Di(µ-2,2´,2´´-nitrilotris(ethanol)-diperchlorato)dinatrium

Endpoint summary

Description of key information

EC50 (bluegill sunfish, 96 h) = 1470 mg/l (mean measured, perchlorate)

EC50 (daphnia, 48h) > 100 mg/l (nominal)

E_rC50 (algae, 72h, growth rate) > 460 mg/l (nominal); NOEC (algae, 72h, growth rate) = 10 mg/l (nominal)

EC50 (microorganisms, 3h) > 1000 mg/l (nominal); NOEC (microorganisms, 3h) = approx. 10 mg/l (nominal)

Additional information

No data are available for the assessment of the acute toxicity potential of the substance to fish. For this reason data on the dissociation substances were used for the the evaluation of short-term toxicity to fish. For algae, daphnia and microorganisms there are available data on the substance toxicity potential.

Short-term toxicity to fish

Three studies from literature are used for the assessment of the toxicity of perchlorate to the fish after 96 hours of exposure. In one study, ten zebrafish Danio rerio lavrae were exposed to the substance in five concentrations in a static-renewal test according to ASTM E729 -90. LC50 and their 95 % confidence limits were detrmined using the probit procedure; LC50 (96 h) = 1365 mg/l (measured). In another study, ten juvenille zebrafish Danio rerio (per replicate) were exposed to five concentrations of the substance in the static-renewal test according to the ASTM Standard E792 -96; LC50 (96 h) = 2532 mg/l (measured). The toxicity to rainbow trout fry and juvenille bluegill sunfish was assessed in a flow-through test according to EPA OPPTS 850.1075 and ASTM E729-96. The fish were exposed to the substance for 96 hours. Biological observations and test monitoring were performed on a daily basis at minimum. EC50 was used instead of LC50 and it was based not only on mortality but in addition on severe effects, such as loss of equilibrium and immobilization. No mortality was observed in the control or the sodium control in both tests. No sublethal effects were observed during the test; all observations were either of mortality or normal behavior. Rainbow trout: EC50 (96 h) = 2010 mg/l (mean measured); NOEC (96 h) = 1460 mg/l; LOEC (96 h) = 2760 mg/l. For bluegill sunfish: EC50 (96 h) = 1470 mg/l (mean measured); NOEC (96 h) = 547 mg/l; LOEC (96 h) = 1260 mg/l. In all three tests a control run in parallel and test concentration analysis were measured at the test initiation and end. Water parameters such as temperature, dissolved oxygen, and pH were also measured in test chambers on a daily basis.

Two studies from literature are used for the assessment of the toxicity of triethanolamine to fish. In one study, the toxicity of test material to fish was assessed in the flow-through test. Twenty Fathead minnows were exposed to the substance at five concentrations for 96 hours. Fish were observed for mortality, behaviour and toxicity signs at 2-8, 24, 48, 72 and 96 hr after start initiation. Water temperature, dissolved oxygen and pH measurements were made in each exposure chamber daily where fish survived. The LC50 (concentration causing 50 % mortality of the fish) and EC50 (concentration causing 50 % of the fish to show an adverse effect) were estimated. Affected fish lost schooling behaviour, were hypoactive and darkly colored, had increased respiration and lost equilibrium prior to death; LC50 (96 h) = 11.8 g/l (measured), EC50 (96 h) = 11.8 g/l (measured). In another study, the toxicity to fish was evaluated according to APHA (1971), Method no. 231. Ten Goldfish were exposed to the test substance (test concentrations not specified) for 24 hours. The test was discontinued after 24 h since the TL_mvalue was higher than 5000 mg/l. TL_m, the concentration at which 50 % of the fish survived the test was obtained by interpolation from a graph of the logarithm of the concentration versus mortality; LC50 (24 h) > 5000 mg/l (measured).

For chemical safety assessment an EC50 of 1470 mg/l is used based on a study on perchlorate. This value is one of the lowest values obtained in all the studies (on triethanolamine and perchlorate) available (worst case senario). A lowest value determined in another study was 1365 mg/l (LD50) but even if this value is lower, it is not used for the chemical safety assessment since an EC50 instead of LC50 is used since it takes in consideration severe effects and not only mortality.

