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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
For details on endpoint specific justification please see read-across report in section 13 or find a link in cross-reference “assessment report”.
Reason / purpose for cross-reference:
assessment report
Reason / purpose for cross-reference:
read-across source
Duration:
5 d
Dose descriptor:
NOEC
Effect conc.:
0.062 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
cell number
Remarks on result:
other: Water from White river: pH 7.3, 299 mg/L CaCO3, 68 mg/L suspended solids
Duration:
5 d
Dose descriptor:
NOEC
Effect conc.:
0.078 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
cell number
Remarks on result:
other: Laboratory water: 20 mg/L CaCO3
Conclusions:
The source substance DHTDMAC was tested for toxicity towards freshwater green algae (Selenastrum capricornutum; EU-RAR; Lewis and Wee, 1983) in a 5 d growth inhibition test (according to literature protocol). The test was performed both based on laboratory water and river water (68 mg/l suspended solids, 0.2 µg/l MBAS). The following results relevant for the target substance DTDMAC were determined:
Laboratory water:
NOEC (Selenastrum capricornutum; 5 d; yield; nom., act. ingr.) = 0.078 mg/l; algistatic concentration (nom., act. ingr.): 0.228 mg/l
River water (68 mg/L susp. solids):
NOEC (Selenastrum capricornutum; 5 d; yield; nom., act. ingr.) = 0.062 mg/l; algistatic concentration (nom., act. ingr.): 0.708 mg/l
Executive summary:

The study used as source investigated the toxicity towards freshwater green algae using the source substance DHTDMAC. The study results determined for the source substance were considered applicable to the target substance. Justification and applicability of the read-across approach (structural analogue) is outlined in the read-across report in section 13 or find a link in cross reference “assessment report”.

Description of key information

Toxicity figure are based on river water testing. Although the river water test with DTDMAC and Pseudokirchnerella subcapitiata has resulted in a higher NOEC of 0.37 mg/L than with DHTDMAC and Selenastrum capricornutum (NOEC 0.062 mg/L) the latter value is taken as a worst case in deriving the PNEC aquatic because of the read across approach used for DTDMAC throughout this assessment (see reasoning for the read across approach).

Key value for chemical safety assessment

EC50 for freshwater algae:
1.17 mg/L
EC10 or NOEC for freshwater algae:
0.062 mg/L

Additional information

A more recent test on the submission substance DTDMAC itself (Akzo, 2010) was performed compliant with GLP and according to the current OECD 201 (2006). It is reliable without restrictions. Nonetheless, the more conservative result from read-across to DHTDMAC is taken as a worst case in deriving the PNEC aquatic because of the read across approach used for DTDMAC throughout this assessment (see further details on this and other available data below).

In this new test on DTDMAC, the following final nominal test concentrations were prepared: Control, 0.01, 0.03, 0.11, 0.37 and 1.2 mg/L. Test item concentrations were analytically verified.

In this 72-h algae (Pseudokirchneriella subcapitata) toxicity test with DTDMAC using river water (bulk approach; susp. solids 17.2 mg/L, DOC 2 mg/L), the following 72 h effect concentrations were determined (measured initial):

ErC50 > 1.2 mg/L;

ErC10 = 0.58 mg/L;

NOEC = 0.37 mg/L;

LOEC = 1.2 mg/L

These results on DTDMAC are corroborated by published data determined on the source substance DHTDMAC. In this supporting study by Roghair et al. (1992) toxicity towards freshwater green alga Scenedesmus pannonicus was tested in a 96 h growth inhibition test (according to Netherlands standard NNI method 6506, 1984). Most relevant parameters for this study type are reported in the scientifically valid publication, including details on the test item used. Accordingly, it was assigned a Klimisch reliability score of 2 (Klimisch et al., 1997). The test was performed in sterilized and filtered lake water water (suspended solids concentration: 1-4 mg/L; DOC: 5.5-5.9 mg/L). The following results relevant for the target substance DTDMAC were determined:

Experiment 1:

NOEC (Scenedesmus pannonicus; 96 h; growth; nom., act. ingr.) = 0.787 mg/L;

Experiment 2:

NOEC (Scenedesmus pannonicus; 96 h; growth; nom., act. ingr.) = 0.441 mg/L;

Overall result (geometric mean NOEC):

NOEC (Scenedesmus pannonicus; 96 h; growth; nom., act. ingr.) = 0.589 mg/L.

