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Toxicity to aquatic algae and cyanobacteria

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Description of key information

With high probability acutely not harmful to fresh water aquatic algae.

Acutely harmful to marinewater algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
500 mg/L
EC50 for marine water algae:
21 mg/L

Additional information

Considering the toxicity of 3 -aminopropan-1 -ol (CAS 156 -87 -6) to aquatic algae, experimental data are available for fresh and marine water.

A static non-GLP 72 -h test with algae was conducted according to the German standard DIN 38412 p 9 (similar to OECD 201). The 72-hour ErC50 was 97.6 mg/L (nominal, BASF AG, Rep. no.:2/0022/89/t72). However, the observed effects are considered to be due to a pH-shift in the test water at higher test item concentrations; after neutralization, no adverse effects were observed (72 -h ErC50 > 500 mg/L, nominal):

The key study for acute toxicity to algae was performed using not-pH-adjusted test solutions. As the test substance causes an pH-shift to more alkaline conditions with increasing test substance concentrations, the test solutions of 500 mg/L and 62.5 mg/L were also tested after pH-adjustment.

The test solutions without pH-adjustment showed initial pH values between 8.23 and 10.61. The acceptable pH range for fish is given in the OECD TG 201 as pH 6.6 to 9.6. This pH range is only kept in the test concentrations of 31.25 mg/L or less (pH <= 9.7), while the other test solutions showed initial pH values above 9.6. While no significant effect was observed in the treatments with acceptable pH values after 72 h, no growth rate increase was determined in the treatments with a high pH (≥ 62.5 mg/L). It should be emphasized that no significant toxically effect was determined during an exposure of 72 h in the test concentrations of 500 and 62.5  mg/L with adjusted pH (pH range: 8 – 9.5). Therefore, it must be concluded that the observed toxicity effect is due to the pH shift, but not due to an inherent toxic effect of the test substance.

The test concentrations were not analytically verified. However, the substance is assumed to be stable due to the substances' water solubility (e.g. see IUCLID Chapter 4.8 ), its low vapor pressure (VP = 0.149 hPa @25°C; BASF AG, 1992) and its low Henry's Law Constant (HLC = 4.95E-05 Pa m³/mol, calculated with the EPI Suite v4.11, BASF SE 2016).

Moreover, it is concluded, that the significant adsorption is not expected for the substance (KOCWIN v2.00, EPISuite v4.11: log Koc = 0.33 (MCI Method), logKoc = -0.13 (Kow method) / Franco&Trapp, log Koc at pH 7 = 1.19, pKa= 10.22, SPARC v4.6)

In addition, the substance was tested under marine conditions according to ISO 10253 (Eide-Haugmo, 2009/2012), using Skeletonema costatum as test organism. The 72-h ErC50 was determined to be 21.0 mg/L (pH values are not specified). This study was selected as key study for marine water.

However, within the trophic level of aquatic algae, there are marked differences in sensitivity between freshwater and saltwater algae indicating that freshwater and saltwater data should not be pooled for hazard assessment and PNEC derivation. The derivation of the PNECaqua (marine) is, therefore, based on the available acute data for freshwater organisms providing a complete dataset for three trophic levels (see IUCLID chapter 6).

In conclusion, while the substance with high probability is not acutely harmful to aquatic freshwater algae, it is acutely harmful to aquatic algae in marine environment.