SPECTRUM

Chemical Fact Sheet

Chemical Abstract Number (CAS #) 72435
CASRN 72-43-5
Synonymsp,p'-Methoxychlor
Benzene, 1,1'-(2,2,2-trichloroethylidene)bis[4-methoxy-
1,1,1-Trichloro-2,2-bis(4-methoxyphenyl)ethane
Ethane, 1,1,1-trichloro-2,2-bis(p-methoxyphenyl)-
p,p'DMDT
Methoxcide
Dimethoxy DDT
Metox
Analytical Methods EPA Method 505
EPA Method 508
EPA Method 525.2
EPA Method 617
EPA Method 625
EPA Method 8081
EPA Method 8270
Molecular FormulaC16H15Cl3O2

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

Use VET: ECTOPARASITICIDE AN EXCELLENT REPLACEMENT FOR DDT WHERE APPLICATION MAY CONSTITUTE HAZARD TO WARM-BLOODED ANIMALS OR SUSCEPTIBLE PLANTS. IT IS RARELY PHYTOTOXIC, & INJURY IS NEGLIGIBLE EVEN ON DDT-SUSCEPTIBLE CROPS SUCH AS CUCURBITS. IT IS APPROVED IN US FOR USE ON 78 AGRIC CROPS (INCL SEVERAL TYPES OF SEEDS), WITH RESTRICTIONS ON USE OF TREATED SEEDS. FOR USE AS INSECTICIDE ON BEEF CATTLE, DAIRY CATTLE, GOATS, SHEEP, & SWINE & FOR SPRAY TREATMENT OF BARNS, GRAIN BINS, MUSHROOM HOUSES, & OTHER AGRIC PREMISES . Methoxychlor has been utilized extensively for the control of biting flies in both northern and southern regions of Canada. 0.25-1.0% AS DIP; 0.5-1.0% AS AEROSOL SPRAY--CATS, DOGS, SWINE; 1.0-3.0% AS AEROSOL SPRAY--CATTLE; 1.0-5.0% IN OIL BASE FOR BACKRUBBERS--CATTLE; 2.0-5.0% DUST BAGS--CATTLE HORN FLIES 5.0-50.0% AS SPOT TREATMENT DUSTS ON LIVESTOCK; TABLESPOONFUL DOSES ONLY OF THE 50% CONCN ON CATTLE; UP TO 2.0% DUSTS ON HAMSTERS, MICE, AND RATS; 2.0-5.0% AS A PREMISE SPRAY Insecticide effective against mosquito larvae and house-flies. A contact & stomach insecticide effective against a wide range of pests, but not aphids, in field & forage, fruit & vegetable crops.
Consumption Patterns INSECTICIDE FOR LIVESTOCK & POULTRY, 43%; ALFALFA, 29%; CITRUS, 29% (1982)
Apparent Color PURE METHOXYCHLOR FORMS COLORLESS CRYSTALS ; DIMORPHIC CRYSTALS ; CRYSTALS FROM DIL ALCOHOL ; White to light yellow solid ; A white crystalline solid ; Technical methoxychlor is a pale buff to gray flaky powder
Odor Slightly fruity
Melting Point 89 DEG C
Molecular Weight 345.65
Density 1.41 at 25 DEG C
Odor Threshold Concentration 4.7 mg/kg in water
Sensitivity Data SLIGHTLY IRRITATING TO SKIN.
Environmental Impact Release of methoxychlor to the environment is expected to occur primarily due to its use as an insecticide. Other sources of release may include loss during manufacturing, formulation, packaging, and disposal of methoxychlor. If released to soil, methoxychlor is expected to remain immobilized primarily in the upper layer of soil although a small percentage may migrate to lower depths, possibly into groundwater as suggested by the detection of methoxychlor in some groundwater samples. Under anaerobic conditions, biodegradation appears to be the dominant removal mechanism; however, under aerobic conditions, biodegradation is expected to be less rapid and possibly negligible. Rapid primary degradation of methoxychlor has been observed under anaerobic conditions in flooded soils (half-lives 1 week to < 2 months). Major degradation products under anaerobic conditions are dechlorinated methoxychlor (DMDD) and mono- and di-hydroxy derivatives of methoxychlor and DMDD. Methoxychlor may undergo indirect "sensitized" photolysis on the soil surfaces and it may undergo chemical hydrolysis in moist soils (half-life > 1 year). If released to water, methoxychlor may be removed or transported by several different mechanisms. Methoxychlor may adsorb to suspended solids and sediments or it may bioaccumulate in certain aquatic organisms, although fish are reported to metabolize methoxychlor fairly rapidly. Methoxychlor may undergo direct photolysis (half-life 4.5 months) or indirect "sensitized" photolysis (half-life <5 hours) depending upon the presence of photosensitizers. 1,1-Bis(p-methoxyphenyl)-2,2-dichloroethylene (DMDE) is a major photolysis product of methoxychlor. Volatilization of methoxychlor may be significant (half-life 4.5 days from a shallow river) and methoxychlor may also biodegrade under anaerobic conditions (half-life < 28 days in sediments) or aerobic conditions (half-life >100 days in sediments). Oxidation and chemical hydrolysis are not expected to be significant fate processes. If released to the atmosphere, methoxychlor may exist in either vapor or particulate form. Methoxychlor may undergo reaction with photochemically generated hydroxyl radicals (estimated vapor phase half-life 3.7 hours) or physical removal by settling out or washing out in precipitation. The most probable route of exposure to methoxychlor would be inhalation or dermal contact during home use of this insecticide, inhalation of airborne particulate matter containing methoxychlor or ingestion of food or drinking water contaminated with methoxychlor. The US Food and Drug Administration (FDA) estimated average daily intake of methoxychlor Fiscal year 1981/1982 0.004 ug/kg body wt day.
