Benzimidazole

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

SMALL SPILLS AND LEAKAGE: Should a spill occur while you are handling this chemical, FIRST REMOVE ALL SOURCES OF IGNITION, then you should dampen the solid spill material with 60-70% ethanol and transfer the dampened material to a suitable container. Use absorbent paper dampened with 60-70% ethanol to pick up any remaining material. Seal the absorbent paper, and any of your clothes, which may be contaminated, in a vapor-tight plastic bag for eventual disposal. Solvent wash all contaminated surfaces with 60-70% ethanol followed by washing with a soap and water solution. Do not reenter the contaminated area until the Safety Officer (or other responsible person) has verified that the area has been properly cleaned.

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.

RECOMMENDED RESPIRATOR: Where the neat test chemical is weighed and diluted, wear a NIOSH-approved half face respirator equipped with an organic vapor/acid gas cartridge (specific for organic vapors, HCl, acid gas and SO2) with a dust/mist filter. (NTP, 1992)

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 108(SRC), determined from a structure estimation method(2), indicates that benzimidazole is expected to have high mobility in soil(SRC). Volatilization of benzimidazole from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 3.7X10-7 atm-cu m/mole, using a fragment constant estimation method(3). Benzimidazole is not expected to volatilize from dry soil surfaces, based upon an estimated vapor pressure of 7.6X10-5 mm Hg(SRC), determined from a fragment constant method(4). There is no information on benzimidazole migration in soil, but benzimidazole-based fungicides Benlate and thiabendazole TBZ did not migrate any appreciable distance in soils(5). These fungicides applied to soil surfaces at 100 ug/g did not move more than 25 mm into the soil(5). Benzimidazole was inhibitory to individual strains of soil bacteria that could degrade benzimidazole-based fungicides(6); furthermore, benzimidazole did not support the growth of mixed cultures of microbes that could grow on benzimidazole-based fungicides(7). In contrast, in soil, repeated applications of benzimidazole led to its enhanced degradation(8). These findings suggest that benzimidazole degradation in soils is cometabolic, and that isolation of the appropriate pure cultures that perform the cometabolism has not yet been achieved(SRC).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 110(SRC), determined from an estimation method(2), indicates that benzimidazole is not expected to adsorb to suspended solids and sediment in water(SRC). At low pHs, when benzimidazole (pKa = 5.3(8)) exists in a primarily protonated form, it is expected to adsorb to suspended solids and sediments. Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 3.7X10-7 atm-cu m/mole(4). According to a classification scheme(5), an estimated BCF of 2.1(SRC), from a log Kow of 1.32(6) suggests the potential for bioconcentration in aquatic organisms is low. Benzimidazole is degraded in soils(7), and therefore biodegradation in water may be an important fate process.

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), benzimidazole, which has an estimated vapor pressure of 7.6X10-5 mm Hg at 25 °C(2), is expected to exist in the both the vapor and particulate phases in the ambient atmosphere. Vapor-phase benzimidazole 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 3.6 hours(SRC), calculated from its rate constant of 3.6X10-11 cu cm/molecule-sec at 25 °C(3). Particulate-phase benzimidazole may be removed from the air by wet and dry deposition(SRC). Benzimidazole absorbs light at 245, 271 and 278 nm, and therefore, has little potential for direct photolysis at environmental wavelengths (>290 nm).

The Koc of benzimidazole is estimated as 110(SRC), using a log Kow of 1.32(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that benzimidazole is expected to have high mobility in neutral and basic soils. Benzimidazole's pKa of 5.3(4) indicates that it will be in the protonated form in acidic environments, and will tend to adsorb to soil particles and clays.

AEROBIC: No wastewater degradation data for benzimidazole are available(1). Using several different water and soils as sources of inocula, and using benzimidazole as a sole carbon and energy source, no pure cultures of benzimidazole-degraders were found; furthermore, the compound did not support the growth of any bacteria that grew on benzimidazole-based fungicides(2,3). Pseudomonads and Bacillus species (both of which could degrade benzimidazole-based fungicides) were completely inhibited by benzimidazole at concentrations ranging from 500 to 1000 ug/ml, respectively(2). However, in the aerobic soil environment, benzimidazole (10 ug/g) was completely degraded in 10 days when the soils had been pre-exposed to the compound(4). This suggests that benzimidazole biodegradation is cometabolic, and likely occurs in soils as well as in natural waters.

