1,2-Dichloroethane, data available

Relatively little information is available on the health effects of 1,1-dichloroethane in humans or animals. However, the limited data available in animals indicate that it is less toxic than its isomer,... 

Exposure Levels in Humans. Although relatively recent estimates of the size of the population occupationally exposed to 1,1-dichloroethane are available from NIOSH, monitoring data on workplace exposures are generally limited, with a few observations about 1,1-dichloroethane included in detailed studies of 1,2-dichloroethane. A study of the levels of 1,1-dichloroethane in the inhaled and exhaled air and drinking water of college students in Texas and North Carolina found low levels (<0.49 ppb) of 1,1 - dichloroethane in the personal air quality monitors of the Texas students, whose campus bounded a petrochemical manufacturing area, but none in samples of their exhaled breath. Additional information on the availability of biomarkers that could be used to indicate human exposure to 1,1-dichloroethane would be helpful. 

No specific information is available on the sorption of chloroethanes in the aquatic enviromhent. The experimental data available (Dilling etaL, 1975) on the analogs could be used to estimate the extent of sorption of chloroethanes. For 1,1-dichloroethane and 1,1,1-trichloroethane, the maximum sorption would be 22% at 750 mg L of dry bentonite clay and 40% at 500 mg L of peat moss. 

The vapor is thea withdrawa from the stiH as distillate. The changing Hquid composition is most coavenieafly described by foUowiag the trajectory (or residue curve) of the overall composition of all the coexistiag Hquid phases. An exteasive amouat of valuable experimental data for the water—acetoae—chloroform mixture, including biaary and ternary LLE, VLE, and VLLE data, and both simple distillation and batch distillation residue curves are available (93,101). Experimentally determined simple distillation residue curves have also been reported for the heterogeneous system water—formic acid—1,2-dichloroethane (102). 

The available data in animals suggest that inhaled 1,1-dichloroethane may be nephrotoxic. However, this finding is limited to one species (cat) and was not observed in three other species tested under the same conditions. Another effect observed in animals but not humans following inhalation exposure to 1,1-dichloroethane exposure is fetotoxicity. Suggestive, but inconclusive, evidence of carcinogenicity was obtained in an oral chronic bioassay of 1,1-dichloroethane in rats and mice. 

The database for the health effects of 1,1-dichloroethane in experimental animals is lacking, and the studies reviewed consisted primarily of one subchronic inhalation study, one inhalation developmental toxicity study, and two oral chronic bioassays. No information is available on the effects of 1,1-dichloroethane following dermal exposure. The limited information available in animals suggests that 1,1-dichloroethane may be nephrotoxic, fetotoxic, and possibly carcinogenic. The data also indicate that 1,1-dichloroethane is considerably less toxic than 1,2-dichloroethane and the tetrachlorinated aliphatics. 

Genotoxicity. With one exception, the genotoxic potential of 1,1-dichloroethane has been investigated almost exclusively using in vitro assays. Though the available data are conflicting,... 

Characterization of 1,1-dichloroethane s metabolism relies heavily on in vitro data. These studies reveal that the biotransformation process is mediated by cytochrome P-450 with hepatic microsomes being the most effective. Identification of products in these microsomal studies allows for the prediction of metabolic pathways. However, exposure to 1,1-dichloroethane under in vivo conditions may alter substrate availability and consequently alter the metabolic scheme. In vivo studies would provide a better understanding of the rate and extent of 1,1- dichloroethane metabolism and a more realistic perspective of its metabolic fate. This information would allow more accurate prediction of the potential of 1,1-dichloroethane to induce toxic effects, and aid in devising methods to detoxify exposed persons. 

No information was found on the ambient concentrations of 1,1-dichloroethane in soil, or on the current disposal of waste products containing the compound in landfills. The compound has more commonly been detected in ambient air and groundwater samples taken at hazardous waste sites, and it is expected that the lack of available soil monitoring data is at least in part due to rapid partitioning of 1,1-dichloroethane released to soils to these other media. 

While electrocapillary data amenable to thermodynamic analysis of ion adsorption are available only at the nitrobenzene-water interface, a considerable number of double layer capacitance data have been compiled at both nitrobenzene-water and 1,2-dichloroethane-water interfaces. From a thermodynamic point of view the analysis of capacitance data is less straightforward, since to be equivalent to capillary data, the capacitance data must be supplemented by an independently determined integration constant. The presence of ion-pair formation between ions in the aqueous phase and the ions in the organic phase, a recently proposed concept based on capacitance measurements [56], should be able to be substantiated thermodynamically from electrocapillarity measurements. A detailed discussion of capacitance data has been given in the review by Samec [12]. 

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