(E)-2-Chloro-3-(dichloromethyl)-butenedioic acid

During a survey of 12 U.S. water treatment plants conducted between 2000-2002, the highest level of halogenated furanones (as a sum) occurred at a plant that disinfected water containing 11.3 mg/L of TOC and 0.27 mg/L of bromide with chlorine-chloramines (2380 ng/L in plant effluent drinking water) and at a plant that disinfected water containing 3.5 mg/L of TOC and 0.21 mg/L of bromide with chlorine dioxide-chlorine-chloramines (1000 ng/L in the distribution system). The authors noted that an effort was made to selects plants that treat water with high TOC and/or bromide to enable detection of priority disinfection byproducts. The median concentration of halogenated furanones (as a sum, measured in plant effluent) was 310 ng/L, with a 75th percentile concentration of 610 ng/L and a maximum concentration of 2,380 ng/L(1). /Halogenated furnanones/

Using a structure estimation method based on molecular connectivity indices(1), the Koc of (E)-2-chloro-3-(dichloromethyl)-butenedioic acid can be estimated to be 54(SRC). According to a classification scheme(2), this estimated Koc value suggests that (E)-2-chloro-3-(dichloromethyl)-butenedioic acid is expected to have high mobility in soil. The estimated pKa of (E)-2-chloro-3-(dichloromethyl)-butenedioic acid is 2.3(3), indicating that this compound will almost exist in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4).

(E)-2-Chloro-3-(dichloromethyl)-butenedioic acid's formation in water as a result of chlorine-treatment processes(1) may result in its release to the environment through various waste streams(SRC). Disinfection byproducts are formed when chlorine or other disinfectants, which are used to control contaminants in drinking water, react with naturally occurring organic and inorganic matter present in water(2,3).

An estimated BCF of 3 was calculated in fish for (E)-2-chloro-3-(dichloromethyl)-butenedioic acid(SRC), using an estimated log Kow of 1.5(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).

An estimated pKa of 2.28(1) indicates (E)-2-chloro-3-(dichloromethyl)-butenedioic acid will exist almost entirely in the anion form at pH values of 5 to 9 and therefore volatilization from water surfaces is not expected to be an important fate process(2). (E)-2-Chloro-3-(dichloromethyl)-butenedioic acid is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 6.9X10-6 mm Hg(SRC), determined from a fragment constant method(3).

/GENOTOXICITY/ ... The strong Ames mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2 (5H)-furanone (MX) and its geometric isomer E-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (E-MX) have been shown to be present in chlorinated drinking waters. MX accounts for approximately 30% and E-MX for a few percent of the overall mutagenicity. MX and E-MX are unstable in water and undergo both pH dependent isomerization (MX in equilibrium E-MX) and hydrolytic degradation. ... The MX analogues 3-chloro-4-(dichloromethyl)-2 (5H)-furanone (red-MX) and 2-chloro-3-(dichloromethyl)-2-butenedioic acid (ox-MX) have also been identified in chlorinated water. However, the relatively low mutagenicity of these compounds suggests that their contribution to the overall mutagenicity of chlorinated water is of only moderate significance.

/GENOTOXICITY/ The mutagenic activities of the chlorinated butenoic acids recently identified in chlorinated drinking waters were determined by the Salmonella microsome assay and by the SOS chromotest. The Salmonella typhimurium tester strains TA97, TA98 and TA100 were used without and with S9 mix. In the SOS chromotest Escherichia coli PQ37 was used as an indicator organism with and without metabolic activation. In addition, the extremely potent Ames test mutagen (Z)-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (MX, in the open form), was studied by the micronucleus test with mice using intraperitoneal treatment. The results of the Salmonella assay and the SOS chromotest showed that MX was by far the most potent mutagen of the compounds tested. Mutations were also induced by the reduced form of MX, (Z)-2-chloro-3-(dichloromethyl)-4-hydroxybut-2-enoic acid (red-MX), and by the geometric isomer of MX, (E)-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (EMX). However, since the solution of EMX contained approximately 5% MX, most of its activity might be attributable to MX. The oxidised form of EMX, (E)-2-chloro-3-(dichloromethyl)-butenedioic acid (ox-EMX), was marginally active in the SOS chromotest only. All these compounds were directly acting mutagens and in the presence of metabolic activation (S9 mix) they did not generate mutagenicity. The oxidized form of MX, (Z)-2-chloro-3-(dichloromethyl)-butenedioic acid (ox-MX), was not mutagenic at the dose levels tested. MX did not induce micronuclei in the bone marrow of mice.

The rate constant for the vapor-phase reaction of (E)-2-chloro-3-(dichloromethyl)-butenedioic acid with photochemically-produced hydroxyl radicals has been estimated as 3.5X10-12 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 5 days at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). The rate constant for the vapor-phase reaction of (E)-2-chloro-3-(dichloromethyl)-butenedioic acid with ozone has been estimated as 1.6X10-18 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(1). This corresponds to an atmospheric half-life of about 7 days at an atmospheric concentration of 7X10+11 ozone molecules per cu cm(2). (E)-2-Chloro-3-(dichloromethyl)-butenedioic acid is expected to undergo hydrolysis in the environment due to the presence of functional groups that hydrolyze under environmental conditions(3). (E)-2-Chloro-3-(dichloromethyl)-butenedioic acid contains chromophores that absorb at wavelengths >290 nm(3) and therefore may be susceptible to direct photolysis by sunlight(SRC).

DRINKING WATER: (E)-2-Chloro-3-(dichloromethyl)-butenedioic acid has been targeted for a Nationwide Occurrence Study in the US(1). The compound was detected in a sample from the distribution system of a municipality in North Carolina, which chlorinates at a rate of 5 mg Cl/L(1). Concentrations were 961 ng/L in fulvic acid, 306 ng/L in humic water, and 53 ng/L in drinking water(2).

(E)-2-Chloro-3-(dichloromethyl)-butenedioic acid's formation in water as a result of chlorine-treatment processes may result in its release to the environment through various waste streams. Disinfection byproducts are formed when chlorine or other disinfectants, which are used to control contaminants in drinking water, react with naturally occurring organic and inorganic matter present in water. If released to air, an estimated vapor pressure of 6.9X10-6 mm Hg at tt °C indicates (E)-2-chloro-3-(dichloromethyl)-butenedioic acid will exist in both the vapor and particulate phases in the atmosphere. Vapor-phase (E)-2-chloro-3-(dichloromethyl)-butenedioic acid 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 5 hours. Particulate-phase (E)-2-chloro-3-(dichloromethyl)-butenedioic acid will be removed from the atmosphere by wet or dry deposition. (E)-2-Chloro-3-(dichloromethyl)-butenedioic acid contains chromophores that absorb at wavelengths >290 nm and therefore may be susceptible to direct photolysis by sunlight. If released to soil, (E)-2-chloro-3-(dichloromethyl)-butenedioic acid is expected to have high mobility based upon an estimated Koc of 54. Biodegradation data were not available. The estimated pKa of (E)-2-chloro-3-(dichloromethyl)-butenedioic acid is 2.3, indicating that this compound will almost entirely exist in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts. Volatilization from moist soil and water is not expected because the acid exists as an anion and anions do not volatilize. If released into water, (E)-2-chloro-3-(dichloromethyl)-butenedioic acid is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Hydrolysis may be an important environmental fate process since this compound contains functional groups that hydrolyze under environmental conditions. The most likely pathway by which the general public is exposed to this compound is by ingestion of and dermal contact with treated drinking water and effluent. (SRC)