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Short-term toxicity to fish

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Reference
Endpoint:
short-term toxicity to fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Valeric acid is closely related to butyric acid. Both compounds are straight chain carboxylic acids differing only in chain length by one carbon atom. Physical properties and chemical reactivity will be quite similar. Main structural feature is the carboxylic acid group, which will have a major impact on the effects of both substances in aquatic systems.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Both substances are regarded and asesst as mono-constituent substane of very high purity with neglicable impurities. Both substances and test materials are industrial produced and fulfill above mentioned criteria.

3. ANALOGUE APPROACH JUSTIFICATION
Valeric acid was tested on fathead minnows (Pimephales promelas) in a 96-h static study. No specific guideline was reported, but documentation is sufficient to assign validity and adequate reliability. The test design is similar to OECD TG 203. An unspecified number of test concentrations and 1 control were set up. Two test chambers with 10 fish each were used per test concentration.

Based on nominal concentrations, the 96-h LC50 of valeric acid was 77 mg/L (Mattson, 1976). The LC50 value of butyric acid will be calculated on basis of the LC50 for valeric acid (Mattson, 1976) using the respective molecular weights (88.11 and 102.13).

The 96-h LC50 for butyric acid is assessed to be 66.4 mg/L.
Reason / purpose for cross-reference:
read-across source
GLP compliance:
not specified
Analytical monitoring:
no
Details on sampling:
- no analysis of test substance
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: stock solutions were prepared by adding weighed amounts of test chemical to a 9 L glass carboy containing 4 L of Lake Superior water followed by thorough mixing. Test concentrations were produced by pouring stock solution into two glass battery jars.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): none
Test organisms (species):
Pimephales promelas
Details on test organisms:
TEST ORGANISM
- Common name: fathead minnow
- Source: Environmental Research Laboratory, Duluth
- Age at study initiation (mean and range, SD): 4 to 8 weeks
- Length at study initiation (length definition, mean, range and SD): 1.1 to 3.1
- Weight at study initiation (mean and range, SD): no data
- Feeding during test; no

ACCLIMATION
- Acclimation period: at least 48 hr
- Acclimation conditions (same as test or not): under flowing water 11 cm deep in a holding trough (360 cm long by 58 cm wide by 31 cm deep)
- Type and amount of food: Glencoe trout chow no. 3 granules
- Feeding frequency: no data
- Health during acclimation (any mortality observed): no data
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
18 - 22 °C
pH:
<= 5.9
Dissolved oxygen:
> 4.0 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): closed by glass cover
- Material, size, headspace, fill volume: 3 L cylindrical glass battery jars filled with 2 L of test water
- Aeration: no
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): no data
- Biomass loading rate: ca. 1 g/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: natural water from Lake Superior, water parameters not further specified

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: no data
- Light intensity: no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- visible abnormalities and mortality: after 1, 48, and 96 h
- pH: at the beginning and one or two times in the course of the test
- dissolved oxygen: at the beginning and one or two times in the course of the test
- temperature: daily in two of the test containers
- analytical quantification of test concentrations: no measurements

TEST CONCENTRATIONS
- Spacing factor for test concentrations: no data, test concentrations not specified
- Justification for using less concentrations than requested by guideline: no data
- Range finding study: yes
- Test concentrations: three to five widely spaced test concentrations differing by a factor of 10 or more and a control
- Results used to determine the conditions for the definitive study: no data
Key result
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
66.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Remarks on result:
other: complete immobilization of the fish was equated with death. Effect concentration calculated based on Source substance and mole weight ratio
Reported statistics and error estimates:
LC50 was determined by standard graphical procedures (American Public Health Association, 1971).
Validity criteria fulfilled:
not specified
Conclusions:
Based on nominal concentrations, the LC50 (96 h) for fish (Pimephales promelas) is 77 mg/L.
Executive summary:

Valeric acid was tested on fathead minnows (Pimephales promelas) in a 96-h static study. No specific guideline was reported, but documentation is sufficient to assign validity and adequate reliability. The test design is similar to OECD 203. An unspecified number test concentrations and 1 control were set up. Two test chambers with 10 fish each were used per test concentration.

 

Based on nominal concentrations, the 96-h LC50 was 77 mg/L for valeric acid(Mattson, 1976).

Via mole weight ratio a respective 96 -h LC50 for butyric acid of 66.4 mg/L was derived.

Description of key information

No valid data could be located regarding the short-term toxicity of butyric acid to fish.
To compensate for this lack of data, information resulting from valeric acid as supporting substance is used as substitute.
Supporting substance valeric acid: in a valid short-term toxicity fish test similar to OECD TG 203, the LC50 of valeric acid was determined to be 77 mg/L (Mattson, 1976).
The LC50 for butyric acid (conversion using the respective molecular weights) is ca. 66.4 mg/L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
66.4 mg/L

Additional information

The short-term toxicity of butyric acid to fish was investigated in several studies. Exposure period was only 24 or 48 h. This does not comply with recent test guideline requirements, thus reliability of these studies is low. The data can not be used to determine the acute toxicity of butyric acid to fish.

 

As valid data are not available to assess the short-term toxicity of butyric acid to fish, data for valeric acid as supporting substance will be used based on following reasons.

 

Valeric acid is closely related to butyric acid. Both compounds are straight chain carboxylic acids differing only in chain length by one carbon atom. Physical properties and chemical reactivity will be quite similar. Main structural feature is the carboxylic acid group, which will have a major impact on the effects of both substances in aquatic systems. Thus, it is justified to use valeric acid as supporting substance in the evaluation of the acute toxicity of butyric acid to fish.

 

Supporting substance valeric acid

 

The study was performed similar to OECD TG 202 with some restrictions (no analysis of test substance, limited reporting). Reliability is assessed to be 2.

 

Mattson 1976

 

Valeric acid was tested on fathead minnows (Pimephales promelas) in a 96-h static study. No specific guideline was reported, but documentation is sufficient to assign validity and adequate reliability. The test design is similar to OECD TG 203. An unspecified number of test concentrations and 1 control were set up. Two test chambers with 10 fish each were used per test concentration.

 

Based on nominal concentrations, the 96-h LC50 of valeric acid was 77 mg/L (Mattson, 1976).

 

Butyric acid: short-term toxicity to fish

 

The LC50 value of butyric acid will be calculated on basis of the LC50 for valeric acid (Mattson, 1976) using the respective molecular weights (88.11 and 102.13).

 

The 96-h LC50 for butyric acid is assessed to be 66.4 mg/L.