SCIENTIFIC EVALUATION SECTION

Transcription

1 FLORIDA DEPARTMENT OF AGRICULTURE AND CONSUMER SERVICES DIVISION OF AGRICULTURAL ENVIRONMENTAL SERVICES BUREAU OF PESTICIDES SCIENTIFIC EVALUATION SECTION ENVIRONMENTAL FATE AND EFFECTS OF PERMETHRIN: ACTIVE INGREDIENT USED AS AN ADULTICIDE JAMES R. COOPER MAX A. FEKEN DRAFT AUGUST 8, 2003 SUPPLEMENTAL REVIEW Permethrin Adulticide Page 1 of 23

2 This review is a summary of the best technical information available on a given product or active ingredient in an attempt to address present or future issues and their potential impact on pesticide use, water quality, endangered species, worker protection, human and ecological health. Conclusions drawn in this review are tentative and based on current research supplied by the registrant and available in the literature. This review includes both quantitative and qualitative information. The Scientific Evaluation Section welcomes comments and discussion of these issues. This review is not an endorsement of any brands or active ingredients named in this document. Mention of a trademark or a proprietary product does not constitute a guarantee or a warranty of the product by Florida Department of Agriculture and Consumer Services, and does not imply its approval to the exclusion of other products that may also be available. The author(s) can be reached by mail at: Bureau of Pesticides 3125 Conner Boulevard, Building No. 6, Mail Station 1650 Tallahassee, Florida or call the Section Secretary at: ( ) Web Site: Permethrin Adulticide Page 2 of 23

3 Special Review Review of pesticide environmental fate data for: The aerial use of permethrin in the control of mosquitoes NOTE: THIS DATA AND EVALUATION ARE BASED ON THE CONFIDENTIAL INFORMATION PROVIDED TO FDACS AS TRADE SECRET. CONFIDENTIAL DATA B NOT A PUBLIC RECORD PURSUANT TO FIFRA SECTION 10. Table of Contents Introduction... 4 Label Information... 4 Active Ingredient... 5 Summaries of Environmental Fate Studies... 6 Model Simulations... 7 Environmental Fate Studies... 8 Hydrolysis... 8 Aqueous Photolysis... 8 Aerobic Soil Metabolism... 8 Anaerobic Soil Metabolism... 8 Aerobic Aquatic Metabolism/Aquatic Dissipation... 8 Soil Adsorption/Desorption... 8 Bioaccumulation to 1000X in fish viscera, 570 to 610X whole fish, 180 to 230X in filet... 8 Field Dissipation... 8 Summary:... 8 AQUATIC AND TERRESTRIAL ECOLOGICAL RISK ASSESSMENT FOR PERMETHRIN... 9 Introduction... 9 Toxicity to Non-Target Organisms Wild Mammal Toxicity Avian Acute and Reproductive Toxicity Fish and Aquatic Invertebrate Toxicity Non-Target Insect Toxicity Effects on Aquatic Plant Growth Exposure and Risk Characterization Terrestrial Exposure and Risk Aquatic Exposure and Risk Summary Permethrin Adulticide Page 3 of 23

4 Introduction Permethrin is a synthetic pyrethroid used as broad spectrum insecticide for the control of mosquitoes, termites, and many pests associated with the garden, greenhouse, household, storage, and agricultural production. Pyrethroids are contact insecticides that quickly penetrate the nervous system. They produce a quick knock down and can be very toxic to insects at low concentrations. Label Information Product Names: Biomist ULV Permanone Manufacturer/Registrant: Clarke Bayer Active Ingredients Permethrin 30.0% Piperonyl Butoxide 30.0% Inert Ingredients (Not on labels) 40.0% Formulation and Use: Permethrin is applied as dusts, emulsifiable concentrates, smokes, ultra low volumes (ULV), and as wettable powders. Biomist contains 2.52 pounds of permethrin and 2.52 pounds of piperonyl butoxide per gallon Application Rate: Aerial Mosquito Application: For a 1:2 Biomist/solvent dilution, mix 1 pint Biomist with 2 pints diluent and apply aerially at a maximum rate of one fluid ounce per acre (0.007 pounds/acre). Some Product Use Restrictions and Recommendations: - Do not apply this product with 30 meters of a lake or stream. - Do not allow spray treatment to drift on pastureland cropland, poultry ranges, or water supplies. - Biomist: In Florida, do not apply by aircraft except in an emergency situation and with the approval of the FDACS. - Label Warnings Environmental Hazards: This product is extremely toxic to fish and aquatic invertebrates. Do not apply directly to water, to areas where surface water is present, or to intertidal areas below the mean high tide mark. Permethrin Adulticide Page 4 of 23

5 Active Ingredient CAS No: Empirical Formula: C 21 H 20 O 3 Cl 2 Molecular Weight: Chemical Class: Pyrethroid Chemical Name: (3-phenoxyphenyl)-methyl (+)cis-trans-3-(2,2-dichloroethenyl) -2,2-dimethylcyclopropanecarboxylate Physical State: Bulk Density: Odorless, colorless crystalline solid or 1.19 to 1.27 g/cm 3 pale brown viscous liquid. Water Solubility:.055 ppm at 25ºC ph :? (1% solution) Melting Point: 34 to 35º C Boiling Point: 220 ºC Vapor Pressure: Henry s Law Constant: 1.5 x 10-8 mm Hg 1.4 x 10-6 atm m 3 /mol Oxidizing/reducing potential: NA Corrosion characteristic: None Flammability: NA Reactivity: NA Permethrin Adulticide Page 5 of 23