Short-term toxicity to aquatic invertebrates

The acute toxicity of the substance to Daphnia magna was determined in a 48 -hr limit static test, according to OECD Guideline 202 and EU Method C.2. Twenty daphnids were exposed to only one concentration of the substance, at 100 mg/l. No immobilised daphnia were observed at the tested concentration nor in the control group. In parallel, potassium dichormate as a reference substance was tested. As no immobilised daphnia were noted up to the tested concentration; EC50 > 100 mg/l (nominal).

Toxicity to aquatic algae and cyanobacteria

The effects of the test substance on the growth of Desmodesmus subspicatus, was tested in a 72 - hr test according to the OECD guideline 201 and EU Method C.3. Eight different concentrations of the substance, ranging from 2.2 - 460.0 mg/l, a reference substance and a control, were in contact for 72 hour with the algae. The cells were counted at the beginning and after 24, 48 and 72 hours of exposure and the percentage inhibition of growth rate, area under the growth curve - biomass integral and yield were estimated. The concentration - inhibition percentages for each response were plotted in graphs.

E_rC50 (72 h) > 460 mg/l (nominal), NOEC (growth rate) = 10 mg/l (nominal),E_bC50 (72 h) = 380 mg/l (nominal) and E_yC50 (72 h) = 230 mg/l (nominal).

Toxicity to microorganisms

The inhibitory effect of the substance to the microorganisms was assessed in a pretest and a main test according to OECD guideline 209 and EU Method C.11. In the pre-test, the substance was tested in four different concentrations (1; 10; 100; 1002 mg/l), and was in contact with the activated sludge taken from a biologic domestic sewage treatment plant. After 3 hours, the respiration rate was determined by the measurement of the oxygen concentration over a period of five minutes. A verification experiment (main test) was later conducted by using three concentrations of the substance (500; 1000; 1500 mg/l). Control and reference substance were also tested in both tests. The inhibition of oxygen consumption was calculated by comparison with the controls. The log concentration-inhibition percentage was presented in a graph and the EC50 was interpolated from the graph; based on the pretest and main test an EC50 (3 h) > 1000 mg/l (nominal) was obtained whereas based on the pre-test (in the main test it was not determinable) a NOEC (3 h)≈ 10 mg/l (nominal) obtained.

The EC50 of perchlorate for fish after 96 hours of exposure was 1470 mg/l based on measured concentrations. The LC50 for triethanolamine after 96 hours of exposure was much higher: 11800 mg/l. The EC50 values for daphnia and algae after 48 and 72 hours of exposure were higher than the highest tested concentrations, 100 mg/l and 460 mg/l respectively. EC50 microorganisms was found to be higher than 1000 mg/l. For algae, daphnia and microorganisms, the values are based on nominal concentrations whereas the measured concentrations were based not on the measurement of the substance it self but on the measurement of triethanolamine; the substance dissociates in water into sodium, perchlorate and triethanolamine. Taking in consideration the results of all the trophic levels, it seems that daphnia is the most sensitive organism, even if the EC50 could be expected to be higher than the highest tested concentration.

The substance is ultimately biodegradable since it biodegrades completely (100.3 %) at 19 days; even after 8 days the biodegradation is equal to 97.3 % based on DOC removal. On the contrary, the substance (more precisely triethanolamine that is one of the dissociation substances) is very stable abiotically since it remains stable in the water for a period of 10 days. The substance dissociates in water into sodium, perchlorate and triethanolamine therefore it could be assumed that the dissociation substances are also readily biodegradable and abiotically stable. Despite the low potential for abiotic degradation the substance is not expected to persist in the aquatic environment due to its ready biodegradability. The high water solubility and the low lipophilicity of the substance suggest a low potential for bioaccumulation and a low aquatic toxicity. The low potential of perchlorate for bioaccumulation was confirmed by the BCF determined in a Bluegill sunfish bioconcentration test in which a BCF of 0.70 l/kg was determined. This value is much lower than the threshold for bioaccumulation (≥ 500).