Environmental Fate Terrestrial Fate: The persistence and disappearance (washoff or dryfall) of methoxychlor from mature soybean foliage was investigated in a small field plot study under natural rainfall conditions in 1977 and 1978. Methoxychlor washoff rate was 8 or - 4% of the amount on plants (prior to rain) per cm of rainfall, regardless of time after application. Total seasonal washoff for 1978 accounted for 33.5% of the applied pesticide; however, 30.5% of the total loss was removed by washoff on the second day after application. Dryfall or dislodgeable residue accounted for less than 1% of the amt applied. The amt of dryfall was greater in plots entered by workers than in those where entry was avoided. TERRESTRIAL FATE: If released to soil, methoxychlor is expected to remain immobilized primarily in the upper layer of soil, although a small percentage may migrate to lower depths, possibly into groundwater as suggested by the detection of methoxychlor in some groundwater samples. Under anaerobic conditions, biodegradation appears to be the dominant removal mechanism; however, under aerobic conditions biodegradation is expected to be less rapid. Under anaerobic conditions major degradation products are dechlorinated methoxychlor (DMDD) and mono- and dihydroxy- (dimethylated) derivatives of methoxychlor and DMDD. Methoxychlor may undergo indirect "sensitized" photolysis on the soil surfaces and it may undergo chemical hydrolysis in moist soils (half-life approx 1 year). Methoxychlor underwent rapid primary degradation in 4 types of flooded soil under anaerobic conditions (half-life 1 week to 2 months), but degraded less rapidly under aerobic conditions in 4 types of upland soil (half-life >3 months) . After 100 days incubation in a soil, negligible degradation of methoxychlor was observed under aerobic conditions and 73% degradation was observed under anaerobic conditions . AQUATIC FATE: If released to water, methoxychlor may be removed or transported by several different mechanisms. Methoxychlor may adsorb to suspended solids and sediments or it may be taken up and bioaccumulate in some aquatic organisms, although fish are reported to metabolize methoxychlor fairly rapidly. Methoxychlor may undergo direct photolysis (half-life 4.5 months) or indirect "sensitized" photolysis (half-life= 5 hours) depending upon the presence of photosensitizers. 1,1-Bis(p-methoxyphenyl)-2,2-dichloroethylene (DMDE) is a major photolysis product of methoxychlor. Methoxychlor may volatilize significantly (calculated half-life 4.5 days from a shallow river) and it may biodegrade under anaerobic conditions (half-life < 28 days) or aerobic condition (half-life >100 days) in sediments. Under anaerobic conditions major degradation products are dechlorinated methoxychlor (DMDD) and mono- and dihydroxy derivatives of methoxychlor and dechlorinated methoxychlor. Oxidation and chemical hydrolysis are not expected to be significant fate processes. ATMOSPHERIC FATE: If released to the atmosphere, methoxychlor may exist in either vapor or particulate form. It may undergo reaction with photochemically generated hydroxyl radicals (estimated vapor phase half-life = 3.7 hours) or be physically removed by settling out or washing out in precipitation. ATMOSPHERIC FATE: Wind erosion of methoxychlor-contaminated earth is a route by which the pesticide can enter the atmosphere. TERRESTRIAL FATE: Methoxychlor is a moderately persistent compound. Residues have been demonstrated to remain in the soil for up to 14 months.
Drinking Water Impact Methoxychlor was added to the head waters of the Twin Falls Canal Co canal system (0.3 ppm) and subsequently determined in water at a location approx 75 miles away by gas-liquid chromatography. Methoxychlor residues peaked at the sampling site at 45-46 hr after most of the applications. The highest residue level at that time was 1.4 ppb; the mean peak level was 1.1 ppb. SURFACE WATER: During July 1981, methoxychlor was detected in subsurface water taken from the Niagara River, 5 samples, 1 pos, 0.0010 ppb detected . During 1980-81, in surface water taken from Niagara-on-the-Lake, 75 samples, 5 pos, 0.1 ppt mean concn detected . During July 1976, in James River near Hopewell, VA, trace amounts (<8 ppt) detected . During 1974-75 in Lake Superior, 16 samples, 0.02 ppb max. concn detected, 0.015 ppb mean concn detected . During 1971-72 in tributary of Lake Michigan, 2.9-89.1 ppt methoxychlor detected . In 1983, methoxychlor was found in 11 of 14 samples taken from Lake Ontario, at a maximum concn of 0.086 ng/L(6). GROUNDWATER: Methoxychlor has qualitatively been identified in groundwater in NJ and CA . During 1978, methoxychlor was identified in groundwater below irrigated farmland in Nebraska at concn ranging from well below detection limits to 0.01 ppb . Methoxychlor was detected in 0.7% of groundwater samples taken at CERCLA waste sites (<500 sites tested) and 0.8% of samples at RCRA sites (>1,500 sites) . DRINKING WATER: Methoxychlor was detected in drinking water supplies in rural SC: Chesterfield County, 45.8% pos, concn range ND-312 ppb, mean concn. 33 ppt, Hampton County, 63.6% pos, concn range ND-100 ppb, mean concn 23 ppt .

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