Octadecylnaphthalene

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Remarks:

study based on C12 naphthalene

Adequacy of study:

key study

Study period:

Start : 7 December 2012 Completion : 13 December 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study without deficiencies

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The batch of Alkylated Naphthalene tested was a clear amber slightly viscous liquid with unknown purity. No correction was made for the purity/composition of the test substance. The test substance was not completely soluble in test medium at the loading rates initially prepared. Therefore, 1-Litre test bottles were filled with 200 ml of test substance mixtures in Milli-RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA) with initial loading rates of 2.5 times the final loading rate. These mixtures were stirred in closed dark brown bottles for approximately 24.5 hours. Subsequently, 16 ml synthetic medium, 250 ml sludge and Milli-RO water up to 500 ml were added resulting in the required loading rates. Optimal contact between the test substance and test organisms was ensured applying continuous aeration and stirring.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Municipal sewage treatment plant: 'Waterschap Aa en Maas', Heeswijk-Dinther, The Netherlands, receiving predominantly domestic sewage.

The sludge was coarsely sieved (1 mm), washed and diluted with ISO-medium. A small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids (3.4 g/l of sludge, as used for the test). The pH was 7.6 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic medium was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Hardness:

CaCl2.2H2O 211.5 mg/l
MgSO4.7H2O 88.8 mg/l
NaHCO3 46.7 mg/l
KCl 4.2 mg/l

Test temperature:

18.3 to 20.8

pH:

7.1 to 7.2

Dissolved oxygen:

The aeration was adjusted in such a way that the dissolved oxygen concentration at the start was above 60-70% saturation (60% of air saturation is > 5 mg/l at 20°C)

Nominal and measured concentrations:

In a combined limit/range-finding test loading rates of 10, 100 and 1000 mg/l were tested. Concentrations were not measured.

Details on test conditions:

Contact time: 3 hours, during which aeration and stirring took place.
Vessels: All glass open bottles/vessels.
Water: Milli-RO / Milli-Q water Tap-water purified by reverse osmosis (Milli-RO) and subsequently passed over activated carbon and ion-exchange cartridges (Milli-Q) (Millipore Corp., Bedford, Mass., USA).

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

See attached table with full results.
NOEC and EC50 are greater than 1000 mg/L.

Results with reference substance (positive control):

The EC50 of 3,5-dichlorophenol 9.9 mg/L was in the accepted range of 2 to 25 mg/l for total respiration.

Reported statistics and error estimates:

For Alkylated Naphthalene no EC50 could be calculated because the test substance proved to be non-toxic (EC50 > a loading rate of 1000 mg/l).

Validity criteria fulfilled:

yes

Remarks:

The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/l for total respiration. Other criteria were acceptable also.

Conclusions:

Alkylated Naphthalene was not toxic to waste water (activated sludge) bacteria at or below a loading rate of 1000 mg/l (NOEC).
The EC50 exceeded a loading rate of 1000 mg/l.

Executive summary:

A respiration test with activated sludge was conducted with Alkylated Naphthalene with a contact time of 3 hours. The study procedures were based on the OECD guideline No. 209, 2010. The batch of Alkylated Naphthalene tested was a clear amber slightly viscous liquid with unknown purity. No correction was made for the purity/composition of the test substance. The test substance was not completely soluble in test medium at the loading rates initially prepared. Therefore, 1-Litre test bottles were filled with 200 ml of test substance mixtures in Milli-RO water with initial loading rates of 2.5 times the final loading rate. These mixtures were stirred in closed dark brown bottles for approximately 24.5 hours.

Subsequently, synthetic medium, sludge and Milli-RO water were added resulting in the required loading rates. Optimal contact between the test substance and test medium was ensured applying continuous aeration and stirring during the 3-hour exposure period. Thereafter, oxygen consumption was recorded for a period of 9-10 minutes.

In a combined limit/range-finding test loading rates of 10, 100 and 1000 mg/l were tested. The highest loading rate was tested in triplicate, lower concentrations consisted of one replicate. In addition, blank-controls and a nitrification control of the sludge were included. Furthermore, an abiotic control and the highest concentration with a nitrification inhibitor were tested.

In the combined limit/range-finding test no inhibition was observed at the two highest test concentrations, the lowest loading rate only showed a minor biologically insignificant inhibition (3%). Therefore no statistics was performed and the NOEC was considered to be the highest test concentration.

The EC50 was above the highest loading rate tested (1000 mg/l).

There was no significant oxygen uptake from abiotic processes and the results at 1000 mg/l with a nitrification inhibitor showed a very slight heterotrophic inhibition of the respiration rate.

The batch of activated sludge was checked for sensitivity by testing the reference substance 3,5-dichlorophenol, which showed normal sensitivity.

The study met the acceptability criteria prescribed by the protocol and was considered valid.

In conclusion, was not toxic to waste water (activated sludge) bacteria at or below a loading rate of 1000 mg/l (NOEC).

The EC50 exceeded a loading rate of 1000 mg/l.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

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:

EC50

Effect conc.:

> 1 000 mg/L

Remarks on result:

not measured/tested

Remarks:

based on read-across

Conclusions:

Based on read-across the EC50 for the substance is set at >1000 mg/L. The NOEC is 1000mg/L.

Description of key information

In a study on an analogue, the EC50 exceeded a loading rate of 1000 mg/l.
The analogue was not toxic to waste water (activated sludge) bacteria at or below a loading rate of 1000 mg/l which was set as the NOEC.

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

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

Alkylated Naphthalene was not toxic to waste water (activated sludge) bacteria at or below a loading rate of 1000 mg/l (NOEC). The EC50 exceeded a loading rate of 1000 mg/l.