HSDB Sample Entry

Environmental Fate/Exposure Potential
(HSDB Section 7) Prepared by SRC.

Hazardous Substances Data Bank Record #6452-Fenamiphos

1. SUBSTANCE IDENTIFICATION

NAME OF SUBSTANCE - NAME
FENAMIPHOS

CAS REGISTRY NUMBER - RN
22224-92-6

SYNONYMS - SY (2)
Phosphoramidic acid, (1-methylethyl)-, ethyl 3-methyl-4-(methylthio)phenyl ester

MOLECULAR FORMULA - MF
C13-H22-N-O3-P-S

7. ENVIRONMENTAL FATE/EXPOSURE POTENTIAL

ENVIRONMENTAL FATE/EXPOSURE SUMMARY - ENVS Fenamiphos' production and use as an nematicide results in its direct release to the environment. If released to the atmosphere, fenamiphos should exist in both the vapor and particulate phases based on an experimental vapor pressure of 1X10-6 mm Hg at 25 deg C. Vapor-phase fenamiphos is degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals with an estimated half-life of about 2 hours. Particulate-phase fenamiphos may be physically removed from the air by wet and dry deposition. Measured Koc values ranging from 94-370 suggest that fenamiphos will have moderate to high mobility in soil. Fenamiphos rapidly degrades in soil through a combination of biodegradation, thiooxidation, and photolysis on the soil surface. The main transformation product of these processes is fenamiphos sulfoxide. Half-lives from days to weeks are measured in untreated soils; half-lives of one to a few days are measured in previously treated soils due to microbial acclimation. In natural water, fenamiphos had a half-life of 1.8 days. The main compound formed was fenamiphos sulfoxide. Fenamiphos was converted to fenamiphos sulfoxide through thiooxidation (over a period of 16 hours in water) and via photolysis in aqueous solution (complete degradation required 90 minutes). Volatilization from water surfaces is not expected based on an estimated Henry's Law constant of 9.7X10-11 atm-cu m/mole. This compound may bioconcentrate in aquatic organisms given an estimated BCF of 170; a measured BCF of 468 in earthworms was reported. Exposure to fenamiphos may occur occupationally during its production or use as a nematicide. (SRC)

NATURAL OCCURRING SOURCES - NATS (1)
NO DATA

ARTIFICIAL SOURCES - ARTS (1) [(1) Gianessi LP, Puffer CA; Insecticide Use in US Crop Production. Resources For the Future, Inc. Washington, DC: November (1992) (2) Tomlin C; The Pesticide Manual. A World Compendium. Incorporating "The Agrochemicals Handbook". 10th ed. Bath, UK: The Bath Press. p.423 (1994)] Fenamiphos's production and use as an nematicide(1) results in its direct release to the environment through various waste streams(SRC). Fenamiphos is used as an insecticide for tobacco; 52655 acres were sprayed in NC, 25600 acres in SC, 11347 acres in TN, and 9024 acres in VA (census as of 1987)(2).

ENVIRONMENTAL FATE - FATE (1) [(1) Bilkert JN, Rao PSC; J Environ Sci Health B20: 1-26 (1985) (2) Briggs GG; J Agric Food Chem 29: 1050-59 (1981) (3) Green RE et al; in Soil Science Society of America. SSSA Spec Publ 32(Sorption and Degradation of Pesticides and Organic Chemicals in Soil): 209-25 (1994) (4) Lee CC et al; J Contam Hydrol 1: 211-25 (1986) (5) Kotcon JB, Winner M; Bull Environ Contam Toxicol 50: 35-42 (1993) (6) Tomlin C; The Pesticide Manual. A World Compendium. Incorporating "The Agrochemicals Handbook". 10th ed. Bath, UK: The Bath Press. p.423 (1994)] TERRESTRIAL FATE: According to a recommended classification scheme, measured Koc values ranging from 94 to 370(1,2,3,4) indicate that fenamiphos will have moderate to high mobility in soil(SRC). Fenamiphos is rapidly degraded in soil through both thiooxidative and microbial processes. Within 21 days of field application, 74% of the initially applied fenamiphos was transformed to fenamiphos sulfoxide(4). Only trace quantities of fenamiphos were present after this time period (k1 = 0.33/day, t1/2 = 2.1 days)(4). 55 days following application of 14C-fenamiphos to control soil, 80.9% of the label was found in an acetone extract, 5.4% was fenamiphos, 54.6% was fenamiphos sulfoxide, 15.9% was fenamiphos sulfone, 5% was present as other products, 10.6% was present as volatiles and 14CO2, and 8.5% was unextractable(4). Fenamiphos was present in samples of Hagerstown cherty silt loam soil 9 days following field application but not 83 days later; however, very little of the degraded compound was present in its oxidized forms (fenamiphos sulfoxide, fenamiphos sulfone)(5). Soil half-lives of several weeks are measured under both aerobic and anaerobic conditions(6).

