Octadecylnaphthalene

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Remarks:

study on C12 naphthalene

Adequacy of study:

key study

Study period:

from 21 January 2013 to April 11, 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: guidance test with GLP compliance

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

other: Commission Regulation (EC) No 440/2008 of 30 May 2008, Part C: Methods for the determination of ecotoxicity, Publication No. L142, C.2. "Daphnia Sp. Acute Immobilisation Test".

Qualifier:

according to guideline

Guideline:

other: ISO International Standard 6341: "Water quality - Determination of the inhibition of the mobility of Daphnia magna Straus - Acute toxicity test, Third edition, 1996-04-01.

Qualifier:

according to guideline

Guideline:

other: Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, December 14, 2000.

GLP compliance:

yes

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
no data

Analytical monitoring:

yes

Details on sampling:

Frequency: at t=0 h and t=48 h
Volume: 1 ml from the approximate centre of the test vessels
Storage: Samples were stored in a freezer until analysis.

Vehicle:

no

Details on test solutions:

All test solutions were individually prepared. Preparation of test solutions started with loading rates that were magnetically stirred for one day to ensure reaching maximum dissolution in test medium. This resulted in clear solutions containing a floating layer. Consequently, these were left to settle for another day after which the clear and colourless Water Accommodated Fractions (WAFs) were collected by means of siphoning. The final test solutions were all clear and colourless.

Test organisms (species):

Daphnia magna

Details on test organisms:

Species: Daphnia magna (Crustacea, Cladocera) (Straus, 1820), at least third generation, obtained by acyclical parthenogenesis under specified breeding conditions.
Source: In-house laboratory culture with a known history.
Validity of batch: Daphnids originated from a healthy stock, 2nd to 5th brood, showing no signs of stress such as mortality >20 %, presence of males, ephippia or discoloured animals and there was no delay in the production of the first brood.
Characteristics: For the test selection of young daphnids with an age of < 24 hours, from parental daphnids of more than two weeks old.
Feeding: Daily, a suspension of fresh water algae
Medium: M7

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

180 mg/l expressed as CaCO3

Test temperature:

The temperature of the test medium was 19.8-19.9°C at the start of the test. The temperature continuously measured in a temperature control vessel varied between 19.1 and 19.7°C during the test.

pH:

7.9-8.0

Dissolved oxygen:

8.6-9.5 mg/l

Salinity:

no data

Nominal and measured concentrations:

nominal: WAFs prepared at loading rates of 10, 18, 32, 56 and 100 mg/l.
measured: 0.62 mg/l

Details on test conditions:

Controls: Test medium without test substance or other additives.
Test vessels: 100 ml, all-glass. A net was included just below the surface as a physical barrier.
Medium: Adjusted ISO medium
Number of daphnids: 20 per concentration
Loading: 5 per vessel containing 80 ml of test solution
Light: 16 hours photoperiod daily
Feeding: No feeding
Aeration: No aeration of the test solutions
Introduction of daphnids: Within 22 minutes after preparation of the test solutions.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.62 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.62 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Analysis of the samples taken at the start of the final test showed measured concentrations for peak 1 varying between 0.087 and 2.6 mg/l without a clear relation to the loading rate. After 48 hours these concentrations had all decreased to 13-21 % of initial. Similar results were obtained for peak 2. Initially, concentrations ranged between 0.078 and 1.3 mg/l. These concentrations decreased to 19-23 % of initial after 48 hours. The actual test range was based on average exposure concentrations of peak 2, being a worst-case approach (lowest concentrations measured). The range tested corresponded with 0.16, 0.44, 0.29, 0.034 and 0.62 mg/l at the loading rates of 10, 18, 32, 56 and 100 mg/l, respectively.
Despite the presence of a more pronounced floating layer (compared to the combined limit/range-finding test) from 24 hours onwards in the various WAFs prepared, no significant effects were observed in any of the solutions tested. This was likely a result of the use of nets that prevented daphnia reaching the surface. Hence, no effects occurred up to the limit of solubility in test medium.

Results with reference substance (positive control):

The 48 h-EC50 was 0.38 mg/l with a 95 % confidence interval between 0.34 and 0.45 mg/l.
The actual responses in this reference test with K2Cr2O7 were in the lower range of the expected historical responses at the different concentrations, i.e. a 48h-EC50 between 0.3 and 1.0 mg/l. Hence, the sensitivity of this batch of D. magna was in agreement with the historical data collected at WIL
Research Europe.

Reported statistics and error estimates:

No statistical was used because the test substance proved to be non-toxic (EC50 > maximum soluble concentration).

Combined limit/range-finding test

No immobility was observed in WAFs prepared at loading rates of 1.0 and 10 mg/l. In the WAF prepared at 100 mg/l a total of 70 % of the organisms became immobilised. It was however observed that many organisms became trapped at the surface of the treated solutions and in addition floating material deriving from the test substance was observed at the surface of the replicates incubated with the WAF prepared at 100 mg/l. The latter might have affected the mobility of the daphnia despite the fact that microscopic observations showed that no test substance particles were stuck to the antenna of the daphnia or its filtering system.

Validity criteria fulfilled:

yes

Conclusions:

The 48 h-EC50 exceeded 0.62 mg/l, being the average measured concentration in a WAF prepared at a loading rate of 100 mg/l. (EL50)

Executive summary:

The acute toxicity test with Daphnia magna was performed according to OECD guideline No. 202 under GLP compliance. The result showed the test substance did not induce acute immobilisation of Daphnia magna at 0.62 mg/l, being the average measured concentration in a WAF prepared at a loading rate of 100 mg/l after 48 hours of exposure (NOEC). The 48 h-EC50 exceeded 0.62 mg/l, being the average measured concentration in a WAF prepared at a loading rate of 100 mg/l (EL50).

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

weight of evidence

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Remarks:

read-across details

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Remarks on result:

not measured/tested

Remarks:

based on read-across

Conclusions:

Based on a read-across the EL50 of the substance is set at >100 mg/L

Description of key information

In a study on an analogue, the 48 h-EC50 exceeded 0.62 mg/l, being the average measured concentration in a WAF prepared at a loading rate of 100 mg/l.

The EL50 is 100 mg/L.

The data on the analogue can be used as read-across to assess the toxicity towards daphnia (see section 13)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L

Additional information

The acute toxicity test with Daphnia magna was performed according to OECD guideline No. 202 under GLP compliance. The result showed the test substance did not induce acute immobilisation of Daphnia magna at 0.62 mg/l, being the average measured concentration in a WAF prepared at a loading rate of 100 mg/l after 48 hours of exposure (NOEC). The 48 h-EC50 exceeded 0.62 mg/l, being the average measured concentration in a WAF prepared at a loading rate of 100 mg/L (EL50).