Bronopol

Repeated dose toxicity: dermal

Administrative data

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted in the seventies, i.e. prior to implementation of guidelines, and GLP was not compulsory at that time. However, the study was well-documented and the reported data are of scientific accetability.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1973

Materials and methods

Principles of method if other than guideline:

Method: other: no data

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Bronopol

EC Number:

200-143-0

EC Name:

Bronopol

Cas Number:

52-51-7

Molecular formula:

C3H6BrNO4

IUPAC Name:

2-bromo-2-nitropropane-1,3-diol

Test material form:

not specified

Details on test material:

No purity specified.

Test animals

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Details on test animals or test system and environmental conditions:

Source: Hylyne Commercial Rabbits, Cheshire
They were housed individually in metal cages.

Administration / exposure

Type of coverage:

other: non-occlusive

Vehicle:

other: methylcellulose

Details on exposure:

Route of Administration: dermal
At a dose level of 1 ml/kg b.w. the daily application of Bronopol at a concentration of 0.2 and 0.5% corresponds to a dose of 2 and 5 mg/kg bw/day
respectively.
Vehicle: 2,5% methylcellulose.
The residual test substance was removed after each treatment period of 6 hours by gentle washing of the skin application site with a warm dilute soap solution, followed by rinsing with clean water; thereafter the skin was blotted dry with absorbent paper.

Duration of treatment / exposure:

21 days, 6 hours/day

Frequency of treatment:

7 d/week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0.2 other: %

Remarks:

bronopol in 2.5% methyl cellulose, 1 ml/kg bw, corresponding to 2 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

0.5 other: %

Remarks:

bronopol in 2.5% methyl cellulose, 1 ml/kg bw, corresponding to 5 mg/kg bw/day

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: none

Examinations

Observations and examinations performed and frequency:

Observations and examinations included local skin reaction (erythema and oedema), behavioural changes and
signs of toxicity, food consumption, body weight, haematology (packed cell volume, haemoglobin, red cell count,
total and differential white cell count), clinical chemistry (plasma urea, total serum proteins, serum protein,
serum alkaline phosphatase, serum transaminase (SGPT), ophthalmoscopic examination.
Body weights were recorded at test initiation and weekly thereafter; the group mean value (g/rabbit) was calculated. Food consumption for each rabbit was recorded weekly and the group mean food intake (g/rabbit/week) was calculated. The eyes of the animals were examined prior test start and again after 3 weeks of treatment (Keeler indirect ophthalmoscope).

Sacrifice and pathology:

Terminal studies after sacrifice of the animals included macroscopic examination and weighing of inner organs
(thyroid, heart, liver, kidneys, adrenals, and gonads) and microscopic examination of a series of tissues
(adrenal, brain, duodenum, eye, gall-bladder, gonads, heart, ileum, kidney, liver, lymph nodes, marrow smear,
mid-colon, pancreas, pituitary, salivary gland, skin (treated and untreated), spleen, stomach
(glandular and non-glandular), thymus, thyroid, urinary bladder.

Statistics:

Student's t-test and analysis of variance were employed to assess the significance of intergroup differences.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

No mortality and no signs of toxicity were observed.

Dermal irritation:

effects observed, non-treatment-related

Description (incidence and severity):

Local skin reaction (slight to well-defined erythema in 9/10 animals, and slight edema in all animals) was observed in the control rabbits. Similar irritation was seen in rabbits treated with Bronopol 0.2% although possibly with slightly more edema formation and slightly more persistent.Bronopol 0.5% treatment caused progression of slight to well-defined erythema to moderate erythema in 9/10 animals. Edema occurred on the third day and became well defined in all rabbits. Moderate edema developed in 3/5 males.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, non-treatment-related

Description (incidence and severity):

Initial loss of body weight was seen in all groups including controls; weight gain was comparable and no treatment related trend could be observed which would indicate a specific effect of Bronopol on growth.

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

Food consumption of all male and female animals was normal except for 2 animals in group 2 (0.2%) and one animal in group 3 (0.5%) where food consumption was depressed.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

Ophthalmoscopic examination revealed no abnormalities.

Haematological findings:

no effects observed

Description (incidence and severity):

Haematology and clinical chemistry were inconspicious.

Clinical biochemistry findings:

no effects observed

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

The macroscopical examination of the treated skin areas at necropsy revealed a varying degree of inflammatory reaction in control (2 cases) and in the 0.5% bronopol group (one case).One animal treated with 0.2% bronopol showed an isolated area of hyperkeratosis. One animals of the 0.2% bronopol group and 4 animals of the 0.5% bronopol group showed areas of dermal scarring (1 to 8 mm in length). All these reactions were considered to be non-specific and without toxicological significance. Areas of scabbing with associated dermal inflammation were seen in 2 animals treated with 0.5% bronopol. A similar effect also was seen in an animal of the 0.2% bronopol group, however within an untreated skin area. Therefore, this effect was considered to rather be related to the scarification of the skin than to the treatment with bronopol.
Neither gross- nor histopathological treatment-related changes were seen; organ weights were inconspicious.

