Formamide

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study with acceptable restrictions (exposure concentrations in the test and the stability of formamide were not confirmed by chemical analysis)

Qualifier:

equivalent or similar to guideline

Guideline:

other: German Industrial Standard DIN 38412, Part 9

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Scenedesmus subspicatus (renamed to Desmodesmus subspicatus)
- Source (laboratory, culture collection): SAG 86.81

Pre-culture:
- medium:  OECD-medium (OECD 201)
- temperature:  20°C
- culture vessels:  250 mL-Erlenmeyer flasks plugged with gas permeable silicon-sponge caps
- fill volume:  100 mL
- vessels were incubated in an incubation chamber for 72 h  
- vessels were shaken once a day to hold cells in suspension
- illumination:  permanent artificial light
- light intensity:  approx. 120 µE/(m2*s) 

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

23°C

Nominal and measured concentrations:

7.81, 15.63, 31.25, 62.5, 125, 250, 500 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: 20 mL tubes plugged with gas permeable silicon-sponge caps
- Type (delete if not applicable): test was performed in non-sealed vessels
- Material, size, headspace, fill volume: 10 mL
- Aeration:
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density:
- Control end cells density:
- No. of organisms per vessel: 10000 exponentially-growing cells
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates):


GROWTH MEDIUM
- Standard medium used: yes/no
- Detailed composition if non-standard medium was used:


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD-medium (OECD 201)


OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH:
- Photoperiod: permanent artificial light
- Light intensity and quality: approx. 120 µE/(m2*s)
- Salinity (for marine algae):


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : samples were taken at regular intervals (0, 24, 48, 72, 96 h)
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
- Chlorophyll measurement: fluorescence (in vivo chlorophyll-a fluorescence at 685 nm as an indicator for the biomass (pulsed excitation with light flashes having a wavelength of 435 nm))
- Other: pH-values

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

125 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

250 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

259 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 500 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 500 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

96 h

Dose descriptor:

LOEC

Effect conc.:

> 500 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

96 h

Dose descriptor:

EC10

Effect conc.:

> 500 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

> 500 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Reported statistics and error estimates:

Effect values:
- Statistical comparisons of the endpoints with the control values were performed using ToxRatPro (Version 2.09).
The results (mg/L) were estimated for the endpoints growth rate and biomass integral

All values refer to nominal concentrations of formamide. No chemical analysis of the test substance was carried out.

Effect values:

Statistical comparisons of the endpoints with the control values were performed using ToxRatPro (Version 2.09).
The following results (mg/l) were estimated for the endpoints growth rate (r) and biomass integral (b):

Growth rate	72 h	96 h
EC10	259	> 500 (3712)
EC50	> 500 (14924)	> 500 (130370)
LOEC	250	> 500
NOEC	125	>= 500

Biomass integral	72 h	96 h
EC10	33	70
EC50	> 500 (554)	> 500 (1141)
LOEC	31.25	125
NOEC	15.63	62.5

During the 96 h exposure to formamide, cell densities (relative fluorescence values) were as follows (average of 6 replicates):

Nominal test concentration (mg/L)	Cell density (fluorescence)
	0h	24 h	48 h	72 h	96 h
0	43.2	208.9	760.3	2397.3	3831.8
7.81	44.2	215.3	764.9	2320.7	4081.7
15.63	42.2	214.5	707.2	2231.1	4014.2
31.25	44.0	222.0	637.4	2127.1	4007.1
62.5	40.3	213.8	617.5	2121.1	3881.6
125	39.5	179.6	588.0	1937.6	3914.7
250	43.0	149.9	413.0	1396.0	3447.9
500	41.4	146.2	407.8	1383.9	3370.9

Original effect values based on cell density as given in the report:

	24 h	48 h	72 h	96 h
EC20	177 mg/L	79.5 mg/L	129.5 mg/L	-- mg/L
EC50	-- mg/L	-- mg/L	-- mg/L	-- mg/L

     
pH values at test start (w/o algae) and after 96 h (inoculated assays): 

Nominal test concentration (mg/L)	pH (at start)	pH (96 h)
0	8.2	9.4
7.81	8.1	9.5
15.63	8.1	9.5
31.25	8.1	9.5
62.5	8.1	9.5
125	8.1	9.5
250	8.1	9.5
500	8.1	9.4

Validity criteria fulfilled:

yes

Conclusions:

Since the substance is hydrolytically stable and has no potential for evaporation, the study is acceptable for assessment although the substance concentrations were not verified by analytical monitoring. The NOEC and EC50 at both 72 and 96 hours was greater than 500 mg/L.

Description of key information

The toxicity of formamide to algae was studied in a 96-h static test with the green alga Scenedesmus subspicatus (renamed Desmodesmus subspicatus) according to German Industrial Standard DIN 38412, Part 9. The 72 - and 96 -hour EC50 values for growth rate and biomass integral were above the highest concentration tested (> 500 mg/l) (Key study). Significant differences in cell growth and biomass integral were observed in the higher test concentrations. The 72-hour NOEC values were 15.6 mg/l for biomass integral and 125 mg/l for growth rate.

Key value for chemical safety assessment

EC50 for freshwater algae:

500 mg/L

EC10 or NOEC for freshwater algae:

500 mg/L