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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2002
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The read-across approach should be used to support the assessment of m-toluidine (3-methylaniline, CAS No. 108-44-1, EC No. 203-583-1) and data gap filling using fate and (eco)toxicity data of p-toluidine (4-methylaniline, CAS No. 106-49-3, EC No. 203-403-1). Together with the o-toluidine (2-methylaniline, CAS No. 95-53-4, EC No. 202-429-0), they make up the structural isomers of methylated aniline. The different substitution pattern lead to minor difference in chemical reactivity of the substances.
It is reasonable to assume and experimentally verified that source and target substance have nearly identical behavior in physico-chemical and (eco) toxicological studies. Studies regarding o-toluidine allow a comprehensive data evaluation, supporting the read-across approach and clarifying the quantitatively similar effects of the substances. While all three isomers exhibit effects in the same range, no clear tendency can be derived. However, in some effects, p-toluidine is slightly stronger than the other isomers. Therefore, the read-across also considers the worst-case approach.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
All substances are structural isomers of methylated aniline. The structures consist of a benzene ring, a methyl group and an amino group, substituted directly to the ring. They have a clear identity with high purity ( > 99 %). (see Justification Document for Details.)

3. ANALOGUE APPROACH JUSTIFICATION
Source and target substances are isomers of methylated aniline. The structures consist of a benzene ring, a methyl group and an amino group, connected directly to the benzene ring. All isomers employ the same empirical formula: C7H9N, and molecular weight: 107.1531 g/mol. A methyl group is substituted either in meta- or in ortho- or para- position to the amino group of the aniline ring. Source and target substances are isomers and therefore have very similar chemical structures and can be regarded as homologous structures. The only difference between both substances is displayed by the position of the methyl group. In addition to only little differences in structure between these substances, there are further data, which confirm the similarity concerning behavior. Due to the common structural aspects, the main physico-chemical parameters like vapour pressure, water solubility, octanol/water partition coefficient, organic carbon partition coefficient and dissociation constant are in the same range.For m-toluidine and p-toluidine, the main ecotoxicological parameters like short-term toxicity on Daphnia and fish, toxicity on algae, and long-term toxicity on Daphnia are in the same range. It is shown that Daphnia is the most sensitive aquatic organism for both isomers.
Overall, based on the comparable composition of source and target, their similar physico-chemical properties and ecotoxicological effects the read-across approach for assessment of the boiconcentration factor and the long-term toxicity towards fish is justified.
Reason / purpose for cross-reference:
read-across source
Guideline:
other: "Bioaccumulation test of chemical cubstance in fish and shellfish", order of the prime minister, the minister of health and welfare, the minister of international trade and industry No 1, Japan, 1974
Principles of method if other than guideline:
This guideline corresponds to OECD Guideline 305C (Bioaccumulation: Test for the degree of bioconcentration in Fish), 1981
GLP compliance:
not specified
Test organisms (species):
Cyprinus carpio
Route of exposure:
aqueous
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
28 d
Nominal and measured concentrations:
10 and 100 µg/L (nominal)
Type:
BCF
Value:
< 1.3
Remarks on result:
other: Conc.in environment / dose:100 µg/l
Type:
BCF
Value:
< 13
Remarks on result:
other: Conc.in environment / dose:10 µg/l

judgement: low bioconcentration

 

lipid content of fish

-         start of testing: 2.80%

-         end of testing: 2.95%

Validity criteria fulfilled:
not specified
Remarks:
Since the test is poorly reported the validity criteria cannot be assessed sufficiently. Nevertheless the test is considered as valid based on the data given.
Conclusions:
With a BCF of < 1.3 at 100 µg/L and < 13 at 10 µg/L the substance has a very low potential for bioaccumulation.
Executive summary:

As there is no data available for m-toluidine, read across with p-toluidine (CAS No. 106-49-0) is proposed to cover this endpoint. m-Toluidine and p-toluidine are isomers and have very similar chemical structures. Their main physico-chemical parameters (vapour pressure, water solubility, octanol/water partition coefficient, organic carbon partition coefficient and dissociation constant) are in the same range. The main ecotoxicological parameters like short-term toxicity on Daphnia and fish, toxicity on algae, and long-term toxicity on Daphnia are also in the same range. It is shown that Daphnia is the most sensitive aquatic organism for both isomers. Therefore a read across between these two substances to cover physico-chemical and ecotoxicological endpoints for m-toluidine seems to be justified. More details regarding the read across justification are depicted in the annex of the Chemical Safety Report (CSR).

According to a guideline which corresponds to OECD Guideline 305C (Bioaccumulation: Test for the degree of bioconcentration in Fish), a BCF of < 1.3 at 100 µg/L and < 13 at 10 µg/L was determined on fish (Cyprinus carpio) for p-toluidine. The test was conducted by EA, Japan: "Investigation of the Ecotoxicological Effects of OECD High Production Volume Chemicals", Office of Health Studies, Environmental Health Department, Environment Agency, Japan.

Description of key information

With a BCF of < 1.3 at 100 µg/L and < 13 at 10 µg/L the substance has a very low potential for bioaccumulation.

Key value for chemical safety assessment

BCF (aquatic species):
13 dimensionless

Additional information

As there is no data available for m-toluidine, read across with p-toluidine (CAS No. 106-49-0) is proposed to cover this endpoint. m-Toluidine and p-toluidine are isomers and have very similar chemical structures. Their main physico-chemical parameters (vapour pressure, water solubility, octanol/water partition coefficient, organic carbon partition coefficient and dissociation constant) are in the same range. The main ecotoxicological parameters like short-term toxicity on Daphnia and fish, toxicity on algae, and long-term toxicity on Daphnia are also in the same range. It is shown that Daphnia is the most sensitive aquatic organism for both isomers. Therefore a read across between these two substances to cover physico-chemical and ecotoxicological endpoints for m-toluidine seems to be justified. More details regarding the read across justification are depicted in the annex of the Chemical Safety Report (CSR).

According to a guideline which corresponds to OECD Guideline 305C (Bioaccumulation: Test for the degree of bioconcentration in Fish), for p-toluidine a BCF of < 1.3 at 100 µg/L and < 13 at 10 µg/L was determined on fish (Cyprinus carpio) for p-toluidine. The test was conducted by EA, Japan: "Investigation of the Ecotoxicological Effects of OECD High Production Volume Chemicals", Office of Health Studies, Environmental Health Department, Environment Agency, Japan.

An experimentally determined logKow of 1.4 for m-toluidine supports this consideration that the substance has a low potential for bioaccumulation.

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