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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

96 h acute toxicity studies have been performed with the chlorinated isocyanurates NaDCC and TCCA and the degradation substance CYA.     

Key value for chemical safety assessment

LC50 for freshwater fish:
0.23 mg/L

Additional information

Studies are available for sodium dichloroisocyanurate and trichloroisocyauric acid

The chlorinated isocyanurates (trichloroisocyanuric acid and sodium dichloroisocyanurate) produce free available chlorine, in the form of hypochlorous acid (HOCl) as they dissolve in water. As the equilibria involve all of the possible chlorinated isocyanurates, the toxicity of trichloroisocyanuric acid (TCCA), sodium dichloroisocyanurate (NaDCC) and sodium dichloroisocyanurate dihydrate (NaDCC.2H2O) will be virtually equivalent at the same available chlorine concentration. The parent compound for all chlorinated isocyanurates is isocyanuric acid (cyanuric acid). All of the chlorinated isocyanurates are essentially equivalent, once they are dissolved in water at the low concentrations at which they are used.

Based upon the available chlorine content and the dissociation constants for the chlorinated isocyanurate species, TCCA is considered to be the most toxic, or reactive form. Therefore test results for this species will be considered as the "worst-case" for the chlorinated isocyanurates allowing read-across for the less reactive dichlorinated forms.

Additionally studies are available for the degradation substance CYA. The chlorinated isocyanurates are unstable in the environment, because the free available chlorine is rapidly reduced. CYA, or its salt, is the stable degradation product. Therefore, CYA, or its sodium salt, is the substance of interest for chronic ecotoxicity studies

NaDCC:

One study in fish is avaialble for NaDCC (Anderson K 2002). In this study the saltwater species inland silversides were exposed to nominal concentrations of 0.625, 1.25, 2.5, 5.0 and 10.0 mg/L based on range-finding test reseults. The 96 h LC50 was determined to be 1.21 mg/L.

TCCA:

Three acute fish studies have been performed with TCCA with freshwater species. In a study with rainbow trout (Bowman 1987) ten fish were exposed to nominal concentrations 0.056, 0.10, 0.18, 0.32, 0.56 and 1.0 mg/L nominal concentrations of trichloroisocyanuric acid and a control. The 96 h LC50 was determined to be 0.24 mg/L based on nominal test concentrations. In a study with bluegill sunfish (Barrows 1984) ten fish were exposed to 0.062, 0.13, 0.25, 0.5 and 1 mg/L nominal concentrations of trichloroisocyanuric acid. The 96 h LC50 was determined to be 0.23 mg/L. In another study with bluegill sunfish (Bowman 1987) ten fish were exposed to 0.18, 0.32, 0.56, 1.0 and 1.8 mg/L nominal concentrations of trichloroisocyanuric acid and a control. The 96 h LC50 was determined to 0.4 mg/L.

CYA:

Acute fish studies were performed with the freshwater species bluegill sunfish, rainbow trout and fathead minnow. Bluegill sunfish were exposed to a nominal concentration of 1000 mg/L cyanuric acid for 96 h. The LC50 was > 1000 mg/L. No mortalities or adverse effectes were observed. Rainbow trout and fathead minnow were exposed to nominal concentrations of 210, 370, 650, 1200 and 2100 mg/L cyanuric acid for 96 h. No mortalities were observed and the LC50 was determined to be > 2100 mg/L for both species.

The lowest LC50 dervied from the three aquatic studies on freshwater fish was > 1000 mg/L based on nominal concentrations.

An acute fish study was performed with one saltwater species inland silver sides (Anderson 2002).. Fish were exposed to nominal concentrations of 500, 1000, 2000, 4000 and 8000 mg/L cyanuric acid. No mortalities occured at the highest concentration tested. The LC50 was determined to be > 8000 mg/L.