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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Swisher et al. (1967) provided results from a continuous biodegradation study with activated sludge.  Results indicate a NOEC of > 270 mg/L Na3NTA (> 200 mg/L NTA).  A read-across approach from H3NTA to Na3NTA is applied (for justification of read-across please refer to IUCLID section 13).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
270 mg/L

Additional information

Swisher et al. (1967) presented results from continuous and semicontinuous biodegradation study for NTA and is considered the Key Study. Results indicated a NOEC of > 270 mg/L Na3NTA (>200 mg/L NTA).

Bringmann et al. (1980) provided a toxicity threshold value of > 400 mg/L NTA (>540 mg/L Na3NTA) for  Chilomonas paramaecium using an analogous method of the cell multiplication test. Bringmann & Kuhn (1977) determined the toxicity threshold (TT) value of (EC5) of >10,000 mg/L Nitrilotriacetic acid (NTA) for Pseudomonas putida using an analogous method of the cell multiplication test. Bringmann (1978) and Bringmann and Kuhn (1980) provided results for microorganisms using an analogous method of the cell multiplication test where the EC5 was >800 mg/L NTA (>1,100 mg/L Na3NTA) for both studies. While these studies provide support for the toxicity of NTA to protazoan species, the purpose of the protazoan tests were not for effects to STP. Therefore, they were determined to be not relevant for calculating the PNEC. Canton and Sloof (1982) provided an EC50 range of 3,200 -5,600 mg/L NTA for Pseudomonas fluorescens eight hour exposure. This study is not considered valid as glucose was used as the testing substrate. All of the studies (except for Swisher et al.) are considered unreliable but can be used as weight of evidence for the toxicity of NTA to microorganisms. Results from these studies are generally within the same toxicity range. As described in the EU Risk Assessment - Trisodium Nitrilotriacetate Report (2005), it can not be ruled out that toxic effects could be due to nutrient deficiency caused by the chelating effects of NTA and the resulting reduced concentrations of essential metals within the test solutions. However, these results can provide a conservative approach.

 Test Duration  Effect Measured  Endpoint  Endpoint Value (mg/L)  Reference  Reliability
 Pseudomonas fluorescens  8 hr  cell inhibition / biomass  EC50  3,200 - 5,600  Canton and Sloof 1982  3 -not reliable
 Pseudomonas putida  16 hr  cell inhibition / biomass  EC5  > 10,000  Bringmann and Kuhn 1977   3 -not reliable
 Chilomonas paramaecium  48 hr  cell inhibition / biomass  toxicity threshold > 400H3NTA or > 540 Na3NTA  Bringmann et al. 1980   3 -not reliable
 Entosiphon sulcatum  72 hr  cell inhibition / biomass  toxicity threshold > 800 H3NTA or > 1,100 Na3NTA  Bringmann 1978   3 -not reliable
 Uronema parduzci  72 hr  cell inhibition / biomass EC5  > 800 H3NTA or > 1,100 Na3NTA  Bringmann and Kuhn 1980   3 -not reliable
 activated sludge  90 days  biodegradation  NOEC > 200 H3NTA or> 270 Na3NTA  Swisher et al. 1967  2 - reliable with restrictions