Diclofop-methyl

Group I Containers: Combustible containers from organic or metallo-organic pesticides (except organic mercury, lead, cadmium, or arsenic compounds) should be disposed of in pesticide incinerators or in specified landfill sites. /Organic or metallo-organic pesticides/

Group II Containers: Non-combustible containers from organic or metallo-organic pesticides (except organic mercury, lead, cadmium, or arsenic compounds) must first be triple-rinsed. Containers that are in good condition may be returned to the manufacturer or formulator of the pesticide product, or to a drum reconditioner for reuse with the same type of pesticide product, if such reuse is legal under Department of Transportation regulations (eg 49 CFR 173.28). Containers that are not to be reused should be punctured ... and transported to a scrap metal facility for recycling, disposal or burial in a designated landfill. /Organic or metallo-organic pesticides/

Avoid contact with flames or sparks.

Avoid contact or inhalation of spray mist. Wash thoroughly after using and change clothing. Do not take internally.

SRP: Contaminated protective clothing should be segregated in such a manner so that there is no direct personal contact by personnel who handle, dispose, or clean the clothing. Quality assurance to ascertain the completeness of the cleaning procedures should be implemented before the decontaminated protective clothing is returned for reuse by the workers. Contaminated clothing should not be taken home at end of shift, but should remain at employee's place of work for cleaning.

Tolerances are established for the combined residues of the herbicide diclofop-methyl (methyl 2-(4-(2,4-dichlorophenoxy)phenoxy) propanoate) and its metabolites, 2-(4-(2,4-dichlorophenoxy)phenoxy)propanoic acid and 2-(4-(2,4-dichloro-5-hydroxyphenoxy)phenoxy)propanoic acid, in or on the following raw agricultural commodities: Barley, grain: 0.1 ppm; Barley, straw: 0.1 ppm; Flaxseed: 0.1 ppm; Lentils: 0.1 ppm; Pea seeds (dry): 0.1 ppm; Soybeans: 0.1 ppm; Wheat, grain: 0.1 ppm; and Wheat, straw: 0.1 ppm.

Excerpt from ERG Guide 171 [Substances (Low to Moderate Hazard)]:

Goggles, rubber gloves, hat, impermeable pants and shirts, waterproof boots.

Aerial pilots are not to be involved in the mixing and loading unless /gloves, waterproof boots, impermeable pants and shirts, goggles and a cartridge type respirator/ is worn. Pilots must wear a cartridge type respirator during application unless the air craft is equipped with an air-filter system.

LC50 Rainbow trout 0.35 mg/l/96 hr /Conditions of bioassay not specified/

LC50 Coturnix >5000 ppm/5 days

TERRESTRIAL FATE: In soil, dichlorfop-methyl will be slightly mobile to immobile(1) based on experimental and estimated Koc values ranging from 2400 to 16,000(2-4). Hydrolysis follows the adsorption of dichlorfop-methyl onto clays(5). After application onto sandy loam plots in May (1.25 kg/ha), only 15% of the applied dichlorfop-methyl was solvent recoverable by October and 37% was associated with the soil in a bound form(6). It has been shown that dichlorfop-methyl undergoes rapid hydrolysis by microorganisms through carboxylation and ether cleavage(7,8). In moist soil, hydrolysis of the ester to the corresponding acid, dichlorfop, is rapid and complete within 9 days(5).

TERRESTRIAL FATE: Following spray application on a wheat field, air samples taken at six different heights above the crop canopy during the first 7 days did not show measurable levels of dichlorfop-methyl, thus indicating minimal losses due to volatilization(1). Analysis of the soil showed that the ester was rapidly hydrolyzed to dichlorfop acid which then underwent decomposition(1). After 126 days, approximately 20% of the initial amount applied could still be recovered from the soil as dichlorfop acid(1). Approximately 27% of the dichlorfop-methyl applied was intercepted by the wheat canopy(1). It was assumed that the remaining 73% had infiltrated down to the soil under the crop canopy(1). There was a rapid decline in the total dichlorfop in the crop canopy so that 5 days after application 5% of the initial amount of dichlorfop applied remained, most being in the form of dichlorfop acid. After 32 days, dissipation of dichlorfop from the crop was essentially complete(1). No dichlorfop acid residues were observed in the mature grain or straw at harvest 88 days after application(1).

