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1. Executive Summary 

EFED typically completes a preliminary problem formulation for the ecological risk, 

environmental fate, and endangered species assessments to be conducted as part of the 

Registration Review of the insecticide/miticide chlorfenapyr. In the case of chlorfenapyr, 

all uses occur indoors, underground (termiticide), or involve small quantities (crack and 

crevice treatment) and are not expected to result in significant ecological exposure 

because greenhouse/indoor and underground uses have limited opportunity for outdoor 

residues, drift, runoff, and wildlife exposure.

The preliminary problem formulation identified two risk concerns that could result in outdoor 

environmental exposure. First, was a concern regarding label language (EPA Reg. No. 

000241-00374) for fruiting vegetables grown in a greenhouse that stated “Compost any 

discarded plant material that has been treated,” EFED concluded in the preliminary 

problem formulation that exposure was possible and an ecological risk assessment 

needed to be performed. Subsequently, the registrant has modified this label to prohibit 

composting of chlorfenapyr-treated material. Therefore, EFED no longer considers 

composting to be a viable exposure route for chlorfenapyr to ecological receptors.

A second concern of EFED’s in the preliminary problem formulation dealt with 

chlorfenapyr being applied to soil underlying a concrete slab prior to the slab being 

poured (during construction) (EPA Reg. No. 000241-00392). In the event that a major 

rain event occurs after treatment and prior to pouring of the concrete slab, there is a 

potential for exposure to chlorfenapyr in adjacent areas via runoff from the use site. 

EFED concluded that such exposure is possible because the label does not specify that 

the amount of time between application of chlorfenapyr and the pouring of the concrete 

slab be minimized. As of the time of this document, the label language has not been 

modified. EFED continues to believe that such language should appear on the label. 

However, at this time, EFED does not believe this exposure route is sufficient in and of 

itself to warrant the collection of additional fate and effects data or the development of an 

ecological risk assessment. 

2. Current Chlorfenapyr Uses 

The currently registered crop/sites, use groups, and registration numbers for chlorfenapyr 

are listed in Table 1. These uses are taken from the LUIS report (dated: July 23, 2009) 

prepared by the Biological and Economic Analysis Division (BEAD) of the U.S. EPA 

Office of Pesticide Programs. 

Table 1. Complete List of Chlorfenapyr Uses by Registration Number.

Crop/Site Use Group Reg.No 

Commercial Storages/Warehouses Premises Indoor Non-Food 

000241-00392 

007969-00285 

MS02002300 

Commercial/Institutional/Industrial Premises/Equip. 

(Indoor) Indoor Non-Food 

000241-00392 

007969-00285 

MS02002300 
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Table 1. Complete List of Chlorfenapyr Uses by Registration Number.

Crop/Site Use Group Reg.No 

Dairies/Cheese Processing Plant Equipment (Food 

Contact) Indoor Food 

000241-00392 

007969-00285 

MS02002300 

Eating Establishments Indoor Food 

000241-00392 

007969-00285 

MS02002300 

Egg Packing Plants (Commercial) Indoor Food 

000241-00392 

007969-00285 

MS02002300 

Eggplant Greenhouse Food Crop 000241-00374 

Feed Mills/Feed Processing Plants Indoor Food 

000241-00392 

007969-00285 

MS02002300 

Food Processing Plant Equipment (Food Contact) Indoor Food 000241-00392 

MS02002300 

Food Processing Plant Premises (Nonfood Contact) Indoor Food 007969-00285 

Food Stores/Markets/Supermarkets Premises Indoor Food 000241-00392 

MS02002300 

Food/Grocery/Marketing/Storage/Distribution Facility 

Premise Indoor Food 

000241-00392 

007969-00285 

MS02002300 

Fruiting Vegetables Greenhouse Food Crop 000241-00374 

Greenhouses-In Use Greenhouse Food Crop 000241-00374 

Groundcherry (Strawberry Tomato/Tomatillo) Greenhouse Food Crop 000241-00374 

Hospitals/Medical Institutions Premises 

(Human/Veterinary) Indoor Medical 

000241-00392 

007969-00285 

MS02002300 

Household/Domestic Dwellings Indoor Residential 

000241-00392 

007969-00285 

MS02002300 

Household/Domestic Dwellings Indoor Premises Indoor Residential 

000241-00392 

007969-00285 

MS02002300 

Household/Domestic Dwellings Outdoor Premises Outdoor Residential 

000241-00392 

007969-00285 

MS02002300 

Meat Processing Plant Premises (Nonfood Contact) Indoor Non-Food 

000241-00392 

007969-00285 

MS02002300 

Nonagricultural Outdoor Buildings/Structures Terrestrial Non-Food Crop* 000241-00392 

