Hexachlorocyclopentadiene

Endpoint summary

Description of key information

The short-term toxicity to the aquatic environment of Hexachlorocyclopentadiene was investigated using reliable studies and literature data available on the substance. The substance was found to be toxic to freshwater species such as fish, invertebrates, and algae. Aquatic invertebrate was identified as the most sensitive species with a 48-hour EC50 of 0.039 mg/l, resulting from a short-term toxicity study performed on Daphnia magna according to a method similar to the OECD Testing Guideline 202.

Considering that the 48-hour EC50 for algae is below 1 mg/l, Hexachlorocyclopentadiene meets the criteria for classification as Aquatic Acute 1; H400 in accordance with Regulation (EC) N° 1272/2008. This Classification is consistent with the Harmonised Classification of Hexachlorocyclopentadiene as Aquatic Acute 1; H400.

A M-factor of 10 is proposed for the acute aquatic toxicity of the registered substance, based on the lowest 48-hour EC50 of Hexachlorocyclopentadiene being comprised between 0.01 mg/l and 0.1 mg/l, in accordance with Regulation (EC) N° 1272/2008.

 

There is no available data on the chronic toxicity of Hexachlorocyclopentadiene to the aquatic environment. As the substance is being registered under REACH in the 10-100 tonnage band there is no requirement for information on long-term studies to aquatic species. Therefore the Classification of the registered substance for chronic effects is based on the short-term toxicity to the aquatic environment and the biodegradation of the substance.

An assessment was performed on the ready biodegradability of Hexachlorocyclopentadiene based on available literature data on the substance. It was concluded that it was expected to be inherently biodegradable but not readily biodegradable. Therefore it does not meet the criteria to be considered as ‘rapidly biodegradable’ according to Regulation (EC) N° 1272/2008.

Considering that the 48-hour EC50 for algae is below 1 mg/l and the substance is not ‘rapidly biodegradable’, Hexachlorocyclopentadiene meets the criteria for classification as Aquatic Chronic 1; H410 in accordance with Regulation (EC) N° 1272/2008. This Classification is consistent with the Harmonised Classification of Hexachlorocyclopentadiene as Aquatic Chronic 1; H410.

A M-factor of 1 is proposed for the chronic aquatic toxicity of the substance. There is no NOEC available in order to determine the M-factor in accordance with Regulation (EC) N° 1272/2008, so expert judgement was used. A M-factor was considered as sufficient based on the expected inherent biodegradability, hydrolysis, and phototransformation in water of the substance.

 

Desmares-Koopmans (2003) investigated the toxicity of Hexachlorocyclopentadiene to STP microorganisms during a study performed according to the OECD Testing Guideline 209. The EC50 derived from the test was >100 mg/l with an EC10 = 100 mg/l over a duration of 0.5 hours. These results had no impact on the Classification of the substance.

 

A Harmonised Classification as Aquatic Acute 1; H400 and Aquatic Chronic 1; H410 is currently attributed to Hexachlorocyclopentadiene for its toxicity to the aquatic environment.