AQUATIC FATE: Dichlorfop-methyl will be essentially non-volatile from water based upon an estimated Henry's Law constant of 3.8X10-8 atm-cu m/mol(1,2,SRC). Dichlorfop-methyl has aqueous base-catalyzed half-lives of 6.3 days at pH 9, 63 days at pH of 8, and 1.7 years at pH of 7(3,SRC). Dichlorfop-methyl is expected to have moderate bioconcentration(SRC). Adsorption to sediment may be possible based on high Koc values of 2400 to 16,000(2,4,5,SRC). Dichlorfop-methyl biodegrades faster in the presence of sediment than with water(6).

ATMOSPHERIC FATE: Based on an experimental vapor pressure of approximately 2.5X10-7 mm Hg at 20 °C(1), dichlorfop-methyl will exist in the vapor and particulate phases in the ambient atmosphere(2). In the vapor phase, it will degrade in the atmosphere by reaction with photochemically produced hydroxyl radicals with an estimated half-life of 21 hrs(3). Physical removal of particulate dichlorfop-methyl from air is likely to occur through wet and dry deposition(SRC).

Because dermal absorption is an important route of exposure to chlorophenoxy herbicides, biological monitoring is useful in estimating the absorbed dose. Urine concn provide the most accurate estimate of body burden; because of slow absorption, it is best to collect samples after a few days of exposure. /Chlorophenoxy herbicides/

Using a structure estimation method based on molecular connectivity indexes, the Koc for dichlorfop-methyl can be estimated to be about 4000(1). The Koc for dichlorfop-methyl can be estimated to be about 2400 based on an estimated water solubility of 3 mg/L(3) and a regression derived equation(2). Koc for dichlorfop-methyl has also been determined to be 16,000(4). According to a suggested classification scheme(5), these estimated and experimental Koc values suggest that dichlorfop-methyl will be slightly mobile to immobile in soil.

The risk of soft tissue sarcoma following possible exposure to phenoxy acid herbicides was studied in 354,620 Swedish men, who were employed in agriculture or forestry according to a national census in 1960. This cohort was further divided into six subcohorts, on assumed exposure to phenoxy acid herbicides. The reference cohort encompassed 1,725,845 Swedish men employed in other industries. All persons were followed up in the cancer environment register during the period 1961-79. A total of 331 cases of soft tissue sarcomas was observed in the study cohort and there were 1,508 cases in the reference group (relative risk 0.9; 95% confidence interval, 0.8-1.0). No subcohort of agricultural or forestry workers showed any significantly increased relative risk, nor was there any significant difference in relative risk between the subcohorts. Despite the greatly increased use of phenoxy acid herbicides from 1947 to 1970, no time related increase in the relative risk of soft tissue sarcoma was found in the total cohort or in any of the subcohorts. /Phenoxy acid herbicides/

In 1977, a number of patients with soft tissue sarcomas and previous exposure to phenoxyacetic acids were described. Following from these observations, a matched case-control study was made. The results showed that exposure to phenoxyacetic acids or chlorophenols gave an approximately six-fold increase in the risk factor for this type of tumor. It was not possible to determine, however, whether the carcinogenic effect was exerted by these compounds or by impurities such as chlorinated dibenzodioxins and dibenzofurans that in almost all cases were part of the commercial preparations. /Phenoxyacetic acids and chlorophenols/

A number of men with malignant lymphoma of the histiocytic type and previous exposure to phenoxy acids or chlorophenols were observed and reported in 1979. A matched case-control study has therefore been performed with cases of malignant lymphoma (Hodgkin's disease and non-Hodgkin's lymphoma). This included 169 cases and 338 controls. The results indicate that exposure to phenoxy acids, chlorophenols, and organic solvents may be a causative factor for malignant lymphoma. Combined exposure of these chemicals seemed to increase the risk. Exposure to various other agents was not obviously different in cases and in controls. /Phenoxy acids and chlorophenols/

