesticide/synergist active ingredients that are not tested at varying synergist:active 

ingredient ratios. The need for synergist data is discussed in the EFED Registration Review 

Problem Formulation for Piperonyl Butoxide, dated December 13, 2010 (USEPA, 2010, 

D378420). The PBO Problem Formulation is available in the PBO registration review docket at 

www.regulations.gov (EPA-HQ-OPP-2010-0498). 

With respect to pyrethrins ecological data, multiple aquatic toxicity studies were previously 

submitted for a pyrethrins end-use product containing 6% pyrethrins and 60% PBO. Data are 

available for freshwater and estuarine/marine fish and invertebrates (see Section 4. Receptors). 

This data will be considered in the upcoming ecological risk assessment for pyrethrins, as well as 

any additional applicable information that is generated through the comprehensive PBO testing 

strategy. 

3.3. Environmental Fate and Transport 

Table 3.10 summarizes the environmental fate/transport properties of pyrethrin. For information 

about the physicochemical properties of this compound, refer to Table 3.2.

 30
Table 3.10. Summary of Environmental Fate Properties for Pyrethrin 

Study Value and unit 

Major Degradate 

Minor Degradates

MRID # or 

Citation 

Classification

of Study 

Abiotic Hydrolysis 

25±1°C 

Half-life1

 = 

pH 5 no evidence of degradation 

pH 7 no evidence of degradation 

pH 9 14 days 

Major degradate: 

chrysanthemic acid (53.9–

64.5% at 21–30 days at pH 

9) 

43188201 

Acceptable Half-life1

 = 

pH 5 no evidence of degradation 

pH 7 no evidence of degradation 

pH 9 17 days 

Major degradate: 

chrysanthemic acid (54–

64% at 21 days, and was 

60–62% at 30 days). Also a 

dimer derived from the 

hydrolysis product 

pyrethrolone (MW=320), 

identified as the single main 

alcohol-derived degradate, 

in a parallel test at pH 9. 

43567502 

Direct Aqueous 

Photolysis (pH 7, 

irradiated with 

sunlight in Irvine, CA) 

Half-life1

 = 

~1 hr for the isomerization 

11.8 hours, for the combination 

of pyrethrin and the (E)-Isomer 

of pyrethrin 1 

Major degradate: (E)-isomer 

of pyrethrin 1(50.7–55.7% 

AR at 2 hr) 

More than 24 minor 

products (<10%) 

43096601, 

43567601 Supplemental 

Soil Photolysis 

(natural sunlight from 

California at 24±2°C) 

Half-life = 

<1 day in a sandy loam 

Numerous minor 

degradation products (<10% 

AR) 

43096602 Supplemental 

Atmospheric 

Degradation 

Half-life1

 = 

0.036 days for hydroxyl radical 

0.012 days for ozone reaction 

N/A EPISuite 

v.4.0 N/A 

Aerobic Soil 

Metabolism (at 75% of 

0.33 bar moisture at 

25±1°C) 

Half-life1

 = 

9.5 days 

sandy loam from ND 

Major unidentified: Reg-3 

(29.7% at 3 days) 

Minor degradate: 

chrysanthemic acid (4.0% at 

3 days) 

43499803 Supplemental 

Aerobic Aquatic 

Metabolism (25±1°C) 

Half-life1

 = 

Flooded sandy loam soil: 

10.5 days for the total system 

(study lasted only 30 days) 

In the water, the parent at 7.6% 

initially and was last detected at 

14 days with 0.4% AR 

Major degradate: 

Water: chrysanthemic acid 

(11.5–14.0% at 14–30 days) 

Sediment: chrysanthemic 

acid (8.1% at 14 days) 

43499802 Supplemental 

 31
Table 3.10. Summary of Environmental Fate Properties for Pyrethrin 

Study Value and unit 

Major Degradate 

Minor Degradates

MRID # or Classification

Citation of Study 

Anaerobic Aquatic 

Metabolism (25±1°C) 

Half-life1

 = 

Flooded sandy loam soil: 

86 days 

The parent compound was not 

detected in the water phase. 

Major degradate: 

Water phase: 

Chrysanthemic acid (10.3% 

AR at 90 days) 

Chysanthemum dicarboxylic 

acid (14.2% AR, 364 days) 

In the sediment phase, 

Jasmolin-1 (10.0% AR at 

364 days) 

Chrysanthemic acid ( 7.0% 

AR, single replicate, at 3 

days) and other minor 

unidentified degradates 

(each ≤6.6% AR) 14CO2 (13.49% AR at 364 

days) 

43499801 Supplemental 

Freundlich solid-water 

distribution coefficient 

(KF) 

All soils were domestic. 

KF, 1/n, soil texture 

198 L/kg, 1.10, sand 

268 L/kg, 0.91, sandy loam 

430 L/kg, 1.05, silty loam 

310 L/kg, 0.92, silty clay loam 

Mean KF = 301.5 L/kg 

Note: Inspection of the data 

shows that the KF model 

represents the mobility of 

pyrethrin 1 better than KFOC. 

N/A 43096603 Acceptable 

Freundlich organiccarbon normalized 

distribution coefficient 

(KFOC) 

KFOC, 1/n, soil texture 

37847 L/kg, 1.10, sand 

12472 L/kg, 0.91, sandy loam 

74175 L/kg, 1.05, silty loam 

16190 L/kg, 0.92, silty clay 

loam 

Note: Inspection of the data 

shows that the KF model 

represents the mobility of 

pyrethrin 1 better than KFOC. 

N/A 43096603 Acceptable 

Volatility from Soil 

(Laboratory) 

50–75% of field 

moisture capacity 

Limited volatility, ≤0.002 

μg/cm2

·hour from Mutchler 

sandy loam soil. Maximum 

mean air concentrations were 

5.839–7.316 μg/m3

. 

After 30 days, volatilized 

residues totaled a maximum 

of ~16% of which ~9% was 

CO2, ~0.3% was pyrethrin, 

~10% chrysanthemic acid, 

and ~≤2.4 of two minor 

degradates. 

43096604 Acceptable 

Terrestrial Field 

Dissipation 

Dissipation Half-life1,2 = 

Bare plots of sandy loam soils in 

Porterville, CA, Pinehurst, GA, 

and Mason, MI: 

~1-2 days 

NA 42745501 Supplemental 

 32
Table 3.10. Summary of Environmental Fate Properties for Pyrethrin 

Study Value and unit 

Major Degradate 

Minor Degradates

MRID # or Classification

Citation of Study 

Bioconcentration 

Factor (BCF) – 

Bluegill Sunfish 

(Lepomis 

macrochirus) 

Water temp. 170C 

Mean or Steady State BCF= 

873X viscera; 127X edible 

tissues; 471x whole fish. 

Depuration was rapid; by day 1, 

77% of the accumulated 

[

14C]residues were eliminated 

from the edible tissues, 66% 

from the nonedible tissues, and 

68% from the whole fish. In the 

edible tissue, of the extracted 

radioactivity pyrethrin 1 was 

56.4% and 19.6% in the 

nonedible tissue. 

Major degradates: 

In the edible tissue, 

chrysanthemic acid was 

29.5%, and three Unknowns 

totaled 23.2%. In the 

nonedible tissue, 

chrysanthemic acid was 

32.9%, and five Unknowns 

totaled 21.8%. 

43302301, 

43884102 Acceptable 

Abbreviations: wt=weight; NA=Not Available; N/A=Not Applicable. 1Half-lives were calculated using the singlefirst order equation and nonlinear regression, unless otherwise specified. 2

The value may reflect both dissipation and 

degradation processes. 

Pyrethrin is a naturally occurring substance that contains six esters that are biologically active. 

As it has been said earlier, all the pyrethrins have the same backbone structure, with the 

exception of variations in the substitutions in the external or outermost groups. Due to the fact 

that all the pyrethrins have very similar structures, the environmental fate studies were conducted 

and well characterized with only one of the pyrethrins: pyrethrin 1. Diastereoisomers could have 

somewhat different basic properties. In this case the differences are in the substituents at two 

sites. The substituents at -R are expected to have low reactivity, with the ethene being slightly 

more reactive. In any case, the driving fate reaction is the breaking of the ester bond which is 

away from -R. On the other hand, in the case of -R’, we have two different moieties. The 

methyl moiety will be relatively unreactive, while the acetyl group (ester bond) will be 

susceptible to hydrolysis, resulting in an acid and an alcohol. It is noted from the Table 3.2 that 

the water solubility of the various pyrethrins varies due to some structure variations among them, 

however, since the environmental fate of only pyrethrin 1 was characterized, its solubility will be 

used in the models. This may add some uncertainty to the final ecological risk assessment. 

Nevertheless, EFED does not expect major differences in the overall biotic and abiotic 

degradation of the pyrethrins. 

In general, the environmental fate and transport data base of pyrethrin 1 is adequate to 

characterize the environmental fate, drinking water, and ecological exposure of the pyrethrins. 

There are no mobility and little persistence data for the degradates of pyrethrin 1. In addition, 

studies using radiolabeling on the cyclopentene side of the ester linkage were not conducted and 

cold analysis was not performed in the cyclopentene labeled studies (with the exception of one 

study of hydrolysis). Consequently, there was no analysis of potential degradates containing the 

cyclopentene ring originating from the cleavage of the carboxylate ester linkage. 

Degradation and Metabolism

Pyrethrin 1 was relatively stable in sterile aqueous pH 5 and pH 7 buffer solutions that were 

incubated in the dark at 25°C for 30 days. In pH 9 solutions, pyrethrin 1 hydrolyzed with a 

 33
calculated half-life of 14 days and 17 days in two separate studies. The major degradation 

product identified was chrysanthemic acid at up to 64% of the applied at 21 days. 

In an aqueous photolysis experiment, pyrethrin 1 isomerized to the (E)-isomer of pyrethrin 1 

(which reached a maximum 50.7–55.7% of the applied amount at 2 hours post-treatment ) with 

an observed half-life of approximately 1 hour in sterile solutions (pH 7) that were irradiated with 

sunlight in Irvine, California. The overall calculated half-life of dissipation of pyrethrin 1 and its 

(E)-isomer was 11.8 hours. In a soil photolysis study [14C]-pyrethrin photodegraded with an 

observed half-life of <1 day. The registrant reported half-life was 12.9 hours. The test was 

conducted in sandy loam soil from ND that was treated at 9.0–9.6 ppm, and irradiated with 

natural sunlight in California at 24°C. In the irradiated soil, [14C]-pyrethrin was 66.0-49.3% of 

the applied amount at 0 hours posttreatment, ranged from 42.8 to 59.0% at 1 through 4 hours, 

and was only 11.7-21.1 % at 24 hours. In contrast, the dark control samples degraded with a 

reported half-life of 82.9 hours (~3.5 days). In the dark control, [14C]-pyrethrin comprised 66.7-

73.9% of the applied through 4 hours posttreatment, and was 57.6% at 24 hours. 

The reported half-life of [14C]-pyrethrin 1 applied at 1 ppm, in an aerobic sandy loam soil 

adjusted to 75% of field capacity and incubated in the dark at 25°C was 9.5 days. The 

degradation was reported as biphasic [half-lives were 3.2 days (0–14 day data) and 23.5 days 

(14–59 day data)]. Chrysanthemic acid was a minor identified metabolite. Another band 

(which appears to consist of multiple peaks) could not be identified. 

[

14C]-Pyrethrin 1 degraded with a half-life of 10.5 days in flooded sandy loam soil incubated at 

25°C in an aerobic aquatic dissipation study. In an anaerobic aquatic dissipation study the halflife of pyrethrin 1 was 86 days. The behavior of the system was reported to be bi-phasic (86 

days being the half-life for the total system and 27.8 days for 0–31 day data). In both instances, 

chrysanthemic acid was reported as a major metabolite. Also, chysanthemum dicarboxylic acid 

was reported at a maximum of 14.2% AR at 364 days, and in the sediment phase, jasmolin-1 was 

10.0% AR at 364 days. 

It is noted that in all the studies, the material was radiolabeled in the cyclopropane ring. As a 

result, the degradate that is most likely to be observed is chrysanthemic acid. Material 

radiolabeled in the cyclopentenolone ring would result in different degradation products; 

however, the first step in the degradation of pyrethrin 1 is the rupture of the ester bridge, 

resulting in a carboxylic acid, and an alcohol. The resulting molecules are expected to lose their 

pyrethroid toxicological activity; therefore, in the final ecological risk assessment, they will not 

be considered of concern. Furthermore, the available data show that chrysanthemic acid does not 

reach high levels except upon hydrolysis at pH 9. In the many of the studies multiple degradates 

at very low concentrations were observed, but not characterized. The only significant isomer 

observed in the aqueous photolysis study was the (E)-isomer of pyrethrin 1; however, the halflife of pyrethrin 1 was reported for the photolysis of pyrethrin 1 plus the isomer (as if it was 

parent) in the calculation (the resulting half-life was less than one day). 

Soil Sorption and Mobility

Based on batch equilibrium experiments, [14C]pyrethrin 1 was noted to have a relatively low 

 34
mobility in sand, sandy loam, silt loam and silty clay loam soil:calcium chloride solution slurries 

(1:100, w:v). The mean KF value was 301.5 L/kg. 

Field Dissipation

A study, providing marginally supplemental data (bare ground soils in CA, GA, and MI) appears 

to indicate that dissipation in the field is very rapid (~1-2 days). The test substance was 

pyrethrum extract (mixture of pyrethrins I and pyrethrins II). The results appear to confirm what 

would be expected from the laboratory studies. 

Potential transport mechanisms for a pesticide include surface water runoff, spray drift, and 

secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or more 

distant ecosystems. Surface water runoff and spray drift are expected to be the major routes of 

exposure for pyrethrins to non-target organisms. The magnitude of transport via secondary drift 

depends on the pyrethrins’ ability to be mobilized into air and its eventual removal through wet 

and dry deposition of gases/ particles and photochemical reactions in the atmosphere. Therefore, 

physicochemical properties of pyrethrins that describe its potential to enter the air from water or 

soil (e.g., Henry’s Law constant and vapor pressure), pesticide use data, modeled estimated 

concentrations in water and air, and available air monitoring data are considered in evaluating 

the potential for atmospheric transport of pyrethrins. Pyrethrins have a moderately low vapor 

pressure (2.03 x 10-5 torr) and a low Henry’s Law constant (7.7x10-7 atm-m3

/mol); thus, 

volatilization from water and soil surfaces is expected to be very low. Pyrethrins’ potential for 

volatilization is also reduced significantly because it adsorbs strongly to soils. Pyrethrins’ 

estimated atmospheric half-life is short (~0.04 days for the hydroxyl radical reaction), indicating 

a low potential for transport via volatilized active substance (as opposed to present in suspended 

solids). 

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 pyrethrins, 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. The stressor in this case is the pyrethrin pesticide. Spray drift and runoff exposures are 

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

described in the Overview Document (USEPA, 2004), this risk assessment uses a surrogate 

species approach in its evaluation of pyrethrins. 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 and chronic ecological effects of pyrethrins to these non-target 

taxonomic groups. 

 35
Terrestrial Species 

For terrestrial species, data were submitted for both pyrethrum extract. In addition, mammalian 

toxicity studies with end-use products containing pyrethrins and the synergist PBO. A summary 

of the most sensitive endpoints from the available toxicity studies conducted with aquatic species 

is presented in Table 4.1 and the mammalian end-use product data is summarized in Table 4.2. 

