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Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 (72 h) > 100 mg/l (nominal)

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information

The toxicity of CAS 27344-06-5 to the unicellular freshwater green alga Pseudokirchneriella subcapitata was determined according to the OECD 201. The aim of the study was to assess the effects on growth rate and yield production over a period of 72 hours. The study was conducted under static conditions. Five concentrations were tested in a geometrical series with a dilution factor of 3.16 (nominal): 2.00, 6.32, 2.0, 63.2, 200 mg/l. All concentration levels and the control were analytically verified via HPLC-DAD: the test item in the fresh media (0 hrs) were in the range of 102 to 113 % of the nominal values at all tested concentration levels; the measured concentrations in the old media (72 hrs) were in the range of 29 to 33 % of the nominal values of all concentrations. Microscopic evaluation of the cells at the start and end of exposure revealed no morphological abnormalities. The No Observed Effect Level was stated at 11.3 mg/l for inhibition of both growth rate and yield after 72 hours and the ErC50 (72h) was stated as greater than 111 mg/l (meas. geom. mean).

It has to be taken into account that stilbene-type fluorescent whitening agents (FWAs) undergo photoisomerization. Taking into account the available information about the phototransformation in water (Kramer 1996, IUCLID section 5.1.3), equilibrium in distribution between the FWAs' E/Z isomers is expected to be in the range of 300 - 310 nm and lower/higher wavelengths are characterized by the predominance of the Z-isomer specie or vice-versa. Thus, during the test, it is expected that the analyses measured only one of the two isomers present in the tested solutions because the determination of the test item concentration was carried out by HPLC-DAD at the wavelength of 350 nm. Furthermore, considering the fact that substance is very soluble, not abiotically rapidly degraded and that in the study report no abnormalities of the test solution were observed, it is expected that the low concentration levels recorded at 72 hours are attributable to the method of analysis, rather than to the substance disappearance.

Data from the similar substances CAS 4193-55-9, 70942-01-7 and 16470-24-9 are taken into account.

These analogous are all dihydroxyethylamino derivative disulphonated sodium salt,, disulphonated sodium/potassium salt and tetrasulphonated sodium salt, respectively; their water solubilities are 48.2, 13.45 and 650 g/l, respectively, which are lower and higher than the substance under registration.

Acute toxicity for Green algae (Pseudokirchnerella subcapitata) was evaluated in the 72 hours screening test, according to the OECD guideline 201 in CAS 70942-01-7. A single dose was administrated at 100 mg/l, at which the grown inhibition was recorded at 2 % (Solvias AG., 1999).

The result was confirmed with the outcomes on analogous dihydroxyethyl derivatives sodium salt (CAS 4193-55-9) and the tetrasulphonated sodium salt (CAS 16470-24-9); in both cases a value of EC50 greater than 100 mg/l was set.