Potassium triboron pentaoxide

Sediment toxicity

Administrative data

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

8 July to 5 August 2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2011

Report date:

2011

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 219 (Sediment-Water Chironomid Toxicity Test Using Spiked Water)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Details on test material:

Sigma Aldrich, Boric Acid, Lot No. 079k0115. Purity 99.9%

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Analytical measurements were made on additional replicate systems at day 0 and day 28 for determination of test substance concentrations in overlying water.

Test substrate

Vehicle:

no

Details on sediment and application:

Fine industrial sand, washed, was used as an inorganic substrate for the larvae

Test chambers were prepared 1 day before introduction of organisms, maintained under test conditions

Test organisms

Test organisms (species):

Chironomus riparius

Details on test organisms:

Laboratory cultures used to provide 1st instar (1-day old) individuals at test initiation. Age was confirmed by measurement of head capsule widths of a representative sample.

Breeding conditions: Cultured at room temperature (21-25 degrees C) in laboratory culture water.
Handling of egg masses and larvae: Egg masses collected and isolated in freshwater, maintained at 20 degrees C.
- Feeding during test: prepared invertebrate food- a suspension of commercial fish flake food
- Amount: Daily, 2.5-3 ml of 2.0 mg/ml during 1st 10 days, 6-8 ml for remainder

Study design

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

artificial sediment

Limit test:

no

Exposure duration

Duration:

28 d

Exposure phase:

total exposure duration

Test conditions

Hardness:

140 to 162 mg CaCO3/L

Test temperature:

19.4 to 21.7 degrees C

pH:

7.5 to 8.7

Dissolved oxygen:

5.2 to 9.3 mg/L (60 to 95% saturation)

Ammonia:

0.00003 to 0.0168 micrograms/L (un-ionized)

Nominal and measured concentrations:

Nominal concentrations definitive test : 0 (control), 2.5, 5.0, 10, 20, 40 and 80 mg B/L.
Geometric Mean Measured Overlying Water Total Concentrations: 0.298, 3.06, 5.93, 11.0, 20.4, 43.3, and 89.3 mg B/L
Geometric Mean Measured Overlying Water Added Concentrations: 0, 2.76, 5.63, 10.7, 20.1, 43.0, and 89.0 mg B/L

Details on test conditions:

Test chambers were 1-L glass jars containing approximately 255 g of sediment (clean washed sand) Sediment depth was approximately 2 cm. Dilution water (600 mL) was added to each replicate chamber using a deflector to minimize disturbance of the sediment. Water depth was approx 8 cm, so the water: sediment volume ratio was approx 4:1. Polypropylene emergence traps with nylon mesh were used to monitor adult midge emergence. Chambers were left for 1 d to equilibrate before the test started.

At least 7 replicate chambers were prepared for each treatment level and control. Two were used to provide samples for chemical analysis and 3 chambers were used for biological observations. 20 midge larvae were added to each chamber for the chemical and biological observations. Seven different exposures were tested, a control and six treatments. Larvae were impartially added to cups, then the cups randomly assigned to a replicate chamber.

Overlying water was aerated during the test beginning 24 h after addition of the organisms by gentle bubbling. Midges were fed 2.5 to 3 ml of a commercial flake fish food suspension (2.0 mg/ml) for the first 10 d, then 8 ml daily for the remainder of the test. Algae were added during the first 3 days as food for the first instar larvae. Lighting was 16 h: 8 h light:dark cycle with a 30 m transition period. Light intensity was 520 lux. Temperature was maintained at 20 +/- 2 degrees C by keeping the test chambers in a flowing water bath. Water was not replaced during the test.

Emergence of adult flies was monitored from day 18. Presence of adults or exuviae in traps was monitored. Adult flies were identified by gender.