6 Summaries of Environmental Fate Studies Partition Coefficients: Organic matter/ Water, K OC = 16,400 to 550,00 Florida sand ( Koc = 194,000, Kd = 446) Soil /Water, K D = 344 to 1517 Octanol/Water Partition Coefficient, Log K = 6.1 Hydrolysis Half-life: Stable at ph 5 and 7, and 49 days at ph 9 Anaerobic Soil Half-life: Aerobic Soil Half-Life: 32 to 64 days, 204 days 3 to 6 weeks, < 28 days Aerobic Aquatic Metabolism: Sediment/seawater: 2.5 days Freshwater?: days Photolysis Half-life: Water: 30 days Aqueous: 19 to 27 hours (pond water) Seawater: 14 days Air: 4.6 days Anaerobic Aquatic Metabolism: 113 to 174 days Field Dissipation: 17 days (North Carolina) 43 days (Illinois) Foliar Half-life: Wash Off Fraction: 10 days 0.30 Permethrin Adulticide Page 6 of 23

7 Model Simulations EXAMS The EXAMS (Exposure Analysis Modeling System), version 2.98 was used to model pesticide behavior in surface water. The Georgia farm pond scenario was used with a 30 cm water column depth and a 5 cm sediment depth. Each pesticide was applied once at the maximum rate directly to the water surface. A comparison of the pesticide parameters is provided in the following table. Parameter Chlorpyrifos Permethrin Resmethrin Sumithrin Application Rate, lbs/acre Solubility (water), ppb Partition Coefficients Kow Koc Kd Vapor Pressure, torr Melting Point, ºC Henrys Constant,atm m 3 /mol Hydrolysis T½ (days) ph 5 ph 7 ph 9 Aquatic T½ days Photolytic Water Metabolism Sediment Metabolism Soil T½, days Aerobic Anaerobic ,000 10, x x ,200,000 86, x x ,400,000 50, x x 10-7 Stable to , x x to 26 1 Permethrin Adulticide Page 7 of 23

8 Environmental Fate Studies Hydrolysis Aqueous Photolysis Half-life = 79.7 days at ph = 5, 25ºC Aerobic Soil Metabolism Sandy loam soil, ph 5.9, 1.0% organic matter, 25C Applied 1 ppm, incubated for 64 days Half-life: Cis = 12 days, Trans = 5 days Anaerobic Soil Metabolism Memphis silt loam (ph = 5, 0.7% organic matter) Applied 0.1 to 1.00 ppm permethrin to 50 g soil /75 ml water Half-life: Trans = 32 to 34 days, Cis = 64 days. Metabolites were dichlorovinyl acid, and 3-phenoxybenzyl alcohol Aerobic Aquatic Metabolism/Aquatic Dissipation Soil Adsorption/Desorption Bioaccumulation 950 to 1000X in fish viscera, 570 to 610X whole fish, 180 to 230X in filet Depuration is rapid with 73 to 83% by 14 days. Field Dissipation Summary: Permethrin is not likely to volatilze from plant leaves or from moist soil or water due to its moderately low vapor pressure and Henry s law constant. Permethrin binds strongly to clay and organics in soil and sediment which restricts its movement with leachate and runoff. Since permethrin is relatively immobile in a wide range of soils and has a very low solubility it is not expected to leach through the soil profile and make it to ground water. Movement to surface water is possible through spray drift and movement with eroding soil and sediment. Report prepared by: James R. Cooper Bureau of Pesticides, Scientific Evaluation Section FDACS, Tallahassee, Florida Date: XXXX, 2003 Permethrin Adulticide Page 8 of 23

9 AQUATIC AND TERRESTRIAL ECOLOGICAL RISK ASSESSMENT FOR PERMETHRIN Introduction This review examines the risk to non-target organisms from the use of permethrin as an aerially applied mosquito adulticide. Currently there are several adulticide products registered in Florida containing permethrin (with some also containing the synergist, piperonyl butoxide) including Permanone, BioMist, Punt, and Aqua Reslin. However, aerial applications of these products are not permitted in the state of Florida for adult mosquito control, although the original intention for this prohibition is unclear. The labels for these products include the following statement: IN FLORIDA: Do not apply by aircraft except in emergency situations and with the approval of the Florida Department of Agriculture and Consumer Services. While it appears that this restriction was added to the label based on the potential for mosquito resistance, concerns for adverse effects to aquatic organisms from the use of permethrin may have also been a motivating factor. In the past, restrictions (i.e., buffers) on permethrin and other products containing synthetic pyrethroids were added to labels out of concern for aquatic toxicity. However, many of these determinations were made in exclusion of environmental fate data or data associated with the use of ULV applications for mosquito control. Therefore, this report attempts to determine the ecological risk associated with the use of permethrin as an aerial adulticide using both environmental fate and effects data. In addition, environmental fate and toxicity data are presented for resmethrin and sumithrin, both are synthetic pyrethroids that are currently registered in Florida for use as aerial adulticides. While this risk assessment does not address issues related to mosquito resistance directly, the environmental fate section may prove helpful in estimating the potential for resistance development. Permethrin RTU (Permethrin 6.92%) For Mosquito Control: Aerial applications should be done by suitable aerial ultra low volume (ULV) equipment capable of producing droplets with an mass median diameter (MMD) of 50 microns or less with no more than 2.5% exceeding 100 microns. Flow rate and swath width should be set so as to achieve 2.0 to 6.0 fluid ounces of product ( to lbs ai) per acre. Environmental Hazard Restrictions: This product is highly toxic to fish and aquatic invertebrates. 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 apply when weather conditions favor drift from treated areas. Drift and runoff from treated areas may be hazardous to aquatic organisms in neighboring areas. Do not allow spray treatment to drift on pastureland, cropland, poultry ranges or water supplies. Do not contaminate water when disposing of equipment washwaters. Permethrin Adulticide Page 9 of 23

