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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
April - May 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
Basic solution was shaken for 72 h before initiation of the study
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.19 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
dissolved
Basis for effect:
other: yield
Remarks on result:
other: 016 - 0.24
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
<= 0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
other: yield
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
< 0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
other: yield

 

The EyCxvalues [mg/L] with 95% confidence interval

Time of exposure

24 h

48 h

72 h

EyC10

0.13

(0.06 – 0.21)

0.13

(0.08 – 0.17)

0.15

(0.09 –0.20)

EyC20

0.23

(0.12 – 0.32)

0.19

(0.13 – 0.24)

0.21

(0.15 – 0.27)

EyC50

0.65

(0.49 – 0.87)

0.42

(0.34 – 0.51)

0.42

(0.35 – 0.49)

LOEC/72 h

≤ 0.10 mg/L

NOEC/72 h

< 0.10 mg/L

2,4,6-trinitrotoluene (TNT) -Endpoints of growth rate in the definitive test based on nominal test item concentrations

The ErCxvalues [mg/L] with 95% confidence interval

Time of exposure

24 h

48 h

72 h

ErC10

0.19

(0.10 – 0.28)

0.26

(0.19 – 0.33)

0.36

(0.29 – 0.43)

ErC20

0.37

(0.24 – 0.49)

0.41

(0.32 – 0.49)

0.51

(0.43 – 0.58)

ErC50

1.30

(1.04 – 1.67)

0.99

(0.87 – 1.14)

0.96

(0.88 – 1.06)

LOEC/72 h

0.40 mg/L

NOEC/72 h

0.20 mg/L

2,4,6-trinitrotoluene (TNT) -Endpoints of yield in the definitive test based on geometric mean test item concentrations

The EyCxvalues [mg/L] with 95% confidence interval

Time of exposure

24 h

48 h

72 h

EyC10

0.04

(0.01 – 0.08)

0.04

(0.02 – 0.06)

0.05

(0.03 – 0.07)

EyC20

0.09

(0.04 – 0.14)

0.07

(0.05 – 0.10)

0.08

(0.06 – 0.11)

EyC50

0.37

(0.25 – 0.56)

0.20

(0.15 – 0.26)

0.19

(0.16 – 0.24)

LOEC/72 h

≤ 0.03 mg/L

NOEC/72 h

< 0.03 mg/L

2,4,6-trinitrotoluene (TNT) -Endpoints of growth rate in the definitive test based on geometric mean test item concentrations

The ErCxvalues [mg/L] with 95% confidence interval

Time of exposure

24 h

48 h

72 h

ErC10

0.07

(0.03 – 0.12)

0.10

(0.07 – 0.14)

0.15

(0.12 – 0.19)

ErC20

0.17

(0.10 – 0.25)

0.20

(0.15 – 0.24)

0.25

(0.21 – 0.30)

ErC50

0.92

(0.69 – 1.28)

0.65

(0.56 – 0.76)

0.64

(0.57 – 0.71)

LOEC/72 h

0.14 mg/L

NOEC/72 h

0.10 mg/L

Validity criteria fulfilled:
yes
Remarks:
The validity criteria were met according to OECD Guideline No 201.
Conclusions:
In the algae toxicity test the estimated ErC50/72 h is 0.96 mg/L and EyC50/72 h is 0.42 mg/L – based on nominal concentrations of 2,4,6-trinitrotoluene (TNT).
The LOEC value for yield after 72 h is lower or equal 0.1 mg/L and NOEC value is lower than 0.1 mg/L. The LOEC and NOEC values (growth rate) after 72 h are 0.4 mg/L and 0.2 mg/L, respectively.
Since the recovery of 2,4,6-trinitrotoluene at test termination was below 80% of initial concentrations, the ECx values were determined both based on nominal concentration and based on geometric mean of determined 2,4,6-trinitrotoluene concentrations.
In the algae toxicity test the estimated EyC50/72 h is 0.19 mg/L and ErC50/72 h is 0.64 mg/L – based on geometric mean concentrations of 2,4,6-trinitrotoluene (TNT).
The LOEC value for yield after 72 h is lower or equal 0.03 mg/L and NOEC value is lower than 0.03 mg/L. The LOEC and NOEC values (growth rate) after 72 h are 0.14 mg/L and 0.10 mg/L, respectively.
Executive summary:

The growth of the green algaewas investigated in a 72 hours static toxicity laboratory study in glass flasks of 250 mL capacity, containing 100 mL of each treatment per replicate. The initial density of algae was1 x 104cells/mL.The following concentrations of the test item2,4,6-trinitrotoluene (TNT)were applied:0.1; 0.2; 0.4; 0.8; 1.6 and 3.2 mg/L.

The number of algae cells was determined by indirect method i.e. by spectrophotometric measurement of absorbance after 24, 48 and 72 hours of the test.

The chemical analyses content of test item2,4,6-trinitrotoluene (TNT)performed by validated method confirmed correct preparation of test concentrations.

At test initiation the content of2,4,6-trinitrotoluene (TNT)in test concentrations were in range91.9 – 100.0%of nominal.

At test termination(t72)the content of2,4,6-trinitrotoluenein the lowest test concentration 0.1 mg/L was below limit of detection (LoD). The content of2,4,6-trinitrotoluenein test concentrations 0.2 and 0.4 mg/L was below limit of qualification (LoQ). The content of2,4,6-trinitrotoluenein test concentrations 0.8; 1.6 and 3.2 mg/L wasin range 41.3 – 88.1% of initial concentrations.

No morphological changes in algal cells were observed at the end of the test.

Since the recovery of 2,4,6-trinitrotolueneat test termination was below 80% of initial concentrations,the ECxvalues were determined both based on nominal concentration and based on geometric mean of determined2,4,6-trinitrotolueneconcentrations.

Description of key information

According to OECD guideline No 201 green algae growth inhibition static test was performed for 72 hours. The following concentrations of the test item 2,4,6-trinitrotoluene (TNT) were applied: 0.1; 0.2; 0.4; 0.8; 1.6 and 3.2 mg/L. In the algae toxicity test the estimated EyC50/72 h is 0.42 mg/L and ErC50/72 h is 0.96 mg/L – based on nominal concentrations of 2,4,6-trinitrotoluene (TNT). The LOEC value for yield after 72 h is lower or equal 0.1 mg/L and NOEC value is lower than 0.1 mg/L. The LOEC and NOEC values (growth rate) after 72 h are 0.4 mg/L and 0.2 mg/L, respectively.

Since the recovery of 2,4,6-trinitrotoluene at test termination was below 80% of initial concentrations, the ECx values were determined both based on nominal concentration and based on geometric mean of determined 2,4,6-trinitrotoluene (TNT) concentrations.

In the algae toxicity test the estimated EyC50/72 h is 0.19 mg/L and ErC50/72 h is 0.64 mg/L – based on geometric mean concentrations of 2,4,6-trinitrotoluene (TNT).

The LOEC value for yield after 72 h is lower or equal 0.03 mg/L and NOEC value is lower than 0.03 mg/L. The LOEC and NOEC values (growth rate) after 72 h are 0.14 mg/L and 0.10 mg/L, respectively.

In accordance with Regulation EC 1272/2008 (CLP) and basend on available data substance can be classified as hazardous to the aquatic environment chronic category 2 as 1 mg/L < LC50 < 10 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
0.19 mg/L
EC10 or NOEC for freshwater algae:
0.1 mg/L

Additional information