Merphos

298.502

298.51

205-761-4

RN743HTX76

27720

3278|2903

DTXSID6024173

PALE AMBER LIQUID

2931900090

75.9

8.70

Emulsifiable oil.

0.99-1.01 g/cm³ @ Temp: 20 °C

100 °C

115-134 °C @ Press: 0.08 Torr

295 DEG F

INDEX OF REFRACTION: 1.55 @ 20 °C/D

SOL IN ACETONE, ETHYL ALCOHOL, BENZENE, HEXANE, KEROSENE, DIESEL OIL, HEAVY AROMATIC NAPHTHAS, XYLENE, METHYLATED NAPHTHALENE

1.2E-05mmHg at 25°C

MILD CHARACTERISTIC ODOR

No rapid reaction with air. No rapid reaction with water.

Sulfides, Organic

Organothiophosphates, such as MERPHOS, are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrides. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides.

III

6.1(b)

3278

TG5600000

P264, P270, P301+P312, P330, P501

H302

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

USEPA/OHEA; Health & Environmental Effects Profile for Merphos Oxide (1988)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]: Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Containers may explode when heated. Runoff may pollute waterways. (ERG, 2016)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]: SMALL FIRE: Dry chemical, CO2 or water spray. LARGE FIRE: Water spray, fog or regular foam. Move containers from fire area if you can do it without risk. Dike fire-control water for later disposal; do not scatter the material. Use water spray or fog; do not use straight streams. FIRE INVOLVING TANKS OR CAR/TRAILER LOADS: Fight fire from maximum distance or use unmanned hose holders or monitor nozzles. Do not get water inside containers. Cool containers with flooding quantities of water until well after fire is out. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks engulfed in fire. For massive fire, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from area and let fire burn. (ERG, 2016)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]: As an immediate precautionary measure, isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids. SPILL: See ERG Table 1 - Initial Isolation and Protective Action Distances on the UN/NA 3278 datasheet. FIRE: If tank, rail car or tank truck is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2016)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]: Do not touch damaged containers or spilled material unless wearing appropriate protective clothing. Stop leak if you can do it without risk. Prevent entry into waterways, sewers, basements or confined areas. Cover with plastic sheet to prevent spreading. Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. DO NOT GET WATER INSIDE CONTAINERS. (ERG, 2016)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]: Wear positive pressure self-contained breathing apparatus (SCBA). Wear chemical protective clothing that is specifically recommended by the manufacturer. It may provide little or no thermal protection. Structural firefighters' protective clothing provides limited protection in fire situations ONLY; it is not effective in spill situations where direct contact with the substance is possible. (ERG, 2016)|FOR PROTECTION DURING APPLICATION WEAR HAT, LONG-SLEEVED SHIRT, TROUSERS. IN ADDITION, MIXER/LOADERS MUST WEAR RUBBER OR NEOPRENE GLOVES.

SLIGHT, WHEN EXPOSED TO HEAT OR FLAME. ...CAN REACT VIGOROUSLY WITH OXIDIZING MATERIALS.

Merphos was found in only 1 of 2479 (0.04%) air samples taken between 1970 and 1972 as part of a national pesticide air monitoring program(1). The positive sample contained 8.8 ng/cu m of merphos and was from North Memphis, TN in 1971(1) and was 275 m from a formulation plant(2).

LD50 Rabbit percutaneous 5-10 g/kg|LD50 Rat oral male 1,475 mg/kg|LD50 Rat oral female 910 mg/kg|LD50 Rat dermal male 690 mg/kg|For more Non-Human Toxicity Values (Complete) data for MERPHOS (7 total), please visit the HSDB record page.

Merphos will be released to the environment as a result of its use as a defoliant on cotton preparatory to machine harvesting(1,2) for which it is used as an aqueous emulsion(3). It may also be released during its production, transport, formulation, and disposal.