10 Aqua Reslin (Permethrin 20% and Piperonyl Butoxide 20%) For Mosquito Control: Aerial applications may be applied either diluted or undiluted at rates of lbs to lbs ai/acre by fixed wing or rotary aircraft that are capable of making a ULV application. Use of ULV equipment and nozzles such as rotary atomizer or similar type that produce droplet volume median diameters (VMD) less than 60 microns is recommended. Aerial applications should be made at an altitude of feet. Do not apply when ground wind speed exceeds 10 mph. Environmental Hazard Restrictions: This product is extremely toxic to fish and aquatic invertebrates. 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 apply when weather conditions favor drift from treated areas. Drift and runoff from treated areas may be hazardous to aquatic organisms in neighboring areas. Do not contaminate water when disposing of equipment rinsate. Do not apply when wind speeds exceed 10 mph. This pesticide is highly toxic to bees exposed to direct treatment on blooming crops or weeds. Do not apply this product or allow drift when bees are actively visiting the treatment area. Applications should be timed to provide the maximum possible interval between treatment and the next period of bee activity. Other formulations including Permanone, Biomist, Punt, and Kontrol Theses product have various combinations of permethrin and piperonyl butoxide. Applications rates are at lbs permethrin/acre for most of the products. A few have higher applications rates but are lower than the application rate for Permanone RTU (0.023 lbs permethrin/a). Toxicity to Non-Target Organisms Wild Mammal Toxicity Based on the mammalian acute studies submitted for the human health assessment (Table 1), permethrin is considered slightly toxic to wild mammals with an acute oral rat LD 50 of 1,000 mg/kg. No reproductive effects were not evident up to 180 mg/kg bodyweight. Table 1. Mammalian Acute and Chronic Toxicity Toxicity Species Study Type Toxicity Results Category Rat Rat Acute Oral Multigeneration Reproduction LD 50 = 1,000 mg/kg for formulation NOEC = 180 mg/kg; no reproductive effects Slightly toxic N/A Reference 81-1/T /T-8 Permethrin Adulticide Page 10 of 23

11 Avian Acute and Reproductive Toxicity Acute oral and dietary toxicity studies using the technical grade of the active ingredient are required to establish the toxicity of permethrin to birds. Bobwhite quail (Colinus virginianus) and the mallard (Anas platyrhynchos) are the preferred test species used to represent upland gamebirds and waterfowl, respectively. Based on the oral and dietary toxicity studies, permethrin is considered practically non-toxic to birds (Table 2). Table 2. Avian Acute and Dietary Toxicity of Permethrin Species Study Type Toxicity Results Toxicity Category Reference Japanese quail Acute oral LD 50 > 20,000 mg/kg Practically non-toxic N/A Mallard duck Acute oral LD 50 > 2,000 mg/kg Practically non-toxic 71-1(a)/T-10 Bobwhite quail Dietary/subacute LC 50 > 5,200 ppm Practically non-toxic 71-2(a)/T-11 Mallard duck Dietary/subacute LC 50 > 5,200 ppm Practically non-toxic 71-2(b)/T-11 Avian reproductive studies are required by EPA for pesticide registration if birds may be subject to repeated or continuous exposure to the pesticide. The preferred test species for avian reproductive studies are the bobwhite quail and mallard duck. The NOEL for the bobwhite reproductive study was 500 ppm, the highest treatment level tested (i.e., no adverse effects). For the mallard study, the NOEL was 125 ppm, based on significant treatment related reductions in the number of eggs laid at the 500 ppm treatment level. Fish and Aquatic Invertebrate Toxicity Two freshwater fish toxicity studies and one aquatic invertebrate study using the technical grade of the active ingredient are required to establish the toxicity of permethrin to aquatic organisms. For the fish toxicity studies, the preferred species are rainbow trout (Salmo gairdneri) and bluegill sunfish (Lepomis macrochirus) representing a coldwater and a warmwater fish, respectively. Daphnia magna is the preferred test species for determining acute toxicity to freshwater aquatic invertebrates. Permethrin is considered very highly toxic to freshwater and estuarine/marine fish. Permethrin is also considered highly to very highly toxic to freshwater and estuarine/marine invertebrates. Permethrin Adulticide Page 11 of 23