An estimated BCF of 2.1 was calculated for benzimidazole(SRC), using a log Kow of 1.32(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.

The Henry's Law constant for benzimidazole is estimated as 3.7X10-7 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that benzimidazole is expected to be nonvolatile from water surfaces(2). This Henry's Law constant indicates that benzimidazole is essentially non-volatile(SRC) from moist soils. Benzimidazole is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 7.6X10-5 mm Hg at 25 °C(SRC), determined from a fragment constant method(3).

...PHENOXYPROPANEDIOL...CAUSED REVERSIBLE FLACCID PARALYSIS IN ANIMALS. ...SIMILAR EFFECTS /FROM/ BENZIMIDAZOLE.../REPORTED/

BENZIMIDAZOLE DID NOT INDUCE REVERSION RESPONSE IN ESCHERICHIA COLI A 46. SALMONELLA TYPHIMURIUM G 46 DISPLAYED A MUTAGENIC RESPONSE. TRANSITION IN VITRO AS WELL AS IN VIVO.

BENZIMIDAZOLE NON-TOXIC TO LUMBRICUS TERRESTRIS WHEN ADMIN ORALLY.

AT CONCN OF 8.5X10-4 MMOLAR BENZIMIDAZOLE FAILED TO STIMULATE TOBACCO CALLUS GROWTH OR SHOOT FORMATION /IN VITRO/. CONCN OF 0.85 MMOLAR & 1.7 MMOLAR INHIBITED KINETIN-DEPENDENT CALLUS GROWTH, WHEREAS LOWER CONCN HAD NO EFFECT.

For more Non-Human Toxicity Excerpts (Complete) data for BENZIMIDAZOLE (6 total), please visit the HSDB record page.

The rate constant for the vapor-phase reaction of benzimidazole with photochemically-produced hydroxyl radicals has been estimated as 3.6X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 3.6 hours(SRC) at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Benzimidazole is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(3).

Benzimidazole's production and use as a chemical intermediate in the production of agricultural fungicides may result in its release to the environment through various waste streams. If released to air, an estimated vapor pressure of 7.6X10-5 mm Hg at 25 °C indicates benzimidazole will exist in both vapor and particulate phases in the ambient atmosphere. Vapor-phase benzimidazole 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 3.6 hours. Particulate-phase benzimidazole will be removed from the atmosphere by wet and dry deposition. Benzimidazole has little potential for direct photolysis at environmental wavelengths (>290 nm) since it does not absorb light. If released to soil, benzimidazole is expected to have high mobility based upon an estimated Koc of 110. However, a pKa value of 5.3 at 25 °C suggests that at low pH, the protonated form will exist, and will adsorb to organic carbon and clay more strongly than its neutral counterpart. The un-ionized form of benzimidazole will be unlikely to volatilize from soils based upon an estimated Henry's Law constant of 3.7X10-7 atm-cu m/mole and estimated vapor pressure of 7.6X10-5 mm Hg at 25 °C. Benzimidazole is not readily metabolized by isolated soil microbial strains that metabolize benzimidazole-based fungicides, and is inhibitory to some microbes at concentrations ranging from 500 to 1000 ug/g. Hydrolysis of benzimidazole is not expected to occur due to the lack of hydrolyzable functional groups. If released into water, benzimidazole is not expected to adsorb to suspended solids and sediments, based upon its estimated Koc of 108. However, under acidic conditions, due to a pKa of 5.3, adsorption to suspended solids and sediments may occur. The biodegradation of benzimidazole in aquatic systems has not been demonstrated, but it is degraded in soils, which suggests that it will be degraded in waters as well. Volatilization from water surfaces is not expected to be an important fate process, based upon this compound's estimated Henry's Law constant. An estimated BCF of 2.1 suggests the potential for bioconcentration in aquatic organisms is very low. Occupational exposure to benzimidazole may occur through inhalation and dermal contact with this compound at workplaces where benzimidazole is produced or used. (SRC)

LD50 Rat ip 385 mg/kg

LD50 Mouse oral 2910 mg/kg

LD50 Mouse iv 280 mg/kg