1,1-Dibromoethane

Bromine vapour causes irritation and direct damage to the mucous membranes. Elemental bromine also burns the skin. The bromide ion is a central nervous system depressant and chronic exposure produces neuronal effects. This is called bromism and can result in central reactions reaching from somnolence to coma, cachexia, exicosis, loss of reflexes or pathologic reflexes, clonic seizures, tremor, ataxia, loss of neural sensitivity, paresis, papillar edema of the eyes, abnormal speech, cerebral edema, delirium, aggressiveness, and psychoses. (L625, L626, L627)

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 35(SRC), determined from a structure estimation method(2), indicates that 1,1-dibromoethane is expected to have very high mobility in soil(SRC). Volatilization of 1,1-dibromoethane from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.3X10-3 atm-cu m/mole(SRC), using a fragment constant estimation method(3). 1,1-Dibromoethane is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 25.6 mm Hg(4). Biodegradation data are not available for 1,1-dibromoethane(SRC, 2005).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 35(SRC), determined from a structure estimation method(2), indicates that 1,1-dibromoethane 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 1.3X10-3 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 2 hours and 6 days, respectively(SRC). According to a classification scheme(5), an estimated BCF of 6(SRC), from an estimated log Kow of 1.9(6), suggests the potential for bioconcentration in aquatic organisms is low(SRC). The rate constant measured for the neutral hydrolysis reaction of 1,1-dibromoethane is 2.4X10-7 per minute at 25 °C which corresponds to a half-life of 5.5 years(7). Biodegradation data are not available for 1,1-dibromoethane(SRC, 2005).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 1,1-dibromoethane, which has a vapor pressure of 25.6 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 1,1-dibromoethane 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 64 days(SRC), calculated from its rate constant of 2.50X10-13 cu cm/molecule-sec at 25 °C(3). 1,1-Dibromoethane does not contain chromophores that absorb at wavelengths >290 nm and therefore is not expected to be susceptible to direct photolysis by sunlight(SRC).

Bromine is a powerful oxidizing agent and is able to release oxygen free radicals from the water in mucous membranes. These free radicals are also potent oxidizers and produce tissue damage. In additon, the formation of hydrobromic and bromic acids will result in secondary irritation. The bromide ion is also known to affect the central nervous system, causing bromism. This is believed to be a result of bromide ions substituting for chloride ions in the in actions of neurotransmitters and transport systems, thus affecting numerous synaptic processes. (L626, L627, A543)

Bromine vapour causes irritation and direct damage to the mucous membranes. Symptoms include lacrimation, rhinorrhoea, eye irritation with mucous secretions from the oropharyngeal and upper airways, coughing, dyspnoea, choking, wheezing, epistaxis, and headache. The bromide ion is a central nervous system depressant producing ataxia, slurred speech, tremor, nausea, vomiting, lethargy, dizziness, visual disturbances, unsteadiness, headaches, impaired memory and concentration, disorientation and hallucinations. This is called bromism. (L626, L627)

Using a structure estimation method based on molecular connectivity indices(1), the Koc of 1,1-dibromoethane can be estimated to be 35(SRC). According to a classification scheme(2), this estimated Koc value suggests that 1,1-dibromoethane is expected to have very high mobility in soil.

An estimated BCF of 6 was calculated for 1,1-dibromoethane(SRC), using an estimated log Kow of 35(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).