National Industrial Chemicals Notification and Assessment Scheme

16.3.1Aquatic organisms

Literature values for toxicity of trichloroethylene to microorganisms give a 24 h E(I)C₅₀ value range from 115 mg/L to 960 mg/L, although an IC₅₀ of 13 mg/L has been measured for a methanogenic bacteria. Toxicity thresholds for microorganisms range from 65 to 1200 mg/L.

Trichloroethylene has been shown to both inhibit and stimulate the growth of algae and aquatic plants, depending on species and trichloroethylene concentration. EC₅₀ values for aquatic plants and algae range from 8 mg/L to 150 mg/L.

Toxicity tests for trichloroethylene with aquatic invertebrates have been carried out, although many of the results are based on nominal concentrations. 48h L(E)C₅₀ values range from 2.2 mg/L to 132 mg/L. To overcome volatility, two static tests have been carried out on Daphnia magna and Mysidopsis bahia (mysid shrimp) using sealed containers. These gave a 48h EC₅₀ of 7.8 mg/L and 96h EC₅₀ of 14 mg/L.

A natural pond field experiment in 1981 (conducted in Germany) observed complete mortality of Daphnia magna in two test ponds within 3 days after exposure to an initial concentration of 110 mg/L, a concentration much higher than might be expected, except in a major accident situation. Approximately 70% mortality was observed after 3 days at an initial concentration of 25 mg/L (the half-life of trichloroethylene in these experiments was 2.7 days). At the end of the 43 day observation period, the daphnid population had recovered. However, species richness and abundance of phytoplankton remained severely depressed at the end of the observation period following exposure to 25 mg/L. The results of subsequent field studies in natural pond communities indicate that similar effects occur following continuous exposure to lower concentrations of trichloroethylene for longer periods of time. For example, exposure to 1.0 to 1.5 mg/L trichloroethylene for 11 weeks caused reductions of up to 70% in the population of Daphnia pulex (Government of Canada, 1993).

fish

The toxicity of trichloroethylene to various fish species has been measured with LC₅₀ values ranging from 16 mg/L to 213 mg/L. Several of the tests are flow-through tests and the lowest result from these tests is the 96 h LC₅₀ for Jordanella floridae (American flagfish) of 28.3 mg/L. Chronic toxicity tests on this species have been carried out and the No Observed Effect Concentration (NOEC) was 5.76 mg/L.

Based on these results, trichloroethylene can be described as practically non-toxic to microorganisms; moderately to practically non-toxic to aquatic plants, algae and aquatic invertebrates; and slightly to practically non-toxic to fish.

Table 38 - Selected highest toxicity values of trichloroethylene to the
aquatic compartment.

Species	Conditions	Result (ppm)
Microorganisms
Activated Sludge	OECD Guideline 209, activated sludge respiration inhibition test (S)	EC50 260
Pseudomonas putida	16 h, inhibition of cell multiplication (S; NC)	LOEC=65
Aquatic plants/algae
Microcystis aeruginosa (Blue green algae)	8 d growth rate	LOEC=63
Phaeodactylum tricornutum (Marine diatom)	Photosynthesis	EC50=8
Scenedesmus subspicatus	96 h, inhibition of cell multiplication	EC10 46-61
Selenastrum capricornutum (Green algae)	96 h, growth rate	NOEC 175
Aquatic invertebrates
Daphnia magna	48 h, EPA-660/3-75-009, age <24 h. (S; NC)	EC50=18 NOEC=2.2
Daphnia magna	48 h, age 4-6 days. (S)	EC50 =7.8
Mysidopsis bahia (Mysid shrimp)	96 h, (S; MC)	EC50=14
Fish
Limanda limanda (Flatfish dab)	96 h (F; NC)	LC50=16
Oncorhynchus mykiss (Rainbow trout)	48 h (S; NC)	LC50=42
Pimephales promelas (Fathead minnow)	48 h (S; NC)	LC50=32-56