Chlorinated ethanes are used as industrial solvents and in the production of other organochlorine compounds. They are also used as dry-cleaning agents, as anaesthetics, in the manufacture of plastics and textiles and in the production of tetraethyllead and vinyl chloride (CCME 1992). Chloroethanes are also formed in small amounts by the aqueous chlorination of effluents.

Potential sources of contamination include direct discharge of wastewaters, accidental spillages and deposition from the atmosphere. Low level contamination of surface water by rainwater was reported by McConnel (1977) who measured the concentration of 1,1,1-TCA in two UK upland reservoirs before and after a period of prolonged rain in November 1974. The concentrations of 1,1,1-TCA in the reservoirs increased from 13 to 21 ppb at one site and from 12 to 41 ppb at the other. The levels occurring in rainwater are low (generally less than 0.1 µg l^-1) and it is thought that contamination of surface and groundwater is more likely to result from direct discharge of solvents to water or accidental spills to the ground, rather than by transfer of solvent vapour from the air (Pearson and McConnel 1975).

Information summarised in Rees and Bowen (1992) concluded that major global producers of 1,1,1-TCA included the United States, Western Europe and Japan. For 1983, global production of 1,1,1-TCA was estimated to be 537 ktonne/year. Production of 1,1,2-TCA is thought to be much lower, and was around 80 ktonne/year in 1983 (ECETOC 1988). The consumption of 1,1,1-TCA in Western Europe increased in the 1960s and 1970s as 1,1,1-TCA replaced other more reactive chemical compounds, but has remained fairly constant at around 150 ktonne/year since 1979 ( CEFIC 1986). UK consumption was estimated to account for just over 20% of the total European consumption at around 30 ktonne/year in 1984 (CEFIC 1986).

Chlorinated ethanes are low-molecular weight saturated compounds containing two carbon atoms in which one or more hydrogen atoms have been substituted with chlorine. With the exception of hexachlorethane, all chloroethanes are low-boiling liquids, most are relatively volatile and water-soluble. In general, both volatility and water solubility decrease with increasing chlorine substitution. Volatilisation can be considered to be the primary removal process from water (CCME 1992).

Rates of disappearance of around 90% within one to two hours have been reported for both isomers of TCA from slowly stirred water. Similar rates were observed in the presence of natural absorbents, such as limestone and peat (Dilling et al 1975).

In saltwater waters, Pearson (1982) estimated typical levels to be around 0.01 µg l^-1 in offshore areas and 0.15 µg l^-1 for inshore areas. In Liverpool bay, in an area receiving discharges from 1,1,1-TCA production, levels were much higher at 0.2 to 3.3 µg l^-1 (Pearson and McConnel 1975).

Monitoring data from the National Rivers Authority and the National Monitoring Programme Survey of the Quality of UK Coastal Waters are presented in Appendix D. Monitoring data are available for trichloroethane, but no water column concentrations were found to exceed the EQS value (see Appendix D).

The available data suggest that concentrations of trichloroethanes in UK coastal and estuarine water are unlikely to exceed relevant quality standards derived for the protection of saltwater life.

Pearson and McConnel (1975) determined the levels of 1,1,1-TCA in a wide range of organisms chosen to represent a wide range of trophic levels. Most of the samples were taken from Liverpool Bay, an area where the main UK organochlorine plants are situated. However, other samples taken from the Thames Estuary, the Firth of Forth and Tees Bay also showed some degree of contamination. The levels of 1,1,1-TCA (in µg/kg wet tissue) are:

Plankton 0.03-10.7;

Saltwater algae 10-25;

Molluscs 0.05-10;

Crustacea 0.7-34;

Fish flesh 0.7-5;

Fish liver 1-15;

Water birds eggs 3-30;

Water bird liver 1-4;

Seal liver 0.2-4;

Seal blubber 8-24.

Direct photolysis, oxidation and hydrolysis are not expected to be significant removal processes for chloroethanes in the aquatic environment. TCA has been shown to undergo both chemical and biotic degradation, but the long half-lives for the reactions involving both isomers suggest that degradation is not an important loss mechanism from surface water. Little or no degradation of chloroethanes was found during standard BOD (biochemical oxygen demand) bottle test (Pearson and McConnel 1975).

