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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
In aqueous media, the target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0) dissociates into the three compounds methacrylic acid (CAS 79-41-4), chromium trichloride (CAS 10025-73-7) and propan-2-ol (CAS 67-63-0). Hence, methacrylic acid, chromium trichloride and propan-2-ol will be present regardless whether the target substance itself or methacrylic acid, chromium trichloride and propan-2-ol, respectively, were used as test material. Moreover, dissociation of the target substance (CAS 15096-41-0) is to be expected in aquatic environmental systems, which allows the read across between the target substance (CAS 15096-41-0) and the source substance chromium trichloride (CAS 10025-73-7).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The purity of the the source substance chromium trichloride which was used in the test with Scenedesmus capricornutum (reference 6.1.3-3) is unknown. The target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0), has a purity of 100 % (w/w).

3. ANALOGUE APPROACH JUSTIFICATION
Experimental data i.e. acute toxicity studies with aquatic algae were available for chromium trichloride. The source substance was tested in an study similar to OECD Guideline 201. This study revealed a 96-h NOEC and EC50 of 0.08 mg/L and 397 µgL (nominal, based on chromium(III)) . The information given on source substance is considered to be sufficient to cover the required endpoint information for the target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0).
Reason / purpose for cross-reference:
read-across source
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
397 µg/L
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
chromium(III)
Basis for effect:
growth rate
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
2 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
chromium trichloride hexahydrate
Basis for effect:
growth rate
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
In aqueous media, the target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0) dissociates into the three compounds methacrylic acid (CAS 79-41-4), chromium trichloride (CAS 10025-73-7) and propan-2-ol (CAS 67-63-0). Hence, methacrylic acid, chromium trichloride and propan-2-ol will be present regardless whether the target substance itself or methacrylic acid, chromium trichloride and propan-2-ol, respectively, were used as test material. Moreover, dissociation of the target substance (CAS 15096-41-0) is to be expected in aquatic environmental systems, which allows the read across between the target substance (CAS 15096-41-0) and the source substance methacrylic acid (CAS 79-41-4).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The purity of the source substance methacrylic acid which was used in the test with Scenedesmus capricornutum (reference 6.1.5-1), had an analytical purity of 99.87 %. The target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0), has a purity of 100 % (w/w). Thus, the purity of the test materials is comparable.

3. ANALOGUE APPROACH JUSTIFICATION
Experimental data i.e. acute toxicity studies with aquatic algae were available for methacrylic acid. The source substance was tested in an study according to OECD Guideline 201. This study revealed a 72-h NOEC and EC50 (growth rate) of 8.2 mg/L and 45 mg/L, respectively. The information given on methacrlic acid is considered to be sufficient to cover the required endpoint information for the target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0).
Reason / purpose for cross-reference:
read-across source
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
530 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1 260 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
In aqueous media, the target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0) dissociates into the three compounds methacrylic acid (CAS 79-41-4), chromium trichloride (CAS 10025-73-7) and propan-2-ol (CAS 67-63-0). Hence, methacrylic acid, chromium trichloride and propan-2-ol will be present regardless whether the target substance itself or methacrylic acid, chromium trichloride and propan-2-ol, respectively, were used as test material. Moreover, dissociation of the target substance (CAS 15096-41-0) is to be expected in aquatic environmental systems, which allows the read across between the target substance (CAS 15096-41-0) and the source substance propan-2-ol (CAS 67-63-0).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The purity of the source substance propan-2-ol which was used in the test with Scenedesmus quadricauda (reference 6.1.5-5) is unknown. The target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0), has a purity of 100 % (w/w).

3. ANALOGUE APPROACH JUSTIFICATION
Experimental data i.e. acute toxicity studies with aquatic algae were available for propan-2-ol. This study revealed a 7-d toxicity threshold value (equivalent to LOEC) of 1800 mg/L (nominal/measured not specified). The information given on propan-2-ol is considered to be sufficient to cover the required endpoint information for the target substance complexation reaction products of Tetrachloro-μ-hydroxy(μ-methacrylato-O:O')dichromium, isopropylalcohol and water (CAS 15096-41-0).
Reason / purpose for cross-reference:
read-across source
Duration:
7 d
Dose descriptor:
other: toxicity threshold
Effect conc.:
1 800 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
other: mean extinction level

Description of key information

The 96-h NOEC and EC50 of the structural analogue chromium trichloride (CAS 10025-73-7) was determined to be 0.08 mg/L and 397 µg//L (nominal, based on chromium(III)).

