tetraethyl silicate

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), tetraethyl silicate, which has a vapor pressure of 1.88 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase tetraethyl silicate 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 16 hours(SRC), calculated from its rate constant of 2.5X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Tetraethyl silicate does not contain chromophores that absorb at wavelengths >290 nm(4) and therefore is not expected to be susceptible to direct photolysis by sunlight(SRC).

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

An estimated BCF of 3 was calculated for ethyl silicate(SRC), using an estimated log Kow of 0.04(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 tetraethyl silicate is estimated as 2.0X10-5 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that tetraethyl silicate may volatilize from water surfaces(2). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(2) is estimated as 2.9 days(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 25 days(SRC). Henry's Law constant of tetraethyl silicate indicates that volatilization from moist soil surfaces may occur(SRC). Tetraethyl silicate may volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 1.88 mm Hg(3).

The rate constant for the vapor-phase reaction of tetraethyl silicate with photochemically-produced hydroxyl radicals has been estimated as 2.5X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 16 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Tetraethyl silicate is expected to undergo hydrolysis in the environment similar to most alkoxysilanes(2). Tetraethyl silicate is reported to hydrolyze in aqueous conditions(3). Tetraethyl silicate does not contain chromophores that absorb at wavelengths >290 nm(4) and therefore is not expected to be susceptible to direct photolysis by sunlight(SRC).

Tetraethyl silicate's production and use as a chemical sol-gel(1,2), and in casting(3) and glass frosting(1) processes may result in its release to the environment through various waste streams(SRC).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 10,422 workers (2,566 of these were female) were potentially exposed to tetraethyl silicate in the US(1). Occupational exposure to tetraethyl silicate may occur through inhalation and dermal contact with this compound at workplaces where it is produced or used. It is unlikely that the general population would be exposed to tetraethyl silicate as it is primarily used in weatherproofing mortar and cements or in a manufacturing or research setting, and it hydrolyzes upon contact with water(SRC).

Tetraethyl silicate's production and use in the sol-gel, casting and glass frosting processes may result in its release to the environment through various waste streams; its use as a weatherproofing and protective coating agent may result in its direct release to the environment. If released to air, a vapor pressure of 1.88 mm Hg at 25 °C indicates tetraethyl silicate will exist solely in the vapor phase in the atmosphere. Vapor-phase tetraethyl silicate will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 16 hours. Tetraethyl silicate does not contain chromophores that absorb at wavelengths >290 nm and therefore is not expected to be susceptible to direct photolysis by sunlight. If rele...

irritation eyes, nose; In Animals: lacrimation (discharge of tears); dyspnea (breathing difficulty), pulmonary edema; tremor, narcosis; liver, kidney damage; anemia

Rats fed a dextrose-casein type of diet adequate for normal growth and containing 2% of tetraethylorthosilicate were used to study the effect of sodium chloride and sodium sulfate drinking waters & dietary additions of chloride, sulfate & phosphate on formation of silica urinary calculi. 50% of rats fed the basal-tetraethylorthosilicate diet (2%) developed silica urinary calculi. Addition of 0.2 eq/kg diet of chloride, sulfate or phosphate as sodium salts (phosphate was an equal molar mixture of mono- and dibasic sodium phosphates) resulted in a reduction in silica urinary calculi (P <0.05) by dietary chloride (15% incidence) and phosphate (5% incidence) but not by sulfate (35% incidence).

Eyes, respiratory system, liver, kidneys, blood, skin

LCLo (rat) = 1,000 ppm/4H

Nephrotoxin - The chemical is potentially toxic to the kidneys in the occupational setting.

inhalation, ingestion, skin and/or eye contact

LD50 Rabbit skin 5878 mg/kg

In persons with impaired pulmonary function, especially those with obstructive airway diseases, the breathing of ethyl silicate might cause exacerbation of symptoms due to its irritant properties. ... Persons with pre-existing blood disorders may be more susceptible to the effects of this agent. ... Persons with pre-existing skin disorders may be more susceptible to the effects of this agent.

Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Early intubation at the first sign of upper airway obstruction may be necessary. Positive-pressure ventilation techniques with a bag-valve-mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's (LR) if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Consider vasopressors if patient is hypotensive with a normal fluid volume. Watch for signs of flu...