TERRESTRIAL FATE: If released on soil, merphos would be expected to adsorb strongly to soil(1,SRC) and be oxidized to S,S,S-tributyl phosphorotrithioate (DEF)(2).|AQUATIC FATE: If released in water, merphos will be oxidized to S,S,S-tributyl phosphorotrithioate (DEF). In th Little Miami River, complete oxidation to DEF occurred within an hour(1). The fact that merphos is expected to adsorb strongly to particulate matter in the water column (estimated Koc of 62,000 from structure(2)), apparently did not impede its oxidation(SRC).|ATMOSPHERIC FATE: If released into the atmosphere during spraying operations, merphos will exist as an aerosol and be removed by gravitational settling and be readily oxidized to S,S,S-tributyl phosphorotrithioate (DEF) in the drifting spray(2). Vapor-phase merphos will react with photochemically-produced hydroxyl radicals, with an estimated half-life of 4.9 hr(1).

Water slowly hydrolyzes merphos with the formation of butyl mercaptan, a reaction that is catalyzed by base(6). Merphos will also be oxidized in aerated water. The P(III) to P(V) oxidation is known to be a rapid one, requiring only the presence of oxygen(1). When 1 ug/L of merphos was added to raw water from the Little Miami River, all the merphos was oxidized to S,S,S-tributyl phosphorotrithioate (DEF) within an hour(2). Merphos has a UV absorption band at 304 nm that extends to about 340 nm(3) and therefore merphos may undergo direct photolysis. In field transformation studies of merphos in spray drift, all of the merphos was oxidized to DEF by the time the spray drift had reached the first sampling station, which the authors say indicates a half-life of the order of seconds(1). The authors did not indicate that measures were taken to assure that the merphos was not oxidzed during sampling and analysis, which would affect their results of a half-life of the order of seconds(SRC). In the atmosphere, merphos will exist primarily as the vapor(4). There it will react with photochemically-produced hydroxyl radicals with a rate constant of 78.8X10-12 cu cm/molecule-s(5). Assuming a hydroxyl radical concn of 5X10+5 radicals/cu cm, the half-life of merphos in the atmosphere is estimated to be 4.9 hr(SRC). It is also slowly oxidized by the oxygen in air to tributyl trithiophosphate(6).

Using an estimated log Kow of 7.67(1), one would estimate a BCF of 40,000 for merphos using a recommended regression equation(2). This would indicate that merphos would bioconcentrate in aquatic organisms. However, merphos' rapid oxidation in water would suggest little tendency to bioconcentrate(SRC).

The Koc for merphos estimated from molecular structure is 62,000(1). According to a suggested classification scheme(2), this estimated Koc suggests that merphos would be immobile in soil(SRC).

The Henry's Law constant for merphos estimated from structure activity relationships is 2.27X10-5 atm-cu-m/mol(1). Using this value for the Henry's Law constant, one can estimate a volatilization half-life for merphos of 3.0 days in a model river 1 m deep flowing at 1 m/s with a wind speed of 3 m/s(2,SRC). Similarly, the volatilization half-life of merphos from a model lake 1 m deep, with a 0.05 m/s current and a 0.5 m/s wind is estimated to be 27 days(2,SRC).

Merphos was not detected in any of the 434 wells sampled according to EPA's Pesticides in Ground Water Database(1). Merphos was not detected in any of the 54 wells, primarily municipal supply systems for urban and residential use, in the early 1980s(2).

Merphos was detected in food in FDA's adult Total Diet Study in FY78-82(1). While the commodity group, number of detections and concentration levels were not reported, fewer than 10 of the 1044 composite samples contained the pesticide(1). Merphos was detected in 9 of 6391 domestic agricultural commodities during surveillance sampling between FY82 and FY86(2). The distribution of the residue concentrations were (concentration range in ppm, number): 0.05-0.10, 1; 0.10-0.50, 3; 0.50-1.0, 2; >2.0, 3(2). Of these, 7 samples exceeded EPA's tolerance(2). During the same time period, merphos residues were not found in samples of 12,044 imported agricultural commodities(2).