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

Species 

(common 

name)

Taxa 

Represented Endpoint Concentration 

Test 

Substance 

(% a.i.) Reference

Acute 

Toxicity 

Classification 

Rattus 

norvegicus 

(Laboratory 

Rat) 

Mammals 

LD50 1400 mg/kg bw 

58 

(pyrethrum 

extract) 

42008101 

Acceptable Slightly toxic 

NOAEL 6.4 mg ai/kg bw/day 58 

(pyrethrum 

extract) 

41327501 

Acceptable 

Not 

LOAEL 65 mg/kg bw/day Applicable 

Bobwhite quail 

(Colinus 

virginianus) 

Birds, 

terrestrialphase 

amphibians, and 

reptiles 

LD50 >2000 mg ai/kg bw 

58 

(pyrethrum 

extract) 

42010901 

Acceptable 

 Practically 

non-toxic 

Bobwhite quail 

(Colinus 

virginianus) 

Mallard duck 

(Anas 

platyrhynchos) 

LC50

>5620 mg a.i./kg 

diet 

58 

(pyrethrum 

extract) 

41968801 

Acceptable 

41968802 

Acceptable 

Practically 

non-toxic 

NOAEC No data available Not 

LOAEC Applicable 

Apis mellifera

(Honey bee) 

Terrestrial 

invertebrates 

Contact 

LD50

0.022 μg a.i./bee 

58 

(pyrethrum 

extract) 

41968803 

Acceptable Highly toxic 

Birds

The results of the single acute oral toxicity study available for pyrethrins (pyrethrum extract, 

58% active ingredient) indicate that the chemical is practically non-toxic to avian species on an 

acute oral basis. The acute oral LD50 value for bobwhite quail (Colinus virginianus) is >2000 mg 

a.i./kg bw (MRID 42010901). At the 500, 1000 and 2000 mg ai/kg bw treatment levels, 

observations of toxicity effects included shallow and rapid respiration, prostrate posture, lower 

limb weakness, loss of coordination, lethargy, hyperexcitability, reduced reaction to external 

stimuli, ruffled appearance and twitching. Weight loss was also observed at the 1000 and 2000 

mg ai/kg bw, compared to the control birds. No acute dose-based exposure was estimated in the 

latest Agency ecological risk assessment for pyrethrins (USEPA 2007). However, based on a 

preliminary screen using the highest agricultural application scenario for pyrethrins (see Table 

3.3), the highest peak dose-based EEC is 125 mg/kg bw. This conservative dietary exposure 

prediction is approximately 16 times lower than the highest treatment level tested in the available 

acute oral test with bobwhite quail, at which an LD50 could not be established due to lack of 

mortality. 

 36
No acute avian oral studies with pyrethrins have been submitted for passerine species. 

The results of the sub-acute dietary toxicity studies available for pyrethrins indicate that it can be 

classified as practically non-toxic to avian species on an acute dietary basis. The LC50 is greater 

than 5620 mg a.i./kg bw for bobwhite quail (Colinus virginianus) (MRID 41968801). In this 

study, the NOAEC was determined to be 3160 mg a.i./kg bw, based on reductions in body 

weight gain at the 5620 mg a.i./kg bw treatment level. In a dietary study conducted with mallard 

ducks (Anas platyrhynchos), the LC50 is also greater than 5620 mg a.i./kg bw (MRID 41968802). 

The NOAEC in this study is 1780 mg a.i./kg bw, based on signs of lethargy. Both avian dietary 

studies were conducted with pyrethrum extract, 58% active ingredient. The highest peak 

predicted dietary exposure concentration for birds was 97 mg ai/kg bw, modeled in latest Agency 

ecological risk assessment for pyrethrins (USEPA 2007). Therefore, the predicted dietary 

exposure for birds resulting from pyrethrins use appears to be at least 60 times lower than the 

highest treatment levels in the available avian dietary studies for pyrethrins, at which an LC50

could not be established. 

No avian reproduction studies have been submitted for pyrethrins. 

Mammals

Mammalian toxicity data submitted to the Agency's Health Effects Division (HED) are used to 

approximate toxicity to wild mammals. These studies are typically conducted with laboratory 

rats (Rattus norvegicus) or mice (Mus musculus). No studies evaluating toxicity to wild mammal 

species have been submitted by the registrants for pyrethrins. 

Acute oral, dermal and inhalation mammalian toxicity studies with pyrethrins were submitted to 

the Agency. In addition, chronic dietary and 2-generation rat reproduction studies have also been 

submitted for pyrethrins. These studies are presented in the HED chapter of the Reregistration 

Eligibility Decision Document (RED) for pyrethrins (US EPA, 2006). In addition, registrantsubmitted rat toxicity information for individual products is also available. 

The reported laboratory rat acute oral LD50 value is 1400 mg/kg-bw for pyrethrins (MRID 

42008101). The acute dermal LD50 >2000 mg/kg bw for pyrethrins, based on a study conducted 

with rabbits (MRID 41964801). An acute inhalation conducted with rats resulted in an LC50 

>3.4 mg/L for pyrethrins (MRID 42008002). Based on these reported laboratory rat LD50 values, 

pyrethrins have low to moderate acute toxicity to small mammals via the oral, dermal and 

inhalation basis. 

Additional rat acute oral data were available for crude pyrethrum extract, as well as a number of 

pyrethrins products. See Table 4.2 for an overview of the studies. Based on this subset of data 

for products containing pyrethrins or pyrethrins and PBO, mammalian toxicity appears to be 

similar across products, ranging from practically nontoxic to slightly toxic. 

Table 4.2. Rat acute oral toxicity data for crude pyrethrum extract and pyrethrins end-use products 

Product Percent active ingredient LD50

(mg/kg bw) 

Reference 

 37
Crude pyrethrum extract not reported 787 mg/kg bw for females 

2136 mg/kg bw for males 

MRID 45625301 

Pyganic fogging 

concentrate 

5% pyrethrins ≥ 2000 mg/kg bw (females 

only) 

MRID 45848201 

Pyrocide fogging 

concentrate 

5% pyrethrins, 25% PBO ≥ 500 and < 5000 mg/kg 

bw (both males and 

females) 

MRID 45647601 

Pyrocide concentrate 3% pyrethrins, 30% PBO ≥ 500 and < 5000 mg/kg 

bw (both males and 

females) 

MRID 45807601 

Pyrocide concentrated 

aqueous spray 

1% pyrethrins and 10% 

PBO 

≥ 2000 mg/kg bw (females 

only) 

MRID 45807701 

In the available 2-generation rat reproduction study, the NOAEL is 6.4 mg/kg/day based on 

decreased F1 pup body weight and body weight gain during lactation at the 65 mg/kg/day 

treatment level (MRID 41327501). In the submitted chronic mammalian dietary study with 

pyrethrins, the NOAEL is 4.37 mg/kg/day based on the increased incidence of follicular cell 

hyperplasia in male rats at the 42.9 mg/kg/day treatment level (MRID 41559501). Because 

follicular cell hyperplasia is not clearly linked to the typical ecological endpoints of survival, 

growth and reproduction, the NOAEL of 6.4 mg/kg/day based on decreased F1 pup body weight 

in the 2-generation rat reproduction study is considered the most sensitive endpoint for risk 

estimation at this time. 

Terrestrial Invertebrates

The Agency guideline terrestrial invertebrate tests are for honey bees (Apis mellifera). The acute 

contact LD50 value is 0.022 (with pyrethrum extract) (MRID 41968803). Based on these results, 

pyrethrins are classified as ‘highly toxic’ to honey bees on an acute exposure basis. 

Aquatic Species 

For aquatic species, data were submitted for both pyrethrum extract and an end-use product 

containing pyrethrins and the synergist PBO. In all situations where acute toxicity data with the 

same species were available for both pyrethrum extract and pyrethrins + PBO, the organisms 

were more sensitive to the product containing the synergist (LD50 confidence intervals did not 

overlap). A summary of the most sensitive endpoints from the available toxicity studies 

conducted with aquatic species is presented in Table 4.3. 

Table 4.3. Summary of most sensitive endpoints from submitted aquatic toxicity studies for pyrethrins. 

Exposure 

Scenario 

% Active 

Ingredient Species Exposure Duration Endpoint Reference Acute Toxicity 

Classification 

Freshwater Fish

 38
Table 4.3. Summary of most sensitive endpoints from submitted aquatic toxicity studies for pyrethrins. 

Exposure % Active Exposure Acute Toxicity Species Endpoint Reference 

Scenario Classification Ingredient Duration 

Acute 

Pyrethrum 

extract 

57%

Rainbow Trout 

Oncorhynchus 

mykiss 

96 hours

LC50 = 5.1 μg 

a.i./L 

NOAEC = 3.1 

μg a.i./L

MRID 43082303 

Acceptable 

Very highly toxic 

TEP 

6% 

pyrethrins 

60% PBO

Rainbow Trout 

Oncorhynchus 

mykiss

96 hours

LC50 = 3.2 μg 

a.i./L 

NOAEC= 1.5 

μg a.i./L 

MRID 43082304 

Acceptable

Very highly toxic

Chronic 

Pyrethrum 

extract 

57%

Fathead minnow 

Pimephales 

promelas

30 days 

NOAEC = 1.9 

μg a.i./L 

LOAEC = 3.0 

μg a.i./L 

MRID 43252701 

Acceptable Not applicable 

Freshwater Invertebrates 

Acute 

Pyrethrum 

extract 

57% 

Water flea 

Daphnia magna 48 hours

EC50 = 11.6 μg 

a.i./L 

NOAEC=3.7 

μg a.i./L

MRID 43082305 

Acceptable

Very highly toxic 

TEP 

6% 

pyrethrins 

60% PBO

Water flea 

Daphnia magna 48 hours

EC50 = 6.7 μg 

a.i./L 

NOAEC = 0.5 

μg a.i./L 

MRID 43082305 

Acceptable Very highly toxic

Chronic 

Pyrethrum 

extract 

57%

Water flea 

Daphnia magna 35 days

NOAEC = 

0.86 μg a.i./L 

LOAEC = 2.0 

μg a.i./L

MRID 43252702 

Acceptable 

Not applicable 

 39
Table 4.3. Summary of most sensitive endpoints from submitted aquatic toxicity studies for pyrethrins. 

Exposure % Active Exposure Acute Toxicity Species Endpoint Reference 

Scenario Classification Ingredient Duration 

Acute 

Pyrethrum 

extract 

57%

Sheepshead 

minnow 

Cyprinodon 

variegatus

96 hours

LC50 = 16 μg 

a.i./L 

NOAEC = 7.4 

μg a.i./L

MRID 43082307 

Acceptable

Very highly toxic

TEP 

6% 

pyrethrins 

60% PBO 

Sheepshead 

minnow 

Cyprinodon 

variegatus

96 hours

LC50 = 3.8 μg 

a.i./L 

NOAEC = 1.6 

μg a.i./L 

MRID 43082308 

Acceptable Very highly toxic 

Chronic No data available 

Estuarine/Marine Invertebrates 

Acute 

Pyrethrum 

extract 

57%

Saltwater mysid 

Americamysis 

bahia

96 hours

LC50 = 1.4 μg 

a.i./L 

NOAEC=0.29 

μg a.i./L

MRID 43082311 

Acceptable 

Very highly toxic 

TEP 

6% 

pyrethrins 

60% PBO 

Saltwater mysid 

Americamysis 

bahia

96 hours

LC50 = 0.14 μg 

a.i./L 

NOAEC = 

0.084 μg a.i./L

MRID 43082312 

Acceptable 

Very highly toxic 

Chronic No data available

Freshwater Fish

The acute toxicity studies available to the Agency demonstrate that pyrethrins (pyrethrum 

extract) can be classified as very highly toxic to freshwater fish. The acute LC50 value is 5.1 μg 

a.i./L for rainbow trout and the acute LC50 value is 10 μg a.i./L for bluegill sunfish (MRIDs 

43082303 and 43082301). Both endpoints are based on mean-measured concentrations of 

pyrethrins active ingredient. 

The previously submitted studies also demonstrate that pyrethrins products formulated with the 

synergist PBO are more toxic than the pyrethrum extract to freshwater fish, but within an order 

of magnitude difference. The toxicity observed in acute freshwater fish toxicity studies with 

Pyrenone Crop Spray (6% pyrethrins and 60% PBO) resulted in an LC50 value of 3.2 μg a.i./L 

for rainbow trout and an LC50 value of 3.4 μg a.i./L for bluegill sunfish (MRID 43082304 and 

 40
43082302). Both endpoints are based on mean-measured concentrations of pyrethrins active 

ingredient. 

An acceptable 30-day early-life stage study with fathead minnows (Pimephales promelas) was 

submitted to evaluate the effects of chronic exposure to pyrethrins on freshwater fish (MRID 

43252701). The study demonstrated that chronic exposure to concentrations as low 3.0 μg a.i./L 

has the potential to cause reproductive toxicity, based on a significant reduction in the number of 

eggs hatched and body weight in the 3.0 μg a.i./L treatment level relative to the controls (73% 

vs. 87% for egg hatch; 0.29 mg vs. 0.33 mg for body weight). The NOAEC for this study is 1.9 

μg a.i./L. 

No freshwater fish full life cycle study has been submitted for pyrethrins. 

Estuarine/Marine Fish

The acute toxicity studies available to the Agency demonstrate that pyrethrins can be classified 

as very highly toxic to estuarine/marine fish. Exposure to pyrethrum extract resulted in an acute 

LC50 value of 16 μg a.i./L for sheepshead minnow, and pyrethrins formulated with PBO yielded 

an acute LC50 value of 3.8 μg a.i./L for sheepshead minnow in a submitted toxicity test (MRIDs 

43082307 and 43082308). 

No estuarine/marine fish full life cycle study has been submitted for pyrethrins. 

Freshwater Invertebrates

The acute toxicity studies available to the Agency demonstrate that pyrethrins can be classified 

as very highly toxic to freshwater invertebrates. The acute EC50 value for pyrethrins (pyrethrum 

extract, 57% active ingredient) is 11.6 μg a.i./L based on a test with waterfleas (Daphnia magna) 

(MRID 43082305). Another submitted study with Daphnia magna indicates that pyrethrins 

formulated with PBO has greater toxicity than pyrethrins alone, with an EC50 of 6.7 μg a.i./L 

(MRID 43082306). 

In addition to the registrant-submitted studies for pyrethrins, one acute freshwater invertebrate 

toxicity test conducted by the U.S. Fish and Wildlife Service (1969) is available (MRID 

05009242). Based on the overview provided, a study conducted with pyrethrum (active 

ingredient not reported) exposure to scuds (Gammarus lacustris) resulted in a 96 hour LC50 of 12 

μg a.i./L. The results of this study indicate a similar response between daphnids and amphipods 

to pyrethrins exposure. However, no additional details on test conditions, raw data and data 

analysis are available for this study, so the test is considered supplemental information for the 

upcoming risk assessment. 

 41
An acceptable guideline life-cycle studies with waterfleas (Daphnia magna) reports a NOAEC of 

0.86 μg a.i./L for pyrethrins (pyrethrum extract, 57% active ingredient. The LOAEC for this 

study is 2.0 μg a.i./L, based on reductions in the number of young produced per female (MRID 

43252702). 

In addition to studies submitted that examine the effects of pyrethrins to aquatic invertebrates in 

the water column, a 28-day benthic invertebrate study with the midge Chironomus riparius has 

been submitted to the Agency (MRID 48141101, in review). This study was conducted with 

sediment spiked with pyrethrum extract, and conducted in accordance with OECD Guideline 

218: Sediment-Water Chironomid Toxicity Test Using Spiked Sediment. Percent emergence and 

development rate were calculated, and emergence rate was determined to be statistically lower 

than the controls at the highest nominal treatment level, 1000 mg a.i./kg sediment (49% 

emergence in this treatment compared to 74% in the negative control). There is substantial 

uncertainty in using the results of this study quantitatively in the upcoming ecological risk 

assessment, as the measured concentrations in the sediments were 10 to 17% of the nominal test 

concentrations on Day 0, and the measured levels of pyrethrins fell to <3 to 5% by Day 28. In 

addition, this study did not examine reproductive parameters. 

Estuarine/Marine Invertebrates

The acute toxicity studies available to the Agency demonstrate that pyrethrins can be classified 

as very highly toxic to estuarine/marine invertebrates. A submitted study with pyrethrum extract 

(57% active ingredient) and mysid shrimp (Mysidopsis bahia) resulted in an LC50 value of 1.4 μg 

a.i./L (MRID 43082311). Based on an additional submitted study with pyrethrins formulated 

with PBO (6% pyrethrins; 60% PBO), showed increased sensitivity to the product, with an LC50

value of 0.14 μg a.i./L (MRID 43082312) 

Pyrethrins appear to be less toxic to estuarine/marine bivalves than shrimp, based on submitted 

studies with the eastern oyster (Crassostrea virginica). For bivalves, the EC50 value is 86 μg 

a.i./L for pyrethrum extract and 26 μg a.i./L for formulated pyrethrins with PBO (MRIDs 

43082309 and 43082310). 