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

20.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

mortality

Remarks on result:

other: added boron

Effect concentrations 2

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

43 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

mortality

Remarks on result:

other: added boron

Effect concentrations 3

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

20.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

other: emergence

Remarks on result:

other: added boron

Effect concentrations 4

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

43 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

other: emergence

Remarks on result:

other: added boron

Effect concentrations 5

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

43 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

development rate

Remarks on result:

other: added boron

Effect concentrations 6

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

43 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

emergence rate

Remarks on result:

other: added boron

Effect concentrations 7

Duration:

28 d

Dose descriptor:

EC10

Effect conc.:

40.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

other: total adult emergence

Remarks on result:

other: added boron (30.2 - 50.8)

Effect concentrations 8

Duration:

28 d

Dose descriptor:

EC10

Effect conc.:

42.7 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Basis for effect:

mortality

Remarks on result:

other: added boron

Effect concentrations 9

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

20 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

other: mortality and emergency

Remarks on result:

other: added boron

Effect concentrations 10

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

40 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

other: mortality, emergence and development rate

Remarks on result:

other: added boron

Details on results:

The nominal concentrations were added in the effect concentrations table, following the usual practice that a nominal concentration may be used if the measured values are reasonably close to the nominal.

Percent emergence in the controls was 97% which exceeded the minimum of 70% emergence specified in the OECD 219 guideline for valid results.

All chemical and physical parameters for the 28 day study were within expected ranges, except for a 9 h period where temperature rose to 22.6 degrees due to water bath heater malfunction. This was judged to have no effect on the results as control performance met criteria and all treatments were equally affected.

Light intensity: 520 lux (day 0).

Reported statistics and error estimates:

Statistical analysis based on one-way ANOVA followed by Dunnett's test. ECx estimates obtained from probit method and trimmed Spearman-Karber method if poor fit in the probit approach.

Any other information on results incl. tables

Measured Overlying Water Concentrations and Endpoint Values

Group	Nominal Exposure (mg-B/L)	Measured Day 0 Exposure (mg-B/L)	Measured Geomean Exposure (mg-B/L)	Mean measured added boron	Survival	Emergence	Gender Ratio*	Development rate
Control	0	0.429	0.298	0	98%	97%	1.6	0.048
T1	2.5	3.22	3.06	2.76	98%	95%	0.5	0.044
T2	5	6.03	5.93	5.63	100%	98%	0.5	0.045
T3	10	10.4	11	10.7	97%	92%	0.8	0.045
T4	20	21.6	20.4	20.1	100	90%	0.5	0.043
T5	40	44.3	43.3	43.0	87%**	80%**	0.9	0.044
T6	80	87.6	89.3	89.0	0%**	0%**	--	--**

* Ratio is males:females

* Significantly different from control value (p<=0.05)

The gender ratio was reduced in all treatments above the control. However, there was no dose-related pattern; the most highly exposed group (T5) with emergent flies was most similar to controls. In addition, the test with spiked sediments showed virtually the reversed pattern of gender ratio, again with no evident dose-response pattern.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Expressed as nominal added boron the NOEC values for survival and percent emergence were 20 mg B-added/L and LOECs were 40 mg B-added/L. The NOEC value for development rate was 40 mg B-added/L.

Based on survival and percent emergence, the NOEC (total) was 20.4 mg B/L and LOEC (total) was 43.3 mg B/L. The EC10 (total) for survival was 43.0 mg B/L. The EC10 (total) for percent emergence was 40.8 mg B/L (95% CI 30.5 to 51.1 mg B/L) The NOECs (total) for time to emergence for males and females (calculated separately and combined) were 43.3 mg B/L. The NOECs (total) for development rate for males and females (calculated separately and combined) were 43.3 mg B/L.

Expressed as added boron the NOEC values for survival and percent emergence were 20.1 mg B-added/L and LOECs were 43.0 mg B-added/L. The NOEC value for development rate was 43.0 mg B-added/L. The EC10 for survival would be 42.7 mg B-added/L and the EC10 for percent emergence would be 40.5 mg B-added/L.

Analyses of the overlying water at test initiation and termination documented that the boron concentrations were relatively constant in the overlying water. This suggests that the silica sand sediment did not remove any significant amount of the boric acid spiked into the water.