2-naphthol

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15.01.2018-16.02.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

Due to a lower population density at the testing time, only 10 daphniae per test were use instead of 20.

GLP compliance:

no

Remarks:

accredited by DAkkS

Analytical monitoring:

not specified

Vehicle:

yes

Remarks:

test samples diluted in water

Details on test solutions:

The test vessels contained a final volume of 10 mL (2-naphthol stock solution and dilution water). For each dilution stage and a control solution (contains only water) two 30 mL-test tubes with 5 daphniae were prepared. The test tubes were covered with Kapsenberg caps and left for 48 h. Incubation was performed at room temperature (20-22°C) in a 12 h/12 h light-dark rhythm without feed portion. The daphnia mobility was checked and documented after 24 h and 48 h.

Test organisms (species):

Daphnia magna

Details on test organisms:

Daphnia magna Straus

Test type:

static

Water media type:

freshwater

Limit test:

no

Test temperature:

20-22°C

pH:

7,5 (+/-0,2)

Dissolved oxygen:

8,7 (+/-0,3) in the beginning of the test
7,7 (+/-0,7) in the end of the test

Salinity:

dilution water:
25 ml 0,08 M CaCl2-solution
+ 25 ml 0,02 M MgSO4-solution
+ 25 ml 0,03 M NaHCO3-solution
+ 25 ml 0,003 M KCl in 1 l deionised water

Conductivity:

606 µS/cm (dilution water)

Nominal and measured concentrations:

0.60, 0.75, 1.00, 1.20, 1.50, 2.40, 4.00 and 6.00 mg/L

Reference substance (positive control):

no

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2.07 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

A daphnia is assessed as immobile provided that it did not move independently or after slight swinging 10 s as a minimum. Other effects of the test substance on daphniae like coloration or special stress behaviour were not observed.

The relevant concentration range for the calculation of the EC₅₀-value was determined in preliminary tests.

Tab. 1:Mobility of Daphnia magna Straus at different concentrations of 2-Naphthol

concentration [mg/l]	Mobility of Daphnia magna after
	24 h		48 h
	Amount	%	Amount	%
0,60	10	100	10	100
0,75	9	90	9	90
1,00	9	90	8	80
1,20	8	80	7	70
1,50	6	60	6	60
2,40	10	100	5	50
4,00	3	30	3	30
6,00	6	60	0	0

Validity criteria fulfilled:

yes

Remarks:

Reference samples did not fall below 95% daphnia mobility. Oxygen content at the test end was always above 3 mg/L.

Conclusions:

In a study according to OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test), a 48 h EC50 = 2,07 mg/L was determined.

Executive summary:

The acute toxicity of 2-naphthol to Daphnia magna was investigated in a study according to OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) under semi-static conditions. The endpoint examined was immobilization. The daphnids (5 animals/concentration) were exposed to nominal concentrations of 0.60, 0.75, 1.00, 1.20, 1.50, 2.40, 4.00 and 6.00 mg/L 2 -naphthol.

The 48 h EC50 was determined to be 2.07 mg/L based on nominal concentrations.

The testing/validity criteria laid down in the OECD guideline 202 are fulfilled. This study is regarded as reliable without restriction.

Thus, a 48 h EC50=0.134 mg/L (recalculated based on initial concentrations) has to be taken into account for the assessment.

Description of key information

The short-term toxicity of 2-naphthol to aquatic invertebrates was determined according to OECD Testing Guideline 202.

The species was Daphnia magna.

Preliminary tests were conducted to determine the concetrations to be used during the definitive test.

As a result of the preliminary studies, concentration of 0.60, 0.75, 1.00, 1.20, 1.50, 2.40, 4.00, 6.00 mg/L were used for the definitive test.

The 48-hour EC50 was 2.07 mg/L based on nominal concentrations.

Thus, a 48-hour EC50 = 0.134 mg/L (recalculated based on initial concentrations) has to be taken into account for assessment.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

2.07 mg/L