Chlorinated ethanes in freshwater and marine water
Toxicant default guideline values for protecting aquatic ecosystems
Extracted from Section 8.3.7 ‘Detailed descriptions of chemicals’ of the ANZECC & ARMCANZ (2000) guidelines.
The default guideline values (previously known as ‘trigger values’) and associated information in this technical brief should be used in accordance with the detailed guidance provided in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality.
Description of chemical
The nine chemicals comprising chlorinated ethanes are generally volatile solvents. Boiling points and octanol-water partition coefficients increase with increasing chlorine substitution: Log Kow for 1,1,2,2-tetraCE is 2.39, for pentaCE it is 3.22 and for hexaCE it is 4.14. The analytical practical quantitation limit for 1,1,2-TCE and hexachloroethane is currently 1 µg/L (NSW EPA 2000).
Chlorinated ethanes are commonly used as industrial solvents, dry-cleaning agents, anaesthetics, and in the production of other organochlorines, textiles, tetraethyl lead fuel additives and plastics, particularly polyvinyl chloride, as well as in many household products such as detergents, fumigants, correction fluid, varnishes and rust removers (CCREM 1987, HSDB 1996). Hexachloroethane is used in explosives, smokebombs and pyrotechnics as an inhibitor, as a degasser in aluminium production and a flame retardant (Sax & Lewis 1987). In 1983 in Canada, over 15,000 tonnes of chloroethanes were produced.
Most chlorinated ethanes are relatively volatile and water-soluble. The major route for removal of chlorinated ethanes from water is by volatilisation, usually with half-lives of <1 h (Dilling et al. 1975, Dilling 1977). Photolysis, hydrolysis and oxidation in water are not expected to be significant pathways for removal of chloroethanes and they are only expected to adsorb slightly to organic-rich material (McConnell et al. 1975, CCREM 1987) or sediments (Pearson & McConnell 1975).
There was little biodegradation of chloroethanes during standard biochemical oxidation demand (BOD) tests (CCREM 1987). All except hexachloroethane, have log Kow values <3 and are not expected to bioaccumulate significantly. The steady-state bioconcentration factors for bluegills Lepomis macrochirus (USEPA 1978, 1980q) were all less than 70, except for hexachloroethane (139). They were rapidly depurated with a biological half-life of <2 days (HSDB 1996).
Toxicity data from short-term tests on chloroethanes (CE) are tabulated in Table 8.3.12 of the ANZECC & ARMCANZ (2000) guidelines. Only a few chronic NOEC data are reported for chloroethanes as follows.
Freshwater fish: one species, Pimephales promelas, 32-d NOEC (growth), 29 mg/L.
Freshwater crustacean: one species, Daphnia magna, 28-d NOEC (growth, reprod.), 11-42 mg/L.
Freshwater algae: two species, green and blue–green algae, 8-d NOEC (growth) 360 and 53 mg/L.
Marine annelids: one species, 9-15-d NOEC (mortality, reprod.), 200-400 mg/L.
The low reliability trigger value calculated on quantitative structure activity relationship (QSAR) data (1900 µg/L with 95% protection) was below most chronic NOEC figures, except for an apparently anomalous golden orfe LC50 of 1800 µg/L. Alternative low reliability protection levels were 99% 1000 µg/L, 95% 1900 µg/L, 90% 2600 µg/L, 80% 4000 µg/L.
Freshwater crustaceans: one species, 17-d mortality and reproduction, of 1.3 mg/L (1300 µg/L), and a 4-d NOEC for growth of 7.9 mg/L (7900 µg/L)
Freshwater fish: one species, 14-d mortality of 130 mg/L.
Marine fish: one species, 4-d acute NOEC of 43 mg/L.
Low reliability trigger values were derived using QSAR data: at protection levels of 99% 130 µg/L, 95% 270 µg/L, 90% 400 µg/L and 80% 650 µg/L.
Freshwater fish: one species, 15-28-d NOEC mortality of 18-29 mg/L.
Freshwater crustaceans: one species, D. magna 21-28-d NOEC reproduction of 18-26 mg/L; 21-d mortality of 32 mg/L; 28-d growth of 13 mg/L, giving an ACR of 7.3.
Freshwater mollusc: one species, Lymnaea stagnalis, 16-d NOEC hatching of 10 mg/L.
Marine fish: one species, Pleuronectes platessa, 8-d NOEC mortality of 3 mg/L.
Marine crustacean: one species, Artemia salina, 21-d NOEC reproduction of 10 mg/L.