ENVIRONMENTAL FATE - FATE (2) [(1) Anderson JPE et al; pp. 184-92 in Proc Int Symp Environ Aspects Pestic Microbiol. Anderson JPE et al (eds) (1992) (2) Ou LT et al; in Soil Science Society of America, SSSA Spec Publ 32(Sorption and Degradation of Pesticides and Organic Chemicals in Soil): 253-60 (1994) (3) Miller GC et al; in Amer Chem Soc Div Environ Chem. 193rd Natl Mtg 27: 463-65 (1987) (4) Crepeau KL et al; Bull Environ Contam Toxicol 46: 512-18 (1991)] TERRESTRIAL FATE: Fenamiphos transformation is greater in soils from previously-treated than non-treated plots due to microbial acclimation. Soil exposed to repeated applications of fenamiphos showed increased rates of degradation up to 10-20 times higher (rates of up to 35 ug/mg microbial C/7 days after 4 applications) than untreated soil (rate = 2 ug/mg microbial C/7 days)(1). Soil which had received annual applications of fenamiphos for 15 years was able to degrade this compound in 1 day vs. 3 days for non-treated soil(2). Fenamiphos exposed to sunlight on the surface of 3 soils varying in organic matter from 0.53%, 2.2% and 6.3% had a photooxidative loss of 45%, 51%, and 25%, respectively(3). In moist soils(SRC), fenamiphos may be rapidly converted to fenamiphos sulfoxide(4).

ENVIRONMENTAL FATE - FATE (3) [(1) Lacorte S et al; Environ Sci Technol 29: 431-38 (1995) (2) Crepeau KL et al; Bull Environ Contam Toxicol 46: 512-18 (1991) (3) Barcelo D et al; Toxicol Environ Chem 38: 183-99 (1993) (4) Lee CC et al; J Contam Hydrol 1: 211-25 (1986) (5) Meylan WM, Howard PH; Environ Toxicol Chem 10: 1283-93 (1991) (6) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 5-4, 5-10 (1990) (7) Bowman BT, Sans WW; J Environ Sci Health B18: 667-83 (1983) (8) Franke C et al; Chemosphere 29: 1501-14 (1994) (9) Connell DW, Markwell RD; Chemosphere 20: 91-100 (1990)] AQUATIC FATE: 50 ug/L fenamiphos, added to filtered estuarine water, had a half-life of 1.8 days(1). The main compound formed was fenamiphos sulfoxide(1). Fenamiphos was chemically converted to fenamiphos sulfoxide over a period of 16 hours in water(2). Only 2% of the original concentration of fenamiphos remained after 30 minutes irradiation in aqueous solution; complete degradation required 90 minutes(3). Fenamiphos sulfoxide is a main transformation product of the photolysis of fenamiphos(3). Fenamiphos sulfoxide is also the main transformation product of fenamiphos during soil degradation studies(4). Fenamiphos is not expected to volatilize from water surfaces based on an estimated Henry's Law constant of 9.7X10-11 atm-cu m/mole(SRC), developed using a fragment constant estimation method(5). An estimated BCF value of 170(6,SRC), from an experimental log Kow(7), suggests that fenamiphos may bioconcentrate in aquatic organisms(SRC) according to a recommended classification scheme(8). A BCF of 468 was measured for earthworms(9).

ENVIRONMENTAL FATE - FATE (4) [(1) Bidleman TF; Environ Sci Technol 22: 361-367 (1988) (2) Wauchope RD et al; Rev Environ Contam Toxicol 123: 1-36 (1991) (3) Meylan WM, Howard PH; Chemosphere 26: 2293-99 (1993)] ATMOSPHERIC FATE: According to a suggested classification scheme(1), an experimental vapor pressure of 1X10-6 mm Hg at 25 deg C(2,SRC) indicates that fenamiphos will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase fenamiphos is degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be about 2 hours(3,SRC). Particulate-phase fenamiphos may be physically removed from the air by wet and dry deposition (SRC).

