Hydrogen iodide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11.06.2019 - 30.09.2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

April 13, 2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

May 30, 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Remarks:

ion chromatography with conductivity detection

Details on sampling:

One replicate of the stock solution and duplicate samples from the freshly prepared test media of all test concentrations and the control were taken at the start of the test.
For the determination of the stability of the test item under the test conditions and of the maintenance of the test item concentrations during the test period, duplicate samples from the test media of all test concentrations and the control were collected at the end of the test (after 48 hours) by pouring together the contents of the test beakers of each treatment.

Vehicle:

no

Details on test solutions:

A stock solution of 16.95 mg test item/L corresponding to 10 mg hydroiodic acid/L was prepared by dissolving 18.12 mg test item into 1069.03 mL test water by intense stirring for 15 minutes. Adequate volumes of this stock solution were diluted with test water to prepare the test media of the desired test concentrations.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Strain/clone: Straus, clone 5
- Age at study initiation: 1.75 to 19.15 hours old.
- Source: in-house laboratory culture
- Method of breeding: The daphnids were bred in the laboratories of the testing facility under similar temperature and light conditions as used in the test. The cultivation of the parental daphnids was performed in Elendt M4 medium.
- Feeding during test : none

ACCLIMATION
- Acclimation period: Was not necessary, since the test was performed in the same medium as the culturing.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

2.5 mmol/L (= 250 mg/L) as CaCO3

Test temperature:

20.7 - 21.1 °C

pH:

7.8 - 8.0

Dissolved oxygen:

8.6 - 8.7 mg/L

Nominal and measured concentrations:

Nominal concentrations: control, 2.0, 0.91, 0.41, 0.19, 0.09 mg Hydroiodic acid/L, corresponding to 3.39, 1.54, 0.69, 0.32 and 0.153 mg test item/L
Measured concentration: 97 % of the nominal at the start and 95 % of the nominal at the end of the study

Details on test conditions:

TEST SYSTEM
- Test vessel: beakers
- Type: covered with a lid to reduce the loss of water due to evaporation and to avoid the entry of dust into the solutions
- Material, size: glass, 100 mL
- Volume of solution: 60 mL
- Aeration: none
- 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/preparation of dilution water: Elendt M4, prepared according to OECD 202
- Alkalinity: 0.9 mmol/L
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light : 8 h dark
- Light intensity: 530 - 840 lux

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.01 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

other: EC20

Effect conc.:

0.8 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC10

Effect conc.:

0.685 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.41 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

LOEC

Effect conc.:

0.91 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

mobility

Details on results:

After 48 hours of exposure no immobilisation of the test animals was observed in the control and up to and including the test item concentration of 0.41 mg hydroiodic acid/L. At the concentration of 0.91 mg hydroiodic acid/L, 7 animals were immobile and 20 animals were immobile at the concentration of 2.0 mg hydroiodic acid/L.

Results with reference substance (positive control):

The most recent test with the reference item resulted in 24-h EC50 of 0.932 mg/L and 48-h EC50 of 0.672 mg/L (95 % CI: 0.598 - 0.757 mg/L), respectively. The results indicate that the sensitivity of the daphnids was consistent with the level proposed by the OECD 202 guideline (24-h EC50 between 0.6 and 2.1 mg potassium dichromate/L).

Biological results

Table 1. Summary of Biological Results

Nominal Concentration	% of immobilised daphnids after
[mg hydroiodic acid/L]	24 hours	48 hours
Control	0	0
0.09	0	0
0.19	0	0
0.41	0	0
0.91	0	35
2.0	30	100
EC50 [mg hydroiodic acid/L]:	>2.0	1.01
95 % CI [mg hydroiodic acid/L]:	n.d.	0.848 - 1.21
EC20 [mg hydroiodic acid/L]:	1.94	0.800
95 % CI [mg hydroiodic acid/L]:	0.595 - >2.0	0.675 - 0.949
EC10 [mg hydroiodic acid/L]:	0.547	0.685
95 % CI [mg hydroiodic acid/L]:	0.257 - 1.16	0.542 - 0.868
NOEC [mg hydroiodic acid/L]:	0.91	0.41
LOEC [mg hydroiodic acid/L]:	2.0	0.91

Values refer to nominal test concentrations
CI: Confidence interval
n.d.: not determinable
NOEC and LOEC were determined directly from the raw data.