12 Table 3. Fish Acute Toxicity of Permethrin Species Study Type Toxicity Results Toxicity Category Reference Table 4. Aquatic Invertebrate Acute Toxicity of Permethrin Species Study Type Toxicity Results Toxicity Category Reference Rainbow trout 96-hour/static LC 50 = 2.9 µg ai/l Very highly toxic 72-1(b)/T-12 Bluegill sunfish 96-hour/static LC 50 = 5.0 µg ai/l Very highly toxic 72-1(a)/T-12 Fathead minnow 96-hour/static LC 50 = 5.7 µg ai/l Very highly toxic 72-1(a)/T-12 Channel catfish 96-hour/static LC 50 = 7.2 µg ai/l Very highly toxic 72-1(a)/T-12 Striped mullet 96-hour/flowthrough LC 50 = 5.5 µg ai/l Very highly toxic 72-1(a)/T-12 Inland silverside 96-hour/flowthrough LC 50 = 6.1 µg ai/l Very highly toxic 72-1(a)/T-12 Sheepshead minnow 96-hour/static LC 50 = 7.8 µg ai/l Very highly toxic 72-3(a)/T-12 Daphnia magna 48-hour/static EC 50 = 7.2 µg ai/l Very highly toxic 72-2(a)/T-12 Freshwater scud 96-hour/static LC 50 = 0.17 µg ai/l Very highly toxic N/A Crayfish 96-hour/flowthrough LC 50 = 210 µg ai/l Highly toxic 72-2(a)/T-12 Midge larvae 48-hour/static LC 50 = 0.56 µg ai/l Very highly toxic N/A Mayfly nymphs 96-hour/flowthrough LC 50 = 0.1 µg ai/l Very highly toxic N/A Fiddler crab 96-hour/static LC 50 = 2.39 µg ai/l Very highly toxic N/A Stone crab larvae 96-hour/static LC 50 = µg ai/l Very highly toxic N/A Pink shrimp 96-hour/flowthrough LC 50 = 0.22 µg ai/l Very highly toxic N/A Mysid Shrimp 96-hour/flowthrough EC 50 = µg ai/l Very highly toxic 72-3(a)/T-12 Eastern oyster 96-hour/flowthrough EC 50 > 536 µg ai/l N/A N/A Freshwater fish early life-stage and freshwater aquatic invertebrate life-cycle tests may be required by EPA if the end-use product is applied directly to water or expected to be transported to aquatic environments from the intended use sites. In addition, if the pesticide is intended for use such that its presence in water is likely to be continuous or recurrent regardless of toxicity, and/or the actual or estimated environmental concentration in water resulting from use is greater than 0.01 of any acute LC 50 or EC 50 value then a fish early life-stage and an aquatic invertebrate life-cycle test will be required. Only a few chronic toxicity test were performed to assess the chronic toxicity of permethrin to aquatic organisms. However, most of these studies were older (1970s) and considered only supplemental according to EPA standards. Permethrin Adulticide Page 12 of 23

13 Chronic Toxicity to Fish No acceptable chronic toxicity data was available. Chronic Toxicity to Invertebrates A flow-through life cycle toxicity test with Daphnia magna resulted in an NOEC of µg/l, based on significant treatment related effects on the number of young produced at µg/l. The MATC was calculated to be µg/l. Non-Target Insect Toxicity Permethrin is considered highly toxic to honeybees (Apis mellifera) with oral and contact LD 50 values of 0.13 and µg/bee, respectively. Effects on Aquatic Plant Growth Only data for the marine diatom, Skeletonema costatum, was available. The EC 50 for this study was 92 ppb. Exposure and Risk Characterization For a Tier I ecological risk assessment, a Risk Quotient (RQ) is determined by dividing the Expected Environmental Concentration (EEC) by the appropriate toxicity value. The risk quotient is then compared to the Level of Concern (LOC) developed by EPA to assess the potential for adverse acute and chronic effects to terrestrial and aquatic organisms. A presumption of risk occurs when an RQ equals or exceeds an LOC (Table 5). Table 5. Risk Quotients (RQs) and Limits of Concern (LOCs) Presumed Risk Category Risk Quotient (RQ) Level of Concern (LOC) Acute High Terrestrial: EEC 1 /LC 50 or LD 50 /a.i. per ft 2 Aquatic: EEC/LC 50 or EC 50 Terrestrial: RQ 0.5 Aquatic: RQ 0.5 Acute Restricted Use Terrestrial: EEC 1 /LC 50 or LD 50 /a.i. per ft 2 Aquatic: EEC/LC 50 or EC 50 Terrestrial: 0.2 RQ<0.5 Aquatic: 0.1 RQ<0.5 Acute Endangered Species Terrestrial: EEC 1 /LC 50 or LD 50 /a.i. per ft 2 Aquatic: EEC/LC 50 or EC 50 Terrestrial: 0.1 RQ<0.2 Aquatic: 0.05 RQ<0.1 Chronic Risk EEC/NOEC RQ 1 1 EEC = Estimated Environmental Concentration (ppm); Terrestrial Exposure and Risk For foliar applications, wild mammal and avian exposure values (EECs) were generated for permethrin using the Kenaga (modified by Fletcher et al., 1994) estimates of potential concentrations in food items (Table 6). The predicted 0-day maximum and mean EECs expected Permethrin Adulticide Page 13 of 23

