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Oxamyl

Overview
 
CAS Number: 23135-22-0
Synonyms: Methyl N',N'-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamimidate, Vydate, Vydate L
Contaminant Type: Chemical

Oxamyl is a carbamate pesticide for control of insecticide, mites and nematodes [1511]. Its chemical name is methyl N',N'-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamimidate, with trade names of Vydate and Vydate L [1511].

Oxamyl was first registered in 1974 [1511]. It is used on many crops, including apples, bananas, carrots, celery, citrus and cotton etc [1511]. Cotton accounts for most of the usage; approximately 600 thousand pounds out of 800 thousand pounds of oxamyl active ingredient is used on cotton on an annual basis [1511]. Oxamyl is not applied for residential uses [1511].  Oxamyl can over stimulate the nervous system and cause nausea, dizziness, confusion [1511]. Very high exposures, for example, from accidents or major spills, can cause respiratory paralysis and death [1511].

The U.S. Environmental Protection Agency established a maximum contaminant level (MCL) of 0.2 mg/L and a maximum contaminant level goal (MCLG) of 0.2 mg/L for oxamyl in drinking water.  Adsorption onto granular activated carbon is the designated Best Available Technology for control of oxamyl.

Oxamyl is highly soluble in water.  Its major degradates identified in fate studies were oxime and dimethyloxamic acid (DMOA) [1511]. Hydrolysis of oxamyl depends on pH; it degrades rapidly in neutral or alkaline conditions (30% degradation in six hours at pH 9.1), but more stable in acidic conditions (no degradation in 11 days at pH 4.7) [1518]. Degradation by photolysis appears significant in acidic surface water but not in soil [1511]. Oxamyl degrades in soil by chemical and biological processes [1511]. Under aerobic conditions, oxamyl has a half-life of two to four weeks in soil; under anaerobic conditions, its half-life is less than one week in soil [1511].

Oxamyl concentrations in groundwater were generally between 1 to 2 ppb based on a non-chemical specific study in Suffolk County, Long Island and a prospective groundwater study in cotton growing area of North Carolina [1511]. Oxamyl was not detected in 432 wells monitored in California that were not necessarily located close to an agriculture field, according to well data reported to the Department of Pesticide Regulation between 1996 and 1997 [1519]. In finished drinking water, less than 0.1% of approximately 13,000 systems detected oxamyl, while no system had oxamyl concentration above the MCL [1516].

Date of Literature Search: July 2009



1511 USEPA; 2000; Interim Reregistration Eligibility Decision (IRED) - Oxamyl; Interim Reregistration Eligibility Decision (IRED) - Oxamyl; EPA 738-R-00-015. pp. 7-10, 18, 27. Office of Prevention, Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington, D.C.
1516 USEPA; 2003; Occurrence Estimation Methodology and Occurrence Findings Report for Six-Year Review of National Primary Drinking Water Regulations; Occurrence Estimation Methodology and Occurrence Findings Report for Six-Year Review of National Primary Drinking Water Regulations; EPA-815-R-03-006. pp. 22 and 28. Office of Water.
1518 Harvey, J. and Han, J.C.; 1978; Decomposition of oxamyl in soil and water; Decomposition of oxamyl in soil and water; 26:3:536
1519 California Environmental Protection Agency; 1998; Sampling for Pesticide Residues in California Well Water: 1997 Update of the Well Inventory Database; Sampling for Pesticide Residues in California Well Water: 1997 Update of the Well Inventory Database; EH98-04. pp. 6-9. Department of Pesticide Regulation.



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