Analytical results

The quantification of the active ingredient iodide of the test item in the test samples was performed using ion chromatography with conductivity detection. At the start of the test 97 % of the nominal test concentrations were found (average of all test concentrations). After 48 hours test duration, 95 % of the nominal value was determined (average of all test concentrations). During the test the daphnids were exposed to a mean of 96 % of nominal.

Table 2. Summary of Analytical Results

Sample Description [mg hydroiodic acid/L]	% of nominal*	RSD [%]	n
Control	n.a.	n.a.	4
0.09	94	3	4
0.19	96	3	4
0.41	100	3	4
0.91	96	2	4
2.0	95	2	4

* mean value of all measured samples per treatment group
RSD: relative standard deviation per treatment group
n: number of analysed samples
n.a.: not applicable

Validity criteria fulfilled:

yes

Conclusions:

The 48-hour NOEC was determined to be 0.41 mg hydroiodic acid/L and the 48-hour EC50 value was calculated to be 1.01 mg hydroiodic acid/L.

Executive summary:

The toxic effect of the test item to Daphnia magna was assessed in a static concentration-response test performed according to OECD 202 under GLP. Daphnids were exposed to test item concentrations of control, 2.0, 0.91, 0.41, 0.19, 0.09 mg Hydroiodic acid/L, corresponding to 3.39, 1.54, 0.69, 0.32 and 0.153 mg test item/L for 48 hours under static conditions. After 48 hours of exposure no immobilisation of the test animals was observed in the control and up to and including the test item concentration of 0.41 mg hydroiodic acid/L. At the concentration of 0.91 mg hydroiodic acid/L, 7 animals were immobile and 20 animals were immobile at the concentration of 2.0 mg hydroiodic acid/L. The 48-hour NOEC was determined to be 0.41 mg hydroiodic acid/L. The 48-hour LOEC was determined to be 0.91 mg hydroiodic acid/L and the 48-hour EC50 value was calculated to be 1.01 mg hydroiodic acid/L. The initial concentrations and the maintenance of the exposure concentrations during the test were verified in the analytical part. All reported results refer to nominal values since the concentrations of the test item were within ± 20 % of the nominal concentrations during the test.

Description of key information

The 48-hour NOEC was determined to be 0.41 mg hydroiodic acid/L and the 48-hour EC50 value was calculated to be 1.01 mg hydroiodic acid/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

1.01 mg/L

Additional information

The toxic effect of the test item to Daphnia magna was assessed in a static concentration-response test performed according to OECD 202 under GLP. Daphnids were exposed to test item concentrations of control, 2.0, 0.91, 0.41, 0.19, 0.09 mg Hydroiodic acid/L, corresponding to 3.39, 1.54, 0.69, 0.32 and 0.153 mg test item/L for 48 hours under static conditions. After 48 hours of exposure no immobilisation of the test animals was observed in the control and up to and including the test item concentration of 0.41 mg hydroiodic acid/L. At the concentration of 0.91 mg hydroiodic acid/L, 7 animals were immobile and 20 animals were immobile at the concentration of 2.0 mg hydroiodic acid/L. The 48-hour NOEC was determined to be 0.41 mg hydroiodic acid/L. The 48-hour LOEC was determined to be 0.91 mg hydroiodic acid/L and the 48-hour EC50 value was calculated to be 1.01 mg hydroiodic acid/L. The initial concentrations and the maintenance of the exposure concentrations during the test were verified in the analytical part. All reported results refer to nominal values since the concentrations of the test item were within ± 20 % of the nominal concentrations during the test (reference 6.1.3-1).