14 on various avian and mammalian food items were based upon the maximum single application rate of lbs ai/acre and 100% deposition. The peak EEC was estimated using the maximum application rate applied once a week for 4 weeks and a foliar half-life of 8 days. Table 6. Estimated Environmental Concentrations (EECs) on Avian and Mammalian food items following a single application (0-day) and multiple applications Initial (0-day) EEC (ppm) Peak EEC (ppm) 2 Average 90-day EEC 2 Food Items Maximum Mean Maximum Mean Maximum Mean Short grass Tall grass Broadleaf plants and small insects Fruits, pods, seeds, and large insects Based on the maximum labeled application rate and estimates from Hoerger and Kenaga (1972) as modified by Fletcher et al. (1994). 2 Based on four applications, 7-day interval between applications, and the foliar half-life of 8 days. Based on the properties of permethrin the maximum concentration is expected to occur immediately after the final application (four applications total with a 7-day application interval) of adulticide. Using the initial expected concentration for short grass and a foliar half-life of 8 days, the maximum peak EEC is 11 ppm and the mean peak EEC is 3.9 ppm. For wild mammals, the acute risk quotient value was generated using the estimated LC 50 values based on the laboratory rat LD 50 values and the maximum and mean EECs. In addition, RQs were calculated for three separate weight classes of mammals (15, 35, and 1000g) with decreasing metabolism (i.e., decreasing % body weight consumed per day). Table7. Mammalian Acute RQs Based on the Lab Rat LD 50 of 1,000 mg/kg and Maximum and Mean EECs. Small Mammal % Body Wt EEC in diet (ppm) Acute Dietary RQ 2 Body Wt (g) Category Consumed 1 Maximum Mean Maximum Mean Herbivores < Insectivores <0.001 < <0.001 <0.001 Granivores <0.001 < <0.001 < EPA-recommended values 2 RQ = EEC (ppm) [LD 50 (mg/kg)/ % Body Weight Consumed] The results indicate that acute LOCs are not exceeded (Table 7). Therefore, acute adverse effects to small mammals from dietary exposures are not expected. Based on a lack of Permethrin Adulticide Page 14 of 23

15 reproductive effects up to 180 mg/kg bodyweight in rats, chronic adverse effects to wild mammals are not anticipated. Table 8. Avian Acute and Chronic RQs Based on a Bobwhite Quail LC 50 > 5,200 ppm and Mallard Reproductive NOEL of 125 ppm. Avian Food Items Acute Dietary RQ Chronic Dietary RQ Maximum Mean Maximum Mean Short grass <0.002 < Tall grass <0.001 < Broadleaf plants/insects <0.001 < Seeds <0.001 < <0.001 The RQ calculated for acute avian risk is less than 0.002, based on the maximum EEC and an LC 50 value greater than 5,200 ppm for bobwhite quail (Table 8). Therefore, the acute LOCs for avian species are not exceeded. The chronic risk of permethrin to avian species was evaluated using the NOEL values obtained from the mallard reproduction study. When the maximum expected environmental concentration (11 ppm estimated on shortgrass) or the maximum 90-day average (2.9 ppm) is divided by the mallard NOEC of 125 ppm, the chronic LOC is not exceeded for birds. Acute or chronic adverse effects to avian species via dietary exposure are not expected from the use of permethrin as an adulticide. In addition, based on the overall low toxicity of permethrin to birds, acute adverse effects to birds are not expected from either inhalation or dermal exposure. Aquatic Exposure and Risk Tier I Risk Characterization The potential risk to aquatic organisms was determined using aquatic EEC values generated by the EXAMS model. For a Tier I risk assessment, it is assumed that 100% of the application rate is deposited on a surface waterbody (see Environmental Fate section). This is a conservative assumption since, unlike agricultural applications, aerial applications of adulticides typically use droplet sizes that are likely to drift long distances in order to contact flying mosquitoes over large areas. Using 100% deposition, the instantaneous (peak) EEC value (8.67 ppb) was used to define acute exposure based on the highest application rate of lbs ai/acre aerially applied to a 30- cm deep waterbody (Table 9). Multiple applications were not modeled since permethrin quickly moves (within hours) from the water column into the sediment (Figure 1). Permethrin Adulticide Page 15 of 23

16 Table 9. Estimated Environmental Concentrations (EECs) of Permethrin in a 30-cm and 2- m Deep Waterbody Application Rate Peak 96-hour 21-day 60-day 30-cm lb ai/a lb ai/a m lb ai/a lb ai/a Figure 1. EXAMS simulation of permethrin concentrations in the water column of a 30 cm deep waterbody Legend lbs/acre Permethrin Permethrin Parts per Billion Days After Application An application rate of lb ai/a (Aqua-Reslin), which represents a more typical application rate for products containing both permethrin and the synergist piperonyl butoxide, was also modeled and resulted in a peak EEC of 2.30 ppb in a 30-cm deep waterbody (Table 9). Peak EECs for both applications in a 2-m deep pond (EPA standard pond) were determined to be 1.30 ppb and 0.39 ppb for each application rate, respectively. The fate of permethrin in both waterbodies were similar, although permethrin persisted for a slightly longer period in the deeper water as a result of the greater volume of water per unit area of sediment. However, even in the 2-m deep waterbody, concentrations of permethrin fell below 0.1 ppb in less than 2 days. In Table 10, toxicity values were compared with the EECs for the 30-cm deep waterbody. Permethrin Adulticide Page 16 of 23

