Trisodium dihydrogen -N,N-[bis[2-[bis(carboxylatomethyl)amino]ethyl]]glycinate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Publised December 1984

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

The source substance (EDTA 2Na) and the target substance (DTPA 3Na) are the disodium and trisodium salts of their respective aminopolycarboxylic acids, and are therefore structurally similar. The purity/impurity profile of the source substance is not reported in the source publication (Arch. Hydrobiol. Suppl.67, 4, 479-492, December 1984), but since the target material is > 99.9% pure and contains no detectable impurities, the extrapolation of short-term aquatic toxicity properties from the source material to the target material is considered valid as a ‘worst case' scenario. There were no published test guidelines followed nor indication of GLP. However, the study was well conducted and documented, according to generally accepted scientific principles, and was considered reliable with restrictions (Category 2).

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

no guideline followed

Principles of method if other than guideline:

The action of EDTA in batch cultures of Scenedesmus quadricauda at concentrations of 100, 200 and 400 mg/L and the effects of manipulation of macro- and micro-elements concentrations were investigated.

GLP compliance:

not specified

Specific details on test material used for the study:

Specified as EDTA, Na2EDTA.2H2O in the published paper

Analytical monitoring:

yes

Details on sampling:

Every 24 hours for the first three days and generally less frequently thereafter.

Vehicle:

no

Test organisms (species):

Scenedesmus quadricauda

Details on test organisms:

Scenedesmus quadricauda (TURP.) BREB., strain GREIFSWALD/15 from the institute of Botany, Czechoslovak Academy of Science, Trebon.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

23 d

Hardness:

Not reported

Test temperature:

25 +/- 0.1 ºC

pH:

6.8 (adjuted with Sodium hydroxide

Dissolved oxygen:

The algal suspensions were bubbled with a mixture of air and 1.5% carbon dioxide

Salinity:

Not applicable

Conductivity:

No data

Nominal and measured concentrations:

Nominal concentrations 100, 200 and 400 mg/L EDTA
Achieved concentrations of EDTA were measured at each time of algal sampling, on Days: 0,1,2,5,6,7,8,9,12,13,15,19, 21and 23.

Details on test conditions:

The algal culture was precultivated in a medium corresponding to 1/10 of the concentrations used in the study medium. The precultivated culture was then filtered through a filter paper (SCHLEICHER & SCHULL-blue ribbon), the cells were washed twice by repeated resuspension in freshly distilled water and filtration, and finally resuspended again in a small volume of distilled water to give a thick suspension. An adequate quantity of this suspension was then used for the inoculation of each test flask to the initial dry mass concentration of approximately 0.2 g/L.

All of the culture media were prepared in freshly distilled water and not sterilised. The algal cultures were grown in 2-1 ROUX flasks (material SIAL, Czechoslovakia) in an apparatus for batch cultivation. The flasks were continuously illuminated from one side only with either fluorescent tubes (TESLA 40 W neural light) or high pressure sodium discharge lamps (TESLA SHA 400). The irradiance of the algal cultures was 57 Wm3 in the case of the fluorescent tubes and 330Wm3 in the case of the sodium discharge lamps.
1g samples of the cultures were taken on Days: 0,1,2,5,6,7,8,9,12,13, 15,19,21and 23 for determination of cell number (microscopically in a BURKER counting chamber), dry mass (5ml duplicates filtered and dried at 105 ºC) and chlorophyll a + b (disintegration, extraction with acetone and spectrophotometry).

Reference substance (positive control):

no

Key result

Duration:

23 d

Dose descriptor:

NOEC

Effect conc.:

400 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

23 d

Dose descriptor:

NOEC

Effect conc.:

400 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

400 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Chlorophyll concentration

Details on results:

Higher concentrations of EDTA (Na2EDTA.2H2O; 400mg/L) when in surplus over trace elements in the nutrient solution, inhibit cell division, chlorophyll synthesis and the production of algal biomass, especially in the earlier phase of algal growth. No negative influence of the higher concentrations of EDTA was observed when the concentration of the trace elements in the nutrient material was increased correspondingly to the increased EDTA concentration. EDTA depletion from the solutions was observed in the experiments where a surplus of EDTA was accompanied by a corresponding surplus of trace elements. The highest decrease in EDTA concentration corresponded to the highest rate of cell division. The influence of the light source on the decomposition of EDTA in the algal nutrient solution was also studied, but no decomposition of EDTA by the light source was proved.

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

The source substance (EDTA 2Na) and the target substance (DTPN 3Na) are the disodium and trisodium salts of their respective aminopolycarboxylic acids (Ethylene diaminetetraacetic acid and Diethylenetriaminepentaacetic acid), and are therefore structurally similar. The structural and chemical similarities of EDTA and DTPA have been acknowledged in EU risk management analysis (RMOA for DTPA salts, Dec. 2014). The two substances have high water solubility and would be fully dissociated in the aquatic environment. The target substance is neutral (pH 7.5) in solution which is comparable to the test conditions used for the toxicity study to aquatic algae with EDTA 2Na (pH 6.8). The organic acid moieties of the respective substances have a similar chelating mode of action and would be expected to exert long-term adverse effects by the sequestration of essential metal ions, rather than specific acute toxicity. The extrapolation of aquatic toxicity potential from the source to the target material is therefore considered valid.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

> 400 mg/L

Nominal / measured:

nominal

Conclusions:

The NOEC of DTPA trisodium salt to algae is predicted to be greater than 400 mg/L.

Executive summary:

Using a read-across approach from a study conducted on the structural analogue EDTA 2Na, the NOEC of DTPA trisodium salt to algae is predicted to be greater than 400 mg/l (on stoichiometric basis). The two substances are structurally similar, particularly when ionised in the aqueous environment. The lack of effect at this concentration is dependent on the balance of nutrients to avoid nutritional limitations caused by the sequestrating mechanism of action of the two substances.

Description of key information

Using a read-across approach from a study conducted on the structural analogue EDTA, the NOEC of DTPA trisodium salt to algae is predicted to be greater than 400 mg/l (on stoichiometric basis). The two substances are structurally similar, particularly when ionised in the aqueous environment. The lack of effect at this concentration is dependent on the balance of nutrients to avoid nutritional limitations caused by the sequestrating mechanism of action of the two substances. The structural and chemical similarities of EDTA and DTPA have been acknowledged in EU risk management analysis (RMOA for DTPA salts, Dec. 2014).

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

400 mg/L

Additional information

Higher concentrations of EDTA (Na2EDTA.2H2O; 400mg/L) when in surplus over trace elements in the nutrient solution, inhibit cell division, chlorophyll synthesis and the production of algal biomass, especially in the earlier phase of algal growth. No negative influence of the higher concentrations of EDTA was observed when the concentration of the trace elements in the nutrient material was increased correspondingly to the increased EDTA concentration. EDTA depletion from the solutions was observed in the experiments where a surplus of EDTA was accompanied by a corresponding surplus of trace elements. The highest decrease in EDTA concentration corresponded to the highest rate of cell division. The influence of the light source on the decomposition of EDTA in the algal nutrient solution was also studied, but no decomposition of EDTA by the light source was proved.