MS02002300 

Ornamental and/or Shade Trees Greenhouse Non-Food Crop 000241-00374 

Ornamental Herbaceous Plants Greenhouse Non-Food Crop 000241-00374 

Ornamental Non-flowering Plants Greenhouse Non-Food Crop 000241-00374 

Ornamental Woody Shrubs And Vines Greenhouse Non-Food Crop 000241-00374 

Pepino (Melon Pear) Greenhouse Food Crop 000241-00374 

Pepper Greenhouse Food Crop 000241-00374 

Pets (Unspecified) Indoor Non-Food 

000241-00392 

007969-00285 

MS02002300 
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Table 1. Complete List of Chlorfenapyr Uses by Registration Number.

Crop/Site Use Group Reg.No 

Poultry Processing Plant Premises (Nonfood Contact) Indoor Food 

000241-00392 

007969-00285 

MS02002300 

Sewage Systems Aquatic Non-Food Industrial 

000241-00392 

007969-00285 

MS02002300 

Tomatillo Greenhouse Food Crop 000241-00374 

Tomato Greenhouse Food Crop 000241-00374 

Zoos Indoor Non-Food 

000241-00392 

007969-00285 

MS02002300 

* The Use Group designation, Terrestrial Non-Food Crop, is confusing because it refers to use on building 

and structures below concrete slabs, within the soil around foundations, and in and around cracks and 

crevices. It is probably meant to indicate “some terrestrial application that is not to a food crop.” However, 

a literal interpretation would be “application to some crop other than food.” 

The majority of these uses occurs in enclosed indoor environments; and therefore, are 

assumed by EFED to have no complete exposure pathways to ecological receptors and, 

therefore, pose no risk to these receptors. However, several of the uses in Table 1 merit 

further explanation because these use group names may appear to result in outdoor 

exposures to ecological receptors: 

• Household/Domestic Dwellings Outdoor Premises (Outdoor Residential) and 

Nonagricultural Outdoor Buildings/Structures (Terrestrial Non-Food Crop) – 

refers to uses that form a zone or barrier in the soil surrounding a building or 

structure (under concrete slab flooring and adjacent to basement walls) during 

construction and crack and crevice treatments that are used on existing buildings 

and structures. Pre-construction uses of chlorfenapyr result in the pesticide 

sequestered by soils under the floor of, or adjacent to the basement walls of, a 

building. Post-construction and crack and crevice treatments are limited to a 9.4 x 

10-5 lbs ai per 2 sq. feet every four weeks. Therefore, assuming 4 sides of a 

building are treated with sides 10’ high by 100’ long (4000 ft2

) would result in a 

maximum treatment of 0.18 lbs ai to the building. However, EFED believes such 

applications would be unlikely to create a significant exposure pathway to 

ecological receptors because: most structurally sound buildings have far fewer 

cracks and crevices than the maximum application rate allows; much of the 

applied pesticide would be retained inside the crevice or crack; and much of the 

pesticide that was dislodged from its application site would be retained in any soil 

and/or landscaping at the base of the treated wall. 

• Sewage Systems (Aquatic Non-Food Industrial) – is a crack and crevice 

treatment that is used in cracks in the concrete slab flooring around floor drains. 

The intent is not to discharge the chemical to the sewer system but, rather, to 

prevent ground-dwelling insects from entering a building through cracks in the 

flooring around the drain. The label specifies that the drain must lead to a sewage 

system (and thus presumably, would be greatly diluted if some of the pesticide 

went down the drain) to prevent the use of the chemical around drains that may 
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discharge immediately outside of the building (where relatively little dilution 

might occur). 

• Zoos (Indoor Non-Food) – is also a crack and crevice use that is used on 

buildings enclosing zoo animals. 

3. Chlorfenapyr Persistence

Chlorfenapyr and its degradates have been shown to be highly persistent. Chlorfenapyr's 

persistence is typified by a laboratory aerobic soil metabolism half-life of 1.4 years and 

its observed comparable field dissipation "half-life" of 1.3 years (MRID 44452621, 

43492850). Chlorfenapyr is essentially stable to laboratory hydrolysis and anaerobic soil 

metabolism. Chlorfenapyr also has an organic carbon partition coefficient (Koc) of 

11,500 L/kg and thus binds to organic particulates and is generally immobile in soil. 

