Bronopol

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish, juvenile growth test

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007-APRIL-10 to 2007-JUNE-19

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 215 (Fish, Juvenile Growth Test)

Version / remarks:

No deviations that affected the integrity of the findings.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Days 0, 3, 7, 10, 15, 17, 21, 24 and 28 in all effect concentrations and the NOEC
Days 0 and 28: control

Vehicle:

no

Details on test solutions:

Test water control, 0.32, 1.0, 3.2, 10 and 32 mg a.s./L
The application solution of the highest test concentration was prepared once a week by dissolving 109.7 g of the test substance in 4.0 L of purified water by intense stirring for 10 minutes. The application solutions of the lower test concentrations were prepared by serial dilution of this stock.
The stability of the test substance in the application solutions during the renewal period had been confirmed in pre-tests.
A few drops of HCl were added for stabilization purposes of the application solutions during the use. The application solutions were protected from light and continuously stirred.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Species/strain: Rainbow trout, Oncorhynchus mykiss
Source: P. Hohler, trout breeding station, Zeiningen, Switzerland
Wild caught: No
Age/size: Not specifdied in the report
Kind of food: Commercial fish diet: HOKOVIT 502, 1.2 mm
Amount of food: Acclimatization: 2% of mean initial fish wet weight
Feeding frequency: Daily amount splitted into two equal portions at 5 hour intervals
Post-hatch transfer time: Not applicable
Time to first feeding: Not applicable
Feeding of animals during test: Yes
4% of mean initial fish wet weight increased
weekly by 25% relative to the initial food ration




Juvenile fish were held for more than 2 weeks in the laboratory under similar conditions as used in the test. Furthermore, they were acclimated to the test water, temperature and light conditions for 7 days prior to the start of the test. At the start of the test, 10 fish were introduced into each aquarium in random order.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Hardness:

169 – 239 mg/L as CaCO3

Test temperature:

Control and 0.32 mg a.s./L: 13.6 – 14.0°C
1.0 and 2.61 mg a.s./L: 13.7-14.1°C
9.35 and 30.0 mg a.s./L: 13.6-14.1°C

pH:

7.5 – 7.7

Dissolved oxygen:

8.8 – 9.4 mg O2/L

Control: 8.8-9.4 mg O2/L
0.32 mg a.s./L: 8.8-9.3 mg O2/L
1.0 mg a.s./L: 8.9-9.3 mg O2/L
2.61 mg a.s./L: 8.9-9.2 mg O2/L
9.35 mg a.s./L: 8.8-9.3 mg O2/L
30.0 mg a.s./L: 8.9-9.4 mg O2/L

Salinity:

Not applicable

Conductivity:

Not specified in the report

Nominal and measured concentrations:

The nominal test concentrations were 0.32, 1.0, 3.2, 10 and 32 mg a.s./L.
The concentration of Bronopol in the test medium was measured only at the highest concentration level resulting in no observable effects (3.2 mg a.s./L) and all effect treatment levels (10 and 32 mg a.s./L) yielding arithmatic mean measured concentrations of 2.61, 9.35 and 30.0 mg a.s./L. In addition, a blank control group was tested.

For specific details, please also see "any other information on results incl. tables", Table 1.

Details on test conditions:

TEST SYSTEM
- Test vessel: 60 L glass aquaria (54 x 29 x 39 cm, L x W x H)
- Type (delete if not applicable): open / closed
- Material, size, headspace, fill volume: 60 L glass aquaria, containing 48 L test medium
- Aeration: no
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate): 6
Test water flew continously into mixing chambers (2 L volume) at a rate of 12 L/h, i.e., 244 L/d, regulated by flow-meters. Digital dispensers were used to dose 14 mL/h (20 dosages of each 0.7 mL/h) of the appropriate application solution to the corresponding mixing chamber. The test medium was continuously stirred in the mixing chamber.
In regards of the volume of test medium of approximately 48 L in the test chambers the flow rate was equivalent to an approximate 6-fold volume exchange per day.
The test media of all treatment groups appeared clear throughout the test period.

- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1

- Biomass loading rate: volume/animal=4.8 L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Local tap water; non-chlorinated well water of drinking quality subjected to ion exchange procedure to reduce the total hardness.


OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16/8h light/dark
- Light intensity: 140-440 lux



RANGE-FINDING STUDY
Performed, but no details given

Reference substance (positive control):

no

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

2.61 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

Bronopol was demonstarted to be sufficiently stable in the test medium during the test period. Except the Day 3, Day7 and Day 21 measurement at the 3.2 mg a.s./L treatment level showing 54, 78 and 74% of nominal, respectively, recovery of Bronopol was always 80% of nominal.
Mortality was a more sensitive parameter than body weight gain as indicator of Bronopol toxicity to juvenile trout. Whilst at the range of test concentrations there was a concentration-effect relationship for lethal effects with 0% mortality up to and including the 2.61 mg a.s./L treatment level increasing to 10 and 50% at the following concentrations of 9.35 and 30.0 mg a.s./L, respectively, body wet weight gain of surviving fish was not affected up to and including the maximum test concentration of 30.0 mg a.s./L.

