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Chemical Fact Sheet

Chemical Abstract Number (CAS #) 15972608
CASRN 15972-60-8
SynonymsAlachlor
Metachlor
Lasso
2-Chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide
Analytical Methods EPA Method 505
EPA Method 525.2
EPA Method 645
EPA Method 8081
Molecular FormulaC14H20ClNO2

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use HERBICIDE FOR GRASSES & BROADLEAF WEEDS ON CORN & SORGHUM, SOYBEANS, PEANUTS, COTTON, VEGETABLES, FORAGE CROPS. It is a selective pre and early post emergence herbicide for annual broadleaf control in crops such as beans, beets, cabbage, corn, cotton, ornamentals, peanuts, peas, potatoes, sorghum, soybeans, sugarcane, sunflowers, and tobacco. Selective systemic herbicide for control of most annual grasses and many broad leaved weeds in maize, sorghum, groundnuts, soya beans, lima beans, oilseed rape, brassicas, radish, oil radish, cotton, sunflowers, sugar cane, potatoes, peas, tobacco, some ornamentals.
Consumption Patterns 57% AS A SELECTIVE HERBICIDE FOR GRASS & BROADLEAF WEEDS ON CORN & SORGHUM; 43% AS A SELECTIVE HERBICIDE FOR GRASS & BROADLEAF WEEDS ON SOYBEANS; LESS THAN 1% AS A SELECTIVE HERBICIDE FOR GRASS & BROADLEAF WEEDS ON PEANUTS, COTTON, VEGETABLES, & FORAGE CROPS (1974)
Apparent Color CRYSTALLINE SOLID ; CREAM COLORED SOLID AT ROOM TEMP ; Colorless to yellow crystals
Odor ODORLESS
Boiling Point 100 DEG C @ 0.02 MM HG, 135 DEG C @ 0.3 MM HG
Melting Point 40-41 DEG C
Molecular Weight 269.77
Density 1.133 @ 25 DEG C/15.6 DEG C
Sensitivity Data SRP: Mild eye and skin irritant.
Environmental Impact Alachlor is a herbicide used on a number of crops to control annual grasses and many broad-leaved weeds. The release of alachlor in the environment occurs during the manufacture and particularly as a result of its application in the field. In soil, alachlor is transformed to its metabolites primarily by biodegradation. The half-life of alachlor disappearance from soil is about 15 days, although very little mineralization has been observed. Alachlor is highly to moderately mobile in soil and the mobilization decreases with an increase in organic carbon and clay content in soil. In water, both photolysis and biodegradation are important for the loss of alachlor, although the role of photolysis becomes important in shallow clean water, particularly in the presence of sensitizers. The bioconcentration of alachlor in aquatic organisms is not important. The half-life of alachlor due to reaction with hydroxyl radicals in the atmosphere has been estimated to be 2.1 hrs. Partial removal of alachlor will also occur as a result of dry and wet deposition. Alachlor has been widely detected in surface water and groundwater around applied farmlands. The applicators of the herbicide are the most likely people for exposure to alachlor via inhalation and dermal routes.
Environmental Fate TERRESTERIAL FATE: RESULTANT AVG PERSISTENCE OF RECOMMENDED RATES: 6-10 WK BUT MAY VARY DEPENDING ON SOIL TYPE AND CLIMATE CONDITIONS. TERRESTRIAL FATE: In lab and field experiments, the persistence was in the order: propachlor less than alachlor which was equal to dimethachlor which was less than metazachlor and metazachlor was less than metolachlor. Increase of temp by 10 degrees reduced the half-life by a factor of 1.9-2.5. The Arrhenius activation energy for alachlor was 57.0 kJ/mol. The half-life of alachlor in soils was found to be 7 to 14 days. Four major metabolites of alachlor were observed but only two were identified: 2-chloro-2',6'-diethylacetanilide and 1-chloro-acetyl-2,3-dihydro-7-ethylindole. TERRESTRIAL FATE: Biodegradation will be the most important process by which alachlor will be lost from most soils . Although biotransformation of alachlor from soil was rapid, very little mineralization products were observed . This indicates that biotransformation proceeds via cometabolism . Some loss of alachlor from soil will occur as a result of photolysis by sunlight, but photolysis will not be competitive with biodegradation . The range of log Koc values (2.08-2.18)(9) indicate that alachlor would have a high to medium mobility in soil . Experimental results confirms that alachlor absorbs weakly to moderately to soil and the leaching of alachlor from soil is high to medium(5-6). The presence of continuous pores or channels in soil will increase the mobility of alachlor in soil(7-8). TERRESTRIAL FATE: Volatilization of alachlor from poorly adsorbing moist soil to the atmosphere may be significant if assisted by solar heating and high winds . Volatilization from dry soil may not be significant(1,3). The half-life of alachlor in soil ranges from 4-49 days(1-2,4-7) with an average of 15 days in field soil(7). Alachlor residues may still be found in some soils after 1 yr(6). AQUATIC FATE: Under aerobic conditions, microorganisms in sewage and eutrophic lake water transformed 10-21% of alachlor in 6 weeks . However, no mineralization product was isolated leading to the conclusion that the biotransformation proceeded by cometabolism . The disappearance of alachlor in groundwater free of aquifer materials (e.g., sand) was very slow and the half-life was in the range 808-1518 days . When irradiated with 300 nm sunlamps, 1% alachlor in aqueous solution degraded in 135 mins and the reaction was accelerated by sensitizers . Based on a rate constant for the reaction of alachlor with hydroxyl radicals and the concentration of hydroxyl radicals in a typical eutrophic water , the estimated half-life for this reaction would be 38 days. AQUATIC FATE: The rate of volatilization of alachlor from water will be