A previous case-control study which used the occupational information available on the New Zealand Cancer Registry found that agricultural workers were at increased risk of developing non-Hodgkin's lymphoma. The findings are now presented for the second phase of the study which entailed interviewing 83 cases of non-Hodgkin's lymphoma registered under code 202 of the International Classification of Diseases together with 168 controls with other types of cancer and 228 general population controls. The findings for the two control groups were similar, and there were no significant differences between cases and controls regarding potential exposure to phenoxyherbicides (odds ratio= 1.4, 90% confidence limits 0.7-2.5, p= 0.26) or chlorophenols (odds ratio= 1.3, 90% confidence limits 0.6-2.7, p= 0.39). The odds ratio for fencing work, necessitating exposure to several potential risk factors including arsenic and sodium pentachlorophenate was 2.0 (90% confidence limits 1.3-3.0, p= 0.01). The odds ratio for employment in a meat works, necessitating potential exposure to 2,4,6-trichlorophenol and zoonotic viruses, was 1.8 (90% confidence limits 1.1-3.1, p= 0.04). There was a significant statistical interaction between the risks associated with these two activities, the odds ratio for involvement in both activities compared with involvement in neither being 5.7 (90% confidence limits 2.3-14.3, p= 0.03). /Phenoxyherbicides, chlorophenols, arsenic, and sodium pentachlorophenate/

In soil, the rate of hydrolysis of dichlorfop-methyl followed the order pH 6.4>7.5>5.5(1). Dichlorfop-methyl appears to be hydrolyzed in soil by hydrolase enzymes associated with viable microorganisms(1). As established in model ecosystems or by direct measurements of soils or waters, dichlorfop-methyl undergoes decarboxylation and ether cleavage reactions in biological systems(2). Dichlorfop-methyl undergoes rapid microbial hydrolysis of the ester bond(3). Dichlorfop, the corresponding acid, was formed and was extensively degraded under aerobic conditions, the final product being CO2(3). Under anaerobic conditions, the degradation proceeded to a small extent, at most, where 3% of the applied radioactivity is accounted for by the degradation product 4-(2,4-dichlorophenoxy)phenol(3). No other metabolite, including CO2 was observed implying a lack of any further degradation(3). In a degradation study of dichlorfop-methyl in moist non-sterile heavy clay, silty clay, and sandy loam soils, an initial and rapid hydrolysis to the corresponding acid was followed by a much slower hydrolytic process so that traces of the ester could still be seen after 10 weeks(4). Dichlorfop-methyl showed significantly more degradation in the presence of nonsterile sediment than in the presence of sterile sediment(5). It also biodegraded faster in the presence of sediment than in water alone(5). No racemization of the ester takes place upon hydrolysis in soil, but inversion of configuration of the hydrolysis products is observed (the S-configuration showed a higher inversion tendency than the R-configuration)(6).

Based upon an experimental water solubility of 3 mg/l(1), the BCF of dichlorfop-methyl can be estimated to be approximately 300 from a regression-derived equation(2). This estimated BCF value suggests moderate bioconcentration in aquatic organisms(SRC).

As the federal pesticide law FIFRA directs, EPA is conducting a comprehensive review of older pesticides to consider their health and environmental effects and make decisions about their future use. Under this pesticide reregistration program, EPA examines health and safety data for pesticide active ingredients initially registered before November 1, 1984, and determines whether they are eligible for reregistration. In addition, all pesticides must meet the new safety standard of the Food Quality Protection Act of 1996. Pesticides for which EPA had not issued Registration Standards prior to the effective date of FIFRA, as amended in 1988, were divided into three lists based upon their potential for human exposure and other factors, with List B containing pesticides of greater concern and List D pesticides of less concern. Methyl 2-(4-(2,4-dichlorophenoxy)phenoxy)propionate is found on List B. Case No: 2160; Pesticide type: herbicide; Case Status: OPP is reviewing data from the pesticide's producers regarding its human health and/or environmental effects, or OPP is determining the pesticide's eligibility for reregistration and developing the Reregistration Eligibility Decision (RED) document.; Active ingredient (AI): Methyl 2-(4-(2,4-dichlorophenoxy)phenoxy)propionate; Data Call-in (DCI) Date(s): 06/05/91, 10/13/95; AI Status: The producers of the pesticide has made commitments to conduct the studies and pay the fees required for reregistration, and are meeting those commitments in a timely manner.

Tolerances are established for the combined residues of the herbicide diclofop-methyl (methyl 2-(4-(2,4-dichlorophenoxy)phenoxy) propanoate) and its metabolites, 2-(4-(2,4-dichlorophenoxy)phenoxy)propanoic acid and 2-(4-(2,4-dichloro-5-hydroxyphenoxy)phenoxy)propanoic acid, in or on the following raw agricultural commodities: barley, flaxseed, lentils, pea seeds (dry), soybeans, and wheat.