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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The ErC50 (growth rate, Desmodesmus subspicatus, 72h) was determined in a GLP guideline test to be 67 mg/l. the NOEC was set to 15 mg/l in this test.
The IC50 (Chlorella vulgaris, 7d) in a study equivalent to OECD201 method but performed for 7 days was reported as 1.064 mg/l indicative of toxici effects of 2-chlorobutane towards algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
67 mg/L
EC10 or NOEC for freshwater algae:
15 mg/L

Additional information

In an OECD 201 GLP-study significant inhibition of algal growth was observed at the two highest concentrations containing 46 and 100 mg/L (nominal concentration).

At the beginning and at the end of the test, the content of the test item in the test solutions was determined using GC-determination. During validation of the analytical method, stability in test medium after 72 hours had been determined as 77%. Loss of test item in the alga study might be caused by unavoidable opening of the test system during measurements of the cell density and ingestion of test item by the alga cells. The measured concentrations at the start of the test ranged between 88 % and 114 % of the nominal concentrations. Therefore, the determination of the biological results was based on the geometric mean of the measured concentrations.

The following results for the test item SBC (sec. Butylchloride) were determined: 





Growth Rate

15 mg/L

30 mg/L

67 mg/L (extrapolated)


15 mg/L

30 mg/L

35 mg/L


15 mg/L

30 mg/L

30 mg/L

In a publication by Wang et al. different chlorinated compounds were tested for toxicity to daphnia, carp and chlorella . The study authors concluded that tolerance for haloalkanes was higher for daphnia than for carp and chlorella. This was shown for 2 -Chlorobutane too, as algae toxicity was found being 1.064 mg/l (IC50), and fish and daphnia toxicity were 316.22 mg/l (LC50) and 707.10 mg/l (LC50) respectively. Consequently, algae seem to be the most sensitive species for aquatic toxicity of halogen alkanes. However, as the publication lack certain details, especially regarding analytics and controls the validity could not be assessed and the result was not considered.