Dimethylisophthalat

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.

SRP: Local exhaust ventilation should be applied wherever there is an incidence of point source emissions or dispersion of regulated contaminants in the work area. Ventilation control of the contaminant as close to its point of generation is both the most economical and safest method to minimize personnel exposure to airborne contaminants.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 36(SRC), determined from a structure estimation method(2), indicates that dimethyl isophthalate is expected to have very high mobility in soil(SRC). Volatilization of dimethyl isophthalate from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 6.1X10-8 atm-cu m/mole(SRC), using a fragment constant estimation method(3). Dimethyl isophthalate is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 9.6X10-3 mm Hg(4). Dimethyl isophthalate, present at 100 mg/L, reached 94 to 102% of its theoretical BOD after 2 weeks using an activated sludge inoculum(5).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 36(SRC), determined from a structure estimation method(2), indicates that dimethyl isophthalate 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 6.1X10-8 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). According to a classification scheme(5), an estimated BCF of 4(SRC), from an estimated log Kow of 1.66(6) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Hydrolysis is not expected to be an important process(SRC) based on estimated hydrolysis half-lives of 350 and 35 days at pHs 7 and 8, respectively(8). Dimethyl isophthalate, present at 100 mg/L, reached 94 to 102% of its theoretical BOD after 2 weeks using an activated sludge inoculum(9).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), dimethyl isophthalate, which has an estimated vapor pressure of 9.6X10-3 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase dimethyl isophthalate 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 25 days(SRC), calculated from its rate constant of 6.4X10-13 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Dimethyl isophthalate does contain chromophores that absorb at wavelengths >290 nm(4) and therefore may be susceptible to direct photolysis by sunlight(SRC).

Using a structure estimation method based on molecular connectivity indices(1), the Koc of dimethyl isophthalate can be estimated to be 36(SRC). According to a classification scheme(2), this estimated Koc value suggests that dimethyl isophthalate is expected to have very high mobility in soil.

/ALTERNATIVE and IN VITRO TESTS/ Comparative toxicity of phthalate esters to HeLa-S3 cells was studied by determining their effect on doubling time of the cells. The toxicity of the esters decreasing in order: diethyl phthalate, butyl phthalyl butyl glycolate, di-iso-butyl phthalate, ethyl phthalyl ethyl glycolate, bis(2-ethylhexyl) phthalate, dimethyl isophthalate, dibutyl phthalate, methyl phthalyl ethyl glycolate, dimethyl phthalate, and dioctyl phthalate.

An estimated BCF of 4 was calculated in fish for dimethyl isophthalate(SRC), using an estimated log Kow of 1.66(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 dimethyl isophthalate is estimated as 6.1X10-8 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that dimethyl isophthalate is expected to be essentially nonvolatile from water surfaces(2). Dimethyl isophthalate is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 9.6X10-3 mm Hg(3).

/LABORATORY ANIMALS: Acute Exposure/ Eye Rabbit 500 mg/26 hr severe toxic effects were observed.

/ALTERNATIVE and IN VITRO TESTS/ To assess the toxicity of dimethyl isophthalate to cells in culture, monolayers of L-cells and chicken embryos cells were overlaid with agar and undiluted dimethyl isophthalate was then applied to paper disks which had previously been placed on the agar overlay. Dimethyl isophthalate was scored as toxic since it created a zone of dead cells in the area adjacent to the test site.

The rate constant for the vapor-phase reaction of dimethyl isophthalate with photochemically-produced hydroxyl radicals has been estimated as 6.4X10-13 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 25 days at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). A base-catalyzed second-order hydrolysis rate constant of 0.23 L/mole-sec(SRC) was estimated using a structure estimation method(2); this corresponds to half-lives of 350 and 35 days at pH values of 7 and 8, respectively(2). Dimethyl isophthalate does contain chromophores that absorb at wavelengths >290 nm(3) and therefore may be susceptible to direct photolysis by sunlight(SRC).

Occupational exposure to dimethyl phthalate may occur through inhalation of aerosols and dermal contact with this compound at workplaces where dimethyl isophthalate is produced or used. Use data indicate that the general population may be exposed to dimethyl isophthalate via dermal contact with and inhalation of products containing this compound. (SRC)