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CAS Number: 22224-92-6
Synonyms: B68138, Bay 68138, Bayer 68138, ENT 27572, Nemacur, Phenamiphos
Contaminant Type: Chemical

Fenamiphos is an organophosphorous pesticide widely used for control of nematodes and thrips. [1509] Its chemical name is ethyl 3-methyl-4-(methylthio)phenyl-(1-methylethyl) phosphoramidate, with the trade name of Nemacur. Fenamiphos was formulated as Nemacur, a product that was intended to be further formulated into a variety of end-use products. [1509] Fenamiphos has been applied on agricultural crops, including citrus, grapes, peanuts, pineapples and tobacco, and non-agricultural sites, such as turf and ornamentals. [1509] Approximately 780,000 pounds of fenamiphos active ingredient was used annually in 2002. [1509]


Fenamiphos was first registered in the United States in 1972.  Due to its effects on extremely vulnerable soils and shallow ground water (less than 50 feet below ground surface), all registrations for the products containing the active ingredient fenamiphos were cancelled and the manufacture and use of fenamiphos was phased out by the end of 2008. [1502, 1510] Extremely vulnerable soils refer to USDA hydrologic soil group A, soils that are excessively drained and are predominately sand or loamy sand. [1509] Fenamiphos is not regulated under National Primary Drinking Water Regulations.


Fenamiphos can overstimulate the nervous system causing nausea, dizziness and confusion. [1509] Very high exposures of fenamiphos can cause respiratory paralysis and death. [1509] Fenamiphos residues in food do not pose risk concerns for people in the United States. [1509] Drinking water exposure is generally not a concern for surface and ground water sources associated with soils that are not extremely vulnerable. [1509] However, shallow ground water sources associated with extremely vulnerable soils would pose risk concerns if used as drinking water sources. [1509]


Fenamiphos has two primary degradates, fenamiphos sulfoxide and fenamiphos sulfone, which are also considered toxic and used in calculating risk to drinking water [1509]. In soil, fenamiphos is subject to photodegradation by natural light on the soil surface, with a half-life of 3.23 hours. [1509] The half-life of aerobic soil metabolism is short, approximately 15.7 days. [1509] While, the anaerobic soil metabolism half-life is long, approximately 87.9 days, which indicated fenamiphos will persist after reaching ground water. [1509]


Fenamiphos and its degradates are mobile and can leach to groundwater and migrate to surface water. [1509] Laboratory studies indicate sulfoxide and sulfone degradates are more mobile than the parent fenamiphos. [1509] Fenamiphos is relatively resistant to hydrolysis in sterile buffered water; half-lives were calculated as 245 days at pH 5.0, 301 days at pH 7.0 and 235 days at pH 9.0. [1506]


Fenamiphos and its degradates were detected in groundwater in Florida and California, the two major fenamiphos use states. [1509] Fenamiphos was detected in nine out of sixteen wells close to citrus use sites monitored in Florida during 1995-1996 at concentrations ranging from 0.10 to 0.58 µg/L. [1509] Another Florida golf course study detected fenamiphos at eight out of forty one courses at concentrations in the range of 0.03 to 0.71 µg/L. [1509] A California monitoring program detected fenamiphos at five out of sixteen wells during 1997- 2000. [1509] Surface water monitoring data for fenamiphos and its degradates are limited. [1509] One monitoring program sponsored by USEPA and US Geological Survey detected fenamiphos degradates at three out of twelve reservoirs at concentrations ranging from 0.005 to 0.033 µg/L, and in the treated drinking water at concentrations ranging from 0.007 to 0.022 µg/L. [1509]


Date of Literature Search: June 2009

1506 Mulford, D.; 1987; Stability of Nemacur in Sterile Aqueous Buffer Solutions; Stability of Nemacur in Sterile Aqueous Buffer Solutions; Available: USEPA, 2002. Interim Reregistration Eligibility Decision (IRED). pp.32 [cited June 10, 2009]
1509 USEPA; 2002; Interim Registration Eligibility Decision (IRED) - Fenamiphos; Interim Registration Eligibility Decision (IRED) - Fenamiphos; EPA 738-R-02-004. pp. 15-21. pp. 32. Office of Prevention, Pesticides and Toxic Substances, Washington, DC.
1510 USEPA; 2008; Fenamiphos; amendment to use deletion and product cancellation order; Federal Register; 73:113:33082. June 11, 2008.