Exposure to merphos would be primarily occupational, especially by inhalation of aerosols or by dermal contact during application. Merphos has been detected in some food and therefore the general population may be exposed to merphos in their diet. (SRC)

3. 3= MODERATELY TOXIC: PROBABLE ORAL LETHAL DOSE (HUMAN) 0.5-5 G/KG, BETWEEN 1 OZ & 1 PINT (OR 1 LB) FOR 70 KG PERSON (150 LB).

Merphos is readily absorbed through the skin.

TOPICAL ADMIN CAUSED MORE PROLONGED INHIBITION OF PLASMA BUTYRYLCHOLINESTERASE ACTIVITY THAN ORAL ADMIN. ORAL MERPHOS WAS RAPIDLY METABOLIZED IN GI TRACT DIRECTLY TO N-BUTYL MERCAPTAN OR FOLLOWING ITS OXIDATION TO S,S,S-TRIBUTYL PHOSPHOROTRITHIOATE. N-BUTYL MERCAPTAN APPARENTLY CAUSED THE LATE ACUTE TOXIC EFFECTS. TOPICALLY ADMIN MERPHOS, WHICH WAS NOT METAB IN GI TRACT, CAUSED DELAYED NEUROTOXICITY BUT DID NOT PRODUCE A LATE ACUTE EFFECT.

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]: Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution. (ERG, 2016)

Excerpt from ERG Guide 151 [Substances - Toxic (Non-combustible)]: Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves. Move victim to fresh air. Call 911 or emergency medical service. Give artificial respiration if victim is not breathing. Do not use mouth-to-mouth method if victim ingested or inhaled the substance; give artificial respiration with the aid of a pocket mask equipped with a one-way valve or other proper respiratory medical device. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. For minor skin contact, avoid spreading material on unaffected skin. Keep victim calm and warm. Effects of exposure (inhalation, ingestion or skin contact) to substance may be delayed. (ERG, 2016)

A CASE OF DELAYED NEUROTOXICITY IN 28-YR-OLD MAN WHO ACCIDENTALLY SPLASHED MERPHOS ON HIS BARE ARMS OVER A PERIOD OF 3 DAYS WHILE WORKING WITH THE DEFOLIANT. APPROX 14 DAYS AFTER EXPOSURE, COMPLETE FACIAL DIPLEGIA DEVELOPED. ELECTROMYOGRAPHY DEMONSTRATED DECREASED VOLTAGE OF MUSCLE ACTION POTENTIAL, DELAYED CONDUCTION VELOCITY IN MOTOR NERVE FIBERS, INCREASED INSERTIONAL ACTIVITY, AND DENERVATION POTENTIALS. HE RECOVERED COMPLETELY.|S,S,S-Tributyl phosphorotrithioate and merphos can produce delayed neurotoxicity in animals. Inhibition of the neurotoxic esterase in lymphocytes was measured in 7 workers exposed during aerial and ground application of these defoliants on cotton fields as was peripheral nerve function. The major route of exposure was via the skin. Lymphocyte neurotoxic esterase was affected in exposed workers according to both intensity and length of exposure. There were no detectable electrophysiological effects. Measurement of neurotoxic esterase in lymphocytes in workers exposed to organophosphates is a rational biomonitor of delayed neuropathy.

Folex

TECHNICAL PRODUCT IS GREATER THAN OR EQUAL TO 95% PURE.|'Folex cotton defoliant' (720 g active ingredient/L)|EMULSIFIABLE CONCENTRATE (6 LB/GALLON).

Phosphorotrithious acid, tributyl ester: ACTIVE|PMN - indicates a commenced PMN (Pre-Manufacture Notices) substance.|Merphos' registration has been cancelled.

AOAC Method 991.07. Nitrogen- and Phosphorus-containing pesticides in finished drinking water. GC with N-P detector. Estimated method detection limit 5.0 ug/L.

Agrochemicals -> Plant Growth Regulators|HERBICIDES