No chronic full life cycle study with estuarine/marine invertebrates has been submitted for 

pyrethrins. 

Plants

No studies evaluating the toxicity of pyrethrins to terrestrial plants, aquatic plants or algae have 

been submitted to the Agency. 

ECOTOX 

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

terrestrial receptors identified in this section. This includes toxicity data on the technical grade 

active ingredient, and when available, formulated products. 

 42
At this time, a full and complete ECOTOX search has not been performed, but will be conducted 

prior to the final risk assessment. 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 pyrethrins 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 (such as NOAEC, EC50, etc.), but rather are intended to identify a dose that 

maximizes a particular effect (such as EC100). Therefore, efficacy data and non-efficacy 

toxicological target insect data will not be included in the ECOTOX open literature search. 

4.2. Incident Database Review 

A review of the Ecological Incident Information System (EIIS, v. 2.1) and Aggregate Incident 

databases for ecological incidents involving pyrethrins was completed on September 1, 2011. 

This database consists of exposure incident reports submitted to the EPA from 1994 to present. A 

search for incidents involving pyrethins was also conducted in the American Bird Conservancy’s 

Avian Incident Monitoring System (AIMS). 

The reports are listed in order of certainty, from highly probable to unrelated. Incidents listed in 

EIIS are categorized by the likelihood that a particular pesticide is associated with that particular 

incident. These classifications include highly probable, probable, possible, unlikely or unrelated. 

“Highly probable” incidents usually require carcass residues or clear circumstances regarding the 

exposure. “Probable” incidents include those where residue information was not available or 

circumstances were less clear than those for “highly probable”. “Possible” incidents occur when 

multiple chemicals may have been involved and the contribution of an individual chemical is not 

obvious. An “unlikely” incident classification is given when a given chemical is considered 

nontoxic to the type of organism involved or the chemical was analyzed and not detected in 

samples. The “unrelated” category is used for incidents confirmed not to involve pesticides. 

The number of reports listed in the EIIS database is believed to be only a small fraction of the 

total incidents involving organism mortality and damage caused by pesticides. Few resources are 

assigned to incident reporting. Reporting by states is only voluntary, and individuals discovering 

incidents may not be informed on the procedure of reporting these occurrences. Additionally, 

much of the database is generated from registrant-submitted incident reports. In addition, 

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. Because of 

these logistical difficulties, EIIS is most likely a minimal representation of all pesticide-related 

ecological incidents. 

 43
Registrants are legally required to provide detailed reports of only “major” ecological incidents 

involving pesticides, while “minor” incidents are reported aggregately. Based on 40 CFR 

§159.184, an ecological incident is considered major and must be submitted to the Agency by the 

registrant if any of the following criteria are met:

Fish or wildlife: 

(A) Involves any incident caused by a pesticide currently in Formal Review4 for 

ecological concerns. 

(B) Fish: Affected 1,000 or more individuals of a schooling species or 50 or more 

individuals of a non-schooling species. 

(C) Birds: Affected 200 or more individuals of a flocking species, or 50 or more 

individuals of a songbird species, or 5 or more individuals of a predatory species. 

(D) Mammals, reptiles, amphibians: Affected 50 or more individuals of a 

relatively common or herding species or 5 or more individuals of a rare or solitary 

species. 

(E) Involves effects to, or illegal pesticide treatment (misuse) of a substantial tract 

of habitat (greater than or equal to 10 acres, terrestrial or aquatic). 

Plants: 

(A) The effect is alleged to have occurred on more than 45 percent of the acreage 

exposed to the pesticide. 

The EIIS database contained 7 major incidents involving pyrethrins. The reports included 

2 fish incidents and 5 plant incidents. In respect to the likelihood that pyrethrins caused the 

reported incidents, the certainty ranged from possible to probable. No unrelated or unlikely 

incidents were listed in EIIS for pyrethrins. Four of the incidents resulted from registered uses, 

two were misuses and one use pattern is unknown. A summary of ecological incidents involving 

pyrethrins included in the EIIS database are listed in Appendix B. 

The AIMS database contains no avian incidents involving pyrethrins. 

All other incidents are classified as ‘minor’. All ecological incidents classified as ‘minor’ only 

need to be aggregately reported as quarterly counts of incidents by the registrant(s). Ecological 

incidents reported in aggregate reports include those categorized as ‘minor fish and wildlife’ (WB), ‘minor plant’ (P-B), and ‘other non-target’ (ONT) incidents. ‘Other non-target’ incidents 

include reports of adverse effects to insects and other terrestrial invertebrates. For pyrethrins, 

the registrants have reported 231 minor plant incidents. All reported incidents occurred 

between 1995 and 2010, and involved currently registered products such as Ortho Rose and 

Flower Insect Killer, Ortho Tomato and Vegetable Insect Killer, Real Kill Rose and Garden 

Insect Spray and Pyganic 5.0, among others. Unless additional information on these aggregated 

incidents becomes available, they will be assumed to be representative of registered uses of 

pyrethrins in the risk assessment. 

 4 Formal Review means Special Review, Rebuttable Presumption Against Registration (RPAR), FIFRA 

section 6(c) suspension proceeding, or FIFRA section 6(b) cancellation proceeding, whether completed or 

not. 

 44
4.3. Ecosystems Potentially at Risk 

Pyrethrins may be applied on a variety of food/feed crops, including (but not limited to), alfalfa, 

nut trees, corn, leafy vegetables, stone fruits, pome fruits, fruiting vegetables, cucurbit 

vegetables, cole crops, onion and soybean. In addition, they may be used on numerous non-food 

sites (e.g. ornamentals, commercial animal housing, outdoor agricultural premises, residential 

sites – outdoors, outdoor eating establishments, and as an adulticide or mosquito control). 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 pyrethrins, 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 potential persistence of pyrethrins under certain circumstances, it is expected to drift 

and/ or runoff due to application to food crops and certain non-crop sites, resulting in possible 

exposure to aquatic ecosystems. Aquatic ecosystems potentially at risk due to the use of 

pyrethrins include water bodies adjacent or downstream 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, such as 

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 

pyrethrins. 

To estimate exposure concentrations, the ecological risk assessment considers applications 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 

 45
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. 

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 

pyrethrins. More sensitive endpoints from acceptable open literature studies will be included in 

the ecological 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 pyrethrins, 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 (USEPA, 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 (USEPA 1998). For this assessment, the risk is stressor-initiated, 

where the stressor is the release of pyrethrins into the environment. The following risk 

hypotheses are presumed for this screening-level assessment: 

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

off-site movement of the compound via agricultural and urban runoff, spray drift, and 

eroded soil leading to exposure of nontarget plants and animals Based on information 

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

EFED assumes that registered uses of pyrethrins have the potential to cause reduced 

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

plants. 

Pyrethrins, when used indoors for uses such as pet shampoos, etc., in accordance with 

current labels, will likely result in off-site movement of the compound via wash-off into 

surface waters via drains and municipal wastewater treatment plants, leading to 

exposure of nontarget aquatic plants and animals. This potential exposure pathway may 

result in adverse effects upon the survival, growth, and/or reproduction of non-target 

aquatic animals and plants. 

 46
Pyrethrins, when used for the treatment of cattle (and certain other animals), in 

accordance with current labels, may result in off-site movement of the compound via 

wash-off of cattle and calves into surface waters, leading to exposure of nontarget 

aquatic plants and animals. This potential exposure pathway may result in adverse 

effects upon the survival, growth, and/or reproduction of non-target aquatic animals and 

plants.

 

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

potential pesticide or stressor (pyrethrins and possible metabolites, as well as synergists), the 

source of the pesticide and/or transport pathways, exposure media, exposure point, biological 

receptor types, and attribute changes. 

6.2. Conceptual Diagram

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

insecticide pyrethrins, which is a natural pyrethroid insecticide, having multiple outdoor 

agricultural and non-agricultural 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 pyrethrins, 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 (Figures 6.1a and 6.1b). They include the potential pesticide or stressor (pyrethrins, 

but the presence of toxicologically important metabolites and/ or synergists cannot be ruled out), 

the sources and/ or transport pathways, exposure media and exposure points, biological receptor 

types and attribute changes. 

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 pyrethrins, the sources and mechanisms of release of the compounds 

are from ground or aerial spray or ULV applications. Note that this conceptual model considers 

agricultural applications as well as certain non-agricultural applications. Surface runoff from the 

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

 47
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. Leaching to groundwater is not considered an important source because the pyrethrins, 

like many other pyrethroids, show low mobility in a variety of soils. Pyrethrins appear to have a 

low potential for volatilization, with a low vapor pressure and Henry’s Law Constants. Further, 

the hydroxyl radical reaction half-life for pyrethrins is ~0.04 days as estimated by quantitative 

structure-activity relationship (QSAR) methods (EPI Suite v.4.0). The short (atmospheric) halflife, the low vapor pressure (~10-5 to ~10-7 torr) and relatively low Henry’s Law constant (~10-7

to ~10-8 atm/m3

-mol), and its binding capacity, suggest that the potential for atmospheric 

transport for pyrethrins is relatively low and that this source of the chemical is of low 

importance, compared to spray drift, runoff and/ or direct contact after application. 

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 and flow (e.g., piped storm drains) from treated areas. Indirect effects 

to aquatic organisms (both fish and aquatic invertebrates) can also occur through impact to 

various food chains. 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 terrestrial plants. The attribute 

changes used to assess risk to terrestrial receptors depend on the type of test (e.g., reduced 

survival, growth, or 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. 

This conceptual model also shows information about the potential for biomagnification for 

pyrethrins (see piscivorous birds and mammals in Fig. 6.1b). The reported value of log octanol/ 

water partition coefficient of 4.3–5.9 (or KOW = 2.0 x 104 – 7.9 x 105

) suggests that pyrethrins 

have the potential to bioaccumulate in aquatic organisms assuming that chemical metabolism is 

negligible. However, the measured bioconcentration factor in fish (Table 3.11) is much lower 

than what would be expected based on KOW alone, which suggests that pyrethrins fish 

metabolism is substantial. Thus, it appears that the potential for bioaccumulation/ 

bioconcentration in aquatic organisms and biomagnification in terrestrial organisms is low. 

Pyrethrins show a range of solubility of 0.2 to 9.0 ppm, a very high KOW and relatively high KFs 

and KFOCs. These properties suggest that the chemicals could partition with the sediments and 

particulate suspended in bodies of water. Pyrethrins are likely to concentrate in the sediments, 

especially after repeated exposures (applications), where they could persist. Such sediments 

could serve as repositories of the chemical for extended periods of time and could potentially be 

toxic to sediment dwelling organisms, affecting the food chain. These issues will also be 

assessed in the risk assessment for pyrethrins. 

 48
Figure 6.1a. Aquatic conceptual model depicting stressors, exposure pathways, and 

potential effects to aquatic organisms from the use of pyrethrins on agricultural and 

certain non-agricultural sites 

**Considered a minor route of exposure 

Stressor 

Source 

Receptors 

Attribute 

Change 

Pyrethrins applied to agricultural or non-agricultural use site 

Spray drift

Aquatic animals 

Invertebrates 

Vertebrates 

Piscivorous mammals 

 and birds** 

Individual organisms 

Reduced survival (2)

Reduced growth

Reduced reproduction 

Food chain 

Reduction in algae and 

 vascular plants 

Reduction in prey 

Modification of PCEs 

 related to prey availability 

Habitat integrity 

Reduction in primary 

 productivity

Surface water/ 

Sediment

Runoff

Aquatic Animals

Invertebrates 

Vertebrates 

Exposure 

Media 

Uptake/gills 

or integument 

Ingestion Ingestion 

Atmospheric 

transport 

Wet/dry deposition 

Soil Leaching to 

Groundwater

Uptake/gills 

or integument 

Aquatic Plants 

Non-vascular 

Vascular 

Uptake/cell, 

roots, leaves Riparian plants

terrestrial 

exposure 

pathways; see 

Figure 6.1b 

Flow (1)

Impervious 

Surfaces

Reduced cover 

Community change 

Modification of PCEs related to 

 habitat 

1

 Includes flow across vegetation and vegetated drainage systems (e.g., swales) and flow across impervious surfaces 

and through impervious (piped) storm drains. 

2

 Immobilization is considered equivalent to mortality in toxicity tests for aquatic invertebrates.

Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological risk. 

 49
Figure 6.1b. Terrestrial conceptual model depicting stressors, exposure pathways, and 

potential effects to terrestrial organisms from the use of pyrethrins on agricultural and 

certain non-agricultural sites 

Stressor 

Source 

Attribute 

Change 

Pyrethrins applied to agricultural or non-agricultural use sites 

Direct 

application Spray drift 

Terrestrial 

vertebrates 

Terrestrial 

Exposure Media 

& Receptors 

invertebrates 

Individual 

organisms 

Reduced survival 

Reduced growth 

Reduced reproduction 

Food chain 

Reduction in prey and food

Modification of PCEs 

 related to prey availability 

Habitat integrity 

Reduction in primary productivity

Reduced cover 

Community change 

Modification of PCEs related 

 to habitat 

Terrestrial plants 

grasses/ forbs, fruit, seeds 

(trees, shrubs) 

Runoff 

Terrestrial 

vertebrates 

Soil 

Ingestion 

Ingestion

Ingestion

Dermal uptake/Ingestion

Atmospheric 

transport 

Root uptake/contact 

Wet/dry deposition

Ingestion

Leaching to

Groundwater Irrigation 

water 

Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological risk. 

The conceptual model for potential risks of pyrethrins to aquatic organisms due to various indoor 

uses of the chemical that could potentially end up in a “drain” and disposed through domestic 

wastewater is depicted in Fig. 6.2. The stressor is the chemical of concern, pyrethrins. It is 

noted that the transport pathway is wastewater flow, the exposure media is the treatment facility 

and the exposure route, receptor, and attribute changes for aquatic organisms are similar to the 

conceptual model for agricultural applications. 

EFED performed a preliminary assessment of the “down-the-drain” uses and found that RQs did 

not exceed any LOCs (see Appendix C). The Division will perform a similar assessment, using 

refined usage information and new endpoints (if any are developed, from newly submitted 

studies) in the Registration Review ecological risk assessment. 

 50
Figure 6.2. Conceptual model for potential risks of pyrethrins to aquatic organisms for 

various indoor uses of the chemical that could potentially end up in the “drain” 

Stressor Pyrethrins applications that could potentially end up “down-the-drain”

Source/ 

Transport 

Pathways 

Domestic wastewater flow; 

Partitioning with sewage sludge 

Source/ 

Exposure 

Media 

Treatment facility 

discharges into surface 

waters 

Exposure 

Route 

Gill/ 

 Integument 

Uptake 

Receptors 

Attribute 

Changes 

Aquatic 

Invertebrates, 

Vertebrates

Individual 

Vertebrates and 

Invertebrates

Reduced survival 

or reproduction 

Aquatic 

Plants

Uptake/ 

Adsorption

Plant Population

Reduced 

population 

growth

 

The conceptual model for potential risks of pyrethrins to terrestrial and aquatic organisms as a 

result of the treatment on cattle or calves is depicted in Fig. 6.3. The stressor is the chemical of 

concern, pyrethrins, and potentially interactions caused by applications with the synergists PBO 

and MGK. The organisms that could be expected to be affected are terrestrial plants, aquatic 

plants and aquatic animals. It is noted that the potential transport pathway, the exposure media 

and the exposure point or route, receptor, and attribute changes for plant and aquatic organisms 

are similar to the conceptual model for agricultural applications Fig. 6.1a. 

 

 51
Figure 6.3: Conceptual model for potential risks of pyrethrins to aquatic organisms as a 

result of the treatment on cattle or calves. 

