(1-hydroxyethylidene)bisphosphonic acid, potassium salt

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:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

It was not compliant with GLP and no analytical monitoring was carried out. Although the report lacks information on the water quality, the dose-response curve is normal so it is thought that good water quality parameters were achieved.

Qualifier:

according to guideline

Guideline:

other: Methods for acute toxicity test with fish, macroinvertebrates, and amphibians. EPA 66013-75-009. April 1975 from the ecological research series.

Deviations:

no

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:

- 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

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): Mon, Wed, Fri

- 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.:

6.75 mg/L

Nominal / measured:

nominal

Conc. based on:

other: active acid

Basis for effect:

other: adult survival and number of offspring

Remarks on result:

other: estimated

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 8 first in the controls and then on day 10 in the other treatment levels with the exception of the 25 mg/L treatment where time to first brood was recorded on day 14. Observations were made on alternate days, so it is possible that actual days of time to first brood may have been less.

Reported statistics and error estimates:

For chronic data NOECs were determined by visually comparing the data presented.

Table 1: Effect of D2010 on growth and survival of D. magna after 28 days (average of 4 replicates).

 

Nominal concentrations (mg/L as active acid)	Mortality of parents		Cumulative number of offspring
	No. Alive (± SE)	% mortality
Control	4.3 ± 1.0	14	129.3
25	0.75 ± 0.5	85	14.5
12.5	3.2 ± 0.9	46	22.2
6.75	4.5 ± 0.5	20	80.1
3.37	4.2 ± 0.1	16	121.1

 

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 renewal suggests the parameters to be in acceptable ranges.

The standard error associated with the number of offspring has been reported for each observation in time. However, it is not possible to add standard errors for each observation time. Therefore due to the table format (cumulative # of offspring) and lack of raw data the standard error is not reported. The standard errors are very large and vary from 0.2 to 25. Given that the standard errors of the data at each point are large, it is unlikely that number of offspring in the control and the 3.37 and 6.75 mg/L treatments would have been significantly different.

 

The total average number of offspring does differ between the control, 3.37 and 6.75 mg/L concentrations. Nevertheless, when the values have been compared at a each observation stage of the study (day of offspring count) taking into consideration the standard error, the number of offspring produced at each stage between the control, the 3.37 mg/L and the 6.75 mg/L overlaps. This is true for all observations but the last one at day 28. Should the raw data have been available it would have been possible to make a more definitive evaluation. Therefore the NOEC is considered to be 6.75 mg/L.

Validity criteria fulfilled:

not specified

Remarks:

mortality of controls was <20%, but no data on water quality and pH is reported

Conclusions:

A reliable 28 day NOEC value of 6.75 mg/L has been determined for the effects of the test substance on adult mortality and offspring production of D. magna.

Reference 2

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 3 of the CSR and IUCLID Section 13 for justification of read-across between members of the HEDP category.

Reason / purpose for cross-reference:

read-across source

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

6.75 mg/L

Nominal / measured:

nominal

Conc. based on:

other: active acid

Basis for effect:

other: adult survival and number of offspring

Remarks on result:

other: estimated

Description of key information

28-day NOEC 6.75 mg active acid/L, Daphnia magna, read-across from HEDP-H.

96-hour (sublethal) EC₅₀ 130 mg active acid/L, Crassostrea virginica, read-across from HEDP-H.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Remarks:

as active acid

Effect concentration:

6.75 mg/L

Additional information

A reliable 28-day NOEC value of 6.75 mg active acid/L has been determined for the effects of HEDP-H on adult mortality and offspring production of the freshwater invertebrate Daphnia magna (Monsanto, 1976). The study reflects the lowest value that is available for this endpoint.

A long-term toxicity study of non-assignable reliability is available with HEDP (2-3Na) to D. magna (Henkel, 1984). However, the pattern of mortality and offspring production is erratic and the dose response curve is unusual. It appears that the concentration of the test substance or bioavailability of essential nutrients (Ca) may have posed a problem in the test; however it was not possible to determine the causes of this, as the study provides an insufficient level of detail. Therefore, the study has not been included in the assessment.

 

Additionally, a sub-chronic study with the eastern oyster Crassostrea virginica with HEDP-H is available (EG&G, 1977). This is a reliable study and also a sensitive endpoint (shell growth), determining a 96-hour EC₅₀ (reported as LC₅₀) value of 130 mg active acid/L (reported as 81 ppm (equivalent to 81 mg/l), the value has been converted taking into consideration the density of the test substance).

Lastly, a 28-day NOEC value of >12 mg/L was determined for the effects of HEDP-4Na on Daphnia magna in a reliable study (Gledhill and Feijtel, 1992).

The acid, sodium and potassium salts in the HEDP category are freely soluble in water and, therefore, the HEDP anion is fully dissociated from its sodium or potassium cations when in solution. Under any given conditions, the degree of ionisation of the HEDP 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 HEDP-H, HEDP (1-2Na), HEDP (2-3Na), HEDP-4Na, HEDP-xK or another salt of HEDP.

 

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

1. HEDP is present as HEDP-H or one of its ionised forms. The degree of ionisation depends upon the pH of the system and not whether HEDP (1-2Na), HEDP (2-3Na), HEDP-4Na, HEDP-xK salts, HEDP-H or another salt was added.
2. Disassociated sodium/potassium cations. The amount of sodium/potassium present depends on which salt was added.
3. Divalent and trivalent cations have much higher stability constants for binding with HEDP than the sodium or potassium 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 HEDP-dication (e.g. HEDP-Ca, HEDP-Mg) and HEDP-trication (e.g. HEDP-Fe) complexes in solution, irrespective of the starting substance/test material.

In this context, for the purpose of this assessment, read-across of data within the HEDP Category is considered to be valid.