Effect data:
Mortality: 0, 0, 0, 10 and 50% in the 0.32, 1.0, 2.61, 9.35 and 30.0 mg a.s./L treatment group; respectively.
Abnormal behaviour, i.e., apathy and cessation of food intake, was observed in 0, 0, 0, 10 and 50% of fish in the 0.32, 1.0, 2.61, 9.35 and 30.0 mg a.s./L treatment group, respectively
Mean body wet weight: Day 0 – 1.2 g/fish in all treatment groups;
Day 28 – 3.7, 3.7, 3.9, 3.8, 3.8 and 4.2 g/fish in the 0.32, 1.0, 2.61, 9.35 and 30.0 mg a.s./L treatment group; respectively
Speciifc growth rate 0-28 days: 3.87, 4.11, 4.12, 4.02 and 4.23 in the 0.32, 1.0, 2.61, 9.35 and 30.0 mg a.s./L treatment group, respectively
Based on the mortality data, the NOEC and LOEC were established at mean measured concentration of 2.61 and 9.35 mg a.s./L, respectively.

No further effects except those described above were observed.

For specific details, please also see "any other information on results incl. tables", Table 2.

 

Table 2: Effects of Bronopol on survival and growth of Oncorhynchus mykiss during 28 days of exposure

Nominal concentration [mg a.s./L]	Mean measured concentration [mg a.s./L]	Mortality (by day) [%]	Mean body wet weight – day 0 / day 28 (SD) [g/fish]	Pseudo specific growth rate r^2/ % of control
Blank control	n.d.	0	1.2 (±0.09) / 3.7 (±0.53)	3.99 ±0.55 / --
0.32	-- ^&	0	1.2 (±0.10) / 3.7 (±0.80)	3.87 ±0.74 / 96
1.0	-- ^&	0	1.2 (±0.07) / 3.9 (±0.74)	4.11 ±0.68 / 103
3.2	2.61	0	1.2 (±0.10) / 3.8 (±0.60)	4.12 ±0.56 / 103
10.0	9.35	10 (day 16)	1.2 (±0.10) / 3.8 (±0.81)	4.02 ±0.74 / 101
32.0	30.0	50 (day 15)	1.2 (±0.09) / 4.2 (±1.62)	4.23 ±1.24 / 106

n.d. = not detected;  ^& not analysed since below NOEC

 

Table 3: Validity criteria for fish test according to OECD Guideline 215

	fulfilled	Not fullfilled
Concentration of dissolved oxygen in all test vessels > 60% saturation	X
Difference of water temperature < 1° C between test chambers at any time during test; temperature within a range of 2° C of  the temperature for specific test species	X
Mortality of control animals <10%	X
Increase of fish weight sufficient for detection of the minum variation of growth rate considered as significant	X

 

 

Validity criteria fulfilled:

yes

Remarks:

For specific details, please also see under section results and discussion "any other information on results incl. tables", Table 3.

Conclusions:

Lethal effect regarding juvenile rainbow trouts were observed and an NOEC of 2.61 mg/L (arithmet. mean) can be provided. However, no effects on the specific growth rate were found. Therefore, the NOEC is based on mortality instead of the growth rate.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

NOEC

Effect concentration:

2.61 mg/L

Additional information

Longterm effects on fish were investigated in a key study. A NOEC of 2.61 mg/L could be derived from the results with O. mykiss.

Furthermore, there is a supporting study available.The chronic toxicity of bronopol to rainbow trout (Oncorhynchus mykiss) was investigated in a 49 -day flow-through test according to OECD guideline 210 [Knoll Pharmaceuticals 1996]. Test parameters observed were mortality, sublethal effects, body length, body weight and condition indices.

A LC50 value of nominal 39.1 mg/L was determined. Survival of early life stage rainbow trout was significantly affected by a chronic treatment at nominal test concentrations of 40 mg/L. Mortality for all other test concentrations (2.25 - 21.50 mg/L) was within the control range. For the control, a mortality of 11.25 % was reported, which was in accordance with the validity criteria of OECD guideline 210 requesting a hatching success > 60 % and a post-hatch survival of 70 % for the control gourp. None of the treated groups differed significantly from the control in terms of body weight, length and condition indices. The resulting NOEC, based on mortalilty was 21.5 mg/L.

Analytical monitoring of the test substance revealed a recovery rate which was within 1.6 and 19.5 % of the nominal concentrations. A comparison to reference standards showed that at elevated pH values (8.16 - 8.23) and under aerobic conditions, bronopol seems to preferentially degrade to 2 -bromo-2 -nitroethanol.

Conclusively, there was no evidence for bronopol-related effects on fish growth and a NOEC of 21.5 mg/L could be derived.