Stressor Pyrethrins and PBO used as for the treatment of cattle and other animals 

(Immersion in surface water body or washoff transported nearby or to surface waters) 

Source/ 

Transport 

Pathways 

Surface waters 

Source/ 

Exposure 

Media 

Riparian/ 

Wetland 

Foliage/Soil Receiving Water Body/ 

Sediment 

Exposure 

Route 

Direct Contact/ 

Root Uptake Gill/ 

 Integument 

Uptake 

Receptors 

Attribute 

Changes 

Aquatic 

Invertebrates, 

Vertebrates 

Wetland/ 

Riparian 

Plants 

Individual Plants

Reduced survival, 

growth, or reproduction 

Individual 

Vertebrates and 

Invertebrates

Reduced survival 

or reproduction 

Plant Population

Reduced 

population 

growth 

Aquatic 

Plants 

Uptake/ 

Adsorption

 

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 pyrethrins 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 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 doseresponse 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 or the registrant in response to the 

 52
opening of the Registration Review docket. 

7.1. Stressors of Concern 

The focus of this assessment is on the parent material, pyrethrins. However, the Agency will 

review open literature to identify degradate(s) of potential toxicological concern (e.g.

chrysanthemic acid, pyrethric acid, chrysanthemum dicarboxilic acid, pyrethrolone, cinerolone 

and jasmolone). Also, risk resulting from use of pyrethrins and synergists will be assessed for 

cattle treatments. 

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

occurring in the environment following application), if available, may be presented as part of the 

ecological risk assessment. Pyrethrins may be applied in tank mixtures with other products 

approved for use on registered crops. It is expected that the toxic effect of pyrethrins, 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 pyrethrins 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). A discussion of implications of the available pesticide mixture effects 

data on the confidence of risk assessment conclusions will be addressed in the risk description of 

the final ecological assessment. 

7.2. Measures of Exposure 

In order to estimate risks of pyrethrins 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. Available monitoring data will also be considered when 

describing potential environmental exposure to non-target organisms. 

Measures of exposure are based on aquatic and terrestrial models that predict estimated 

environmental concentrations of pyrethrins using maximum labeled application rates and 

methods, as well as any mitigation measures specifically indicated on the label. 

Additional information on the terrestrial exposure models and screening tools employed in EPA 

ecological risk assessments for pesticides can be found at 

http://www.epa.gov/oppefed1/models/terrestrial/. 

More information on aquatic pesticide exposure models can be found at

http://www.epa.gov/oppefed1/models/water/index.htm. 

Dietary exposure to terrestrial organisms

Measures of exposure for terrestrial mammals, birds, reptiles and amphibians similarly 

incorporate maximum proposed use rates but rely less on fate properties. Terrestrial exposures 

were estimated using a number of methods. For pyrethrins, acute and chronic terrestrial 

 53
exposure estimates are derived directly from empirically determined observations of pesticide 

residues on various terrestrial food items. The Kenaga nomogram, as modified by Fletcher et al, 

(Kenaga and Hoerger, 1972; Fletcher et al, 1994) is used to relate pesticide application rates to 

residues on terrestrial food items. The surface residue concentration (ppm) is estimated by 

multiplying the application rate (pounds active ingredient per acre) by a value specific to each 

food item. For numerous applications for a given use, the exposure model incorporates a firstorder decay rate dependent on the foliar dissipation half-life of the chemical. In the absence of 

foliar dissipation data, a default foliar dissipation half-life of 35 days is used. 

Inhalation, drinking water and dermal exposure

Two screening tools were utilized to assess the potential for pyrethrins exposure to terrestrial 

organisms via inhalation and drinking water exposure. The Screening Tool for Inhalation Risk 

(STIR v.1.0, November 19, 2010) was used to calculate an upper bound estimate of exposure 

using vapor pressure and molecular weight of pyrethrins for vapor phase exposure, as well as the 

maximum application rate and method of application for spray drift. STIR incorporates results 

from several toxicity studies including acute oral and inhalation rat toxicity (oral LD50 = 1400 

mg/kg bw and LC50 >3.4 mg/L, respectively) as well as the most sensitive acute oral avian 

toxicity endpoint (bobwhite quail, LD50 > 2000 mg ai/kg bw). Based on the results of the STIR 

model, inhalation exposure alone was determined not to be a potential pathway of concern for 

avian and mammalian species on an acute basis. 

Inhalation exposure via spray drift and vapor-phase of the pyrethrins alone does not appear to be 

of concern. The analysis of the inhalation route of in STIR does not consider that aggregation 

with other exposure pathways such as dietary, dermal, or drinking water may contribute to a total 

exposure that has a potential for effects to non-target animals. However, the Agency does 

consider the relative importance of other routes of exposure in situations where data indicate that 

pesticide exposures through other routes may be potentially significant contributors to wildlife 

risk (US EPA, 2004). 

The Screening Imbibition Program (SIP v.1.0, Released June 15, 2010) was used to calculate an 

upper bound estimate of exposure using pyrethrin’s solubility (9 mg/L), the most sensitive acute 

avian oral toxicity endpoint (bobwhite quail, LD50 > 2000 mg ai/kg bw) and the most sensitive 

acute and chronic mammalian toxicity endpoints (oral LD50 = 1400 mg/kg bw and NOAEL = 6.4 

mg/kg bw, respectively). Drinking water exposure alone was determined not to be a potential 

pathway of concern for avian and mammalian species on an acute basis or for mammalian 

species on a chronic basis. However, chronic avian data was not available to include in the 

preliminary drinking water screen. 

Although drinking water exposure alone does not appear to be of concern, this does not take into 

account that when aggregated with other exposure pathways (dietary food sources, dermal, 

inhalation) drinking water may contribute to a total exposure that has a potential for effects on 

non-target animals and should be explored further. Because there is a high degree of 

conservatism in the SIP 1.0 exposure estimate, there is limited expectation that use scenarios not 

triggering a SIP 1.0 concern would contribute significantly to aggregate risks from water plus 

diet when a refined water exposure model is incorporated in the actual quantitative risk 

 54
assessment. 

 

Although not available at this time, the Agency is actively pursuing modeling techniques to 

account for dermal exposure via direct application of spray and by incidental contact with 

contaminated vegetation, soil and water. 

Exposure to terrestrial plants

TerrPlant is used by the Environmental Fate and Effects Division (EFED) as a Tier 1 model for 

screening level assessments of pesticides. The purpose of TerrPlant is to provide screening level 

estimates of exposure to terrestrial plants from single pesticide applications. The model does not 

consider exposures to plants from multiple pesticide applications. TerrPlant derives pesticide 

EECs in runoff and in drift. RQs are developed for non-listed and listed species of monocots and 

dicots inhabiting dry and semi-aquatic areas which are adjacent to treatment sites. Once suitable 

terrestrial plant data are submitted to the Agency, this model will be used to determine the 

potential risks to terrestrial plants following pyrethrins applications. 

Aquatic exposure modeling

The models used to predict aquatic EECs are the Pesticide Root Zone Model coupled with the 

Exposure Analysis Model System (PRZM/EXAMS). Also, to estimate aquatic exposure related 

to releases of pyrethrins from domestic wastewater treatment plants, the Exposure and Fate 

Assessment Screening Tool’s (E-FAST2) down-the-drain module will be used. For the 

treatment of cattle, measures of exposure will be calculations assuming direct applications to 

water considering living habits of cattle livestock. 

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

coupled with the input shell PE5.pl (August, 2007) to generate daily exposures and 1-in-10 year 

EECs of pyrethrins, 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 cubic meters volume) with no outlet. PRZM/ 

EXAMS is used to estimate screening-level exposure of aquatic organisms to pyrethrins 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-in10-year 21-day mean is used for assessing aquatic invertebrate chronic exposure. 

At the present time, EFED considers the use of the impervious scenario (a PRZM modeling 

scenario) as the most suitable available modeling approach for simulating runoff from 

impervious surfaces such as roads, sidewalks, patios and parking lots. The PRZM impervious 

scenario may be used in the tier 2 coupled aquatic models PRZM/EXAMS along with the 

 55
residential or other suitable scenario such as rights-of-way (ROW) to obtain EECs. The 

conceptual model for the residential scenario integrates simultaneous modeling of the individual 

use scenario with an impervious scenario. This approach assumes that no watershed is 

completely covered by either the 1⁄4 acre lot (the basis for the residential scenario) or 

undeveloped land (the basis for the ROW scenario) for residential and ROW use patterns; 

therefore, differential amounts of runoff will occur within the watershed. The impervious 

scenario was developed to represent the paved areas within a watershed not including roads, 

parking lots, sidewalks, and buildings outside the 1⁄4 acre lot (the 1⁄4 acre lot scenario accounts for 

impervious surfaces such as buildings within the represented area). By modeling a separate 

scenario for impervious surfaces, it is also possible to estimate that amount of exposure that 

could occur when the pesticide is oversprayed onto this surface. Using two scenarios in tandem 

requires post-processing of the modeled output in order to derive a weighted EEC that represents 

the contribution of both the pervious (i.e., residential and ROW scenarios) and the impervious 

surfaces. 

In general, incorporation of impervious surfaces into the exposure assessment results in 

increasing runoff volume in the watershed, which tends to reduce overall pesticide exposure. For 

the purposes of risk assessment alternate assumptions for percent impervious surfaces, 

percentage of use site treated, and percentage of overspray may be considered in order to 

characterize the assumptions of the ecological risks assessment in the context of the individual 

exposure assessment and risk conclusions. For example, previously tested assumptions used in 

the endangered species assessments may be considered for characterization (i.e., 10% and 30% 

impervious surfaces, 10% lot treated, and 0%, 1% and 10% overspray) unless other relevant 

values can be determined (i.e., modeling may be completed for the impervious surface with 0%, 

1% and 10% overspray to provide lower and upper bound values). The results of these alternate 

modeling exercises may be discussed in the assessment. 

Given the aquatic toxicity of pyrethrins 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. 

To estimate exposure related to releases of pyrethrins from domestic wastewater treatment 

plants, the Agency will rely on the Office of Pollution Prevention and Toxics (OPPT) model, 

Exposure and Fate Assessment Screening Tool (EFAST, version 2.0, or EFAST2, 2007). From 

this model, the Agency will use the “Down-the-Drain” module, which is designed for releases to 

domestic wastewater treatment. It is suitable for all the sources of pyrethrins that could 

potentially be exposed through a “down-the-drain” scenario (i.e., disposed through domestic 

wastewaters). The model provides screening level estimate concentrations of chemicals in 

surface water that may result from household uses and the disposal of consumer products into 

wastewater using a few simple input parameters (production volume and fraction of the chemical 

removed during wastewater treatment). The Agency has conducted a preliminary analysis of the 

exposure resulting from wastewater effluents from POTWs and compared against the available 

acute and chronic endpoints for pyrethrins and has found no RQs exceeded any of the LOCs. At 

 56
the present time, the Agency does not anticipate to require of a POTW treatability study. EFED 

anticipates repeating the analysis for the final ecological risk assessment using more refined 

production volume values provided by BEAD or the registrant and any new endpoints (if any), 

developed during Registration Review. 

Since pyrethrin has uses on rice, the screening-level Tier 1 Rice Model v.1.0 will be utilized to 

obtain estimated exposure concentrations (EECs) related to that use. The Tier I Rice Model v1.0 

relies on an equilibrium partitioning concept to provide conservative estimates of environmental 

concentrations resulting from application of pesticides to rice paddies. When a pesticide is 

applied to a rice paddy, the model assumes that it will instantaneously partition between a water 

phase and a sediment phase. Among the assumptions of this model, the degradation of the 

pesticide and the mass transfer from the aqueous phase to the sediment are not considered. Also, 

volatilization and other dissipation processes are not considered. If LOCs are exceeded using the 

Tier 1 rice model, estimates may be made using a provisional model, PFAM to better 

characterize the risk. However, PFAM is not yet approved for general use for calculating 

pesticide EECs by the Agency. 

There are two possible scenarios whereby pyrethrins residues can enter the aquatic ecosystem 

due to treatment to cattle. First, multiple cattle that are treated with pyrethrins can directly enter 

a water body, and second, rainfall can cause washoff of pyrethrins residues to be transported 

from treated multiple cattle to water bodies via runoff. For these cases, surface water 

concentrations will be calculated using the maximum mass of pyrethrins per animal, spilling into 

a standard farm pond of 1 ha area and 2 m depth or a volume of 2.0 x 107

 L. Surface water EECs 

will be calculated utilizing a suitable program which considers the soil-water partition coefficient 

and the depth of the sediment layer such as the KdCalc (v.1.0 10/02/02). Certain assumptions 

are required for these scenarios. For example, for the first scenario, 20 treated cattle may be 

assumed to enter the water and for the second scenario, a 1000 treated cattle feedlots may be 

assumed (USDA NASS data).5 A maximum of 100% of the active ingredient is assumed to 

wash-off cow hide for pour on products. 

Bioaccumulation

The potential for bioaccumulation for the chemical is assessed using the KABAM model, as well 

the results from bioconcentration in fish studies (e.g. the bioconcentration factors). These 

models are parameterized using relevant reviewed registrant-submitted environmental fate and 

transport data. 

As indicated in Table 3.1 and its associated text in Section 3, pyrethrins appears to have some 

potential to bioconcentrate in aquatic organisms and it appears that there is also some potential to 

biomagnify in terrestrial organisms. The potential for bioaccumulation of pyrethrins will also be 

examined in the risk assessment. Because pyrethrins have a fairly high KOW (2.0 x 104 – 7.9 x 

105

) and the chemical may be persistent in water (despite having a short aqueous photolysis halflife, it could be persistent to hydrolysis at pH 7) and sediments (>10 days of aquatic 

metabolism), there could be a potential for bioaccumulation. The maximum bioconcentration 

 

5 http://www.nass.usda.gov/Surveys/Guide_to_NASS_Surveys/Cattle_On_Feed/index.asp (accessed 02/01/11) 

“Feedlots with 1,000 or more head capacity represent about 85 percent of all fed cattle in the U.S.” 

 57
factor was 471x for whole fish; however, the depuration rate is rapid (half depuration time of <1 

day, MRID Nos. 43302301 & 43884102). Bioaccumulation will be assessed using the results 

from bioaccumulation in fish studies, as well as the KABAM model (KOW (based) Aquatic 

BioAccumulation Model, version 1.0, 2009), adjusting for biotransformation rates. KABAM is 

used to estimate potential bioaccumulation of hydrophobic organic pesticides in freshwater 

aquatic ecosystems and risks to mammals and birds consuming aquatic organisms which have 

bioaccumulated these pesticides. Monitoring data and biotransformation rates in terrestrial 

species will also be evaluated, to assess the potential for bioaccumulation in terrestrial food 

webs. 

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 Observed-Adverse-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., “No-Observed-Adverse-Effect-Concentration”) is the highest test concentration at 

which none of the observed effects were statistically different from the control. 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. 

At the time of the risk assessment, updated information on the potential effects of pyrethrins on 

non-target animals will also collected from the Ecological Incident Information System (EIIS), 

Aggregrate Incident Reports and the Avian Monitoring Information System (AIMS). 

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. 

The assessment of risk for direct effects to non-target organisms makes the assumption that the 

 58
toxicity of pyrethrins to birds is similar to terrestrial-phase amphibians and reptiles. The same 

assumption is made for fish and aquatic-phase amphibians. 

7.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects 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 nontarget 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 pyrethrins 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 point-estimate 

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 pyrethrins. 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 pyrethrins is based on an action 

area. The action area is considered to be the area directly or indirectly affected by 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 pyrethrins 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 sub-lethal 

effects available in the effects literature. Therefore, the action area extends to a point where 

 59
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 pyrethrins should it be required, based on all the available environmental fate information. 

The drinking water assessment will incorporate model estimates of pyrethrins 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 – for description see above – if refinements are required). Ground water 

estimates of concentrations will be obtained 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. Endocrine Disruptor Screening Program 

As required by FIFRA and the Federal Food, Drug, and Cosmetic Act (FFDCA), EPA reviews 

numerous studies to assess potential adverse outcomes from exposure to chemicals. 

Collectively, these studies include acute, subchronic and chronic toxicity, including assessments 

of carcinogenicity, neurotoxicity, developmental, reproductive, and general or systemic toxicity. 

