Demeton-S

Fresh air, rest. Artificial respiration may be needed. Refer for medical attention.

Remove contaminated clothes. Remove contaminated clothes. Rinse and then wash skin with water and soap. Refer for medical attention .

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Give a slurry of activated charcoal in water to drink. Rest. Refer for medical attention .

Biological Exposure Indices (BEI) [ACGIH] - Acetylcholinesterase activity in red blood cells = 70% of individual's baseline; Butylcholinesterase activity in serum or plasma = 60% of individual's baseline; Sample at end of shift; [TLVs and BEIs]

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.

Personal protection: chemical protection suit including self-contained breathing apparatus. Do NOT let this chemical enter the environment. Collect leaking liquid in sealable containers. Absorb remaining liquid in sand or inert absorbent. Then store and dispose of according to local regulations.

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value of 70 measured in an unspecified soil(2), indicates that demeton-S is expected to have high mobility in soil(SRC). Volatilization of demeton-S from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 4.9X10-8 atm-cu m/mole (SRC) derived from its vapor pressure, 2.6X10-4 mm Hg(4), and water solubility, 2,000 mg/L(3). Volatilization from dry soil is not expected(SRC) based on the vapor pressure(3). Demeton-S was photolyzed 69, 74, and 24% when incorporated into 3 different soils and irradiated in natural sunlight for 8 days(4), suggesting direct or indirect photolysis may be an important fate process for this compound on soil surfaces(SRC). The half-life of demeton-S-methyl in soil was reported as 26 days(5), suggesting that demeton-S may be susceptible to biodegradation in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), a Koc value of 70 measured in soil(2), indicates that demeton-S is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 4.9X10-8 atm-cu m/mole (SRC) derived from its vapor pressure, 2.6X10-4 mm Hg(4), and water solubility, 2,000 mg/L(4). According to a classification scheme(5), an estimated BCF of 11(SRC), from its water solubility(4) and a regression-derived equation(3), suggests the potential for bioconcentration in aquatic organisms is low(SRC). The chemical hydrolysis half-life of demeton-S was reported as 53 days at pH 5.7 and 27 °C, with 1,2-bis(ethylthio)ethane identified as its major hydrolysis byproduct(6). Demeton-S was photodegraded when applied to soil surfaces and exposed to natural sunlight(7), suggesting that pholysis may be an important environmental fate process(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), demeton-S, which has a vapor pressure of 2.6X10-4 mm Hg at 25 °C(2), is expected to exist in both the vapor and particulate phase. Vapor-phase demeton-S is degraded in the atmosphere by reaction with photochemically generated hydroxyl radicals. The half-life for this reaction in air is estimated as 5 hours from its rate constant of 8X10-11 cm/molec-sec(SRC), derived using a structure estimation method(3). Particulate-phase demeton-S may be removed from the air by wet or dry deposition(SRC). Demeton-S was photodegraded when applied to soil surfaces and exposed to natural sunlight(4), suggesting photolysis in the atmosphere is possible(SRC).

Dizziness. Nausea. Vomiting. Pupillary constriction, muscle cramp, excessive salivation. Laboured breathing. Convulsions. Unconsciousness.

MAY BE ABSORBED! Muscle twitching. Further see Inhalation.

Redness. Redness. Pain.

Abdominal cramps. Diarrhoea. Further see Inhalation.

This substance may be hazardous to the environment. Special attention should be given to fish and bees. This substance does enter the environment under normal use. Great care, however, should be taken to avoid any additional release, for example through inappropriate disposal.

An estimated BCF of 8 was calculated in fish for demeton-S(SRC), using a water solubility of 2,000 mg/L(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC).

The Henry's Law constant for isosystox is estimated as 4.9X10-8 atm-cu m/mole(SRC) derived from its vapor pressure, 2.6X10-4 mm Hg(1), and water solubility, 2,000 mg/L(1). This Henry's Law constant indicates that isosystox is expected to be essentially nonvolatile from moist soil and water surfaces(2). Isosystox is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(1).

/LABORATORY ANIMALS: Acute Exposure/ The daily administration of 0.75 mg/kg of Demeton-S for 3 days caused a progressive decrease in the cholinesterase activity of the brain, serum and submaxillary glands

/LABORATORY ANIMALS: Subchronic or Prechronic Exposure/ Groups of 12 to 18 female rats fed 50 ppm (48% Demeton-S) for 16 weeks showed signs of poisoning and the growth-rate was affected. No histological changes were observed. Groups receiving 10 and 20 ppm showed severe inhibition of the brain and blood cholinesterase activity, while 3 ppm still gave 30% inhibition of blood cholinesterase activity. One ppm did not cause significant inhibition.

/LABORATORY ANIMALS: Subchronic or Prechronic Exposure/ With daily doses of 2.5 mg of demeton (30% Demeton-S per kg body-weight) for 48 days, no toxic changes were observed (10 animals), but there was an inhibition of blood cholinesterase activity.

/OTHER TOXICITY INFORMATION/ The IC50s for inhibition of cortical AChE activity were: parathion, 390 uM; paraoxon, 0.005 uM; malathion, 210 uM; malaoxon, 0.036 uM; demeton-S, 2.9 uM; DFP, 0.52 uM; and echothiophate, 0.006 uM. The IC50s for inhibition of hippocampal AChE activity were: parathion, 180 uM; paraoxon, 0.003 uM; malathion, 160 uM; malaoxon, 0.035 uM; demeton-S, 1.9 uM; DFP, 0.55 uM; and echothiophate, 0.004 uM. Disulfoton did not inhibit AChE activity over the tested concentration range. Only echothiophate competed with QNB /(quinuclidinyl benzilate, a muscarinic antagonist)/ binding and only at concentrations >100 uM. All organophosphates competed with CD /(cis-methyldioxolane, an agonist that binds to a subtype of muscarinic receptors)/ binding. The inhibition constants (Kis) for inhibition of CD binding in rat cortical membranes ranged from 0.004 to 51 uM, echothiophate being the most potent and parathion the least potent. The Kis in the hippocampal membranes varied from 0.004 to 25 uM, echothiophate being the most potent inhibitor and parathion the least potent. The IC50s for inhibition of AChE activity and Kis for competing with CD binding were significantly correlated in both tissues.

The rate constant for the vapor-phase reaction of demeton-S with photochemically-produced hydroxyl radicals has been estimated as 8X10-11 cu cm/molec-sec(SRC), using a structure estimation method(1). This corresponds to an atmospheric half-life of 5 hours at a hydroxyl radical concentration of 5X10+5 hydroxyl radicals per cu cm(1). The chemical hydrolysis half-life of demeton-S was reported as 53 days at pH 5.7 and 27 °C, with 1,2-bis(ethylthio)ethane identified as its major hydrolysis byproduct(2). The half-life increased to 347 days at 15 °C(2). Demeton-S was photolyzed 69, 74, and 24% when incorporated into 3 different soils and irradiated in natural sunlight for 8 days(3), suggesting direct or indirect photolysis may be an important fate process for this compound(SRC).