negligibly small . In a model ecosystem, 98.2% of alachlor transformed to 8 unidentified products in 33 days . Both biotic and abiotic processes are probably important for the loss of alachlor from water. The bioconcentration of alachlor in aquatic organisms will not be important and fish will rapidly depurate alachlor when placed in uncontaminated water . ATMOSPHERIC FATE: From its vapor pressure (2.2X10-5) mm Hg at 25 deg C , alachlor is expected to be present partially in the vapor phase and partially in the particulate form in air . Based on an estimation method , gas phase alachlor may be removed from the atmosphere with a half-life of 2.1 hrs due to reaction with photochemically produced hydroxyl radicals. Partial removal of particulate alachlor from the air may occur by dry deposition. The fact that alachlor has been detected in rainwater(4-5) suggests it will be removed from the atmosphere by wet deposition as well. TERRESTRIAL FATE: It persists in soil 42-70 days, depending on conditions, loss being by microbial metabolism. Ring-(14)C-labeled alachlor and propachlor were studied in a model eco-system. Alachlor was degraded into eight compounds and propachlor into seven compounds. None were identified. In each case some of the material was unextractable. There was no evidence of magnification of the two compounds or their metabolites in the food chain.
Drinking Water Impact In regions where alachlor was used, analysis of selected wells revealed alachlorat 0.10 to 2.11 ug/l with one sample showing 9.1 ug/l. SURFACE WATER: Alachlor was detected at an average concentration of 0.014 ppb and a concentration range trace-0.13 ppb in 12 of 31 river waters in NJ . It was detected at a concn range 0.006-0.900 ppb in water from the Mississippi River and its tributaries in 1988 , while its concentration along the entire Mississippi River ranged not detected-0.840 ppb in 1984 . During 1984-1985, the maximum concn of alachlor in waters from three stations along the Cedar River, Iowa when overland flow was the major component of river discharge exceeded 20 ppb . Alachlor was detected at mean concn 0.75 ppb and 0.71 ppb in water from Upper Tuttle Creek Lake and Lower Tuttle Creek Lake, respectively in Kansas . SURFACE WATER: Alachlor was detected in 0.4% and 1.4% of water from Grand River and Thames River, Ontario, Canada between 1986-1990 . The concn range of alachlor in Honey Creek, Sandusky River and Maumee River during 1983-1986 was none detected-54.8 ppb . The levels of alachlor in three rural ponds in Ontario, Canada were 0.6-15 ppb . The concn of alachlor in one rural pond in Ontario was 960 ppb as a result of an accidental spill . The concn of alachlor in runoff water from a corn-producing area in Ontario, Canada ranged <0.2-37 ppb . The average concn of alachlor on two occasions in runoff water from an agricultural basin in east-central Iowa were 162 ppb and 64 ppb(6). The concn of alachlor in several other surface waters in the U.S. are also available . RAINWATER/FOGWATER: The concn of alachlor in fogwater collected from Beltsville, MD in 1984 was 1.45 ppb . Alachlor was detected in 30 of 79 rainwater samples collected from several cities in New York state at a concn range 0.02-0.62 ppb . GROUNDWATER: A 1984 survey of U.S. groundwater reported detection of alachlor in waters from four (MD, IA, NE, PA) of 23 states with typical concn of 0.1-10 ppb . A more recent data base (1988) developed to compile information about pesticide contamination in U.S. groundwater from normal agricultural use reports detection of alachlor in groundwater from 14 states . Alachlor has been detected in well waters from use areas in the U.S. with a frequency of <1%(7). In one survey, alachlor was detected in 2 of 33 groundwater samples from Florida at an average conc of 62.3 ppb in the two detectable samples . A 1980 screening of 1174 community wells and 617 private wells in WI found alachlor in one well at a concn >10 ppb . It was also detected in well waters in Nebraska with a frequency of <1% and at a concn range not detected-20.7 ppb and a median concn of 0.09 ppb . In an earlier survey, alachlor was detected in 2 of 14 wells from Nebraska at concn of 0.04 ppb . In some cases, artificial recharging of groundwater by farmland runoff may have caused pesticide contamination in Nebraska groundwater(6). GROUNDWATER: During a 1985-1987 Survey of 119 wells, springs and municipal drinking water throughout AR, alachlor was detected in only one irrigation well at a concn of 5.5 ppb . In 1990, 58 private wells in central Maine were monitored for pesticides and alachlor was found in 7 well waters at a maximum conc of 0.36 ppb . In a statewide survey of farmstead wells in KS, alachlor was detected in 1 of 100 wells at a concn 0.88-1.5 ppb(8). In 1984, several private wells in a small town in upstate NY were found to be contaminated with alachlor at a maximum concn of 660 ppb(6). Contamination of well waters from other states including IA, IL, MN, PA, MA and MD has also been reported(7). Several farm wells in Ontario, Canada were found to be contaminated with alachlor and in one well the concn was reported to be >1000 ppb(3-5). DRINKING WATER: Alachlor was detected in the concn range 0.82-2.3 ppb in drinking waters from three New Orleans drinking water plants . It was also detected at a mean concn range 0.47-2.8 ppb in three tap waters in Columbus, OH . During 1982-1985, alachlor was detected at mean concn ranges of 0.9-3.4 and <0.05-2.2 ppb in raw and municipal drinking waters, respectively of an agricultural community in Ontario, Canada .

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