Key value for chemical safety assessment

EC50 for freshwater algae:
397 µg/L
EC10 or NOEC for freshwater algae:
0.08 mg/L

Additional information

No data on toxicity to auqatic algae was availbale for the substance itself. In aqueous media, the substance dissociates into the three compounds methacrylic acid (CAS 79-41-4), chromium trichloride (CAS 10025-73-7) and propan-2-ol  (CAS 67-63-0). Thus, dissociation of the target substance (CAS 15096 -41 -0) is to be expected in aquatic environmental systems. Therefore, a read across between the target substance (CAS 15096-41-0) and the source substances methacrylate (CAS 79-41-4), chromium trichloride (CAS 10025-73-7) and propan-2-ol (CAS 67-63-0) was conducted. The available studies were assesseed in a weight of evidence approach.

 

Data are available for a short-term toxicity of the structural analogue methacrylic acid was assessed in a static test according to OECD Guideline 201 and in compliance with GLP principles. Pseudokirchneriella subcapitata was exposed over the test duration of 72 hours to nominal concentrations of 0.86, 1.9, 4.1, 9.1, 20, 45 and 100 mg/L. The geometric mean measured concentrations were: 0.85, 2.0, 3.7, 8.2, 19, 45, 100 mg/L. In result, the 72-h EbC50 (biomass) and ErC50 (growth rate) were 20 and 45 mg/L (geometric mean measured), respectively. The NOEC for growth and biomass was both 8.2 mg/L (geometric mean measured). The test is valid

 

The short-term toxicity of the structural analogue methacrylic acid (Severdrup et al, 2001) was assessed in a static test according to OECD Guideline 201 and in compliance with GLP principles. Skeletonema costatum was exposed over the test duration of 72 hours to nominal concentrations. In result, the 72-hErC50 (growth rate) was determined to be >1260 mg/L, respectively. The NOEC for growth was determined to be 530 mg/L (reference 6.1.5-1).

 

The short-term toxicity of the structural analogue chromium trichloride (CAS 10025-73-7) was assessed by Richter, 1982 in a study with Scenedesmus capricornutum similar to OECD Guideline 201 and US EPA OTS 797.1050 (reference 6.1.5-3).  The 96h-ErC50 of the test substance (chromium chloride) was 397 µg Cr/L. Thus, the 96h-ErC50 of chromium trichloride (anhydrous) to the algae can be estimated as 1.21 mg CrCl3/L or 2.0 mg CrCl3.6H2O/L. The effects seen might be caused by the intense violet colour of chromium trichloride hexahydrate solutions, hindering algae access to light, and thus not attributable to algae toxicity. A NOEC of 0.08 mg Cr/L (equivalent of 0.41 mg CrCl3.6H2O/L) was reported too in Concise International Chemical Assessment Document 76 INORGANIC CHROMIUM(III) COMPOUNDS, 2009.

 

The short-term toxicity of the structural analogue propan-2-ol (CAS 67-63-0) was assessed by Bringmann & Kühn, 1980 in a 7-d study with Scenedesmus quadricauda. The concentration of the algal suspension was measured turbidimetrically and expressed by the extinction of the primary light of the monochromatic radiation at 578 nm for a layer of 10 mm thickness. As a result, the 7-d toxicity threshold value (comparable to the LOEC) was determined to be 1800 mg/L (reference 6.1.5-5).

 

Conclusion

The lowest EC50 of 397 µg/L (96-h nominal, based on chromium(III) was determined for the structural analogue chromium trichloride (CAS 10025-73-7). The NOEC (96-h) for chromium trichloride was found to be 0.08 mg/L and 397 µg//L (nominal, based on element chromium(III)). In a worst case approach, the 72-h NOEC and EC50 for the target substance is considered to be 0.08 mg/L and 397 µg/L (0.000397 mg/L), respectively.