Hydrogen cyanide

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

14-16 September 1981

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: scientifically acceptable study documented in sufficient detail

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1981

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Principles of method if other than guideline:

The study closely followed U.S. EPA. 1975. Methods for acute toxicity tests with fish,
macroinvertebrates, and amphibians. Ecological Research
Series (EPA-660/3-75-009)

GLP compliance:

yes

Remarks:

Although GLP was not published at that time the test was performed consistent with the Food and Frug Administration's GLP regulations that were published in the Federal Register, December 22, 1978.

Test material

Test material information

Constituent 1

Reference substance name:

2-hydroxy-2-methylpropionitrile

EC Number:

200-909-4

EC Name:

2-hydroxy-2-methylpropionitrile

Cas Number:

75-86-5

Molecular formula:

C4H7NO

IUPAC Name:

2-hydroxy-2-methylpropanenitrile

Details on test material:

- Name of test material (as cited in study report): acetone cyanohydrin
- Substance type: cyanohydrin
- Physical state: clear amber colored liquid
- Analytical purity: 100% active ingredient
- Lot/batch No.: #29T501-1
- Stability under test conditions: no data reported in the study, from experience and experimental results it can be deduced that acetone cyanohydrin hydrolyses rapidly within minutes to acetone and HCN at testing pH of 7.9 - 8.3
- Storage condition of test material: no data
- Other: received from the Monsanto Chemical Company, St. Louis, Missouri on 29 July 1981

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A clear, colorless working stock solution of 2.0 mg/mL acetone cyanohydrin was prepared by adding 0.20 grams of acetone cyanohydrin to distilled water and diluting to 100 mL in a volumetric flask. 1 For each test concentration, the appropriate volume of the 2.0 mg /mL stock solution was pipetted into 500 mL of dilution water and vigorously mixed with a glass rod. Four hundred and fifty mL of this solution were then divided into three beakers to provide replicate exposure treatments, each containing 150 mL.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Source: laboratory stocks cultured at EG&G, Bionomics
- Age at study initiation (mean and range, SD): <= 24 hours old

Study design

Test type:

static

Water media type:

freshwater

Test conditions

Hardness:

total hardness: as calcium carbonate (CaCO3) of 165 +/- 15 mg/L

Test temperature:

22 +/- 1°C

pH:

7.9-8.3

Dissolved oxygen:

>5.3 mg/L (60% of saturation)

Nominal and measured concentrations:

control, 0.076, 0.13, 0.22, 0.36, 0.60, 1.0 (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): open 250 mL beakers
- Material, size, headspace, fill volume: 200 mL
- Aeration: No
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates):3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted deionized water
- Total organic carbon:The test water was filtered through an Amberlite XAD-7 resin column to remove any potential organic contaminants
- Particulate matter:
- Alkalinity: 120 +/- 10 mg/L as calcium carbonate (CaC03)
- Conductivity: 400-600 micromhos per centimeter
- Culture medium different from test medium: No

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: no data
- Light intensity: SO-70 footcandles


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality


TEST CONCENTRATIONS
control, 0.076, 0.13, 0.22, 0.36, 0.60, 1.0 (nominal)

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

0.27 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 0.19 - 0.38

Remarks:

Range

Effect concentrations 2

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

0.13 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: 0.088 - 0.19

Remarks:

Range

Effect concentrations 3

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.076 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

- Any observations that might cause a difference between measured and nominal values:
Water flea were impartially distributed to each concentration (5 water flea per replicate) within 15 minutes after the test solutions had been prepared.
From experience and experimental results it can be deduced that acetone cyanohydrin hydrolyses rapidly within minutes to form acetone and HCN at the testing pH of 7.9 - 8.3. Therefore the cyanide anion is reponsible for the toxicity of the test solutions against Daphnia magna.

Any other information on results incl. tables

Table 1: Concentrations tested and corresponding observed percentage mortalities for the water flea (Daphnia magna) exposed to acetone cyanohydrin.

Nominal concentration [mg/L]	Percentage mortality
	24 hours				48 hours
	A	B	C	Mean	A	B	C	Mean
1.0	100	80	40	73	100	100	80	93
0.60	60	80	60	67	60	80	80	73
0.36	40	60	80	60	40	60	80	60
0.22	60	60	60	60	100	60	80	80
0.13	40	40	40	40	100	80	60	80
0.076	0	0	0	0	0	0	0	0
control	0	0		0	0	0	20	7

pH at start and 48 hours was 8.3 in all test vessels. Dissolved oxygen was 7.9 - 8.5 mg/l (91 - 97 % saturation) at 22 - 23°C

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

In the controls not more than 10% of the daphnids have been immobilised The dissolved oxygen concentration at the end of the test was >=3 mg/L

Conclusions:

The study is considered as valid with restriction. The study was performed according to the national guidance and documents on good laboratory practice available at that time. The validity criteria of today’s guidelines are fulfilled. Nevertheless the number of replicates is lower than required in today’s guidelines and the test was performed in open systems, but this does not invalidate the study. The test substance is considered as completely hydrolysed to acetone and HCN in the test solutions. Therefore the observed toxicity to Daphnia magna is attributed to the cyanide anion as the active principle for toxicity.

Executive summary:

The 48 –hr-acute toxicity of 2-hydroxy-2-methylpropanenitril to Daphnia magna was studied under static conditions.  15 min after the test solutions have been prepared Daphnids were exposed to control, 0.076, 0.13, 0.22, 0.36, 0.60, 1.0 (nominal) for 48hrs. Mortality/immobilization and sublethal effects were observed daily.  The 48– hour EC₅₀ was 0.13 mg test mat./L.  The 48 – hr NOEC based on mortality was 0.076 mg test mat./L. 
Since 2-hydroxy-2-methylpropanenitril hydrolyses within a few minutes at the pH of 7.9 – 8.3 to acetone and HCN the toxic effect is attributed to the cyanide ion as the active principle.
 
Based on the results of this study, the hydrolysis products of the test material would be classified as very toxic against Daphnia magna.
 
This study is classified as scientifically acceptable for an acute toxicity study with freshwater invertebrates.

Results Synopsis
 
Test Organism: Daphnia magna
Test Type: Static

EC₅₀:  0.13 mg test mat./L                       95% C.I.:  0.088 to 0.19 mg test mat/L
Endpoint(s) Effected:  mortality