These data summarized above fit together very well, are based on a relevant endpoint (growth rate) and an exposure time (72 and 96 h, respectively) over which exponential growth of algae was verified or can reasonably be assumed. Because of this, in spite of the lower toxicity (higher effect values) observed in both of these tests compared to the one used as key value and - ultimately - for PNEC derivation according to the EU RAR on DODMAC (EU, 2002) (NOEC based on yield after 5 days: 0.062 mg/L; EG & G Bionomics, 1981), actually those data are deemed to be of higher reliability and relevance. This is underpinning the conservativeness inherent in following the EU RAR.

Further available data, including the study used for derivation of the PNEC according to the EU Risk Assessment Report on DODMAC, are summarized as follows:

Read across for DTDMAC from structurally similar Quats DHTDMAC/DODMAC can be applied and the corresponding effect data form DHTDMAC/DODMAC used for DTDMAC as well.

From the EU Risk Assessment DODMAC (EU, 2002) the following discussion on algae toxicity is available (slightly adapted, where necessary):

Toxicity to Algae

The toxicity of DODMAC for Selenastrum capricornutum and Microcystis aeruginosa in laboratory water was investigated according to an ASTM method (Lewis & Hamm, 1986). For growth reduction after 96h the EC50 was 0.06 mg/l for Selenastrum capricornutum and 0.05 mg/l for Microcystis aeruginosa (nominal concentrations; pH = 6.8 - 7.2, hardness = 131 - 146 mg/l CaCO3).

An algae study with DODMAC in filtered natural water of the Little Miami River, OH (5.4 mg/l total organic carbon, pH = 8.1 - 8.4, hardness = 171 mg/l CaCO3) was conducted by Versteeg & Shorter, 1993. For Selenastrum capricornutum a 96 h EC50 of 1.12 mg/l was derived for growth reduction (measured concentration) and the algistatic concentration was above 16.4 mg/l. In this study acidic methanol was used as carrier solvent, which had a growth stimulating effect on the algae. (DODMAC was synthesized by a special route which ensures no MTTMAC.)

Another study with DODMAC is cited in ECETOC, 1993, but no test protocol is available (Akzo, 1990a). Selenastrum capricornutum was tested in laboratory and river water but water qualities are not characterized. In river water the EC50 was 1.17 mg/l, in laboratory water an EC50 of 0.46 mg/l was measured after 96 hours (nominal conc.). The EC50 (96h) of 1.17 mg/L is taken as the lowest acute toxicity values of fish, daphnia and algae measured in river water for the DSD and CLP Classification.

Selenastrum capricornutum was also tested with DHTDMAC (no information on purity) in laboratory water according to OECD guideline 201 (Akzo, 1991c). Although the study was initiated by the same sponsor as above it is not clear whether the same test method was used with DODMAC. DHTDMAC was emulsified in the stock solution by a 60 minutes ultrasonic treatment. The test flasks were conditioned by incubation with the test solutions prior to the test. For biomass reduction a 96h NOEC of 0.006 mg/l, an EC10 of 0.013 mg/l and an EC50 of 0.026 mg/l were derived. For effects on the growth rate an EC50 of 0.074 mg/l resulted. The effect values were based on nominal concentrations of the active ingredient although in a preliminary range finding test DHTDMAC concentrations had decreased below the detection limit of 20 µg/l in flasks which were not incubated with algae. A shorter sonication of < 10 minutes resulted in a higher 96h EC50- and NOEC-value of 0.21 mg/l and 0.12 mg/l (no details on test conditions; Akzo, 1991d, cited in ECETOC, 1993).