17 Table 10. Freshwater and Saltwater Fish and Aquatic Invertebrate Acute and Chronic Risk Quotients (RQs) Fish Species Peak EEC (ppb) 96-hr LC 50 (µg/l) Acute RQ (EEC/LC 50 ) 60-Day EEC (ppb) NOEC (mg/l) Chronic RQ (EEC/NOEC) Rainbow trout Bluegill sunfish Fathead minnow Channel catfish Striped mullet Inland silverside Sheepshead minnow Invertebrate Species Peak EEC (ppb) 48 or 96-hr LC 50 (µg/l) Acute RQ (EEC/LC 50 ) 21-Day EEC (ppb) NOEC (µg/l) Chronic RQ (EEC/NOEC) Daphnia Freshwater scud Crayfish Midge larvae Mayfly nymphs Fiddler crab Stone crab larvae Pink shrimp Mysid Shrimp Oyster 8.67 >536 < All acute risk quotients (RQs) were exceeded for both fresh water and estuarine/marine fish. With the exceptions of two relatively insensitive species (crayfish and oyster), all acute risk quotients were exceeded for both freshwater and estuarine/marine invertebrates. In addition, the chronic NOEC for Daphnia magna was exceeded. However, the chronic NOEC was compared to the average concentration over 21-days although the predicted concentration actually drops below the NOEC after 40 hours. Overall, the Tier I screening level assessment demonstrates a potential for acute and chronic adverse effects to both fish and aquatic invertebrates. Tier I is a screening level tier that is used to identify pesticides that may potentially have adverse effects to aquatic and terrestrial organisms. For this particular assessment, some general assumptions are given to provide for a worst-case scenario, one that is not likely to be exceeded in the real world. The assumption of 100% deposition, in particular, represents a worst case scenario for exposure for both terrestrial and aquatic organisms one that is not likely to ever occur for aerial adulticides. Therefore, if a pesticide exceeds levels of concerns in our Tier I assessment, a more realistic exposure scenario should be modeled in order to effectively evaluate the potential for adverse effects in the environment. Based on the potential for both acute and chronic adverse effects to both fish and aquatic invertebrates, a Tier II ecological risk assessment was performed to characterize more realistic exposure scenarios and to utilize additional environmental fate and effects data available for permethrin. Permethrin Adulticide Page 17 of 23

18 Tier II Risk Characterization The purpose of a Tier II risk assessment is to address the uncertainties associated with the screening level (Tier I) assessment by refining the exposure and effects characterization to represent a more realistic scenario applicable to Florida and to better utilize the available data. The main assumptions used in the initial screening assessment that can be refined to represent more realistic inputs into a refined assessment are (Table 11): 1. Water Depth in the Tier I assessment, we modeled a shallow water body (30-cm). To refine the assessment, two waterbodies were modeled. The 2-meter, standard EPA pond, is used to estimate risk to fish and the 30-cm (shallow waterbody) is used to estimate risk to aquatic invertebrates. 2. Exposure Duration peak environmental concentrations were used in the Tier I assessment to estimate acute risk even though the majority of acute toxicity studies are conducted for 96 hours. For compounds that are rapidly removed from the water column to the sediments (i.e., synthetic pyrethroids), it is important to compare the toxicity values to the appropriate exposure estimate (i.e., the 96-hour average concentration). Previous studies have demonstrated (e.g., cypermethrin) in both laboratory and outdoor micro- and mesocosm studies that the toxicity of synthetic pyrethroids are greatly reduced in the presence of sediment and that toxicity is directly associated with the concentration of the substance in the water column (or pore water for benthic invertebrates). 3. Deposition the Tier I assessment assumed 100% deposition. Actual deposition would be much less depending on droplet size. The label for Aqua-Reslin requires that aerial applications be made at an altitude of feet using ULV equipment that can produce a volume medium diameter (VMD) less than 60 microns. A recent study (Zhong et al., 2003) that looked at deposition of ULV aerial applications of fenthion using two types of nozzles, the conventional flat fan nozzle and the high-pressure nozzle, showed that the conventional flat fan nozzle system produces aerosol droplets within micron VMD range resulting in a deposition rate of 15 to 40% of the application rate within the application area (directly under the spray swath). Up to 15% of the application rate deposited just outside of the application area and less than 5% within 0.5 miles from the application area. Less than 2% of the application rate was deposited at any of the sample stations for the high pressure nozzle system that produces aerosol droplets within a micron VMD range. Based on this information, a 20% deposition on a surface water body can be considered a conservative, yet more realistic, estimate of deposition assuming that aerial applications are not made directly over water. For applications using droplets within the micron VMD range, very little deposition would be expected. 4. Application Rate in the Tier I assessment, the application rate used was the maximum rate for all of the permethrin labels (i.e., Permanone RTU). Most adulticide applications using permethrin are made at much lower rates (e.g., Aqua Reslin), particularly for those products that contain both permethrin and the synergist piperonyl butoxide. In addition Permethrin Adulticide Page 18 of 23