Histopathological findings: non-neoplastic:

no effects observed

Details on results:

Local skin reaction (slight to well-defined erythema in 9/10 animals, and slight edema in all animals)was observed in the control rabbits. Similar irritation was seen in rabbits treated with Bronopol 0.2% although possibly with slightly more edema formation and slightly more persistent.Bronopol 0.5% treatment caused progression of slight to well-defined erythema to moderate erythema in 9/10 animals. Edema occurred on the third day and became well defined in all rabbits. Moderate edema developed in 3/5 males. The macroscopical examination of the treated skin areas at necropsy revealed a varying degree of inflammatory reaction in control (2 cases) and in the 0.5% bronopol group (one case).One animal treated with 0.2% bronopol showed an isolated area of hyperkeratosis.One animals of the 0.2% bronopol group and 4 animals of the 0.5% bronopol group showed areas of dermal scarring(1 to 8 mm in length). All these reactions were considered to be non-specific and without toxicological significance. Areas of scabbing with associated dermal inflammation were seen in 2 animals treated with 0.5% bronopol. A similar effect also was seen in an animal of the 0.2% bronopol group, however within an untreated skin area. Therefore, this effect was considered to rather be related to the scarification of the skin than to the treatment with bronopol.
No mortality and no signs of toxicity were observed.
Food consumption of all male and female animals was normal except for 2 animals in group 2 (0.2%) and one animal in group 3 (0.5%) where food consumption was depressed.Initial loss of body weight was seen in all groups including controls; weight gain was comparable and no treatment related trend could be observed which would indicate a specific effect of Bronopol on growth.
Haematology and clinical chemistry were inconspicious.
Ophthalmoscopic examination revealed no abnormalities.
Neither gross- nor histopathological treatment-related changes were seen; organ weights were inconspicious.

Effect levels

1

Key result

Dose descriptor:

NOAEL

Effect level:

0.2 other: %

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: skin irritation

Remarks on result:

other: 2 mg/kg bw/day

2

Dose descriptor:

LOAEL

Effect level:

0.5 other: %

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: skin irritation

Remarks on result:

other: 5 mg/kg bw/day

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 1: Numerical scores awarded to dermal reactions elicited by Bronopol

(group 1: vehicle control; 2: Bronopol 0.2%; 3: Bronopol 0.5%).

Group	Sex	Animal No.	Reaction	Day 0	1	2	3	14	21
1	Male	324	Erythema	0	1	1	1	1	1
			Oedema	0	0	0	0	1	0
		469	Erythema	0	1	1	1	2	1
			Oedema	0	0	0	0	1	1
		478	Erythema	1	1	1	1	1	1
			Oedema	0	0	0	0	1	0
		2438	Erythema	0	1	1	1	1	1
			Oedema	0	0	0	0	0	0
		327	Erythema	0	1	1	1	1	1
			Oedema	0	0	0	0	1	0
	Female	350	Erythema	0	1	1	1	1	1
			Oedema	0	0	0	0	1	2
		2081	Erythema	1	1	1	1	1	1
			Oedema	0	0	0	0	1	0
		2082	Erythema	0	0	0	1	2	1
			Oedema	0	0	0	0	1	0
		332	Erythema	0	1	1	2	2	1
			Oedema	0	0	0	0	2	2
		344	Erythema	0	1	1	1	2	1
			Oedema	0	0	0	0	1	2

Group	Sex	Animal No.	Reaction	Day 0	1	2	3	14	21
2	Male	326	Erythema	1	1	1	1	2	1
			Oedema	0	0	0	0	1	1
		330	Erythema	1	1	1	1	2	1
			Oedema	0	0	0	0	1	0
		476	Erythema	0	1	1	1	2	2
			Oedema	0	0	0	0	1	1
		2054	Erythema	1	1	1	1	2	1
			Oedema	0	0	0	0	1	0
		2473	Erythema	0	0	1	1	1	1
			Oedema	0	0	0	0	1	0
	Female	342	Erythema	0	1	1	2	1	2
			Oedema	0	0	0	0	1	2
		2089	Erythema	0	1	1	1	1	1
			Oedema	0	0	0	0	0	0
		2097	Erythema	0	1	1	1	1	1
			Oedema	0	0	0	0	1	1
		2092	Erythema	0	1	1	1	1	1
			Oedema	0	0	0	0	1	1
		2406	Erythema	0	1	1	1	2	1
			Oedema	0	0	0	0	1	1

Group	Sex	Animal No.	Reaction	Day 0	1	2	3	14	21
3	Male	316	Erythema	0	2	2	2	3	3
			Oedema	0	0	0	1	3	2
		331	Erythema	0	2	2	2	3	3
			Oedema	0	0	0	1	3	2
		2057	Erythema	0	1	2	2	3	3
			Oedema	0	0	0	1	2	1
		2439	Erythema	0	1	1	1	3	3
			Oedema	0	0	0	1	3	3
		2055	Erythema	0	1	1	1	3	3
			Oedema	0	0	0	1	2	2
	Female	336	Erythema	0	1	1	1	3	3
			Oedema	0	0	0	1	2	2
		354	Erythema	0	1	1	2	3	3
			Oedema	0	0	0	1	2	2
		2083	Erythema	0	1	1	2	3	1
			Oedema	0	0	0	1	2	1
		335	Erythema	0	1	1	2	2	1
			Oedema	0	0	0	1	1	1
		337	Erythema	0	1	1	2	3	1
			Oedema	0	0	0	1	2	1

Applicant's summary and conclusion

Conclusions:

CL-Freetext:
Repeated dermal application of Bronopol at 0.2 and 0.5% in methyl cellulose suspension over a period of 21 days was not associated with signs of systemic toxicity or deaths. Severe skin irritation was observed after application of 0.5% Bronopol, whereas 0.2% Bronopol caused skin reaction comparable to, but slightly more persistent than that elicited by the vehicle alone. Correspondingly, NOAEL- and LOAEL-values of 2 mg/kg bw/day and 5 mg/kg bw/day were estimated on the basis of the skin findings.