Pentaboron sodium octaoxide

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Peer-reviewed technical publication that meets basic scientific principles.

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II))

Deviations:

yes

Remarks:

no further details available

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

On day 1, 4, 7 and 10, three 24h samples for each concentration were collected.
All samples were stored at 4°C until analysis.

Vehicle:

no

Test organisms (species):

other: Spirodella polyrrhiza

Details on test organisms:

TEST ORGANISM
- Common name: Duckweed
- Source : existing laboratory culture

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

10 d

Test temperature:

25 +- 1 °C

Nominal and measured concentrations:

Nominal concentrations : 0.5, 3, 6, 17, 25 and 37 mg B/L
To verify B exposure, water samples were analyzed using the colorimetric curcumin method as described by Allen (1974). Mean concentrations of time 0 and 24 hr samples were: 0.9 (control), 3.6, 6.5, 19.2, 24.0, and 40.0 mg B/L. B concentrations for days 4, 6 and 10 were not reported. Authors expressed endpoints based on time 0 concentrations, but mean values are used below.

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 50 ml plastic cups filled with 45 ml of boron-containing nutrient media
- Renewal rate of test solution (frequency/flow rate): daily
- No. of fronds per colony: 14-16
- No. of vessels per concentration (replicates): 6


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: pH stabilized nutrient media (Clatworthy and Harper, 1962)


OTHER TEST CONDITIONS
- Photoperiod, light intensity and quality: 24h light from normal chamber illumination + two 24-in. Lampi Flora Plant lights each fitted with 20 W wide-spectrum fluorescent lights were placed +- 12 in. above the test chambers.


EFFECT PARAMETERS MEASURED :
- Determination of frond number: On day 0 and 10,frond number was determined, and observations of fronds were made. Chlorosis, necrosis and death were observed and classified as abnormal fronds.

Duration:

10 d

Dose descriptor:

LOEC

Effect conc.:

3.6 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Basis for effect:

frond number

Duration:

10 d

Dose descriptor:

NOEC

Effect conc.:

6.5 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Basis for effect:

growth rate

Duration:

10 d

Dose descriptor:

LOEC

Effect conc.:

19.5 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Basis for effect:

growth rate

Details on results:

Total frond production reduced at next higher exposure (3.6 mg B/L) so no NOEC for total frond number can be derived. EC10 values could not be calculated

Reported statistics and error estimates:

Statistical analysis was performed using TOXSTAT 3.5 and ANOVA. The ANOVA and Tukey's HSD were performed to measure statistical differences between boron concentrations on days 0 and 10. These statistical tests were also used to analyze differences in initial concentrations and 24-h sample boron concentrations. Significance was determined using p =< 0.05 for all statistical tests.

Duration	Endpoint	Effect conc.	Nominal/Measured	Conc. based on	Basis for effect	Remarks (e.g. 95% CL)
10 d	LOEC	3.6 mg/L	meas. (not specified)	element	frond number	unbounded LOEC
10 d	EC50	14.3 mg/L	meas. (not specified)	element	frond number
10 d	NOEC	6.5 mg/L	meas. (not specified)	element	growth rate
10 d	LOEC	19.2 mg/L	meas. (not specified)	element	growth rate
10 d	EC50	11.7 mg/L	meas. (not specified)	element	growth rate

Description of key information

The test item boric acid has been evaluated for its toxicity towards the aquatic plant Spirodella polyrrhiza in a study according to EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II). The fresh water plant has been exposed to nominal concentrations of 0.5, 3, 6, 17, 25 and 37 mg B/L for a total of 10 days under semi-static conditions. The EC50 growth rate and NOEC growth rate have been determined to be 11.7 mg B/L and 6.5 mg B/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater plants:

11.7 mg/L

EC10 or NOEC for freshwater plants:

6.5 mg/L