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Ecotoxicological information

Toxicity to aquatic plants other than algae

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Reference
Endpoint:
toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08 July 1987 to 20 July 1988
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
other: EPA Guideline 123-2
Deviations:
yes
Remarks:
See principles of method if other than guideline
Principles of method if other than guideline:
According to the protocol the light intensity for the 5-day toxicity test with Anabaena flos-aquae should be 2000 lux. Cell biomass of Anabaena flos-aquae increased slowly when cultured under this low light intensity. Therefore, the light intensity was increased during culturing and testing of this species to 5000 and 4500 lux, respectively. It is the opinion of the testing laboratory that this did not affect the results of the study.
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Prepared every 3 days as a stock solution by adding test material to M-Type Hoaglands medium. The stock was ultrasonicated (for 10 minutes) to ensure that the test material dissolved.
Test organisms (species):
Lemna gibba
Details on test organisms:
TEST ORGANISM
- Common name: duckweed
- Strain: Lemna gibba G3
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Key result
Duration:
14 d
Dose descriptor:
EC10
Effect conc.:
19 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
frond number
Key result
Duration:
14 d
Dose descriptor:
EC50
Effect conc.:
33 µg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
frond number

The results of this test are detailed in Table 1 below.

Table 1: Mean frond production

   Days of exposure
Exposure concentration (µg/L)  3  6  9  12  14
 Controls  43  103  211  358  463h
 6.3  43  103  223g  399  517h
 13  36  114f  337g  634f  875f
 25  24a  41f  96f  154i  266i
 50  20b,c  18d  23e  22e,j  23e
 100  16  15d  15e  16e  16e
 EC50  48  30  36  33  33

aAll fronds slightly yellow; bAll fronds mostly brown; cMany small individual fronds; dSome fronds brown, individual; eFronds brown, individual; fFronds small, some are yellow; gFronds smaller than controls; hFew yellow fronds; iFew fronds same size as controls, most are very small, few roots observed; jRoots are brown

The EC10, EC50 and EC90 values and their 95% confidence limits were determined by linear regression of the response (percent reduction of frond production, as compared with controls) versus nominal exposure concentration over the range of test concentrations where a clear exposure-response relationship was observed. They are presented in Table 2 below.

Table 2: EC10, EC50 and EC90 values

 Exposure duration  EC10 (µg/L) (95% C.I.)  EC50 (µg/L) (95% C.I.)  EC90 (µg/L) (95% C.I.)
 3 days  8.6 (4.6 -15)  48 (27 -87)  270 (140 -550)
 6 days  10 (3.0 -31)  30 (9.7 -95)  85 (28 -310)
 9 days  19 (7.4 -47)  36 (14 -92)  71 (29 -200)
 12 days  18 (7.2 -44)  33 (14 -82)  63 (26 -170)
 14 days  19 (8.2 -41)  33 (15 -75)  63 (29 -150)
Validity criteria fulfilled:
not specified
Conclusions:
Under the conditions of the test, the 14 day EC50 for inhibition of growth (frond production) of Lemna gibba G3 was determined to be 33 µg/L (95 % C.I. 15-75 µg/L).
Executive summary:

In a GLP compliant effects on aquatic plants study conducted in line with standardised guideline EPA Guideline 123 -2, the effects of the test material on aquatic plants was determined. Aquatic plants were exposed to the test material at nominal test concentrations of 0, 6.3, 13, 25, 50 and 100 µg/L. Under the conditions of the test, the 14 day EC50 for inhibition of growth (frond production) was determined to be 33 µg/L.

Description of key information

The EC50 of the test material was determined to be 33 µg/L according to a study performed in line with EPA Guideline 123-2.

Key value for chemical safety assessment

EC50 for freshwater plants:
33 µg/L
EC10 or NOEC for freshwater plants:
19 µg/L

Additional information

In a GLP compliant effects on aquatic plants study conducted in line with standardised guideline EPA Guideline 123-2, the effects of the test material on aquatic plants was determined. Aquatic plants were exposed to the test material at nominal test concentrations of 0, 6.3, 13, 25, 50 and 100 µg/L. Under the conditions of the test, the 14 day EC50 for inhibition of growth (frond production) was determined to be 33 µg/L.