Sodium salts of [[(phosphonomethyl)imino]bis[ethane-2,1-diylnitrilobis(methylene)]]tetrakisphosphonic acid (5-7 Na:1)

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Please refer to Annex 5 of the CSR and IUCLID Section 13 for justification of read-across from the ATMP category.

Reason / purpose for cross-reference:

read-across source

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 25 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: adult survival and reproduction (no. of offspring)

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to an appropriate national standard method but full details are not available. It was not conducted under GLP and no analytical monitoring was carried out.

Qualifier:

according to guideline

Guideline:

other: US EPA Methods for acute toxicity tests with fish, macroinvertebrates, and amphibians. EPA 66013-75-009. April 1975.

Deviations:

not specified

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: The test substance was diluted to make a stock solution of 100 mg/ml. In a 6 L flask well water and food was mixed. The solution was transferred into 1L volumetric flasks, mixed well, then 200 ml were drawn into the test vessels.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Common name: water flea

- Feeding during test: The daphnids were fed at a concentration of 10 mg/l at each test medium renewal.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Hardness:

The tap water has a hardness of about 16 °dH (93 mg Ca and 12 mg Mg per litre).

pH:

While the test substance is an acid, it was reported to have been neutralised to pH 7. Tap water has a normally pH of around 7.4, and this is thought not have been affected much by the test substance's pH at the concentrations tested.

Dissolved oxygen:

The test medium used was well water, ie. dechlorinated tap water. It is thought that DO was above 40% as per guideline recommendations.

Nominal and measured concentrations:

Nominal test concentrations: 3.37, 6.75, 12.5 and 25 mg active acid/L.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Material, size, headspace, fill volume: 250 ml test beakers filled with 200 ml test solution.

- Renewal rate of test solution (frequency): 2 day renewal

- No. of organisms per vessel: 5

- No. of vessels per concentration (replicates): 4

- No. of vessels per control (replicates): 4



TEST MEDIUM / WATER PARAMETERS

- Source of dilution water: Well water


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : survival and reproduction (offspring produced) at every water renewal (ca. 2 days).



RANGE-FINDING STUDY
A Range Finding study is said to have been conducted previous to the test in order to narrow down the range of concentrations in the test, however details were not reported. A short term acute test with Daphnia was also conducted which determined a 48 h EC50 equivalent to 883 mg active acid/L.

Reference substance (positive control):

no

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 25 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: adult survival and reproduction (no. of offspring)

Details on results:

- Mortality of parent animals: see Table 1 for details.

- Time to first brood release or time to hatch: the data reported shows that offspring were produced by day 9 in all treatment groups.

Reported statistics and error estimates:

For chronic data NOECs were determined by comparing means and standard errors in control vs. treated.

Table 1: Effect of ATMP on growth and survival of D. magna after 28 days (average of 4 replicates).

Nominal concentrations (mg a.a./L)	Mortality of parents		Cumulative number of offspring
	No. Alive	% mortality
Control	4.3 ± 1.2	14	143.7
25	4.0 ± 0.8	20	128.3
12.5	4.2 ± 1.5	16	139.5
6.75	4.2 ± 1.0	16	141.6
3.37	4.7 ± 0.5	6	155.4

 

Result expressed as nominal concentration. Properties of the test substance and evidence from other studies (where concentrations were 

measured) indicate that nominal and measured concentrations are likely to be in good agreement.

Not enough information is reported on water quality, however the frequency of water renewals suggests the parameters to be in acceptable ranges.

 

Validity criteria fulfilled:

not specified

Conclusions:

A 28 day NOEC value of >= 25 mg/L (as active acid) has been determined for the effects of the test substance on adult survival and reproduction of D. magna.

Description of key information

(28 d) NOEC ≥ 25 mg active acid/L (r-a) D. magna

(96 h) NOEC 67 mg active acid/L and an EC₅₀ 187 mg active acid/L on the growth (shell deposition) (r-a) C. virginica

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

>= 25 mg/L

Additional information

No true long-term aquatic invertebrates toxicity data are available with DTPMP acid (CAS 15827-60-8) or any of its salts. However data are available with the related substance ATMP acid (CAS 6419-19-8). A 28 day NOEC value of ≥ 25 mg/L (as active acid) has been determined for the effects of the read-across substance ATMP acid on adult survival and reproduction of D. magna (Monsanto, 1976).

A 96 h NOEC value of 67 mg active acid/L and an EC₅₀ 187 mg active acid/L have been determined for the effects of DTPMP acid on the growth (shell deposition) of the marine eastern oyster Crassostrea virginica (EG&G, 1977). Although not a true long-term study it is a sub-lethal endpoint with a particularly sensitive endpoint for this substance with nutrient chelating properties and thus has been included in this section.

Please refer to Annex 5 of the CSR and IUCLID Section 13 for justification of read-across from the ATMP category.

The acid and salts in the DTPMP category are freely soluble in water and, therefore, the DTPMP anion is fully dissociated from its cations when in solution. Under any given conditions, the degree of ionisation of the DTPMP species is determined by the pH of the solution. At a specific pH, the degree of ionisation is the same regardless of whether the starting material was DTPMP-H, DTPMP (1-3Na), DTPMP (5-7Na), DTPMP (4-8K), DTPMP (xNH4) or another salt of DTPMP.

 

Therefore, when a salt of DTPMP is introduced into test media or the environment, the following is present (separately):

1. DTPMP is present as DTPMP-H or one of its ionised forms. The degree of ionisation depends upon the pH of the media and not whether DTPMP-H, DTPMP (1-3Na), DTPMP (5-7Na), DTPMP (4-8K), DTPMP (xNH4), or another salt was used for testing.

2. Disassociated ammonium, potassium or sodium cations. The amount of ammonium, potassium or sodium present depends on which salt was added.

3. Divalent and trivalent cations have much higher stability constants for binding with DTPMP than the sodium, potassium or ammonium ions so would preferentially replace them. These ions include calcium (Ca²⁺), magnesium (Mg²⁺) and iron (Fe³⁺). Therefore, the presence of these in the environment or in biological fluids or from dietary sources would result in the formation of DTPMP-dication (e.g. DTPMP-Ca, DTPMP-Mg) and DTPMP-trication (e.g. DTPMP-Fe) complexes in solution, irrespective of the starting substance/test material.