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Short-term toxicity to fish

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Description of key information

Key value for chemical safety assessment

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COPPER IODIDE

The environmental hazard associated with copper iodide is assessed in terms of the toxicity of copper and iodide ions released during dissociation of the compound in the aqueous phase.

Summary information on the short-term toxicity of copper and iodide ions to fish is presented below.

COPPER:

See endpoint summary aquatic toxicity.

IODINE:

Short description of key information:

Short term toxicity to fish:

LC50 (96 hours): 1.67 mg/L Oncorhynchus mykiss (rainbow trout)

Key value for chemical safety assessment: 

LC50 for freshwater fish: 1.67 mg/L.

Discussion:

Two short term toxicity to fish studies have been identified for iodine:

- A 96 hour acute study under static conditions that investigated the toxicity of iodine to Rainbow Trout (Oncorhynchus mykiss) (toxicity to Daphnia magna was also investigated) [Laverock MJ, Stephenson M, and Macdonald CR (1995)]. This study is attached under the endpoint study record for section 6.1.1 - short term toxicity to fish.

- An acute study (in static conditions with exposure durations up to 24 hours) that investigated the acute toxicity of iodine to channel catfish [LeValley MJ (1982)].

The 96 hour acute study in rainbow trout has been selected as the key study and a robust study summary of this publication is included for this endpoint. The selection of this study rather than the 24 hour study in catfish is based on the following rationale:

- The 96 hour acute study was conducted according to the Ontario Ministry of the Environment Guidelines (Craig et al. 1983) that is broadly comparable to OECD Guideline 203 with a few deficiencies that are not considered to significantly affect the overall reliability or validity of this study. The acute toxicity study in catfish was not documented in accordance with any testing guidelines.

- The 96 hour acute study was conducted using rainbow trout, which are one of the fish species recommended for testing in OECD Guideline 203 - Fish, Acute Toxicity. The other acute study was conducted in channel catfish which are not listed as a recommended species. Furthermore, there was no detail in the catfish study about whether the fish were obtained under disease controlled conditions.

- For fish toxicity tests, exposure durations less than 96 hours should be treated with caution as these shorter durations lead to higher effect values [ECHA, 2008]. This means that the 24 hour LC50 value in catfish of 0.44 mg/L cannot be considered as reliable compared with the 96 hour LC50 value of 1.67 mg/L derived from Laverock (1995).

- In the acute catfish study, the author noted that iodine concentrations in the 2 hour, 10 hour and 24 hour tests were monitored at 1 hour intervals and that extra chemical was introduced to adjust for the loss of iodine, which the author presumed to be due to photodecomposition and organic matter. The author further acknowledged that these adjustments "undoubtedly introduced some imprecision into the experiment". This raises a large degree of uncertainty about the actual concentrations of iodine exposure in the catfish. Furthermore, it does not appear that constant conditions were maintained. In the 96 hour study in rainbow trout static conditions were maintained throughout the test and the deviation between the initial and final iodine concentrations was less than 20%.

The overall reliability of the 96 hour acute toxicity study in rainbow trout is reliability score 2 - reliable with restrictions. The reliability of the acute toxicity study in channel catfish is reliability score 3 - not reliable.

 

References:

Craig G, Flood K, Lee J, Thomson M (1983): Protocol to determine the acute lethality of liquid effluents to fish. Environment Ontario.

Laverock MJ, Stephenson M, and Macdonald CR (1995): Toxicity of Iodine, Iodide and Iodate to Daphnia magna and Rainbow Trout (Oncorhynchus mykiss ) Arch. Environ. Contam. Toxicol. 29, 344 -350

LeValley MJ (1982): Acute toxicity of Iodine to Channel Catfish (Ictalurus punctatus). Bull. Environm. Contam. Toxicol. 29, 7 -11

OECD (1992): Fish, Acute Toxicity Test. OECD Guideline 203, Adopted by the Council on 17th July 1992.