Marine polychaete: one species, Ophryotrocha labronica, 9-15 d hatching, 33-50 mg/L.
The ACR of 5.5 was applied to freshwater to give a moderate reliability trigger value (TV) but the marine TV was calculated from chronic data (high reliability).
These trigger values at different protection levels are listed in Table 3.4.1 of the ANZECC & ARMCANZ (2000) guidelines.
Freshwater fish: one species, Jordanella floridae, 15-28 d NOEC, reproduction, 2-2.3 mg/L.
Freshwater crustacean: one species, D. magna, 28-d NOEC, reproduction, 5.1 mg/L.
Low reliability trigger values were derived using QSAR estimates at different protection levels: 99% 200 µg/L, 95% 400 µg/L, 90% 500 µg/L and 80% 900 µg/L.
Marine red algae: one species, Champia parvula, 14-d NOEC, growth and reproduction, 10-32 mg/L.
Low reliability trigger values were derived using QSAR estimates at different protection levels: 99% 30 µg/L, 95% 80 µg/L, 90% 120 µg/L and 80% 200 µg/L.
Australian and New Zealand toxicity data
The only chloroethane for which there were Australian or New Zealand data was 1,1,2-trichloroethane (TCE) (Johnston et al. 1990). The measured 96-h LC50 of 1,1,2-TCE, under flow-through conditions, to the Australian eastern rainbowfish Melanotaenia duboulayi was 47 mg/L and to the golden perch Macquaria ambigua was 57 mg/L. These figures were similar to those for mosquitofish Gambusia holbrooki (34 mg/L) and zebrafish Brachydanio rerio (60 mg/L) tested under the same conditions (Johnston et al. 1990), and similar to literature values. The nominal 48-h EC50 to six species of Australian cladocerans at 25°C was between 38 and 96 mg/L at 20°C, compared to 98 mg/L for D. magna and 51 mg/L for US Ceriodaphnia dubia tested under the same conditions (Johnston et al. 1990).
Factors that modify the toxicity of chloroethanes
The high volatility of chloroethanes would lead to rapid loss from the water volume and hence reduced availability. Johnston et al. (1990) reported that toxicity of 1,1,2-TCE increased with increasing temperature. Nominal 48-h EC50 values for the Australian cladoceran C. dubia decreased significantly from 151 mg/L at 15°C, to 123 mg/L at 20°C, 56 mg/L at 25°C and 32 mg/L at 30°C, when tested in covered containers. For the rainbowfish Melanotaenia duboulayi flow-through, measured 96-h LC50 decreased significantly from 66 mg/L at 15°C to 47 mg/L at 25°C and 31 mg/L at 35°C.
There was a slight decrease in toxicity of 1,1,2-TCE to rainbowfish with increases in salinity: the 96-h LC50 at 25°C of 47 mg/L at 40 mg NaCl/L increased to 59 mg/L at 5000 mg NaCl/L. For C. dubia the pattern was a little more complex. The EC50 at 30 mg NaCl/L of 56 mg/L at 25°C first decreased significantly to 30 mg/L at 1000 mg NaCl/L then increased to 52 mg/L at 2000 mg NaCl/L (Johnston et al. 1990).
These are listed in Table 8.3.12 of the ANZECC & ARMCANZ 2000 guidelines. Moderate or high reliability trigger values could only be derived for 1,1,2-TCE (fresh and marine) and HCE (fresh). All other trigger values are low reliability and should only be used as indicative interim working levels.
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HSDB (Hazardous Substances Data Bank) 1996. Micromedex Inc. 31 July 1996.
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McConnell G, Ferguson DM & Pearson CR 1975. Chlorinated hydrocarbons and the environment. Endeavour 34, 13-18.
NSW EPA 2000. Analytical Chemistry Section, Table of Trigger Values 20 March 2000, LD33/11, Lidcombe, NSW.
Pearson CR & McConnell G 1975. Chlorinated C1 and C2 hydrocarbons in the marine environment. Proceedings of the Royal Society of London 189, 305-322.
Sax NI & Lewis RJ Sr (eds) 1987. Hawley’s condensed chemical dictionary. 11th edn, Van Nostrand Reinhold, New York.
USEPA 1978. In-depth studies in hand environmental impacts of selected water pollutants. US Environmental Protection Agency. Contract 68-01-4646.
USEPA 1980q. Ambient water quality criteria for chlorinated ethanes. US Environmental Protection Agency, Washington DC, EPA 440/5-80-029.