Fatty acids, C8-18 and C18-unsatd., zinc salts

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

A standard solution(Zinc Standard: 10 mg/L) was dissolved in 1 % HNO3 and used.

Vehicle:

yes

Details on test solutions:

100.00 mg/L stock solution
The required amount of the test substance 0.1000 g was weighed using a balance(Ohaus, U.S.A.) into
1 L volumetric flask and added to suspend until the 1 L with test water(OECD medium) for preparing
test solution of 100.00 mg/L. This solution was sealed and mixed using a magnetic stirrer(Misung
Scientific. Co., Ltd., Korea) for 48 h and was filtered through a 0.45 μm PVDF membrane filter(Cuota
Lab, Korea).
This 100.00 mg/L stock solution was used for the dilution to prepare each treatment groups.
For the definitive test, 1.00, 1.80, 3.24, 5.80 and 10.49 mg/L was prepared, 10.0, 18.0, 32.4, 58.3 and
104.9 mL of stock solution was added into 1,000 mL volumetric flask and final volume was adjusted
to 1,000 mL using OECD medium.
Per 100 mL were prepared for each treatment group and only culture medium was used for the control
group.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

Species : Freshwater alga, Pseudokirchneriella subcapitata
Culture Room : CentralBio Co., Ltd. Freshwater alga culture room

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Hardness:

No data

Test temperature:

Average, range of temperature : 22.5 ℃

pH:

Average, range of pH
(0 h) : (Control)7.55
(Treatment group)7.56(7.52~7.63)

(72 h) : (Control)7.96(7.89~8.03)
(Treatment group)7.86(7.81~7.99)

Dissolved oxygen:

No data

Salinity:

No data

Nominal and measured concentrations:

nominal concentration = 1.00, 1.80, 3.24, 5.83, 10.49 mg/L
measured concentration = 0.292, 0.532, 0.984, 1.73, 3.00 mg/L

Details on test conditions:

Inoculum cultured alga suspension were added to the flasks containing the test solutions of 100
mL on a clean bench and adjusted to an initial concentration of 5×103~104 cells/mL of algal biomass
per group. Flasks were incubated by continuous shaking(at approximately 100 rpm) at 21~24 oC
under continuous illumination(4440~8,880 Lux) for 72 h. The row and column of the flasks were
rotated at 24 h intervals during incubation in an attempt to equally distribute light intensity.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

ca. 1.042 mg/L

95% CI:

>= 0.898 - <= 1.22

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Results with reference substance (positive control):

Growth EC50 = 0.89 (mg/L)
95 % Confidence Limits = 0.88~0.90(mg/L)

Yield EC50 = 0.39 (mg/L)
95 % Confidence Limits = 0.39~0.39(mg/L)

Validity criteria fulfilled:

yes

Conclusions:

This study evaluated effect on the growth of the freshwater alga (Pseudokirchneriella subcapitata)
caused by the test substance, Fatty acids, C8-18 and C18-unsatd., zinc salts, when exposed to the test
substance for 72 h under the shaking culture and to determine the median effective concentration(EC50)
from the average specific growth rate and yield of each treatment groups. On the basis of the range
finding test, the definitive test was conducted and the treatment levels were selected at 1.00, 1.80, 3.24,
5.83, and 10.49 mg/L, and a control group was prepared for this test.
The biomass in the control group was increased by 166 times or more during the exposure period, and
each coefficient of variation was confirmed to be acceptable in this test.
As a result of the definitive test, the mean measured concentration measured at time point 0 h, 24 h, 48
h, and 72 h at 1.00, 1.80, 3.24, 5.83 and 10.49 mg/L were 0.292, 0.532, 0.984, 1.73 and 3.00 mg/L.
These results were 29.2, 29.6, 30.4, 29.7 and 28.6 % of the nominal concentration.
The test results were determined based on the mean measured concentration. Therefore, all results were
determined on the basis of the mean measured concentration.
The 72 h ErC50 value of Fatty acids, C8-18 and C18-unsatd., zinc salts to Pseudokirchneriella
subcapitata was determined to be 1.042 mg/L(95 % confidence limits: 0.898~1.220 mg/L), NOEC was
0.532 mg/L and LOEC was 0.984 mg/L. EyC50 value was determined to be 0.713 mg/L(95 % confidence
limits: 0.690~0.737 mg/L), NOEC was 0.292 mg/L and LOEC was 0.532 mg/L. The EC50, NOEC and
LOEC were based on the geometric mean measured concentration.

Key value for chemical safety assessment

EC50 for freshwater algae:

1.042 mg/L