These studies include endpoints which may be susceptible to endocrine influence, including 

effects on endocrine target organ histopathology, organ weights, estrous cyclicity, sexual 

maturation, fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. For 

ecological hazard assessments, EPA evaluates acute tests and chronic studies that assess growth, 

developmental and reproductive effects in different taxonomic groups. As part of its 

reregistration decision, EPA reviewed these data and selected the most sensitive endpoints for 

relevant risk assessment scenarios from the existing hazard database. However, as required by 

FFDCA section 408(p), pyrethrins are subject to the endocrine screening part of the Endocrine 

Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Accordingly, as 

 60
part of registration review, EPA will issue future EDSP orders/data call-ins, requiring the 

submission of EDSP screening assays for pyrethrins. For further information on the status of the 

EDSP, the policies and procedures, the current and future chemical lists, the test guidelines and 

the Tier 1 screening battery, please visit our website: http://www.epa.gov/endo/. 

7.9. Preliminary Identification of Data Gaps 

7.9.1. Environmental Fate Data Gaps 

After evaluation of the available data for pyrethrins, the following data gaps for registration 

review have been identified. 

835.4100 Aerobic Soil Metabolism - There is an aerobic soil metabolism study, conducted on a 

single soil system. Aerobic soil metabolism studies with one soil type are generally sufficient for 

the evaluation of transformation pathways. Rates of transformation should be determined in at 

least three additional soils (from Fate, Transport and Transformation Test Guidelines – OCSPP 

Guideline 835.4100 & 835.4200). Thus, aerobic soil metabolism studies are required to be 

conducted in three additional different soils. For metabolism studies, domestic soils are 

preferred. 

835.4200 Anaerobic Soil Metabolism – There is no available study. Anaerobic studies with 

one soil type are generally sufficient for the evaluation of transformation pathways. Rates of 

transformation should be determined in at least three additional soils (from Fate, Transport and 

Transformation Test Guidelines – OCSPP Guideline 835.4100 & 835.4200). The registrant is 

required to perform an anaerobic soil metabolism study, conducted in four different soils. For 

metabolism studies, domestic soils are preferred. 

835.4300 Aerobic Aquatic Metabolism – A study is available, which was conducted in a single 

soil/ sediment system. According to the OCSPP Fate, Transport and Transformation Test 

Guidelines (835.4300 & 835.4400) “At least two sediments and their associated waters are used 

for both the aerobic and the anaerobic studies respectively.” It further says that, “However, there 

may be cases where more than two aquatic sediments should be used, for example, for a 

chemical that may be present in freshwater and/or marine environments. Sediments should be 

representative of intended use sites.” Since pyrethrins have a high potential for use near 

estuarine/ marine areas, one of the required sediment systems should be from estuarine/marine 

environment. Therefore, two additional different sediment systems are required for pyrethrins, 

one of which should be of marine origin. For the metabolism studies, domestic sediments are 

preferred. 

835.4400 Anaerobic Aquatic Metabolism – A study is available in one soil/sediment system. 

According to the OCSPP Fate, Transport and Transformation Test Guidelines (835.4300 & 

835.4400) “At least two sediments and their associated waters are used for both the aerobic and 

the anaerobic studies respectively... However, there may be cases where more than two aquatic 

sediments should be used, for example, for a chemical that may be present in freshwater and/or 

marine environments. Sediments should be representative of intended use sites.” At this time, 

EFED is requiring anaerobic aquatic metabolism studies conducted with two water/ sediment 

 61
systems. Since pyrethrins have a high potential for use near estuarine/ marine areas, one of the 

required sediment systems should be from estuarine/ marine origin. For all the metabolism 

studies, domestic sediments are preferred. 

EFED recommended to waive the Terrestrial and Aquatic Field Dissipation (OCSPP 

835.6100 and 835.6200) data requirements. EFED believes that a new study will not 

substantially change the environmental fate assessment. The parent degrades rapidly and the 

ultimate degradate is CO2, and bound residues in soil. It appears that metabolites produced are 

of no significant environmental concern, as indicated earlier. The proposed use rate is low 

(single application rate of 0.050 lb a.i./acre, seasonal application rate of 0.50 lbs a.i./acre). The 

degradates such as chrysanthemic acid may not reach sufficiently high levels to pose a 

toxicological concern. Based on data from the laboratory studies, at the current application rate, 

in field use conditions the peak degradates’ concentrations are likely to be below 0.01 ppm. 

Other studies: 

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 

quantification for the residues of concern that are lower than the relevant toxicological levels of 

concern. Previous reviews on pyrethrins indicate that there is high concern for acute and chronic 

toxicity to aquatic animals, including those living in the benthos. Certain scenarios triggered 

acute and chronic levels of concern for freshwater and/or estuarine/marine aquatic invertebrates 

and/or for fish and/or 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. Based on the available data at 

this time, the following appear to be the residues of concern for each media, but this could 

change, based upon the results of newly submitted environmental fate and ecological effects 

studies (if any is conducted on the degradates): 

Soil – parent compound 

Water and Sediment – parent, chrysanthemic acid and chrysanthemum dicarboxylic acid 

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, if applicable. There is 

one method for pyrethrins published in the Agency’s ECM website6

 for the analysis of total 

pyrethrins in water only (MRID No. 43884102). The Agency will verify the suitability of this 

method and the appropriateness of its levels of quantitation (0.06 μg/L or ppb). At this time, no 

specific methods have been identified for the analysis of degradates of the pyrethrins. A full 

description of the method validation procedures performed by an independent laboratory should 

also be submitted. It should include the following information (Corbin et al. 2006): (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 

 

6 Available at url: http://www.epa.gov/pesticides/methods/ecmindex.htm 

 62
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. 

EFED Does Not Recommend Requesting a POTW Treatability Study at This Time – The 

Agency has recently requested and provided comments on a protocol developed by the 

Pyrethroid Working Group (PWG) for a bench scale study of wastewater treatment for 

pyrethroids, to assess the percentage removed in the biosolids by the treatment, the amount that 

would degrade during treatment, and the amount that would remain in the wastewater. These 

data have been required for several synthetic pyrethroid compounds to inform removal 

percentages by waste water treatment, which is an input to the Exposure and Fate Assessment 

Screening Tool’s (E-FAST) “Down-the-Drain” module. Based upon (a) a preliminary risk 

assessment performed using the “Down-the Drain” module which does not account for possible 

degradation of the chemical in wastewaters or partitioning with organic matter/ particulate matter 

in wastewaters, (b) a highly conservative production volume estimated value (that assumed all 

consumer indoor plus Pest Control Operator (PCO) volume goes ‘down-the-drain’), (c) default 

wastewater treatment half-lives of 10,000 hr (~417 days) in the primary, aeration and settling 

tanks instead of the EPISuite v.4.0 estimated half-lives range of 30-300 hrs or ~1-12 days), and 

(d) the most conservative stream dilution factor of 1.00 (i.e., no dilution) that results from the 

high end 10th percentile concentration), all of the aquatic RQs were below the acute or chronic 

LOCs. Based on the best available information, at the present time, it is anticipated that this 

study will not be required for pyrethrins (for modeling output files, refer to the Appendix C). 

The Agency is actively evaluating the extent to which ecological risk from pesticide active 

ingredients, such as pyrethrins, via land application of biosolids should be addressed in its 

forthcoming environmental fate and ecological risk assessment and by extension, any additional 

data that may be required. As part of this evaluation, OPP is working closely with the Office of 

Water which regulates land application of biosolids under the Clean Water Act. 

EFED is aware of a study that suggests inhibition of POTW treatment processes is not a 

significant risk due to pyrethrin exposures. A study was submitted to the EU and reported in the 

Draft Assessment Report (DAR) for Pyrethrins (Koopmans 1995). EFED believes that the 

submission of the study to the Agency for further evaluation will be beneficial. 

Table 7.1 lists the status of the environmental fate data requirements for pyrethrins. 

 

 63
Table 7.1. Summary of Environmental Fate Data Requirements for Pyrethrins 

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 1,2,3 Yes 43188201, 43567502 No 

835.2240 Photodegradation in 

Water 1,2,3 Yes 43096601, 43567601 No 

835.2410 Photodegradation on 

Soil 1,2,3 Yes 43096602 No 

835.2370 Photodegradation in 

Air 1,2,3 No Not Available No2

Metabolism Studies-Lab:

835.4100 Aerobic Soil 1,2,3 Yes 43499803 Yes3

835.4200 Anaerobic Soil 1,2,3 No Not Available Yes3 

835.4300 Aerobic Aquatic 1,2,3 Yes 43499802 Yes4

835.4400 Anaerobic Aquatic 1,2,3 Yes 43499801 Yes4 

Mobility Studies:

835.1230 Leaching – 

Adsorption/ Desorption 1,2,3 Yes 43096603 No

835.1410 Volatility (Lab) 1,2,3 Yes 43096604 No 

835.8100 Volatility (Field) 1,2,3 No Not Available No2

Dissipation Studies-Field:

835.6100 Terrestrial Field 

Dissipation 1,2,3 Yes 42745501 No5 

835.6200 Aquatic Field 

Dissipation 1,2,3 Yes 43818501 No5

835.6300 Forestry Dissipation 1,2,3 No Not Applicable N/A 

Ground Water Monitoring Studies:

835.7100 Ground Water 

Monitoring 1,2,3 No Not Available No6

§158.1100 SPRAY DRIFT

201-1 Droplet Size Spectrum 1,2,3 No Not Available No7 

202-1 Drift Field Evaluation 1,2,3 No Not Available No7

Other Studies: 

Environmental Chemistry 

Methods (ECMs) and 

Independent Laboratory 

Validations (ILVs) 

1,2,3 Yes 43884102 Yes8

POTW Treatability Study Indoor Uses No Not Available No9 

 64
Table 7.1. Summary of Environmental Fate Data Requirements for Pyrethrins 

Must Additional 

Does EPA Have Data Be Submitted 

Study Identification 

Use Data To Satisfy Under FIFRA 

Pattern1

This Requirement? Bibliographic Citation 3(c)(2)(B)? 

1. Use Patterns: 1=Terrestrial/Food; 2=Terrestrial/Feed; 3=Aquatic/Food or Non-Food. 

2. EFED recommended a data waiver based on the relatively low vapor pressure and Henry’s Law Constant for pyrethrins, 

and low levels of pyrethrins evolved in an available laboratory volatility study (DP Barcode D300419). Furthermore, the 

predicted environmental half-life for the chemical is short (due to OH radical reaction). 

3. The registrant conducted studies with only one soil system. According to current OCSPP guidelines, four soils are 

required. 

4. Only one sediment system was evaluated while current guidelines require at least two. A study, performed with two 

water/sediment systems is required, one of which should be of marine origin. 

5. EFED recommended a data waiver based on the environmental fate characteristics of the pyrethrins and evaluation of the 

available terrestrial field dissipation study (DP Barcode D227214+). 

6. With high Kd and KOC values, and moderate half-life values, it appears unlikely that leaching will be important for these 

chemicals. EFED recommended a waiver of the study (DP Barcode D300419). 

7. Data requirements covered by submission of the Spray Drift Task Force. 

8. The data requirement remains unfulfilled for pyrethrins, pending evaluation of the available study. 

9. Based upon a preliminary risk assessment performed using the E-FAST’s “Down-the Drain” module and a highly 

conservative production volume value, EFED believes that this study will not be required. 

7.9.2 Effects

For registration review, the following studies are requested to fulfill any data gaps: 

Guideline Number: 850.2100 

Study Title: Avian acute oral toxicity test (passerine species) 

Acute avian oral toxicity data are required for either one waterfowl or one upland game species 

and one passerine species under the Part 158 data requirements (CFR 40 2008) for conventional 

pesticides. Because passerine species have higher metabolic rates due to their smaller sizes than 

either waterfowl or upland game bird species, and because they may utilize different metabolic 

pathways, they may be more or less sensitive to pyrethrins. A recent study reported that at least 

one passerine species (canary, Serinus sp) is sensitive to a formulated pyrethroid, beta cyfluthrin, 

with a calculated LD50 of 170 mg/kg bw (Addy-Orduna et al 2011). The other two species tested 

in this study, shiny cowbird (Order Passeriformes) and eared doves (Order Columbiformes), 

showed decreased sensitivity to beta cyfluthrin (LD50 of 2234 mg/kg bw and 2271 mg/kg bw, 

respectively). Based on a preliminary screen using the highest agricultural application scenario 

for pyrethrins (see Table 3.3), the highest peak dose-based EEC is 125 mg/kg bw. This level of 

acute exposure could be an environmentally-relevant if pyrethrins show the same increase in 

toxicity to passerine species that is indicated by the study with beta cyfluthrin. In order to 

properly characterize risk to passerines, an avian oral toxicity test is requested. A passerine study 

protocol must be submitted for review by the Agency prior to initiation of the study. 

Guideline Number: 850.2300 

Study Title: Avian reproduction test 

No avian reproduction data have been submitted for pyrethrins. The Part 158 (CFR 40 2008) lists 

 65
avian reproduction data as a requirement to support all outdoor products. Studies with 

pyrethroids have shown reproductive effects to avian species at low levels of exposure, including 

cyhalothrin (NOAEC = 5 mg/kg diet; MRID 00153504) and permethrin (NOAEC = 125 mg/kg 

diet; MRID 42322902). In addition, chronic effects were observed in mammalian reproduction 

studies at exposure concentrations that exceeded levels-of-concern for pyrethrins (chronic 

RQ=1.10; US EPA 2006b). Tests are recommended for the technical product with both 

waterfowl and an upland game bird species. 

Guideline Number: 850.1350 

Study Title: Aquatic Invertebrate Life-Cycle (saltwater) 

Previously submitted studies indicate that estuarine/marine invertebrates are among the most 

sensitive taxa to pyrethrins on an acute basis, with effects expected below 2 μg a.i./L. 

The need for a life cycle chronic toxicity of pyrethrins to estuarine/marine invertebrates is 

indicated based on its aquatic toxicity and environmental fate properties according to 40 CFR 

Part 158 data requirements (October 26, 2007). Specifically: 

1. Pyrethrins are intended for use such that its presence in estuarine/marine 

environment in significant concentrations is expected; 

2. The acute LC/EC50 for pyrethrins is substantially lower than the 40 Part 158 

trigger value of 1 mg/L (1.4 μg a.i./L for pyrethrins and 0.14 μg a.i./L for 

pyrethrins + PBO product; Mysidopsis bahia); and 

3. Previous risk assessments have indicated that the aquatic EECs are > 0.01 of the 

acute LC/EC50 values for pyrethrins, which is another condition for triggering an 

estuarine/marine invertebrate life cycle study. In the most recent assessment for 

pyrethrins, the 21-day aquatic estimated exposure concentrations modeled for all 

13 scenarios modeled crop scenarios range from 0.15 - 0.60 μg/L (US EPA 

2006b). 

Guideline Number: OCSPP 850.1760 (in prep), OCSPP 850.1770 (in prep.) and OCSPP 

850.1780 (in prep.) 

Study Title: Whole sediment: chronic invertebrates freshwater and marine 

No chronic sediment toxicity tests for freshwater or marine invertebrates have been submitted for 

pyrethrins to satisfy the Agency’s updated data requirements for outdoor uses in 40 CFR Part 

158 (October 26, 2007). For pyrethrins, available information indicates that benthic organisms 

may be exposed via run-off or spray drift applications used in agricultural, forest, and residential 

settings. Based on calculations in the most recent EFED assessment, the 21-day sediment 

porewater EECs predicted for pyrethrins ranged from 0.03 to 0.20 μg a.i./L (USEPA 2008b). The 

upper end of this range exceeds 0.1 of the most sensitive acute LC/EC50 (1.4 μg a.i./L for mysid 

shrimp), which satisfies one of the criteria for requiring chronic whole sediment toxicity testing 

under 40 CFR Part 158. Furthermore, chronic reproductive effects were seen in water column 

studies with aquatic invertebrates (daphnids), with a NOAEC = 0.86 μg a.i./L and LOAEC = 2.0 

μg a.i./L. 

Pyrethrins are expected to persist in sediments, based on half-lives in submitted soil metabolism 

and aquatic metabolism studies (aerobic soil = 9.5 days; aerobic aquatic metabolism, 10.5 days; 

anaerobic aquatic metabolism, 86 days) (MRIDs 43499803, 43499802 and 43499801). These 

 66
half-life values exceed the 40 CFR Part 158 criterion of 10 days. 

