Butyl Stearate

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.

8 hr Time Weighted Avg (TWA): 10 mg/cu m. /Stearates; does not include stearates of toxic metals/

Excursion Limit Recommendation: Excursions in worker exposure levels may exceed 3 times the TLV-TWA for no more than a total of 30 minutes during a work day, and under no circumstances should they exceed 5 times the TLV-TWA, provided that the TLV-TWA is not exceeded. /Stearates; does not include stearates of toxic metals/

A4; Not classifiable as a human carcinogen. /Stearates; does not include stearates of toxic metals/

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 39,000(SRC), determined from a structure estimation method(2), indicates that n-butyl stearate is expected to be immobile in soil(SRC). Volatilization of n-butyl stearate from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 0.038 atm-cu m/mole(SRC), using a fragment constant estimation method(3). However, adsorption to soil is expected to attenuate volatilization(SRC). n-Butyl stearate is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 5.8X10-6 mm Hg(4). n-Butyl stearate is expected to rapidly biodegrade in aerobic soils as suggested by the rapid biodegradation of structurally similar long-chain fatty acid esters(5-7).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 39,000(SRC), determined from a structure estimation method(2), indicates that n-butyl stearate is expected to adsorb to suspended solids and sediment in water(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 0.038 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). Volatilization half-lives for a model river and model lake are 5 hours and 7 days, respectively(SRC), using an estimation method(3). However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column(SRC). The volatilization half-life from a model pond is estimated to be about 64 hours ignoring adsorption; when considering maximum adsorption the volatilization half-life increases to 12 months(5). According to a classification scheme(6), a estimated BCF of 3, from an estimated log Kow of 7.90(12) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is low. n-Butyl stearate is expected to rapidly biodegrade in aerobic waters as suggested by the rapid biodegradation of structurally similar long-chain fatty acid esters(8-10). An estimated base-catalyzed second-order hydrolysis rate constant of 0.024 L/mole-sec(11,SRC) corresponds to half-lives of 9 and 1 years at pH values of 7 and 8, respectively(11).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), n-butyl stearate, which has a vapor pressure of 5.8X10-6 mm Hg at 25 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase n-butyl stearate 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 15 hours(SRC) from its estimated rate constant of 2.6X10-11 cu cm/molecule-sec at 25 °C(3). Particulate-phase n-butyl stearate may be removed from the air by wet and dry deposition(SRC).

The CIR Expert Panel concluded that the alkyl esters, listed subsequently, are safe in the present practices of use and concentration described in this safety assessment when formulated to be non-irritating.

Safe for use in cosmetics, with qualifications

Using a structure estimation method based on molecular connectivity indices(1), the Koc for n-butyl stearate can be estimated to be about 39,000(SRC). According to a classification scheme(2), this estimated Koc value suggests that butyl stearate is expected to be immobile in soil.

An estimated BCF of 1 was calculated for n-butyl stearate(SRC), using an estimated log Kow of 9.70(1,SRC) and a regression-derived equation(2). According to a classification scheme(3), the estimated BCF suggests the potential for bioconcentration in aquatic organisms is low.

The Henry's Law constant for n-butyl stearate is estimated as 0.038 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that n-butyl stearate is expected to volatilize rapidly 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 approximately 5 hours(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 approximately 7 days(SRC). The volatilization half-life from a model pond 2 m deep is estimated to be about 64 hours ignoring adsorption; when considering maximum adsorption the volatilization half-life increases to 12 months(3). n-Butyl stearate's Henry's Law constant(1) indicates that volatilization from moist soil surfaces may occur(SRC). n-Butyl stearate is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 5.1X10-6 mm Hg(4).

TWO-YEAR FEEDING STUDIES IN THE RAT AT 1.25 AND 6.25% PRODUCED NO EFFECTS ON GROWTH, MORTALITY OR FERTILITY.

... /ORAL, SC OR IP/ DOSES OF 32 G/KG BODY WT /BUTYL STEARATE GIVEN TO 5-6 WK OLD WHITE RATS WEIGHING 60-75 G/ CAUSED NO DEATHS IN THREE SERIES EACH OF FIFTEEN RATS. LETHAL DOSE ... IS THEREFORE OVER 32 G/KG & ... ACUTE TOXICITY ... IS LOW.

The rate constant for the vapor-phase reaction of n-butyl stearate with photochemically-produced hydroxyl radicals has been estimated as 2.6X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 15 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). A base-catalyzed second-order hydrolysis rate constant of 0.024 L/mol-sec(SRC) was estimated using a structure estimation method(2); this corresponds to half-lives of 9 and 1 years at pH values of 7 and 8, respectively(2). n-Butyl stearate is not expected to directly photolyze due to the lack of absorption in the environmental UV spectrum(3).

NIOSH (NOES Survey 1981-1983) has statistically estimated that 56,501 workers (14,513 of these are female) are potentially exposed to n-butyl stearate in the US(1). Occupational exposure to n-butyl stearate may occur through inhalation and dermal contact with this compound at workplaces where butyl stearate is produced or used(SRC). The general population may be exposed to n-butyl stearate via inhalation of ambient air, ingestion of food and drinking water, and dermal contact with this compound due to its use in cosmetics, pharmaceuticals, lubricants, and coatings and use as a flavoring and plasticizer(2,3). n-Butyl stearate has been used as a plasticizer for polymers used in food packaging and has been shown to migrate from the polymer to packaged or stored foods(4); therefore, the general population may be exposed to n-butyl stearate through oral consumption of foods packaged or stored in polymer containers that use n-butyl stearate as an additive(SRC).

Butyl stearate is a food additive permitted for direct addition to food for human consumption as a synthetic flavoring substance and adjuvant in accordance with the following conditions: a) they are used in the minimum quantity required to produce their intended effect, and otherwise in accordance with all the principles of good manufacturing practice, and 2) they consist of one or more of the following, used alone or in combination with flavoring substances and adjuvants generally recognized as safe in food, prior-sanctioned for such use, or regulated by an appropriate section in this part.

Butyl stearate is an indirect food additive for use only as a component of adhesives.

Substances classified as plasticizers, when migrating from food-packaging material shall incl ... butyl stearate.