2,2'-iminodiethanol

Toxicity to aquatic algae and cyanobacteria

Description of key information

Acutely toxic for aquatic algae

Key value for chemical safety assessment

EC50 for freshwater algae:

9.5 mg/L

EC50 for marine water algae:

86.96 mg/L

EC10 or NOEC for freshwater algae:

1.1 mg/L

Additional information

Regarding the toxicity of diethanolamine to algae, data of different studies and screening tests are available covering the freshwater species Pseudokirchneriella subcapitata,  Desmodesmus subspicatus, Ankistrodesmus bibraianus as well as the marine species Phaeodactylum tricornutum. The respective results are summarized in the table below and subsequently discussed in detail:

 

Table: Effect concentrations of diethanolamine, determined for aquatic algae:

	Guideline	Species	Results [mg/L]
Key Study Dow Chemical (1982)	US EPA algal assay bottle test 600/9-78-0718	P. subcapitata	Recalculation with ToxRat v2.10: Test 1: 72-h NOErC: 0.6 72-h ErC10: 1.4 72-h ErC50: 9.5 Test 2: 72-h NOErC: n.d.* 72-h ErC10: 1.1. 72-h ErC50: 19.0 Original result: 96-h ErC50: 2.2 (geom. mean)
Screening Tests (supporting study) BASF AG (1992)	DIN 38412-9; Re-evaluated with ToxRat v2.10	D. subspicatus	Not neutralised: 72-h ErC10: 85.7 72-h ErC50: 107.3 Neutralised: 72-h ErC10: 2.4 72-h ErC50: 14.9
Screening Tests (supporting study) BASF AG (1992)	DIN 38412-9; Re-evaluated with ToxRat v2.10	A. bibraianus	Not neutralised: 72-h ErC10: 30.1 72- ErC50: 57.5 Neutralised: 72-h ErC10: 123.9 72-h ErC50: > 100**
Marine test (supporting study) Libralato et al. (2010)	ISO 10253; Marine algal growth inhibition test	P. tricornutum (marine)	72-h NOErC: < 16 72-h ErC50: 86.96

 

* Not determined (n.d.), due to a multiple sequentially-rejective U-test after Bonferroni-Holm.

** The ErC50 could not be calculated due to the limited number of replicates. However, as the highest concentration tested was 100 mg/L and the ErC10 is already calculated to be > 100 mg/L, the ErC50 is concluded to be clearly > 100 mg/L.

 

Key study:

The most sensitive result was obtained in a GLP study following the US EPA algal assay bottle test 600/9-78-018 (1978) and using the green algae Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum) (DOW Chemical, 1982). The applied calculation method for the specific growth rates by using cell count values is comparable to current guidelines, e.g. OECD 201. Therefore, the reported EC50 for cell count can be regarded as related to the internationally preferred endpoint growth rate (ErC50).

Test 1 and test 2 were re-evaluated by using ToxRat Professional v2.10.

Test 1: The 72-h ErC10 was recalculated to be 1.4 mg/L (72-h EyC10: 0.7 mg/L); the 72-h ErC50 was determined to be 9.5 mg/L (96-h EyC50: 2.7 mg/L). 

Test 2: The 72-h ErC10 was recalculated to be 1.1 mg/L (72-h EyC10: n.d.); the 72-h ErC50 was determined to be 19 mg/L (96-h EyC50: 3.3 mg/L).

 

Supporting freshwater screening tests:

The effect of neutralised and non-neutralised test solutions with diethanolamine was examined in screening studies with Ankistrodesmus bibraianus and Desmodesmus subspicatus in 72-hour static tests following the German Industrial Standard DIN 38412, part 9 (BASF AG, 1992/1444/60, Rep. no 92/1444/60). These screening tests were selected as supporting studies. With neutralised samples, the pH values ranged from 7.7 - 8.1 at test start to 8.0 - 8.5 (without algae), respective 8.3 - 9.0 (with algae) after 72 h. In the non-neutralised samples, the pH values ranged from 7.4 - 8.8 at test start to 7.9 - 8.5 (without algae), respective 8.3 - 9.0 (with algae) after 72 h.

The measured data of the screening tests were re-evaluated with ToxRat v2.10 (BASF SE, 2015). For Ankistrodesmus bibraianus the 72-h ErC50 under non-neutralised conditions was determined to be 57.5 mg/L (ErC10, non-neutralised: 30.1 mg/L). The ErC50 for neutralised test solutions could not be calculated due to the limited number of replicates. However, as the highest concentration tested was 100 mg/L and the chronic value for neutralised test solutions is already calculated to be > 100 mg/L (ErC10, neutralised: 123.9), the ErC50 under neutralised conditions is concluded to be clearly >100 mg/L. The respective 72-h ErC50 values for Desmodesmus subspicatus were 14.9 mg/l (neutralised) and 107.3 mg/l in non-neutralised test solutions (ErC10, neutralised: 2.4 mg/L; ErC10, non-neutralised: 85.7 mg/L).

With respect to potential pH effects, these results seem to be contradictory since in one case higher sensitivity was observed under non-neutralized compared to neutralized conditions, and in the other case this was just the opposite. However, pH neutralisation was carried out in these studies to correct the pH variation associated with  test substance, whereas the pH increases observed in all these tests were due to reduction in dissolved carbon dioxide in the media as the tests progressed (algal photosynthesis). It is likely that this continuing reduction in dissolved CO2 had a far greater effect on pH than preceding neutralisation for test substance. Hence, these differences in test results might also be due to intra-laboratory and/or biological variation (SIDS Initial Report for SIAM 24; Paris, France 17. - 20. April 2007).

 

Marine studies: 

In a supporting study by Libralato et al. (2010) marine algae were tested according to ISO 10253. The test species was Phaeodactylum tricornutum. The concentration of the test item was analytically verified in the stock solution. After 72 h of exposure an EC50 of 86.96 mg/L and a NOEC of < 16 mg/L were determined.

 

 

In conclusion, diethanolamine is supposed to be acutely toxic for aquatic algae.