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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Based on the read-across approach, Veratrole is considered as harmful to algae.

Key value for chemical safety assessment

EC50/LC50 for freshwater algae:
50.5 mg/L
EC10, LC10 or NOEC for freshwater algae:
6.8 mg/L

Additional information

ANALOGS SELECTED FOR THE READ-ACROSS APPROACH

 

1,2-diethoxybenzene (ODEB), CAS: 2050-46-6. This substance has been registered under REACH in 2013, Rhodia is data owner of the algal toxicity study.

 

1,4-dimethoxybenzene (PDMB), CAS : 150-78-7. This substance has been registered under REACH in 2010, Rhodia is data owner of the algal toxicity study.

 

 

READ-ACROSS JUSTIFICATION

The ecotoxicity potential of Veratrole for algae is performed by a read-across approach with 1,2-diethoxybenzene (ODEB) and 1,4-dimethoxybenzene (PDMB). This approach is justified by the information below:

 

1) Structural similarity

The three substances have similar chemical structure.

The only difference between Veratrole and ODEB is that Veratrole has, at the same places on the benzene ring, 2 methoxy functions instead of 2 ethoxy functions for ODEB. Therefore, both substances have similar active function and similar molecular weight.

The only difference between Veratrole and PDMB is that the benzene ring in Veratrole is substituted at the ortho position, whereas the benzene ring in PDMB is substituted at the para position. Therefore, the functions are the same, but the difference of place of substitution can impact the toxicity effect of the substance. This analog has been selected to ensure that the toxicity is not underestimated when making an anlogy with a substance containing ethoxy functions (i.e. for ODEB) instead of methoxy functions.

 

Therefore, using ODEB and PDMB, the similarity in functional groups and in type of benzene substitution is covered. This structural similarities support the fact that they should show similar effect on organisms.

 

 

2) Similar bioavailability

The 3 substances are soluble in water (water solubility at 25°C of 6695 mg/L for Veratrole, 646 mg/L for ODEB, and 785 mg/L for PDMB). They have a low volatility (vapour pressure at 20°C of 73 Pa for Veratrole, 5.7 Pa for ODEB and 5.6 Pa for PDMB), a low potential of bioaccumulation (LogKow values of 1.75-2.22 for Veratrole, 2.64 for ODEB and 2.08 for PDMB). The 3 substances are rapidly biodegradable.

Based on the above information, the 3 substances should show similar bioavailability to organisms in the environment.

 

3) Similar ecotoxicity potential

Data on aquatic toxicity of Veratrole is only available for Daphnids. The 48-hour EC50 for Daphnia magna is >100 mg/L (Study performed in 2012). Acute toxicity data on the same species, Daphnia magna, are available for ODEB and PDMB showing a similar slightly higher sensitivity with a 48-hour EC50 between 10 and 100 mg/L and a 48h EC50 of 52 mg/L respectively. This suggests that the read-across approach with ODEB and PDMB does not underestimate the toxicity potential of Veratrole.

 

To conclude, based on the structural similarity, bioavailability and ecotoxicity potential, the ecotoxicity data obtained on ODEB and PDMB can be used to assess the algal toxicity potential of Veratrole.

 

ODEB is not harmful to algae whereas PDMB is harmful to algae. Consequently, as a worst case approach, Veratrole is considered as harmful to algae.