As the lower chlorinated compounds have slight affinities for lipophilic materials, sorption to organic-rich material is considered to be minimal. In laboratory tests, little or no sorption to inorganic or organic material was observed (Dilling et al 1975) .

An exhaustive literature review on the toxicity of chlorinated ethanes to marine organisms has not been carried out for the purposes of this profile. The information provided in this section is taken from existing review documents (Rees and Bowen 1992). The most sensitive groups of organisms have been identified.

Rees and Bowen (1992) reviewed data on the aquatic toxicity of TCAs. The authors found few data on the toxicity of 1,1,1-TCA to saltwater life and none of the data were from chronic tests. More data were available for 1,1,2-TCA but most are derived from two studies; Pearson and McConnel (1975) report an LC50 of 5 mg l^-1 and Craig (1983) cites an unknown response at 0.5 mg l^-1 of 1,1,1-TCA for the green algae Phaeodactylum tricornutum suggesting that the toxicity of 1,1,1-TCA to algae is around 300 times greater in saltwater than freshwater. These results are very low compared to values obtained from similar tests with 1,1,2-TCA in which 96 hour EC50s for growth of 60, 170 and 200 mg l^-1 were measured for Phaeodactylum tricornutum, Chlorella pyrenoidosa and Chlorella ovalis respectively (Adema and Vink 1981).

Annelids appear to be relatively insensitive to 1,1,2-TCA. Adema and Vink (1981) estimated a 96 hour LC50 of 190 mg l^-1 for Ophyrotrocha diadema. While for three crustacean species, Artemia salina, Crangon crangon and Temora longicornis, 96 hour LC50s of 43 to 52 mg l^-1 for the adult stage were found for 1,1,2-TCA. Three week tests on Artemia larvae estimated an EC50 of 15 mg l^-1 and a No Observable Effect Concentration (NOEC) of 10 mg l^-1 both for reproduction.

For 1,1,1-TCA, LC50 values of 7.5 mg l^-1 for Elminius modestus and 31.2 mg l^-1 for Mysidopsis bahia have been calculated (Pearson and McConnel 1975; US EPA 1980).

Acute LC50s for 1,1,1-TCA in saltwater of 33, 60 and 71 mg l^-1 have been reported for Limanda limanda, Cyprinodon variegatus and Lagodon rhomboides respectively (Pearson and McConnel 1975; Heitmuller et al 1981; Craig 1983). Heitmuller et al (1981) also estimated a 96 hour NOEC of 3.5 mg l^-1 for mortality of Cyprinodon variegatus. No data were found on the chronic toxicity of 1,1,1-TCA. Adema and Vink (1981) estimated a 7-day LC50 for 1,1,2-TCA of 43 mg l^-1 for adult Gobius minutus. A lower 7-day LC50 of 27 mg l^-1 was determined for larval plaice Pleuronectes platessa. Chronic data were available only for the egg/larval stages of Pleuronectes platessa. No effects were observed on the mortality, growth or development over eight weeks at 3.0 mg l^-1 1,1,2-TCA, and an LC50 of 5.5 mg l^-1 was calculated for the same period.

No data could be located for sediment-dwelling organisms.

The potential for bioaccumulation of C1 and C2 hydrocarbons in the field was assessed by Pearson and McConnel (1975). The authors determined the levels of 1,1,1-TCA in the tissues of a wide range of organisms in samples taken from Liverpool Bay (an area where the major organochlorine industries are situated), the Thames Estuary, the Firth of Forth and Tees Bay. They found little evidence to suggest extensive bioaccumulation and transfer to food chains.

With the exception of hexachloroethane, most chloroethanes have low octanol/water partition coefficients. On this basis, only a slight potential to bioaccumulate can be expected.

Potential effects include:

• toxicity of 1,1,1 trichloroethane to algae, invertebrates and fish at concentrations above the EQS of 100 Fg l^-1 (annual average) and 1,000 µg l^-1 (maximum allowable concentration) in the water column;
• toxicity of 1,1,2 trochloroethane to algae, invertebrates and fish at concentrations above the EQS of 300 Fg l^-1 (annual average) and 3,000 µg l^-1 (maximum allowable concentration) in the water column

Next Section                     References