The influence of different test media on the sensitivity of Selenastrum capricornutum towards DHTDMAC (71.4% active ingredient) was investigated by EG & G Bionomics, 1981 b,c,d. Laboratory water with a hardness of 20 mg/l CaCO3 (no further characterization) and algae nutrient enriched White River water (Indiana) of the following quality prior to autoclaving were used: pH = 7.3, total hardness = 299 mg/l CaCO3, 68 mg/l suspended solids, 0.2 µg/l MBAS) In laboratory water a NOEC of 0.078 mg/l and an algistatic concentration of 0.228 mg/l were derived for the reduction of cell number after 5 days (nominal concentrations of active ingredient). The corresponding values for the river water were: NOEC = 0.062 mg/l and algistatic concentration = 0.708 mg/l. This NOEC of 0.062 mg/L is used as the key value for chemical safety assessment, in accordance with the EU RAR on DODMAC (2002). Further data presented in the EU RAR show that results for Microcystis aeruginosa were similar (EG & G Bionomics, 1981 b,c,d).

In ECETOC, 1993, also the toxicity of DHTDMAC containing 4.6% MTTMAC to Selenastrum capricornutum and Microcystis aeruginosa in laboratory water is cited (no details on test conditions, Procter & Gamble, 1974 - 1986). The 5 d EC50-values were 0.13 and 0.12 mg/l and the NOECs for both species were 0.075 mg/l, which are a factor of 2-3 lower than the effect values for DHTDMAC containing 8% MTTMAC derived in EG & G Bionomics, 1981 b,c,d.

In tests with two other river waters, for which the water quality was not characterized in the test protocol, the 5 day algistatic concentrations were 2.58 mg/l and 35.7 mg/l (nominal con­centrations of active ingredient, EG & G Bionomics, 1981 b,c). From the reference Lewis and Wee, 1983, it could be concluded possibly that it might be autoclaved Rapid Creek water in one case and in the other the same water enriched after filtration with 131 mg/l sediment. (Rapid Creek,South Dakota: pH = 6.6 - 7.3, total hardness = 388 - 442 mg/l CaCO3, 131 mg/l suspended solids, < 20 µg/l DBAS). In the tests EG & G Bionomics, 1981 b,c,d isopropanol was used as carrier solvent and DHTDMAC contained 8% MTTMAC.

The toxicity of DODMAC (this is assumed to be DHTDMAC) incorporated in wwtp effluent to Selenastrum capricornutum was reported by Versteeg (1987). Test solutions were prepared from laboratory scale CAS-units as described above for Ceriodaphnia dubia. After 96 hours the EC20-values for growth reduction were in the range of 0.047 and 2.91 mg/l. The toxicity decreased with increasing amounts of added industrial wastewater. In a comparable study from Versteeg & Woltering (1990) DODMAC concentrations in CAS-unit effluents up to 20.3 mg/l had no effect on Selenastrum capricornutum. The test concentrations were produced by treatment of surfactant containing influents of two municipal wwtps in a laboratory scale continuous activated sludge system (CAS). The influent was supplemented with different concentrations of untreated industrial plant waste water. This resulted in different DODMAC concentrations in the effluent matrix. The system was preacclimatized for 32 days. Toxicity to Ceriodaphnia dubia was measured in a 7 d reproduction test with the effluents diluted with river water. MATC-values were lowest in the CAS effluents where no industrial waste water was added additionally with 99 and 267 µg/l DODMAC, which is similar to studies with river water. In the CAS effluents where industrial wastewater was added toxicity was reduced to between 1.0 and 3.75 mg/l, demonstrating the high influence of the effluent matrix. The concentrations of total suspended solids in the first case were 19 and 21 mg/l and in the second case 38 to 111 mg/l might be one possibility of explanation for the different toxicities. The concentration of MTTMAC increased with decreasing toxicity.

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