The third set of trigger criteria for requiring chronic testing (Kd > 50 or log KOW >3 or KOC > 

1000) is also met for pyrethrins (log KOW is 4.5 to 5.9, the mean KOC value is ~35,200 assuming 

it is similar to KFOC, and Kd is 301.5 assuming it is similar to KF). The physicochemical property 

triggers (Kd, KOW and KOC) reflect the propensity of the chemical to partition onto the particulate 

or organic matter phases of sediments. Exceeding any one of the physicochemical property 

triggers listed above is sufficient for indicating the pesticide has reasonable potential for 

partitioning to the sediment compartment. 

Chronic whole sediment 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 (epibenthic v. infaunal species), physiology, and there is 

some evidence suggesting Hyalella is among the more sensitive invertebrates to pyrethroids 

based on water column tests (Maund et al., 2002; Weston and Jackson, 2009). Pyrethrins have 

the potential to enter estuarine/marine water bodies based on current usage patterns that include 

coastal areas. Therefore, testing is also required for an estuarine/marine sediment-dwelling 

invertebrate species. 

Until the final OCSPP guidelines for chronic sediment toxicity tests are published, the registrant 

should submit a protocol to EFED for approval prior to test initiation. 

• Test Method 100.4: Hyalella azteca 42-d Test for Measuring the Effects of Sediment 

Associated Contaminants on Survival, Growth, and Reproduction in USEPA 2000 

Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated 

Contaminants with Freshwater Invertebrates EPA 600/R-99/064 (OCSPP 850.1770, in 

prep.); 

• Test Method 100.5: Life-cycle Test for Measuring the Effects of Sediment-associated 

Contaminants on Chironomus dilutus (formerly known as C. tentans) in USEPA 2000 

Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated 

Contaminants with Freshwater Invertebrates EPA 600/R-99/064 (OCSPP 850.1760, in 

prep.); and 

• Leptocheirus plumulosus in USEPA 2001 Method for Assessing the Chronic Toxicity of 

Marine and Estuarine Sediment-associated Contaminants with the Amphipod 

Leptocheirus plumulosus EPA 600/R-01/020 (OCSPP 850.1780, in prep.). 

Guideline Number: 850.1020 

Study Title: Acute Freshwater Invertebrate Toxicity (Hyalella azteca)

Acute water column tests with Hyallela azteca have been requested in pyrethroid problem 

formulations based on the increased sensitivity of this species to pyrethroid insecticides. The 

850.1020 test guideline for Gammarid amphipods is recommended with appropriate 

modifications to address specific testing needs of H. azteca. The registrant should use OCSPP 

Guideline 850.1020 as a basis for developing the study, and submit a protocol prior to test 

initiation or submit any open literature studies that may fulfill this data gap. 

 67
Guideline Numbers: 850.4150 and 850.4250 

Study Title: Vegetative vigor and Seedling emergence, Tiers I/II 

No acceptable toxicity data are currently available to assess the risk of pyrethrins to non-target 

terrestrial plants. Since pyrethrins have many outdoor uses, vegetative vigor and seedling 

emergence studies are required. In addition, 5 major terrestrial plant incidents have been reported 

to the Agency involving pyrethrins alone or pyrethrins with piperonyl butoxide, a commonly 

used pyrethroid synergist. A total of 231 reported minor plant incidents are attributed to 

pyrethrins use. Phytotoxicity data are needed to assess the impact of pyrethrins on non-target 

terrestrial plants. 

Guideline Number: 850.4400 and 850.5400 

Study Title: Aquatic Plant Growth (algal and aquatic vascular plant toxicity) Tiers I/II 

No acceptable toxicity data are currently available to assess the risk of pyrethrins to non-target 

aquatic nonvascular and vascular plants. Since pyrethrins have many outdoor uses, an aquatic 

plant growth toxicity study is requested with either pyrethrins technical or a typical end-use 

product. 

The Agency is aware that additional pyrethrins data are available for the European Food Safety 

Authority reports (EFSA, 2008). It is recommended that any applicable data generated for the 

European review process be submitted to EPA. 

Table 7.2 lists the status of the ecological effects data requirements for pyrethrins. 

Table 7.2. Ecological Effects Data Requirements for Pyrethrins. 

Data Requirement 

Does EPA Have 

Data To Satisfy 

This 

Requirement? 

Bibliographic 

Citation (MRID) 

Must Additional 

Data Be Submitted 

Under FIFRA 3(c)(2)(B)? 

§158.630 TERRESTRIAL ORGANISM TESTING

850.2100 Acute Avian Oral, 

Quail/Duck/Passerine 

Partially 42010901 Yes1 

850.2200 Acute Avian Diet, Quail Yes 41968801 No

850.2200 Acute Avian Diet, Duck Yes 41968802 No 

850.2300 Avian Reproduction Quail No N/A Yes 

850.2300 Avian Reproduction Duck No N/A Yes 

§158.630 AQUATIC ORGANISM TESTING

850.1075 Acute Fish Toxicity Bluegill Yes 43082301 No 

850.1075 Acute Fish Toxicity Rainbow 

Trout 

Yes 43082303 No 

850.1075 Acute Fish Toxicity (TEP) Yes 43082302, 43082304 No

850.1010 Acute Aquatic Invertebrate Yes 43082305 No 

 68
Table 7.2. Ecological Effects Data Requirements for Pyrethrins. 

Does EPA Have 

Data To Satisfy Must Additional 

Data Requirement 

This 

Requirement? 

Bibliographic Data Be Submitted 

Citation (MRID) Under FIFRA 3(c)(2)(B)? 

850.1010 Acute Aquatic Invertebrate 

(TEP) 

Yes 43082306 No 

850.1075 Acute Est/Mar Toxicity Fish Yes 43082307 No 

850.1075 Acute Est/Mar Toxicity Fish 

(TEP) 

Yes 43082308 No 

850.1035 Acute Est/Mar Toxicity Shrimp Yes 43082311 No 

850.1035 Acute Est/Mar Toxicity Shrimp 

(TEP) 

Yes 43082312 No 

850.1025 Acute Est/Mar Toxicity Mollusk Yes 43082309 No 

850.1025 Acute Est/Mar Toxicity Mollusk 

(TEP) 

Yes 43082310 No 

850.1400 Early Life Stage Fish Yes 43252701 No 

850.1300 Life Cycle Aquatic Invertebrate 

(freshwater) 

Yes 43252702 No 

850.1350 Life Cycle Aquatic Invertebrate 

(saltwater) 

No N/A Yes 

850.1500 Life Cycle Freshwater Fish No N/A No2

850.1730 Bioaccumulation in Fish Yes 43302301, 43884102 No 

OCSPP 850.1760 (in prep.), 850.1770 (in 

prep.) and 850.1780 (in prep.) Whole 

sediment: chronic invertebrates 

freshwater & marine 

No N/A Yes3

850.1020 Aquatic Invertebrate Acute 

Toxicity (Hyalella) No NA Yes4

§158.660 PLANT PROTECTION TESTING

850.4100 Seed Germ, Seedling Emergence No NA Yes5 

850.4150 Vegetative Vigor No NA Yes6 

850.4400, 850.5400 Aquatic Plant Growth No NA Yes7

§158.490 INSECT POLLINATOR TESTING

850.3020 Honey Bee Acute Contact Yes 41968803 No 

850.3030 Honey Bee Residue on Foliage No N/A No 

850.3040 Field Test for Pollinators No N/A No

 69
N/A = Not applicable because no citation is available. 

1

 Data are required for a passerine species. The registrant must submit a protocol prior to conducting this study. 

2

 No additional data is required at this time. The results from the fish early-life stage studies will be used in the upcoming 

risk assessment to evaluate the chronic risk of pyrethrins to fish species. 3

 Until the final OCSPP guidelines for chronic sediment toxicity tests are published, the registrant should submit a protocol 

to EFED for approval prior to test initiation. 

4

 Acute water column tests with Hyallela azteca are requested for pyrethrins and pyrethroids Registration Review ecological 

risk assessments. Guideline 850.1020 should be used as a basis for study development and the registrants should submit a 

protocol prior to test initiation. 

5 Tier II tests required if a tested terrestrial species exhibits a statistically significant detrimental effect in the Tier I study. 

6 Tier II tests required if a tested aquatic species exhibits a statistically significant detrimental effect in a Tier I study. 

7 Study required for aquatic nonvascular and vascular plants. Test may be conducted with technical grade pyrethrins or a 

typical end-use product. 

8. References 

Addy-Orduna, L.M., Zaccagnini, M-E, Canavelli, S.B. and P. Mineau. 2011. Formulated betacyfluthrin shows wide divergence in toxicity among bird species. Journal of Toxicology. Volume 

2011, Article ID 803451: 10 pages. 

Casida J.E., Quistad G.B. Pyrethrum Flowers. Pg. xvii. 1995 Oxford University Press, Inc. New 

York, New York. 

Clark, J.M. and Matsumura, F. 1987. The action of two classes of pyrethroids on the inhibition of 

brain Na-Ca and Ca + Mg ATP hydrolyzing activities of the American cockroach.Comp Biochem 

Physiol C. 86(1):135-45. 

Corbin, M, W. Eckel, M. Ruhman, D. Spatz, N. Thurman, R. Gangaraju, T. Kuchnicki, R. 

Mathew, and I. Nicholson. 2006. NAFTA Guidance Document for Conducting Terrestrial Field 

Dissipation Studies. Available at url: 

http://www.epa.gov/oppefed1/ecorisk_ders/terrestrial_field_dissipation.htm (accessed 01/26/11). 

Di Toro, DM, CS Zarba, DJ Hansen, WJ Berry, RC Swartz, CE Cowan, SP Pavlou, HE Allen, 

NA Thomas and PR Paquin. 1991. Technical basis for establishing sediment quality criteria for 

nonionic organic chemicals using equilibrium partitioning. Environ. Toxicol. Chem. 10:1541-

1583. 

Ecobichon, Donald J. 1991. Toxic Effects of Pesticides. In Casarett and Doull's Toxicology, The 

Basic Science of Poisons, Third Edition. Curtis D. Klaassen, Mary O. Amdur, and John Doull 

editors. Macmillan Publishing Company, NY. 

Essig, K. and Z.J. Zhao. 2001. Preparation and Characterization of a Pyrethrum Extract 

Standard. LCGC 19 ( 7) July 2001, pp. 722-730, available at www.chromatographyonline.com . 

 70
European Food Safety Authority, 2008. Draft assessment report for the active substance 

pyrethrins. Council Directive 91/414/EEC. Volume 3, Annex B, Part 5 B.9.

Food and Agriculture Organization of the United Nations. FAO PESTICIDE DISPOSAL 

SERIES 8. Assessing Soil Contamination: A Reference Manual. Appendix 2. Parameters of 

pesticides that influence processes in the soil. Editorial Group, FAO Information Division: 

Rome, 2000. http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm (accessed 05/20/11) 

GfK Kynetec. (1998-2008). EPA Proprietary Data (Cited in BEAD’s Pyrethrins Chemical 

Profile, USEPA 2011). 

Koopmans, M.S.J. 1995. Determination of ‘Ready’ Biodegradability: Carbon Dioxide (CO2) 

Evolution Test (modified Sturm Test) with Pyrethrum Extract. Notox B.V. 5231 DDHertogenbosh. The Neatherlands. Kenya Pyrethrum Information Centre. Report No. 141964. 

GLP, Unpublished (Study cited in Pyrethrins Draft Assessment Report; Rapporteur Member 

State Italy) 

Matsumura, F. 1985. Toxicology of insects. 2nd ed. Plenum New York. 

Narahashi, T. 1976. Effects of Insecticides on Nervous Conduction and Synaptic Transmission. 

Ch. 9 in: C.F. Wilkinson (ed.), Insecticide Biochemistry and Physiology. 753 pp. Plenum Press, 

New York. 

Solecky, R. 1999. Pyrethrum Extract (Pyrethrins) (addendum). Journal of Medicinal Plants 

Research or JMPR 1999, 273-291 [Same information was obtained from IPCS INCHEM 

Toxicological Evaluations at http://www.inchem.org/documents/jmpr/jmpmono/v99pr11.htm

accessed 09/27/2011] 

Stewart, D. 1998. The Evaluation of Synergistic Action in the Laboratory and Field. p. 173-198 

In: Piperonyl Butoxide: the Insecticide Synergist. Academic Press. 

Tomlin CDS; The Pesticide Manual. 11th Ed. Crop Protection Publ: British Crop Protection 

Council 49 Downing St, Farnham United Kingdom (1997). 

USEPA. 2002. Technical Basis for the derivation of Equilibrium Partitioning Sediment 

Guidelines (ESGs) for the Protection of Benthic Organisms: Nonionic Organics [Draft]. EPA 

Document No. 822R02041. October 2002. 

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. United States Environmental Protection Agency (USEPA). Environmental Fate and 

Effects Division. Office of Pesticide Programs. Available at 

http://www.epa.gov/espp/consultation/ecorisk-overview.pdf (accessed 05/17/2011). 

USEPA. 2006a. Reregistration Eligibility Decision (RED) Document for N-Octyl bicycloheptene 

dicarboximide (MGK-264), List B, Case No. 2430, Office of Chemical Safety and Pollution 

Prevention, Document ID EPA 738-R-06-006, June 2006. 

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USEPA. 2006b. Reregistration Eligibility Decision (RED) Document for Pyrethrins, List B, Case 

No. 2580, Office of Chemical Safety and Pollution Prevention, Document ID EPA 738-R-06-

004, June 2006. 

USEPA. 2007. Hoffmann, M., and J.L. Meléndez. Revised Pyrethrins RED Chapter After 

Additional 60-Day Comment Period, Phase 5. Memorandum to C. O’Connell dated April 4, 

2007. DP Barcode: D338495. OCSPP/OPP/ Environmental Fate and Effects Division 

USEPA. 2008. OPPTS 835.6100 Terrestrial Field Dissipation. EPA 712-C-08-020. October 

2008. Office of Chemical Safety and Pollution Prevention (formerly Office of Prevention, 

Pesticides, and Toxic Substances). United States Environmental Protection Agency. Available at 

http://www.epa.gov/ocspp/pubs/frs/publications/Test_Guidelines/series835.htm (accessed 

05/17/2011). 

USEPA. 2011. BEAD Chemical Profile for Registration Review: Pyrethrin (PC Code 069001). 

Memorandum from Biological and Economic Analysis Division to Pesticide Reevaluation 

Division. 

 

 72
9. Fate and Ecotoxicity Bibliography

Pyrethrins Environmental Fate Bibliography

MRID Citation Reference 

161-1 Hydrolysis 

43188201 Selim, S. (1994) Hydrolysis of Pyrethrin 1 as a Function of pH at 25 degrees C: Lab Project 

Number: P1092011: 93-1147.BTC. Unpublished study prepared by Biological Test Center. 83 p. 

43567502 Selim, S. (1995) Hydrolysis of Pyrethrin 1 as a Function of pH at 25 (degrees) C: Amended 

Report: Lab Project Numbers: P1092011: 93-1147.BTC. Unpublished study prepared by 

Biological Test Center. 163 p. 

161-2 Photodegradation-water 

144749 Bullivant, M.; Pattenden, G. (1973) Fundamental photodegradation pathways for rethrolone 

moieties of the pyrethrin insecticides. Pyrethrum Post 12(2)64-69,75. 

164634 Chen, Y.; Casida, J. (1970) Photodecomposition of pyrethrin I, allethrin, phthalthrin, and dimethrin 

modifications in the acid moiety. Pyrethum Post 10(3):7-16. 

43096601 Selim, S. (1994) Aqueous Photolysis of Pyrethrin 1: Lab Project Number: P1192006. Unpublished 

study prepared by Biological Test Center. 87 p. 

43567501 Selim, S. (1995) Aqueous Photolysis of Pyrethrin 1: Amended Report: Lab Project Numbers: 

P1192006: 93-1203.BTC. Unpublished study prepared by Biological Test Center. 170 p. 

