2,3-dimethylbutane

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

17th March 1993 to 22nd January 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Justification for type of information:

A discussion and report on the read across strategy is given as an attachment in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SBP 60/95 LNH is a C6 -C7 hydrocarbon solvent with a n-hexane content of less than 3%. Being made from hydrogenated feedstock, its aromatics and olefins content is very low.

Analytical monitoring:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The following salts were added to Millipore or reverse-osmosis filtered water: 192 mg/L NaHCO3, 120 mg/L CaSO4.2H2O, 240 mg/L NgSo4.7H2O, 8 mg/L KCl. 100 g/L soil extract in reconstituted water is autoclaved for 15 min. at 120 ºC and added at 20 ml/L. Solids are vacumned filtered. This test medium is mixed with test substance for 24 h, then allowed to settle for 1 h. Aqeous phase was then used in the experiment.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Strain: Strauss, obtained from Institut National de Reschereche Chimique Applique (I.R.Ch.A.), France
- Source: laboratory culture
- Age at study initiation (mean and range, SD): less than 24 hrs old
- Method of breeding: Cultures started with animals less than 24 hours old, and discarded when 28 days old. Young are removed daily, and animals for testing removed 23 hours after last removal. Test young are from 15-28 day cultures from at least the third brood.

ACCLIMATION
- Acclimation period: Young are left for at least one hour prior to the study to select for actively swimming individuals.

Test type:

static

Limit test:

no

Total exposure duration:

48 h

Hardness:

178 mg/L CaCO3

Test temperature:

17-18 ºC

pH:

7.1-8.2

Dissolved oxygen:

9.0-9.5 mg/L

Nominal and measured concentrations:

Nominal: 0.89, 2, 4.5, 10, 22 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 150 mL Erlenmeyer flasks
- Type (delete if not applicable): sealed with black caps
- Material, size, headspace, fill volume: completely filled
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobilization was determined at 24 and 48 h after start of exposure.

Duration:

24 h

Dose descriptor:

EL50

Effect conc.:

12 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 9.8-16 mL

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 2.5-3.7 mL

Duration:

24 h

Dose descriptor:

other: NOEL

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

other: NOEL

Effect conc.:

2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Mortality of control: There was no mortality of control.

Number of Immobilized Daphnia magna    

Concentration (mg/l)	24 hrs	48 hrs
0	0	0
0	0	0
0.89	0	0
0.89	0	0
2.0	0	1
2.0	0	0
4.5	0	10
4.5	0	8
10	0	10
10	0	10
22	10	10
22	10	10

Validity criteria fulfilled:

yes

Conclusions:

The 48-hr EL50 for Daphnia magna was 3.0 mg/L (WAF).

Executive summary:

This study examined the short-term toxicity of the test substance SBP 60/95 LNH to Daphnia magna. Groups of 10 daphnids were exposed to loading rates of 0, 0.89, 2, 4.5, 10, or 22 mg/L test substance. Daphnids were exposed for 48 h, and there was no renewal of test solution. Daphnids were observed at 24 and 48 h after start of exposure for immobilization. The 48-h EL50 for Daphnia magna was 3.0 mg/L (WAF).

Description of key information

There is no data available for this substance. However, key and supporting data is available for the structural analogues Hydrocarbons, C6-C7, isoalkanes, cyclics, <5% n-hexane and Hexane. The data is read across to this substance based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

Hydrocarbons, C6-C7, isoalkanes, cyclics, <5% n-hexane presented a 48-h EL50 (mobility) for Daphnia magna of 3.0 mg/L (WAF).

Hexane presented a 48-h LC50 (mortality) for Daphnia magna of 45 mmol/m³ (WAF).

Additional information

Two study reports were available and input as endpoint records. The studies were scientifically reliable according to Klimish (Klimish et al., 1997) scoring (Klimish 1 and 2).

The study from Shell (1994) examined the short-term toxicity of the test substance SBP 60/95 LNH (Hydrocarbons, C6-C7, isoalkanes, cyclics, <5% n-hexane) to Daphnia magna. Groups of 10 daphnids were exposed to loading rates of 0, 0.89, 2, 4.5, 10, or 22 mg/L test substance. Daphnids were exposed for 48 h, and there was no renewal of test solution. Daphnids were observed at 24 and 48 h after start of exposure for immobilization. The 48-h EL50 for Daphnia magna was 3.0 mg/L (WAF).

The study from Bobra et al. (1983) examined the toxicity of n-hexane to the aquatic invertebrate Daphnia magna. Groups of 10 daphnids were exposed to concentrations of up to 110 mmol/m3 (WAF) of test substance for 48 h. After the exposure, the daphnids were observed for mortality. The 48-h LC₅₀was 45 mmol/m³(WAF).