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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
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:
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
Key result
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
6.75 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
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

% 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.

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.

Description of key information

(28 d) NOEC 9.63 mg/L D. magna (r-a)

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
9.63 mg/L

Additional information

Freshwater

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

An additional long term toxicity study with HEDP-2Na to D. magna is available which is regarded as not reliable. The pattern of mortality and offspring production is erratic and the dose response curve is unusual. Taking the available information of acute toxicity to aquatic invertebrates into account the registrant concluded the acute toxicity of HEDP acid to aquatic invertebrates as 527 mg/L which can be calculated to be equivalent to 754 mg/L HEDP Na4 salt. The apparent NOEC of 0.1 mg HEDP Na2/L from this study would result in an extraordinary acute to chronic ratio of >5000.

The adult daphnia mortalities as well as the number of offspring per adult show an erratic pattern. While at the nominal concentration of 0.3 mg/L 20% (1 individuum) of the adult test organisms died, no additional mortalities were observed up to a nominal concentration of 10 mg/L. The number of offspring per adult follows the same strange pattern. The raw data show that the test solutions were prepared from a set of stock solutions (10, 1, 0.1, 0.01 and 0.001 mg/L). There is an insufficient level of detail to interpret what happened in the test and to clarify whether potentially a mix up of stock solutions was the reason for the erratic effect pattern. The results do not substantiate free of doubt a NOEC of 0.1 mg/L. Therefore the study is disregarded.

No reliable data are available determining the toxicity of HEDP-4Na to aquatic invertebrates, however the study with HEDP acid and D. magna is available.

The results of tests conducted on HEDP and its salts are directly comparable, because the ionisation state will depend only on the pH of the test medium. The counterion is not considered to contribute to effects in aquatic invertebrates. At environmentally-relevant pH values, HEDP will be ionised typically three times, and will form stable complexes with metal ions.

 

Here, the value of 6.75 mg equivalent active acid/L may be directly read-across. It is convenient to convert the result into units of mg HEDP-4Na salt/L.

 

The 28 d NOEC for HEDP 2809-21-4 is 6.75 mg/L, which is equivalent to a 28 d NOEC value of 6.75 * 1.43 = 9.63 mg/L HEDP-4Na (CAS 3794-83-0)

 

Using: MW(HEDP-4Na)/MW(HEDP) = 293.96 / 206.03 = 1.43

 

Additionally, a sub-chronic study with the eastern oyster Crassostrea virginica with HEDP acid is available. This is a reliable study and also a sensitive endpoint (shell growth), determining a 96 h EC50 (reported as LC50) value of 130 mg active acid/L (reported as 81 ppm, the value has been converted taking into consideration the density of the test substance, i e. 1.6).