43567601 Schoenig, G. (1995) Response to EPA Data Evaluation Record for Study Entitled: Aqueous 

Photolysis of Pyrethrin 1: Lab Project Number: P1192006. Unpublished study prepared by 

Biological Test Center. 6 p. 

43773401 Chen, Y.; Casida, J. (1969) Photodegradation of pyrethrin I, allethrin, phthalthrin, and dimethrin: 

Modifications in the acid moiety. J. Agr. Food Chem. 17(2):208-215. 

161-3 Photodegradation-soil 

42146 Holmstead, R.L.; Casida, J.E.; Ruzo, L.O. (1976?) Photochemical Re- actions of Pyrethroid 

Insecticides. (Unpublished study received Aug 22, 1977 under 10182-3; prepared by Univ. of 

California, Dept. of Entomological Sciences, Pesticide Chemistry and Toxi- cology Laboratory, 

submitted by ICI Americas, Inc., Wilmington, Del.; CDL:096330-A) 

60035 Elliott, M.; Farnham, A.W.; Janes, N.F.; et al. (1973) NRDC 145: A more stable pyrethroid. 

Proceedings of the 7th British Insecti- cide Conference ? :721-728. (Also~In~unpublished 

submission received Feb 3, 1977 under 10182-EX-8; submitted by ICI Ameri- cas, Inc., 

Wilmington, Del.; CDL:228194-B) 

66649 Elliott, M.; Farnham, A.W.; Janes, N.F.; et al. (1973) NRDC 143: A more stable pyrethroid. Pages 

721-728,~In~Proceedings, 7th British Insecticide and Fungicide Conference. N.P. (Also~In~ 

 73
unpublished submission received Feb 3, 1977 under 10182-EX-7; submitted by ICI Americas, Inc., 

Wilmington, Del.; CDL:228608-B) 

113574 Miskus, R.; Andrews, T. (19??) Stabilization of thin films of pyre- thrins and allethrin. Pyrethrum 

Post:135-136. (Incomplete; also In unpublished submission received Jan 21, 1977 under 6296-24; 

submitted by Nutrilite Products, Inc., Buena Park, CA; CDL:229731-B) 

113576 Head, S.; Sylvester, N.; Challinor, S. (19??) The effect of pipero- nyl butoxide on the stability of 

films of crude and refined pyrethrum extracts. ?Source unknown|:14-22. (Also In unpublished 

submission received Jan 17, 1977 under 6296-24; submitted by Nutrilite Products, Inc., Buena 

Park, CA; CDL:229731-D) 

141553 U.S. Pyrethrum Culture (1984) Application for EPA Registration: Pyrethrum Powder. Unpublished 

compilation. 581 p. 

40700401 Reddy, G. (1988) Analytical Results of Pyrethrin Photolysis Resi- dues after Exposure to Natural 

Sunlight: SL# 15981-15982. Un- published study prepared by Shrader Laboratories. 96 p. 

43096602 Testman, R. (1994) Soil Surface Photolysis of Pyrethrin 1: Lab Project Number: P1192007. 

Unpublished study prepared by Biological Test Center. 91 p. 

43567602 Schoenig, G. (1995) Response to EPA Data Evaluation Record for Study Entitled: Soil Surface 

Photolysis of Pyrethrin 1: Lab Project Number: P1192007. Unpublished study prepared by 

Biological Test Center. 13 p. 

162-1 Aerobic Soil Metabolism 

43499803 Robinson, R.A. (1994) Aerobic Soil Metabolism of [14C] Pyrethrin 1. XBL Study No. 

XBL93061. XBL Report No. RPT00204. Unpublished Study by XenoBiotic Laboratories, Inc. 

Plainsboro, NJ and Submitted by Pyrethrin Joint Venture/Chemical Speciaties Manufacturers 

Association, Washington, DC. 

162-2 Anaerobic Aquatic Metabolism 

43499801 Robinson, R.A. and M.J. Wisocky (1994) Anaerobic Aquatic Metabolism of [14C] Pyrethrin 1.

XBL Study No. XBL93062. XBL Report No. RPT00205. Unpublished Study by XenoBiotic 

Laboratories, Inc. Plainsboro, NJ and Submitted by Pyrethrin Joint Venture/Chemical Speciaties 

Manufacturers Association, Washington, DC. 

162-4 Aerobic aquatic metab. 

43499802 Robinson, R.; Wisocky, M. (1994) Aerobic Aquatic Metabolism of (carbon 14)Pyrethrin 1: Lab 

Project Number: XBL93063: RPT00193. Unpublished study prepared by Xenobiotic Lab., Inc. 130 

p. 

163-1 Leaching/adsorption/desorption 

 74
43096603 Reynolds, J.; Robinson, R. (1994) Adsorption and Desorption of (carbon 14) Pyrethrin 1 in Four 

Soils: Lab Project Number: 93064: RPT00156. Unpublished study prepared by XenoBiotic 

Laboratories, Inc. 123 p. 

163-2 Volatility - lab 

43096604 Selim, S. (1994) Laboratory Volatility of Pyrethrin 1 from Soil: Lab Project Number: P0693011. 

Unpublished study prepared by Biological Test Center. 101 p. 

164-1 Terrestrial field dissipation 

42745501 Hattermann, D. (1992) LX1180-02 (Pyrethrum + Piperonyl Butoxide) Field Dissipation-Terrestrial 

Study on Bareground in California, Georgia, and Michigan: Lab Project Number: 91189: 

18021E08. Unpublished study prepared by Bio/Dynamics, Inc. 207 p. 

43807101 Brookman, D.; Curry, K.; Smith, C. (1995) Data Waiver Request for the Requirement of a Study 

on Terrestrial Field Dissipation for Degradates of Pyrethrin. Unpublished study prepared by 

Technology Sciences Group, Inc. 28 p. 

164-1 Terrestrial field dissipation with PC Code 069000 

42900401 Hattermann, D. (1992) Pyrenone Crop Spray (Pyrethrum + Piperonyl Butoxide) Field DissipationTerrestrial Study Applied to Bareground in California, Georgia and Michigan: Field and Analytical 

Phases: Lab Project Number: 18021E08: 91189. Unpublished study prepared by Landis 

International, Inc. 220 p. 

164-2 Aquatic field dissipation 

43125701 Hattermann, D. (1994) Piperonyl Butoxide Analytical (and Field) Phase for Pyrenone Crop Spray 

(Pyrethrin + Piperonyl Butoxide): Aquatic Dissipation Study Applied Post-Emergence to 

Barewater in California, Arkansas, and Mississippi: Lab Project Number: 18021V09: 91190. 

Unpublished study prepared by Pharmaco LSR International, Inc. 227 p. 

43195201 Hattermann, D. (1994) Pyrethrin Analytical Phase for Pyrenone Crop Spray (Pyrethrin + 

Piperonyl Butoxide) Aquatic Dissipation Study Applied Post-Emergence to Barewater in 

California, Arkansas, and Mississippi: Lab Project Number: 18021V09: 91190: BD-047-92. 

Unpublished study prepared by Pharmaco LSR International, Inc. and Landis International, Inc. 

152 p 

43818501 Brookman, D.; Curry, K.; Hobson, J.; et al. (1995) Data Waiver Request for the Requirement of a 

Study on Aquatic Field Dissipation of Pyrethrin. Unpublished study prepared by Technology 

Sciences Group, Inc. 34 p. 

165-4 Bioaccumulation in fish 

43302301 Schocken, M. (1994) Bioconcentration Study with (carbon 14) Pyrethrin 1 in Bluegill Sunfish: 

 75
Final Report: Lab Project Number: 94-5-5258: 11572.0993.6125.140. Unpublished study prepared 

by Springborn Labs., Inc. 148 p. 

43884102 St. Laurent, J. (1995) Development and Validation of an Analytical Methodology for the 

Determination of Total Pyrethrins in Water, Acetone, and Fish Tissue: Final Report: Lab Project 

Number: 93-9-4922: 11572.0193.6105.250. Unpublished study prepared by Springborn Labs, Inc. 

87 p. 

201-1 Droplet size spectrum 

144487 Palmisano, J. (1984) Letter sent to J. Haus dated Jun 12, 1984: Acute Inhalation LC50: Rat – 

Particle Size. Unpublished study prepared by Realex Corp. 1 p. 

144911 Shaklee Corp. (1984) [Chemistry Data for Shaklee Natural Pesti- cide]. Unpublished 

compilation. 31 p. 

No MRID 

(Ancillary 

Data) 

Dimenna, G.P. and G.P. Schoenig (1993) Summary of Work Performed to Determined 

Appropriate Storage and Handling Procedures for 14C Pyrethrin 1. Unpublished Study Performed 

by Toxicology/Regulatory Services. Charlottesville, VA and Submitted by Pyrethrin Joint 

Venture/Chemical Specialties Manufacturers Association, Washington, DC. 

171-4B Residue Analytical Methods 

43292701 Hattermann, D. (1994) Pyrethrin Analytical Phase on the Raw Agricultural Commodity residue 

evaluation of Pyrethrin + Piperonyl Butoxide Applied as Pyrenone Crop Spray to Brassica, including 

Field Phase for LX1180-20: Final Report: Lab Project Number: 18014A004. Unpublished study 

prepared by En-CAS Analytical Lab., Pharmaco LSR International Inc. 472 p. 

43298901 Hattermann, D. (1994) Field Phase for LX1180-02 (Pyrethrin + Piperonyl Butoxide) Raw 

Agricultural Commodity Trials on Fruiting Vegetable in Florida, Michigan, New Jersey, North 

Carolina, California, and Texas: Final Report: including Analytical Phase: Lab Project Number: 

18015A005. Unpublished study prepared by Paragon Global Services, En-Cas Analytical Labs, and 

Pharmaco LSR International Inc. 272 p. 

45398401 Hatterman, D. (2001) Field Phase for LX1180-02 (Pyrethrin + Piperonyl Butoxide) Raw Agricultural 

Commodity Trials on Brassica in Arkansas, California, Oregon, New York, Florida, Texas and 

Georgia: Amended Final Report: Lab Project Number: 18014A004: 1714-91-180-02-14D-37/AR. 

Unpublished study prepared by Landis International, Inc. 503 p. 

 

 76
Pyrethrins Ecotoxicity Bibliography 

Avian Oral Toxicity 

MRID Citation Reference 

42010901 Campbell, S. and S.P. Lynn (1991) An Acute Oral Toxicity Study with Pyrethrum 

Extract in the Northern Bobwhite Quail. Wildlife International Ltd. Project No. 326-

103. FIFRA Guideline 71-1. 

Avian Dietary Toxicity 

MRID Citation Reference 

41968801 Grimes, J.; Lynn, S.; Smith, G. (1991) A Dietary LC50 Study with Pyrethrum 

Extract in the Northern Bobwhite Quail: Lab Project Number: 326-101. 

Unpublished study prepared by Wildlife Inter- national Ltd. 62 p. 

41968802 Grimes, J.; Lynn, S.; Smith, G. (1991) A Dietary LC50 Study with Pyrethrum 

Extract in the Mallard: Lab Project Number: 326/102. Unpublished study prepared 

by Wildlife International Ltd. 62 p. 

Acute Toxicity to Freshwater Fish 

MRID Citation Reference 

43082301 Machado, M. (1994) Pyrethrum Extract (FEK-99): A Flow-Through Acute Toxicity 

Test with Bluegill Sunfish (Lepomis macrochirus): Final Report: Lab Project 

Number: 93/8/4916. Unpublished study prepared by Springborn Laboratories, Inc. 

66 p. 

43082302 Machado, M. (1994) Pyrenone Crop Spray (Sample Ref. 13650): A Flow-Through 

Acute Toxicity Test with Bluegill Sunfish (Lepomis macrochirus): Final Report: 

Lab Report Number 93/11/5008. Unpublished study prepared by Springborn 

Laboratories, Inc. 66 p. 

43082303 Machado, M. (1994) Pyrethrum Extract (FEK-99): A Flow-Through Acute Toxicity 

Test with Rainbow Trout (Oncorhynchus mykiss): Final Report: Lab Project 

Number: 93/11/5084. Unpublished study prepared by Springborn Laboratories, Inc. 

65 p. 

43082304 Machado, M. (1994) Pyrenone Crop Spray (Sample Ref. 13650): A Flow-Through 

Acute Toxicity Test with Rainbow Trout (Oncorhynchus mykiss): Final Report: Lab 

Project Number: 93/11/5048. Unpublished study prepared by Springborn 

Laboratories, Inc. 65 p. 

 77
Acute Toxicity to Freshwater Invertebrates 

MRID Citation Reference 

43082305 Putt, A. (1994) Pyrethrum Extract (FEK-99): A Acute Toxicity to Daphnids 

(Daphnia magna) under Flow-Through Conditions: Final Report: Lab Project 

Number: 93/11/5082. Unpublished study prepared by Springborn Laboratories, Inc. 

71 p 

43082306 Putt, A. (1994) Pyrenone Crop Spray (Sample Ref. 13650): Acute Toxicity to 

Daphnids (Daphnia magna) under Flow-Through Conditions: Final Report: Lab 

Project Number: 93/11/5075. Unpublished study prepared by Springborn 

Laboratories, Inc. 82 p. 

05009242 Sanders, H.O. (1969) Toxicity of Pesticides to the Crustacean Gammarus Lacustris. 

Washington, DC, U.S. Bureau of Sport Fisheries and Wildlife. (U.S. Bureau of 

Sport Fisheries and Wildlife Technical Paper 25) 

Acute Toxicity to Estuarine/Marine Organisms 

MRID Citation Reference 

4308

2307 

Machado, M. (1994) Pyrethrum Extract (FEK-99): A Flow-Through Acute 

Toxicity Test with Sheepshead Minnow (Cyprinodon 78ariegates): Final 

Report: Lab Project Number: 93/12/5081. Unpublished study prepared by 

Springborn Laboratories, Inc. 64 p. 

4308

2308 

Machado, M. (1994) Pyrenone Crop Spray (Sample Ref. 13650): A FlowThrough Acute Toxicity Test with Sheepshead Minnow (Cyprinodon 

78ariegates): Final Report: Lab Project Number: 93/11/5037. Unpublished 

study prepared by Springborn Laboratories, Inc. 63 p. 

4308

2309 

Dionne E. (1994) Pyrethrum Extract (FEK-99): Acute Toxicity to Eastern 

Oyster (Crassostrea virginica) under Flow-Through Conditions: Final 

Report: Lab Project Number: 93/11/5032. Unpublished study prepared by 

Springborn Laboratories, Inc. 65 p. 

4308

2310 

Dionne E. (1994) Pyrenone Crop Spray (Sample Ref. 13650): Acute 

Toxicity to Eastern Oyster (Crassostrea virginica) under Flow-Through 

Conditions: Final Report: Lab Project Number: 93/10/4995. Unpublished 

study prepared by Springborn Laboratories, Inc. 67 p. 

4308

2311 

Machado, M. (1994) Pyrethrum Extract (FEK-99): Acute Toxicity to 

Mysid Shrimp (Mysidopsis bahia) under Flow-Through Conditions: Final 

Report: Lab Project Number: 93/12/5097. Unpublished study prepared by 

Springborn Laboratories, Inc. 68 p. 

4308

2312 

Machado, M. (1994) Pyrenone Crop Spray (Sample Ref. 13650): Acute 

Toxicity to Mysid Shrimp (Mysidopsis bahia) under Flow-Through 

Conditions: Final Report: Lab Project Number: 93/12/5077. Unpublished 

study prepared by Springborn Laboratories, Inc. 67 p. 

 78
Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study 

MRID Citation Reference 

4325 Machado, M. (1994) Pyrethrum Extract (FEK-99)-The Toxicity to Fathead 

Minnow (Pimephales promelas) During an Early Life-Stage 

Exposure: Final Report: Lab Project Number: 93-10-4983: 11572. 

0193. 6114. 120. Unpublished study prepared by Springborn Lab., 

Inc. 137 p. 

4325

Putt, A. (1994) Pyrethrum Extract (FEK-99)-The Chronic Toxicity to 

Daphnia magna Under Flow-Through Conditions: Final Report: 

Lab Project Number: 94-1-5116: 11572.0193.6115.130. 

Unpublished study prepared by Springborn Lab., Inc. 165 p. 

