Phthalimide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

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

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: ATCC-22662
- Source (laboratory, culture collection): American Type Culture Collection
- Age of inoculum (at test initiation): 3 days

ACCLIMATION
- Culturing media and conditions (same as test or not): same

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

22.2 - 23.3 °C

pH:

0 h, 6.9 - 7.6; at 72 h, 4.8 - 8.4

Nominal and measured concentrations:

concentration (nominal): 0, 10.6, 19.1, 34.3, 61.7, 111.1, 200.0 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 300 mL net triangle conical glass flask
- Aeration:
- Renewal rate of test solution: none
- Initial cells density: 1 x 10E+4 cells/ml
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates):

GROWTH and TEST MEDIUM
- Standard medium used: OECD

OTHER TEST CONDITIONS
- Photoperiod: no data
- Light intensity and quality: continuous light (4000 - 5000 lux)
- shaking (100 rpm)
- pH treatment: none

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

161 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10.7 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

33.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.6 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Results with reference substance (positive control):

Potassium dichromate (72 h EC 50 = 0.54 mg/L)

Reported statistics and error estimates:

Using ANOVA the NOECr value was 1.1 mg/l. However, this value seems to be extremely low. If the LOEC is divided by the factor between the concentrations of 1.8 mg/l a value of 11.8 mg/l can be calculated. The analytical results for the nominal concentration 34.3 mg/l are therefore questionable. In the concentration of nominal 61.7 mg/l 43.4 mg/l were detected at t 0(h) after 72 h still 10.4 mg/l were detected, representing still 23.9% of the measured concentrations at 0 h. In the concentration 34.3 mg/l a recovery of 23.9% of values at t0h would result in a concentration of 5.45 mg/L. The accompanying chemical analysis detected no test item at all at this concentration level. Therefore the NOEC of 1.1 mg/L should be discussed. The EU-TGD offers an other possibilty to estimate a NOEC. In special cases the LOEC divided by 2 can be used. This would result in a NOEC of 10.7 mg/L.

CONCENTRATIONS
nominal              measured concentration (mg/l)
concentration         (percentage of nominal)
  (mg/l)           0 h           72 h         geom.mean 
-----------------------------------------------------------
control           <0.1           <0.1           <0.1
  10.6            6.5 (61.3)     <0.1 (<0.9)     0.6 (5.7)
  19.1           13.8 (72.3)     <0.1 (<0.5)     0.8 (4.2)
  34.3           22.8 (66.5)     <0.1 (<0.3)     1.1 (3.2)
  61.7           43.4 (70.3)     10.4 (16.9)     21.2(34.4)
 111.1           83.2 (74.9)     46.7 (42.0)     62.3(56.1)
 200.0          160.6 (80.3)    131.7 (65.9)    145.4(72.7)
-----------------------------------------------------------
The test substance is unstable in the test solution due to hydrolysis.
As the half-life of this substance in water is 56.7 h at pH 7 and 1.1 h  at pH 9 (see Section 3.1.2), almost all measured concentrations were much  lower than the nominal ones. No test medium was changed during the  experiment (static). Therefore the geometric mean of the measured  concentrations should be used. Values below the quantification limit are  regarded as 0.05 mg/l, i.e. half of the quantification limit.
EFFECTS (0 h-72 h)
biomass:
EbC50 = 33.4 mg/l (95 % confidential: 6.7-136.5 mg/l)
NOECb = 0.6 mg/l
growth rate:
ErC50 = 161 mg/l (95 % confidential: 140.5-193.4 mg/l)
NOECr = 10.7 mg/l

AVERAGE CELL DENSITY DURING 72 h EXPOSURE
measured        
concentration       cell density (x 10E+4 cells/ml)
at 0 h (mg/l)      0 h      24 h      48 h       72 h
-----------------------------------------------------------
control           1.0       8.9       43.8      270.4
   6.5           1.0       7.8       41.0      259.6
  13.8           1.0       7.5       41.4      229.7
  22.8           1.0       7.3       30.6      253.4
  43.4           1.0       7.1       34.4      197.9
  83.2           1.0       7.0       28.2       73.2
 160.6           1.0       5.5       11.1       19.7
-----------------------------------------------------------

AVERAGE GROWTH INHIBITION DURING 72 h EXPOSURE
measured        
concentration     biomass      growth rate    
at 0 h (mg/l)     (0-72 h) %    (0-72 h) %
-----------------------------------------------------------
control               -              -             
   6.5              5.03           0.7         
  13.8             13.04**         2.9         
  22.8             12.51**         1.2         
  43.4             25.56**         5.7*         
  83.2             62.66**        23.4**       
 160.6             87.07**        46.8**       
-----------------------------------------------------------
Asterisk showed significant difference with control; *(a<0.05) and  **(a<0.01)

Conclusions:

The figures of EC50 and NOEC by biomass is rather safe side than the figures by growth rate.
EbC50 (0-72 h) = 61.6 mg/l for algae
NOECb (0-72 h) = 6.5 mg/l for algae

Executive summary:

A test with Pseudokirchnerella subcapitata on acute toxicity was performed according to the OECD Guideline 201 and the principles of GLP. The results are reported as geometric mean values of the measured values at the start and end of incubations. A 72 h-EbC50 of 33.4 mg/L was measured according to the OECD TG 201 growth inhibition test. A 72 h-NOECb of 0.6 mg/L was determined. Both results are related to the endpoint biomass, which presented lower results than the ones related to the growth rate (72 h-ErC50 = 161 mg/L; 72 h-NOECr = 10.7 mg/L) (EA Japan, 1999).

Description of key information

EbC50 (0-72 h) = 61.6 mg/l for algae
NOECb (0-72 h) = 6.5 mg/l for algae

Key value for chemical safety assessment

EC50 for freshwater algae:

61.6 mg/L

EC10 or NOEC for freshwater algae:

6.5 mg/L