19 data from the Florida mosquito control districts (website link) show that application rates for this and other products containing synthetic pyrethroids are made at much lower rates than lbs ai/a. For further refinement of the assessment, an application rate of lb ai/a was modeled using the labeled rate for aerial applications of Aqua Reslin (20% permethrin and 20% piperonyl butoxide). Table 11. Fish and Aquatic Invertebrate Acute and Chronic Risk Quotients (RQs) Estimated for Various Exposure Scenarios (i.e., Assessment Refinement) Aquatic Scenario Fish RQs Invertebrates 1 RQs 1) Water depth (2-m and 30-cm) ) Exposure duration (96-h) ) Deposition (20%) ) Application rate (0.007 lb ai/a) Water depth + Exposure duration Water depth + Exposure duration + Deposition Water depth + Exposure duration + Application rate All factors combined Excluding the least sensitive aquatic invertebrates (i.e., crayfish and oyster). Each of these model input refinements were looked at individually and in combination to derive Risk Quotients (RQs) and to determine the overall influence that these assumptions have in determining risk to aquatic organisms. In the Tier I risk assessment, fish RQs ranged from 1.1 to 3.0 which exceeds all acute levels of concern (LOCs). The range of RQs for aquatic invertebrates was extensive due, in part, to toxicity values for species that appear to be relatively insensitive to permethrin (i.e., crayfish and oyster). If these two species are removed RQs ranged from 1.2 to 480, which are above all acute LOCs. Changing the water depth from 30-cm to the EPA standard pond depth of 2-m, all of the RQs for fish drop below 0.5, the Acute High toxicity level of concern. However, the Acute Restricted Use ( ) and the Acute Endangered Species ( ) are still exceeded. Risk to aquatic invertebrates remained the same since the depth of 30-cm was considered an acceptable exposure scenario for these organisms. When looking at the assumption of exposure duration, both fish and aquatic invertebrate RQs were greatly reduced when using the 96-hour exposure estimates. Exposure duration is a particularly important factor to considered for synthetic pyrethroids. These compounds have a high affinity for sediments and are quickly removed from the water column. In standard laboratory aquatic toxicity studies, test organisms are placed in treated water containing no sediments and very little dissolve organic carbon. In addition, most of these acute studies are conducted for 96-hours in either static or flow-through systems. Previous studies have shown that the addition of sediment can greatly reduce the toxicity of synthetic pyrethroids by lowering the Permethrin Adulticide Page 19 of 23

20 concentration present in the water column. Toxicity has been shown to be directly correlated with the concentration measured in the water column (or pore water for benthic invertebrates). Therefore, for further refinement of the exposure assessment and risk characterization, the use of 96-hour average predicted environmental concentrations is considered appropriate. Using these exposure values in the assessment, the RQs for fish are reduced to , which are below the Acute High LOC although they still exceed the Acute Restricted Use LOC for the most sensitive fish species. The aquatic invertebrate RQs range from 0.07 to 27, again due to the wide range of sensitivities, which is not surprising considering the different classes of organisms represented by this group. Deposition is a very important parameter for determining risk to non-target organisms from the use of mosquito adulticides. Unlike traditional agricultural applications, adulticides are applied using very small droplet sizes. The aerosol produced is meant to drift and collide with mosquitoes while they are active (i.e., flying). Mosquitoes are, therefore, killed by direct contact with the insecticide droplets. If the droplets are too big, they will deposit directly to the ground which is considered ineffective and wasteful. Therefore, the assumption of 100 percent deposition is very conservative, when, in fact, actual deposition should be much less depending on the droplet size spectrum produced by the spray equipment. A recent study by Zhong et al. (2003) demonstrated that conventional flat-fan nozzles (Tee Jet 8002SS) produced droplet sizes in the micron volume medium diameter (VMD) range. When fenthion was applied using DC-3 aircraft at 300 feet using this equipment, 15% to 40% of the application was deposited directly under the treatment block (under the spray swaths). Up to approximately 15% of the application rate was deposited immediately downwind of the treated block. Deposition was detected for several miles downwind, although detections were less than 5% of the application rate. When high-pressure hydraulic nozzles, that produce droplets in the micron VMD range, no more than 2% of the application rate was detected at any of the sample sites, including in the treated block. Considering that the label for Aqua Reslin specifies the use of ULV equipment and nozzles such as rotary atomizer or similar type that produce droplet VMD s less than 60 microns, a 20% direct deposition to a surface waterbody can be considered a reasonable worst case scenario, if applications are not made directly over water. When using this refined assumption, RQs for fish and aquatic invertebrates were and , respectively. For this particular comparison, all acute risk quotients are exceeded for only the most sensitive fish and aquatic invertebrates, although Acute Restricted Use and Acute Endangered Species are exceeded for other fish and aquatic invertebrates. Application rate is, of course, an important component of the exposure assessment. For permethrin, the majority of products contain the synergist piperonyl butoxide, which enhances the contact toxicity of permethrin to mosquitoes. Since aerial application of these products are made at lb ai/a, this application rate was also modeled in this assessment. Data from the mosquito control districts (website link) also suggests that application rates for permethrin and other synthetic pyrethroids are much lower than the rate for Permanone RTU (0.023 lbs permethrin/a). Lowering the modeled application rate to lb ai/a resulted in RQs of 0.33 to 0.90 for fish and 0.36 to 144 for aquatic invertebrates. Finally, when combining these various exposure parameters to represent a real world scenario, Permethrin Adulticide Page 20 of 23