BIODEGRADATION - BIOD (1) [(1) Green RE et al; in Soil Science Society of America. SSSA Spec Publ 32(Sorption and Degradation of Pesticides and Organic Chemicals in Soil): 209-25 (1994) (2) Anderson JPE et al; pp 184-92 in Proc Int Symp Environ Aspects Pestic Microbiol. Anderson JPE et al (eds) (1992) (3) Ou LT et al; in Soil Science Society of America, SSSA Spec Publ 32(Sorption and Degradation of Pesticides and Organic Chemicals in Soil): 253-60 (1994) (4) Ou LT, Rao PSC; J Environ Sci Health B21: 25-40 (1986) (5) Ou LT; Soil Sci Soc Am J 55: 716-22 (1991)] Degradation half-lives were measured for fenamiphos; four surface collected soils had half-lives of 6-11 days and the same soils with subsurface collection (60-80 cm) had half-lives from 4-10 days (1). Soil exposed to repeated applications of fenamiphos showed increased rates of degradation up to 10-20 times higher (rates of up to 35 ug/mg microbial C/7 days after 4 applications) than untreated soil (rate = 2 ug/mg microbial C/7 days)(2). Soil which had received annual applications of fenamiphos for 15 years was able to degrade this compound in 1 day vs. 3 days for non-treated soil(3). Less than 9% mineralization over 63 days was measured in soils which had no prior application of fenamiphos(4). During a 70 day incubation period, 67.2, 27.8, and 9.8% of applied 14C-fenamiphos was mineralized in soil samples collected 2,3, and 4 years after a previous field application, while 10.8, 11.5, and 9.5% of applied 14C-fenamiphos in the corresponding control samples was mineralized(5).

ABIOTIC DEGRADATION - ABIO (1) [(1) Meylan WM, Howard PH; Chemosphere 26: 2293-99 (1993) (2) Crepeau KL et al; Bull Environ Contam Toxicol 46: 512-18 (1991) (3) Miller GC et al; in Amer Chem Soc Div Environ Chem. 193rd Natl Mtg 27: 463-65 (1987) (4) Barcelo D et al; Toxicol Environ Chem 38: 183-99 (1993) (5) Lacorte S et al; Environ Sci Technol 29: 431-38 (1995)] The rate constant for the vapor-phase reaction of fenamiphos with photochemically produced hydroxyl radicals has been estimated as 7.8X10-11 cu cm/molecule-sec at 25 deg C(SRC) using a structure estimation method(1,SRC). This corresponds to an atmospheric half-life of about 2 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1,SRC). Fenamiphos was chemically converted to fenamiphos sulfoxide over a period of 16 hours in water(2). Fenamiphos exposed to sunlight on the surface of 3 soils varying in organic matter from 0.53%, 2.2% and 6.3% had a photooxidative loss of 45%, 51%, and 25%, respectively(3). An aqueous solution of fenamiphos was irradiated with a xenon lamp(4). Only 2% of the compound remained after 30 minutes; complete degradation required 90 minutes(4). Fenamiphos sulfoxide is a main transformation product of the photolysis of fenamiphos(4). 50 ug/L Fenamiphos, added to filtered estuarine water, had a half-life of 1.8 days(5). The main compound formed was fenamiphos sulfoxide(5). Degradation may have been due to abiotic/biotic degradation or photolysis(SRC).

BIOCONCENTRATION - BIOC (1) [(1) Bowman BT, Sans WW; J Environ Sci Health B18:667-83 (1983) (2) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 5-4, 5-10 (1990) (3) Franke C et al; Chemosphere 29: 1501-14 (1994) (4) Connell DW, Markwell RD; Chemosphere 20: 91-100 (1990)] An estimated BCF value of 170 was calculated for fenamiphos(SRC), using an experimental log Kow of 3.23(1) and a recommended regression-derived equation(2). According to a recommended classification scheme(3), this BCF value suggests that bioconcentration in aquatic organisms may be an important fate process(SRC). A BCF of 468 was measured for earthworms(4).

