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Short-term toxicity to aquatic invertebrates

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Description of key information

There are five short-term invertebrate studies for hydrotrope category substances. These include two GLP compliant studies (EPA OTS 797.1300 and EU Method C.2) and an OECD 202 study, all of which are highly reliable. The Key Study (Collins, 1993) reports an EC50 value for the hydrotropes of >1000 mg/L in the guideline GLP study with the test substance sodium xylenesulphonate.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
1 000 mg/L

Additional information

A range of short-term data is available for aquatic invertebrates from >40.3 to > 1,020 mg/L corresponding to four Hydrotrope category substances. The key study is a 1993 USEPA Guideline study (EPAOTS 797.1300) Aquatic Invertebrate Acute Toxicity. The study was not conducted following GLP principles but there is considerable detail provided. Daphnids were exposed to five nominal test concentrations of sodium xylenesulphonate and immobility was monitored for 48 hours. The exposure was static and there was no analytical measurement. No immobilization was observed in the test concentrations and the nominal 48-hour EC50 was >1000 mg/L active substance.

In a supporting study, the 48 hour EC50 was 1020 mg/L measured active substance based on immobilization of 30% and 50% of the organisms in each of two replicate exposures at this concentration. The flow-through study (Ruetgers-Nease Corporation, 1994) with analytical measurements was conducted with calcium xylenesulphonate. The NOEC was 470 mg/L measured active substance.

The three short-term studies with potentially lower acute toxicity values included the 1995 OECD 202 Guideline supporting study with the test substance sodium xylenesulphonate that reported no immobility of daphnids at any concentration up to the highest concentration tested (100 mg/L); corresponding to an EC50 of >40.3 mg/L active substance. An acute invertebrate toxicity study for sodium cumenesulphonate is a static limit test conducted according to the OECD 202 guideline (1995). No mortality or immobility was observed and the 48-hr EC50 was reported as >100 mg/L (nominal concentration). A 1995 EU Method C.2 study of sodium toluenesulphonate conducted under GLP requirements followed a static test method with analytical confirmation of the test substance. The 48-hour EC50 was 54 mg/L active substance and the NOEC was 35 mg/L active substance. It is not apparent why this study has an order-of-magnitude lower toxicity value than the other four guideline studies. The study result is considered to be an outlier and is not taken into account in PNEC derivation.