Sediment would be its principle latent reservoir in aquatic systems where it would remain 

available for extended periods. 

Because of the persistence of parent and relatively short study durations, only small 

amounts of structurally similar metabolites or degradates were identified in soil in the 

field and lab studies. However, AC 312,094 has been detected at 10% to 16% of parent 

in the radiolabeled North Carolina study (MRID 44452623). This metabolite has 

intermediate mobility characteristics (median Koc around 2200). Coupled with its 

persistence, this means that it has high potential for runoff into surface water with 

comparable amounts in solution and eroding soil if chlorfenapyr is used in outdoor 

environments. 

In general, transformation products appear to approximate or exceed the persistence of 

the parent. Structurally similar metabolites or degradates (AC 312,094, AC 303,267, AC 

303,268, AC 322,118, AC 322,250, AC 325,195, some of which exhibit ecotoxicity) 

were identified in soil in field and/or lab studies. Concentrations of these, when detected 

were typically a few percent each or less of the applied chlorfenapyr. 

4. Chlorfenapyr Toxicity 

Available toxicity data are summarized below and are further discussed in Appendix A. 

These data were obtained from previous assessments (DP Barcode: 241963). In general, 

chlorfenapyr has demonstrated high acute toxicity to terrestrial and aquatic organisms, 

and has demonstrated chronic toxicity at concentrations in the low μg/L range. 

Chlorfenapyr is very highly toxic to birds on an acute basis. The LD50 values for redwinged blackbird (Agelaius phoneiceus), mallard (Anas platyrhynchus), and bobwhite 

quail (Colinus virginianus) are 2.2, 8.3, and 34 mg/kg, respectively (MRIDs 43887004, 

42770227, and 42770228). It is also very highly toxic to waterfowl and passerine species 

and highly toxic to upland gamebirds on an acute dietary basis (MRID 42770229, 

42770230, and 44452613). Chlorfenapyr has also resulted in reproductive and growth 

effects to birds at low concentrations of 1.5 mg/kg-diet. The mallard duck NOAEC value 

of 0.5 mg/kg-diet, which is based on reduced body weight, serves as the chronic toxicity 

endpoint for avian long-term exposure risk calculations (MRID 434928-13). 
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Chlrofenapyr has been shown to be less toxic to mammals compared with birds. Acute 

LD50 values in mammals range from approximately 45 mg/kg-bw to 1152 mg/kg-bw 

(MRIDs 43492828, 42770201, 42770207). A 2-generation mammalian study (MRID 

43492836) produced a NOAEC value of 60 mg/kg-diet (5 mg/kg-bw). 

Chlorfenapyr is highly toxic to honey bees (Apis mellifera) on an acute contact exposure 

basis with a corresponding LD50 value of 0.12 μg/bee. 

In aquatic organisms, acute LC50 values for chlorfenapyr range from 7 μg/L to 12 μg/L in 

freshwater fish (MRIDs 42770231 and 42807801), 60 μg/L in saltwater fish (MRID 

43492816), 6 μg/L to 18 μg/L in freshwater invertebrates (MRIDs 42770232, 43887009), 

2 μg/L in saltwater invertebrates (MRID 43492818), and 0.2 mg/kg to 20 mg/kg sediment 

in benthic organisms (MRIDs 44452619, 44560002). Therefore, on an acute exposure 

basis, chlorfenapyr is very highly toxic to freshwater and estuarine/marine fish and 

invertebrates. Chronic NOAEC values range from 0.2 μg/L in estuarine/marine 

inverterbrates (MRID 43492821) to 4 μg/L (freshwater fish and invertebrates; MRIDs 

43492819 and 43492822). Additional information from the 1998 EFED assessment is 

presented in Appendix A. 

Conclusion 

EFED does not intend to conduct an ecological risk assessment as the majority of 

chlorfenapyr uses are in enclosed environments; and therefore, are assumed by EFED to 

not have complete exposure pathways to ecological receptors and, therefore, pose no risk 

to ecological receptors. 

References 

USEPA. August 31, 1998. Chlorfenapyr (PIRATETM, ALERTTM, AC 303,630) 

Insecticide-Miticide Environmental Fate and Ecological Effects Assessment and 

Characterization for a Section 3 for Use on Cotton. DP Barcode: D241963, D240108, 

D243556, D245813, D246459, D246093, D246661. 140pp. 
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Appendix A. Guideline Toxicity Data as Presented in Previous Assessments (DP 

241963)
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