Honey bee acute contact 

MRID Citation Reference 

Lynn, S.; Hoxter, K. (1991) An Acute Contact Toxicity 

Study with Pyrethrum Extract with the Honey 

Bee: Lab Project No: 326/104. Unpublished 

study prepared by Wildlife International Ltd. 33 

p. 

 

 79
Appendix A. PRD 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 PRD. 

Guideline Numbers and Study Titles: 

• Test Method 100.4 (OCSPP 850.1770, in prep.); Whole sediment: chronic invertebrates 

freshwater (Hyalella azteca) 

• Test Method 100.5 (OCSPP 850.1760, in prep.); Whole sediment: chronic invertebrates 

freshwater (Chironomus dilutus) US EPA 2001, 

• EPA 600/R-01/020 (OCSPP 850.1780, in prep.); Whole sediment: chronic invertebrates 

marine (Leptocheirus plumulosus) 

Rationale for Requiring the Data 

No chronic sediment toxicity tests for freshwater or marine invertebrates have been submitted for 

pyrethrins to satisfy the Agency’s updated data requirements for outdoor uses in 40 CFR Part 158 (October 

26, 2007). For pyrethrins, available information indicates that benthic organisms may be exposed via runoff or spray drift applications used in agricultural, forest, and residential settings. Based on calculations in 

the most recent EFED assessment, the 21-day sediment porewater EECs predicted for pyrethrins ranged 

from 0.03 to 0.20 μg a.i./L (USEPA 2008b). The upper end of this range exceeds 0.1 of the most sensitive 

acute LC/EC50 (1.4 μg a.i./L for mysid shrimp), which satisfies one of the criteria for requiring chronic 

whole sediment toxicity testing under 40 CFR Part 158. Furthermore, chronic reproductive effects were 

seen in water column studies with aquatic invertebrates (daphnids), with a NOAEC = 0.86 μg a.i./L and 

LOAEC = 2.0 μg a.i./L. 

Pyrethrins are expected to persist in sediments, based on half-lives in submitted soil metabolism and 

aquatic metabolism studies (aerobic soil = 9.5 days; aerobic aquatic metabolism, 10.5 days; anaerobic 

aquatic metabolism, 86 days) (MRIDs 43499803, 43499802 and 43499801). These half-life values are 

exceed the 40 CFR Part 158 criterion of 10 days. 

The third set of trigger criteria for requiring chronic testing (Kd > 50 or log KOW >3 or KOC > 1000) is also 

met for pyrethrins (log KOW is 4.5 to 5.9, the average KOC value is 35,200 assuming it is similar to KFOC, 

and Kd is 302 assuming it is similar to KF). The physicochemical property triggers (Kd, KOW and KOC) 

reflect the propensity of the chemical to partition onto the particulate or organic matter phases of sediments. 

Exceeding any one of the physicochemical property triggers listed above is sufficient for indicating the 

pesticide has reasonable potential for partitioning to the sediment compartment. 

Chronic whole sediment 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 (epibenthic v. infaunal species), physiology, and there is some evidence suggesting 

Hyalella is among the more sensitive invertebrates to pyrethroids based on water column tests (Maund et 

al., 2002; Weston and Jackson, 2009). Pyrethrins have the potential to enter estuarine/marine water bodies 

based on current usuage patterns that include coastal areas. Therefore, testing is also required for an 

estuarine/marine sediment-dwelling invertebrate species. 

Until the final OCSPP guidelines for chronic sediment toxicity tests are published, the registrant should 

submit a protocol to EFED for approval prior to test initiation. 

• Test Method 100.4: Hyalella azteca 42-d Test for Measuring the Effects of Sediment Associated 

Contaminants on Survival, Growth, and Reproduction in USEPA 2000 Methods for Measuring the 

 80
Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater 

Invertebrates EPA 600/R-99/064 (OCSPP 850.1770, in prep.); 

• Test Method 100.5: Life-cycle Test for Measuring the Effects of Sediment-associated 

Contaminants on Chironomus dilutus (formerly known as C. tentans) in USEPA 2000 Methods 

for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with 

Freshwater Invertebrates EPA 600/R-99/064 (OCSPP 850.1760, in prep.); and 

• Leptocheirus plumulosus in USEPA 2001 Method for Assessing the Chronic Toxicity of Marine 

and Estuarine Sediment-associated Contaminants with the Amphipod Leptocheirus plumulosus

EPA 600/R-01/020 (OCSPP 850.1780, in prep.). 

Practical Utility of the Data 

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 pyrethrins. The data will reduce uncertainties associated with the current risk assessment for 

benthic species and will improve our understanding of the potential effects of permethrin. 

How could the data impact the Agency’s future decision-making? 

Although there was uncertainty in estimating the effect of pyrethrins on benthic organisms in previous 

assessments, there was a potential risk associated with adverse effects identified for other aquatic 

organisms. Acceptable data for benthic organisms will reduce the uncertainty from the previous 

assessment If the data indicates that registered pyrethrins usage may pose a risk of adverse effects to nontarget benthic organisms 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 which may 

otherwise be avoided, or which are unnecessarily severe. 

 

 81
Appendix B. Reported Pyrethrins Ecological Incident Summaries in the EIIS Database 

Table C-1. Pyrethrins Incident Report Summaries 

Incident # Organism(s) Affected Certainty of 

Involvement 

Legality of 

Use Description 

I021276-024 Fish (Cyprinus carpio) Probable Unknown The Washington Department of 

Agriculture reported that pyrethrins 

applied to control mosquitos had 

drifted to a holding tank and killed 13 

koi. No pesticide concentrations were 

included in the report (Benton County, 

Washington; 8/17/2003). 

I001297-011 Fish (unknown species) Possible Misuse 

(intentional) 

A game preserve employee misused 

Adams Flea and Tick Dust II (active 

ingredients include pyrethrins, 

piperonyl butoxide, carbaryl and silica 

gel by applying it to an ant hill. Heavy 

rain washed the product into a nearby 

pond where 5-6 fish were killed. It is 

not known which one or what 

combination of the four active 

ingredients is responsible for the 

mortality. No pesticide concentrations 

were included in the report (Texas; 

9/2/1994). 

I019897-001 Cherry trees Probable Misuse 

(accidental) 

Cherry trees were damaged by the 

product PyGanic Crop Protection EC 

1.4 (active ingredient pyrethrins). The 

product was applied at 14 times the 

maximum label rate. The trees showed 

heavy leaf damage and dieback. 

Greater than 45% of the orchard trees 

appeared to be affected. The product 

was applied a second time to some 

trees that showed more significant 

aphid infestation and these trees were 

affected more severely than others. No 

pesticide concentrations were included 

in the report (Polk County, Oregon; 

6/2/2008). 

I008693-047 Rose bushes Possible Registered 

use 

A homeowner sprayed approximately 

12 rose bushes with RosePride Rose 

and Flower Insect Killer, active 

ingredients pyrethrins and piperonyl 

butoxide. The product was then reapplied 2 weeks later. The plants died 

following the second application. No 

pesticide concentrations were included 

in the report (Santa Clara County, 

California; 4/22/1999). 

I010017-017 Ornamental plants Possible Registered 

use 

Severe leaf damage occurred two 

weeks after application of RosePride 

 82
Table C-1. Pyrethrins Incident Report Summaries 

Incident # Organism(s) Affected Certainty of Legality of Description Involvement Use 

Rose and Flower Insect Killer to 

ornamental plants at a residence. The 

active ingredients in the product are 

pyrethrins and piperonyl butoxide. No 

pesticide concentrations were included 

in the report (Lincoln County, 

Wisconsin; 3/8/2000). 

I008693-046 Unknown plants Possible Registered 

use 

Phytotoxicity occurred following the 

application of RosePride Rose and 

Flower Insect Killer (active ingredients 

pyrethrins and piperonyl butoxide) to 

unknown plants at a residence. No 

pesticide concentrations were included 

in the report (Muskegon County, 

Mississippi; 4/30/1999). 

I008693-046 Rose bushes Possible Registered 

use 

A homeowner reported that RosePride 

Rose and Flower Insect Killer (active 

ingredients pyrethrins and piperonyl 

butoxide) caused 6 or 7 roses to turn 

brown following application of the 

product. A rose that was not sprayed 

remained healthy. No pesticide 

concentrations were included in the 

report (Sarasota County, Florida; 

2/2/2000). 

 

 83
Appendix C. Pyrethrins Down-the-Drain Risk Assessment 

Summary: No RQ exceeded any of the acute or chronic LOCs. These results were based on the 

following assumptions: 

1. A highly conservative production volume value (all consumer indoor + PCO production 

volume); 

2. Default wastewater treatment half-lives (10,000 hr or ~417 days). It is noted that the 

EPISuite v.4.0 modeled half-lives are 30-300 hr; 

3. A stream dilution factor of 1.00 (i.e., no dilution) that results from the use of the high end 

(or 10th percentile) concentration, which may be compared to SDF = 20-24 for the 50th

percentile. The 10th percentile concentration represents small receiving streams while the 

50th percentile represents midsized stream flows. 

Rough Estimate of the Production Volume

This section shows how a rough estimate of the production volume was obtained. 

In the current assessment, a conservative approach that all non-agricultural uses with a 

potential to be used and disposed through domestic wastewaters, was equivalent to the 

production volume is used. 

Table C-1. Non-agricultural use of pyrethrins across recent years in various site 

categories1, 2

Year Market Segment Sum Of Pounds A.I. Approx. Ave. lbs A.I. 

2000 Consumer - Indoor 52,000 ~82,500 2005 Consumer - Indoor 113,000 

2008 Food Handling <500 

Not Applicable to the 

Down-the-Drain 

Assessment 

2006 Institutional Turf <500 

2002 Lawn Care Operators (LCOs) 3,000 

2006 Lawn Care Operators <500 

2003 Mosquito Abatement 2,000 

2005 Mosquito Abatement 12,000 

2002 Nursery/Greenhouse <500 

2004 Nursery/Greenhouse <500 

2006 Nursery/Greenhouse <500 

2003 Pest Control Operator (PCO) 9,000 9000 

Rough estimate of the production volume from non-agricultural uses 

with potential to be used indoors; value is considered conservative. 

~91,500 lb 

 (or ~41,500 kg) 

1. Data source: Kline and Co., proprietary market surveys, 2002-2008 

2. The area of the table shaded yellow was adapted from BEAD’s Chemical Profile for Pyrethrins 

(USEPA 2011). Area shaded blue (i.e., column with average pounds and row providing the rough 

estimated total A.I. for non-agricultural uses that could potentially reach POTWs) was added by 

EFED. 

Because it is a very unrefined value, the production volume was rounded to one significant 

figure. 

 84
Table C-2. Pyrethrin 1 down-the-drain input values and results 

Production Vol. BCF (whole fish) WWT (%)a Acute EEC (ppb, 1Q10)b Chronic EEC (ppb, 7Q10)b

~40,000 kg A.I. 471 x 91.7 0.0806 0.0806 

1. A removal of 91.7% is obtained from EPISuite v.4.0 using the default treatment t1/2’s (10,000 hr). 

2. 1Q10 - single day of lowest flow over a 10-year period (stream dilution factor = 1.00 means not dilution) 

 7Q10 - 7 consecutive days of lowest flow over a 10-year period (conservative stream dilution factor also = 1.00) 

Table C-3. Acute and chronic RQs for freshwater fish associated with “down-the-drain” uses of 

pyrethrins based on rainbow trout LC50 = 5.1 ug/L and fathead minnow NOAEC = 1.9 ug/L; and, 

acute and chronic RQs for freshwater invertebrates associated with ‘down-the-drain” uses of 

pyrethrins based on Daphnia magna EC50 = 11.6 ug/L and Daphnia magna NOAEC = 0.86 ug/L. 

Peak EEC 

(μg/L) 

Chronic EEC 

(μg/L) 

FW Fish 

Acute RQ 

FW Fish 

Chronic RQ 

FW Invert 

Acute RQ 

FW Invert 

Chronic RQ 

0.0806 0.0806 0.02 0.04 0.01 0.09 

The production volume needs to be above ~125,000 kg to cause the RQ to exceed the acute 

endangered species LOC of 0.05, and above ~425,000 kg to cause the RQ to exceed the chronic 

LOC of 1.00. 

 

 85
Running E-FAST’s Down-the-Drain Module 

Physical/Chemistry Input Screen: 

Chemical’s ID = Pyrethrin 1; 

BCF = 471 

Wastewater treatment removal = 91.7% 

MW = 328.4 g/mol 

Choose modules: Down-the-Drain & Probabilistic Dilution Model (PDM) 

Consumer Disposal Input Screen: 

Production Volume = 40,000 kg/yr 

Exposure Duration = 57 yr 

Choose: Run in PDM 

High End Scenario 

Select “Run Disposal Model” 

 

 86
Partial Output Files from EPISuite v.4.0 for Pyrethrin 1 (only STP results are shown) 

STP Fugacity Model: Predicted Fate in a Wastewater Treatment Facility 

====================================================================== 

 (using 10000 hr Bio P,A,S) 

PROPERTIES OF: Cyclopropanecarboxylic acid, 2,2-dimethyl-3-(2-methyl-1-

propenyl)-, 

2-methyl-4-oxo-3-(2,4-pentadienyl)-2-cyclopenten-1- 

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

Molecular weight (g/mol) 328.46 

Aqueous solubility (mg/l) 0 

Vapour pressure (Pa) 0 

 (atm) 0 

 (mm Hg) 0 

Henry 's law constant (Atm-m3/mol) 7.73E-007 

Air-water partition coefficient 3.16134E-005 

Octanol-water partition coefficient (Kow) 794328 

Log Kow 5.9 

Biomass to water partition coefficient 158866 

Temperature [deg C] 25 

Biodeg rate constants (h^-1),half life in biomass (h) and in 2000 mg/L MLSS 

(h): 

 -Primary tank 0.00 9968.63 10000.00 

 -Aeration tank 0.00 9968.63 10000.00 

 -Settling tank 0.00 9968.63 10000.00 

 

 STP Overall Chemical Mass Balance: 

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

 g/h mol/h percent 

 

Influent 1.00E+001 3.0E-002 100.00 

 

Primary sludge 5.81E+000 1.8E-002 58.08 

Waste sludge 3.28E+000 1.0E-002 32.83 

Primary volatilization 1.28E-005 3.9E-008 0.00 

Settling volatilization 2.87E-005 8.7E-008 0.00 

Aeration off gas 7.09E-005 2.2E-007 0.00 

 

Primary biodegradation 1.70E-002 5.2E-005 0.17 

Settling biodegradation 4.20E-003 1.3E-005 0.04 

Aeration biodegradation 5.53E-002 1.7E-004 0.55 

 

Final water effluent 8.32E-001 2.5E-003 8.32 

 

Total removal 9.17E+000 2.8E-002 91.68

Total biodegradation 7.66E-002 2.3E-004 0.77 

 

 87
 88

Partial Output File from E-FAST: Surface Water Aquatic Exposure Estimates (EECs)

WWT 

REMOVAL 

(%) 

PRODUCTION 

VOLUME 

(kg/yr) 

HOUSEHOLD 

RELEASE 

DAYS 

PRETREATMENT 

RELEASE 

(g/person/day) 

POST-TREATMENT 

RELEASE 

(g/person/day) 

BODY 

WEIGHT 

(kg) 

BCF 

(L/kg) 

91.7 4.00E+04 365.00 3.77E-04 3.13E-05 71.80 471.00 

50th PERCENTILE AQUATIC EXPOSURE ESTIMATES - SURFACE WATER 

DESCRIPTOR Harmonic Mean 30Q5 7Q10 1Q10 

STREAM DILUTION FACTOR 134.85 39.66 24.22 20.08 

CONCENTRATION (μg/L) 5.98E-04 2.03E-03 3.33E-03 4.01E-03 

10th PERCENTILE AQUATIC EXPOSURE ESTIMATES - SURFACE WATER 

DESCRIPTOR Harmonic Mean 30Q5 7Q10 1Q10 

STREAM DILUTION FACTOR 7.95 1.80 1.00 1.00 

CONCENTRATION (μg/L) 1.01E-02 4.48E-02 8.06E-02 8.06E-02