Bis(1-methylethyl)methylphosphonat

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.

The IR and UV laser induced photodestruction of diisopropyl methylphosphonate ... was /examined/. The excimer lasers ArF (193 nm), KrF (248 nm), XeCl (308 nm), quadrupled Nd:YAG (266 nm) and pulsed CO2 laser were used. Samples were irradiated in the vapor and liquid phases. Photodissociation was observed at all irradiation wavelengths, being most efficient when ArF irradiated diisopropyl methylphosphonate /was/ in the vapor phase in the air or O2. Pulsed, focused CO2 radiation led to multiple photon dissociation and pyrolytic destruction. Light hydrocarbon gases were the principal decomposition products. H2, CO, CO2 and water were also detected. The residual liquid is likely to be a P bearing acid.

Effective procedures associated with storage and disposal of chemical warfare (CW) agents are important for the protection of civilian populations from inadvertent release of these agents. Emergency groups as well as citizens in surrounding communities need to know the relative effectiveness of various chemical protective clothing (CPC) ensembles in the unlikely event of such releases. A method has beeen developed for studying permeation of chemical warfare agent simulants through chemical protective clothing materials. The experimental results characterize some commercially available chemical protective clothing materials. Thirteen different chemical protective clothing materials having widely differing compositions were chosen to study the permeation of four different liquid chemical warfare simulants (dimethyl methyl phosphonate, diisopropyl methyl phosphonate, malathion, and dibutyl sulfide) through these chemical protective clothing materials at 25 °C. This permeation study involved a newly developed analytical technique employing room temperature fluorescence quenching of an indicator compound, phenanthrene, on filter paper. Various experimental factors such as breakthrough time, rate of permeation and uptake were investigated. on the basis of breakthrough time, the 13 chemical protective clothing materials could be divided into three groups: most resistant, moderately resistant, and least resistant. Materials in the most resistant category exhibited no permeation by any of the simulants for at least 24 hours. Breakthrough occurred in the least resistant materials in generally less than an hour, and sometimes as soon as a few minutes.

0.34 [mg/m3]

3.7 [mg/m3]

22 [mg/m3]

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 87(SRC), determined from a log Kow of 1.03(2) and a regression-derived equation(3), indicates that diisopropyl methylphosphonate is expected to have high mobility in soil(SRC). Volatilization of diisopropyl methylphosphonate from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 4.4X10-5 atm-cu m/mole(SRC), derived from its vapor pressure, 0.28 mm Hg(5), and water solubility, 1.5X10+3 mg/l(5). One volatilization study indicated that 5% and 22% of diisopropyl methylphosphonate applied to dry and moist soil, respectively, volatilized in 10 days(4). Biodegradation in soil is extremely slow; reported half-lives are 1 and 3 years, for acclimated and unacclimated soil, respectively(6). When 1 mg samples of sarin (GB) (containing diisopropyl methylphosphonate as an impurity) were placed on a snow surface and analyzed for persistence after 2 and 4 weeks, the diisopropyl methylphosphonate in the samples were in the range of 10-100% of the initial concns at both sampling periods(7). Diisopropyl methylphosphonate deposited on soil and maintained in an environmental chamber at 25 °C under tungsten light had an half-life of 26 to 28 days(4). The most likely process responsible for the loss of diisopropyl methylphosphonate is volatilization(4). The half-lives after deposition on foliar surfaces under 65% full sunlight, as opposed to tungsten light, was 4.2 days and 3.6 days for tall fescue grass and short-needle pine, respectively(8). The decreased half-life in grass versus soil may have resulted from increased volatilization due to increased surface area of grass compared with soil or the contribution of an enzymatically-mediated degradative process(8).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 87(SRC), determined from a log Kow of 1.03(2) and a regression-derived equation(3), indicates that diisopropyl methylphosphonate is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 4.4X10-5 atm-cu m/mole(SRC), derived from its vapor pressure, 0.28 mm Hg(7), and water solubility, 1.5X10+3 mg/l(7). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 31 hrs and 13 days, respectively(SRC). Diisopropyl methylphosphonate does hydrolyze, primarily by a base-catalyzed reaction resulting in isopropanol and isopropyl methylphosophonate(4). Using data from two studies(4,9) and extrapolation(SRC), hydrolysis is very slow and will not be important at environmental pHs and temperatures. One study indicated that biodegradation did not occur in natural water during a 12 week period(8). According to a classification scheme(5), an estimated BCF of 1.2(SRC), from its log Kow(2) and a regression-derived equation(6), suggests the potential for bioconcentration in aquatic organisms is low.