SOIL ADSORPTION/MOBILITY - KOC (1) [(1) Bilkert JN, Rao PSC; J Environ Sci Health B20: 1-26 (1985) (2) Briggs GG; J Agric Food Chem 29: 1050-59 (1981) (3) Green RE et al; in Soil Science Society of America. SSSA Spec Publ 32(Sorption and Degradation of Pesticides and Organic Chemicals in Soil): 209-25 (1994) (4) Lee CC et al; J Contam Hydrol 1: 211-25 (1986) (5) Swann RL et al; Res Rev 85: 23 (1983) (6) Loffredo E et al; J Environ Sci Health B26: 99-113 (1991)] The sorption and leaching of fenamiphos was studied in an Arredondo sand (0.80% organic carbon; pH 6.8; 93.8% sand), a Cecil sandy loam (0.90% organic carbon; pH 5.6; 65.8% sand, 19.5% silt, 14.7% clay), and a Webster silty clay loam (3.97% organic carbon; pH 7.3; 18.4% sand, 45.3% silt, 38.3% clay); Koc values of 148, 197, and 249 were measured, respectively(1). In soil column leaching studies, fenamiphos was most strongly retained in the Webster soil(1). Fenamiphos had a measured Koc value of 190 in a Batcombe soil (3.53% organic matter; pH 6.1)(2). Adsorption of fenamiphos was measured in four surface and subsurface soils from Hawaii; Koc values ranging from 94 to 344 (organic carbon content from 1.3-6.22%; pH from 5.3-6.7) were measured in surface soil and values of 73-202 were measured in subsoil (60-80 cm below surface; organic carbon content 0.55-3.19%; pH 5.3-6.8)(3). A Koc of 370 was measured for Molokai silty clay loam (pH=5.8; 1.2% organic carbon)(4). According to a recommended classification scheme(5), these measured Koc values indicate that fenamiphos has moderate to high mobility in soil(SRC). Leaching of fenamiphos was studied using two soil columns, one containing a sandy loam soil (organic carbon 1.1%; pH 7.4) and the other a clay loam soil (organic carbon 2.8%; pH 7.6)(6). Retention was greater in the clay loam soil, resulting in a greater conversion of fenamiphos to its thiooxidized forms(6).

VOLATILIZATION FROM WATER/SOIL - VWS (1) [(1) Wauchope RD et al; Rev Environ Contam Toxicol 123: 1-36 (1991) (2) Yalkowsky SH, Dannenfelser RM; Aquasol Database of Aqueous Solubility. Version 5. College of Pharmacy, University of Arizona - Tucson, AZ PC Version (1992) (3) Lyman WJ et al; Handbook of Chemical Property Estimation Methods. Washington DC: Amer Chem Soc pp. 15-1 to 15-29 (1990)] The Henry's Law constant for fenamiphos is estimated as 1.2X10-9 atm-cu m/mole(SRC) from its experimental values for vapor pressure, 1X10-6 mm Hg(1), and water solubility, 329 mg/L(2). This value indicates that fenamiphos will essentially not volatilize from water surfaces(3,SRC). Fenamiphos is not expected to volatilize from dry or moist soil(SRC) based on its measured vapor pressure, 1X10-6 mm Hg(1,SRC) and Henry's Law constant(1,2,SRC).

WATER CONCENTRATIONS - WATC (1) [(1) Baumann RA et al; Pesticides in Surface Water of the Hogeveense Polder (1989/90). NTIS PB93-102 390. Rijksinstituut Voor De Volksgezondheid En Milieuhygiene Bilthoven (Netherlands). pp. 49 (1991)] SURFACE WATER: Fenamiphos was detected in surface water from the Hogeveense Polder, The Netherlands, at concentrations from 0.3-0.7 ug/L(1).

WATER CONCENTRATIONS - WATC (2) [(1) USEPA; National Pesticide Survey: Survey Analytes. USEPA Off Water. Off Pest Toxic Sub. Fall 1990 NTIS PB93-116 010. (1990) (2) USEPA; Pesticides in Groundwater Database. A Compilation of Monitoring Studies: 1971-1991. National Summary. USEPA Off Pest Programs. Prevention Pesticides and Toxic Substances. (H7507C) USEPA-734-12-92-001 (1992)] GROUNDWATER: Fenamiphos was not detected in water samples collected from 783 rural domestic wells and 566 community water system wells in the United States (detection limit 0.15 ug/L)(1). Fenamiphos was not detected in water samples collected from 763 wells in CA, 74 in FL, 120 in MS, 10 in OR, 188 in TX, or 81 wells in WA (unreported detection limits)(2).

EFFLUENTS CONCENTRATIONS - EFFL (1)
NO DATA

SEDIMENT/SOIL CONCENTRATIONS - SEDS (1)
NO DATA

ATMOSPHERIC CONCENTRATIONS - ATMC (1)
NO DATA

FOOD SURVEY VALUES - FOOD (1)
NO DATA

PLANT CONCENTRATIONS - PLNT (1)
NO DATA

FISH/SEAFOOD CONCENTRATIONS - FISH (1)
NO DATA

ANIMAL CONCENTRATIONS - ANML (1)
NO DATA

MILK CONCENTRATIONS - MILK (1)
NO DATA

AVERAGE DAILY INTAKE - AVDI (1)
NO DATA

BODY BURDEN - BODY(1)
NO DATA