21 the RQs for both fish and aquatic invertebrates are significantly reduced. For example, when looking at the combined effects of water depth, exposure duration, and application rate, the RQs for fish drop below all acute levels of concern (Table 11). Likewise, acute levels of concern are not exceeded for most aquatic invertebrates. However, some of the estuarine/marine species tested appear to be particularly sensitive to permethrin even at trace exposure levels. Overall, the combination of these realistic exposure components help to characterize the true risk to aquatic organisms under realistic, but worst-case, conditions. The combination of these factors appear to indicate that fish are not likely to be adversely impacted from the aerial application of permethrin. In addition, only the most sensitive species of aquatic invertebrates are expected to be adversely effected, and these effects will likely only be temporary, based on the rapid removal of permethrin from the water column. Although, synthetic pyrethroids are considered highly toxic to fish and aquatic invertebrates, environmental fate must be taken into consideration when determining risk. In addition, one must consider any ecological incidences (e.g., fish kills) that may have occurred as a result of the use of a particular product(s) in the field. In this case, the reviewer is not aware of any ecological incidences involving the aerial application of synthetic pyrethroids as adulticides. Two synthetic pyrethroids, sumithrin (Anvil) and resmethrin (Scourge), are currently registered and can be aerially applied in Florida for adult mosquito control. As synthetic pyrethroids, these two compounds are very similar to permethrin both in chemical structure and environmental fate. All of these compounds, once in water, are rapidly removed from the water column into the sediment (Figure 2). Toxicity to aquatic organisms are also similar. Sumithrin is considered highly toxic to fish (LC 50 s from 1.4 to 94 ppb) and aquatic invertebrates (0.025 ppb for mysids). Resmethrin is also considered highly toxic to fish ( ppb) and aquatic invertebrates ( ppb). The reviewer in not aware of any ecological incidences involving the use of these products. In addition, EPA believes that permethrin, sumithrin, and resmethrin when used in mosquito control programs do not pose unreasonable risks to wildlife or the environment (EPA, 2002). Based on similar fate and toxicity, the risk to aquatic organisms from the use of permethrin should be similar to both sumithrin and resmethrin. Finally, many synthetic pyrethroid products contain the synergist piperonyl butoxide to enhance toxicity to insects. Based on information provided by EPA, piperonyl butoxide, although slightly more persistent in water than permethrin, is much less toxic to aquatic organisms. Toxicity is an order of magnitude less than permethrin, particularly for fish. Fish toxicity values are in the ppm range while those for aquatic invertebrates range from 1.25 to 120 ppb. Considering the lower toxicity of piperonyl butoxide and the very low application rates used for mosquito control, adverse effects to aquatic organisms are not expected from the use of piperonyl butoxide. In addition, piperonyl butoxide does not appear to increase to toxicity of permethrin to aquatic organisms based on toxicity studies (i.e., toxicity of the formulated product was similar to technical permethrin for both fish and aquatic invertebrates). Permethrin Adulticide Page 21 of 23

22 Figure 2. EXAMS simulation of pesticide concentrations of permethrin, resmethrin, and sumithrin in the water column of a 30 cm deep waterbody Legend lbs/acre Permethrin Permethrin Resmethrin Sumithrin Parts per Billion Days After Application Summary Based on the Tier I risk assessment, permethrin is not expected to have any adverse effects on terrestrial wildlife. Permethrin is slightly toxic to mammals and practically non-toxic to birds. Permethrin is highly toxic to honey bees through direct contact. Therefore, these products should not be applied or allowed to drift to blooming crops or weeds while bees are active. Applications made during the typical predawn or dusk application periods (when mosquitoes are active) should minimize exposure to bees. From the Tier I screening level assessment, it was determined that permethrin has the potential to adversely impact fish and aquatic invertebrates, when comparing the estimated environmental concentrations derived from very conservative assumptions to values from acute toxicity studies. However, based on the results from the Tier II assessment utilizing realistic exposure factors that would be expected under reasonable worst-case conditions, direct adverse effects to fish are not expected. For typical use scenarios, adverse effects to aquatic invertebrates are not expected; however, adverse effects may occur to sensitive aquatic invertebrates under worst-case conditions (e.g., high deposition rate on a shallow waterbody). Once in the water, permethrin is rapidly (within hours) removed from the water column to the sediments. Therefore, any impacts to aquatic invertebrates are expected to be temporary and localized to shallow water. In Permethrin Adulticide Page 22 of 23

23 addition, these effects are not likely to represent significant impacts to aquatic communities as a whole. Finally, both the environmental fate and toxicity profiles for permethrin are very similar to resmethrin and sumithrin synthetic pyrethroids that can be applied aerially for adult mosquito control in Florida. Based on this ecological risk assessment, there does not appear to be any greater risk to terrestrial or aquatic organisms from the use of permethrin compared to resmethrin or sumithrin. Excluding aerial application of products containing permethrin in Florida should not be based on the potential for risk to non-target organisms since products containing permethrin are not likely to pose a greater risk than either resmethrin or sumithrin. In summary, the reviewer agrees with EPA that pyrethroids, including permethrin, used in mosquito control programs do not pose unreasonable risks to wildlife or the environment (EPA, 2002). Report prepared by: Max Feken Bureau of Pesticides, Scientific Evaluation Section FDACS, Tallahassee, Florida Date: August 8, 2003 Permethrin Adulticide Page 23 of 23