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), diisopropyl methylphosphonate, which has a vapor pressure of 0.28 mm Hg at 25 °C(2), is expected to exist solely in the vapor-phase in the ambient atmosphere. Vapor-phase diisopropyl methylphosphonate is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 5 hrs(SRC), calculated from its rate constant of 8.0X10-11 cu cm/molecule-sec at 25 °C(3) determined using a structure estimation method(3). Diisopropyl methylphosphonate does not absorb radiation >290 nm; therefore, direct photolysis cannot occur(4). Indirect photolysis is insignificant in regard to diisopropyl methylphosphonate's environmental fate in Rocky Mountain Arsenal water; diisopropyl methylphosphonate did not photolyze in either distilled or Rocky Mountain Arsenal water, when exposed to light (>290 nm) for 232 hours (9.7 days)(5).

Although no concns were reported, some uptake of diisopropyl methylphosphonate does appear to occur in plants. Sugar beet, carrot, wheat, and bean plants grown both hydroponically and in soil showed slight bioconcentration relative to the growth medium. Wheat leaves (soil grown) had a BCF of 11.0, the highest of all the plants(3). Repeated application of irrigation water contaminated with diisopropyl methylphosphonate may result in the absorption, translocation, and bioconcentration of diisopropyl methylphosphonate in plant tissue(2). When applied to sugar beet leaves, diisopropyl methylphosphonate was absorbed and translocated to all parts of the plant (except new leaves) after 72 hours. However, diisopropyl methylphosphonate did not translocate when applied to corn leaves. The observation that bioconcentration in plants is low may be a result of metabolism, which is known to occur in mammals and birds(1,4).

Diisopropyl methylphosphonate (DIMP)

8 x 10 ^-2 mg/kg-day

The Koc of diisopropyl methylphosphonate is estimated as 87(SRC), using a log Kow of 1.03(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that diisopropyl methylphosphonate is expected to have high mobility in soil. A 13% reduction in diisopropyl methylphosphonate concn occurred when diisopropyl methylphosphonate-containing medium was circulated for 32 days in a soil percolator to acclimate the soil microorganisms(5). The investigators speculated that adsorption, rather than biodegradation, was responsible for the diisopropyl methylphosphonate reduction because no further diisopropyl methylphosphonate loss occurred during an additional 18 weeks of operation(5). The mobility of diisopropyl methylphosphonate in soil is evidenced by the detection of diisopropyl methylphosphonate in groundwater at the Rocky Mountain Arsenal(4,6). The source of contamination was a waste-disposal pond.

More than 5000 passengers of Tokyo subway trains were injured with toxic chemicals including the nerve gas sarin. Most of the victims examined had marked miosis and decreased serum cholinesterase activity. To monitor the genetic aftereffects of sarin exposure, we measured sister chromatid exchanges (SCEs) of the victims using peripheral blood lymphocytes. The frequency of sister chromatid exchanges was significantly higher in the victims than in the control group. Analyzing results using samples of urine from the victims suggested that the victims were exposed to not only sarin per se, but by-products of sarin synthesis, i.e. diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP) and ethyl isopropyl methylphosphonate (EIMP). Thus, the in vitro SCE-inducing effect of diisopropyl methylphosphonate, diethyl methylphosphonate and ethyl isopropyl methylphosphonate was examined using human lymphocytes and we obtained positive results.

... Diisopropyl methylphosphonate is a by product of the manufacture of /nerve agent/ sarin.

Diisopropyl methylphosphonate is not produced commercially. It is a byproduct in the production of the chemical agent sarin (GB), constituting up to 20% of the chemical agent(1,2), and may also be used to simulate G-type chemical agents(3), and may be released to the environment through various waste streams.

No biodegradation was observed when diisopropyl methylphosphonate was incubated in natural water for 12 weeks or in aqueous medium inoculated with soil microorganisms for 6 weeks(1). Additionally, diisopropyl methylphosphonate degradation was not observed when other carbon sources such as glucose, glycerol and succinate were added to the medium. When diisopropyl methylphosphonate was incubated in soil at 25 degC, slow biodegradation occurred as was evidenced by the evolution of 14-CO2(1). Approximately 1.5% and 5% of the carbon was released as CO2 after 17 weeks in unacclimated and acclimated soil, respectively. The rate limiting step is the enzymatic hydrolysis of diisopropyl methylphosphonate to isopropyl methylphosphonic acid. The estimated half-lives are 1 and 3 years in acclimated and unacclimated soil, respectively(1). When the soil temperature was reduced to 10 degC, no biodegradation was observed. Another soil sample released 13.4% of its original activity as CO2 after 34 weeks of incubation, indicating a half-life of 2 years(1).

A byproduct from the manufacture of the nerve-agent Sarin (constitutes up to 20% of Sarin); [HSDB]

May be used to simulate G-type chemical agents

Phosphonic acid, P-methyl-, bis(1-methylethyl) ester: ACTIVE

Diisopropyl methylphosphonate is a byproduct from the manufacture of the nerve-agent Sarin

Constitutes up to 20% of Sarin