Potassium superoxide

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

publication

Title:

13-Week drinking water toxicity study of hydrogen peroxide with 6-week recovery period in catalase-deficient mice

Author:

Weiner M, Freeman C, Trochimowicz H, de Gerlache J, Jacobi S, Malinverno G, Mayr W, Regnier J

Year:

2000

Bibliographic source:

Food Chem. Toxicol. 38:607-615

Report date:

1999

Reference 2

Reference Type:

publication

Title:

European Union Risk Assessment Report

Author:

European Chemicals Bureau

Year:

2003

Bibliographic source:

European Union Risk Assessment Report. Hydrogen peroxide; CAS No: 7782-84-1; EINECS No: 231-765-0. Final report, 2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Hydrogen peroxide

EC Number:

231-765-0

EC Name:

Hydrogen peroxide

Cas Number:

7722-84-1

Molecular formula:

H2O2

IUPAC Name:

Hydrogen peroxide

Test material form:

liquid

Remarks:

colourless

Specific details on test material used for the study:

Purity: 35% (w/w)

Test animals

Species:

mouse

Strain:

other: C57BL/6NCrlBR

Details on species / strain selection:

C57BL/6NCRlBR mice were chosen due to their particular sensitivity to the test substance because of a deficient detoxification pathway.

Sex:

male/female

Details on test animals or test system and environmental conditions:

Test animals:
- Source: Charles River Laboratories
- Age at study initiation: 5 weeks
- Weight at study initiation:
- Fasting period before study: no data
- Housing: individually in suspended, stainless steel cages with wire bottom
- Diet (e.g. ad libitum): Purina Rodent Chow 5002 (meal) ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 7 days
Environmental conditions:
- Temperature: 65 to 71 °F
- Humidity (%): 41 to 78
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 hours light/12 hours darkness

Administration / exposure

Route of administration:

oral: drinking water

Details on route of administration:

ad libitum

Vehicle:

water

Details on oral exposure:

The treated (and control) water for this study was prepared twice weekly and administered to the animals on the day of preparation. The drinking water solutions were made by adding preweighed amounts of 35% test substance to distilled water. The solutions were mixed in carboys for at least 15 minutes prior to dispending the animals. Following administration, unused portions of treated water were stored refrigerated. All equipment for water solution preparation and administration was passivated with nitric acid before use.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of the 100 ppm test substance stock solution and the 3000 ppm test substance stock solution used to dose mice at the 100 ppm and 3000 ppm levels were taken together with a blank sample and analysed for concentration and homogeneity. A colourimetric analytical method designated Test Method APG No. 332 was applied which uses a ferrus thiocyanate reagent. The colour absorbance was measured with a Perkin Elmer Lambda 18 Spectrophotometer. Subsequently, on each of four date one distilled water blank, one control sample of 100 ppm and 3000 ppm test substance and five samples of 100 ppm and 3000 ppm dose solutions were analysed by the same method. Additionally, the 35% test substance solution was analysed by an iodometric titration at 30 day intervals up to 120 days to test the stability of the solution under the storage conditions (4 °C, vented closed container).

Duration of treatment / exposure:

Approximately 90 days

Frequency of treatment:

ad libitum

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm

Remarks:

nominal in water

Doses / concentrations 2

Dose / conc.:

100 ppm

Remarks:

nominal in water

Doses / concentrations 3

Dose / conc.:

300 ppm

Remarks:

nominal in water

Doses / concentrations 4

Dose / conc.:

1 000 ppm

Remarks:

nominal in water

Doses / concentrations 5

Dose / conc.:

3 000 ppm

Remarks:

nominal in water

No. of animals per sex per dose:

15/sex per treatment group; 10/sex were killed after ceasing the exposure period, whereas 5/sex were submitted to a six week recovery period.

Control animals:

yes

Details on study design:

C57BL/6NCRlBR mice were chosen due to their particular sensitivity to the test substance because of a deficient detoxification pathway.

Examinations

Observations and examinations performed and frequency:

Clinical signs: daily
Mortality: twice daily
Body weight: weekly
Food consumption: weekly
Water consumption: twice weekly
Blood analysis, haematology, clinical chemistry analyses: blood samples were taken immediately before the scheduled necropsy
Ophthalmic examinations: the eyes of all animals were checked for lesions before the study and one week before the study termination and only animals showing no lesions were used in the study

Sacrifice and pathology:

Animals that died before the study termination underwent a complete necropsy upon dicovery of death. Animals sacrificed at their scheduled termination (days 91-93 of treatment period, days 133-134 of recovery period) were anaesthetised, bled for haematology and clinical chemistry determinations, sacrificed via exsanguination then necropsied. Animals were not fasted prior to sacrifice. The weights were determined of brain, liver, kidneys, spleen, testes, adrenals and heart. Samples from various tissues were saved in 10% buffered formalin. All slides of organs and tissues in the control and high dose groups as well as tissues from mice that died out of schedule were investigated by an experienced pathologist and histological examinations were performed on all gross lesions, the tongue, esophagus, stomach, duodenum, ileum, jejunum, caecum, colon and rectum of all animals from all groups.

Other examinations:

-

Statistics:

Body weights, food consumption, water consumption, absolute organ weights, organ:brain weight ratios, haematology and clinical chemistry data were analysed using the Ebar-Squared trend test. The test compared data from the high-dose group to control and computed a p-value to indicate whether the measured parameter was significantly different (p < 0.05 for statistically significant difference). Subsequent analyses compared data from the next highest dosage group to control, in the direction of the overall trend, and generated another p-value. These analyses continued in a stepwise manner for successively lower groups until the p-value was greater 0.05. When the trend test returned a value greater than 0.05, no subsequent comparisons of the lower dosage groups were performed.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

effects observed, treatment-related

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

not examined

Behaviour (functional findings):

not specified

Description (incidence and severity):

Neurobehaviour: no data

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

effects observed, treatment-related

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

No treatment-related deaths occurred and no treatment-related clinical signs were noted at any time of the study. Male and females exhibited significant reductions in body weight at 3000 ppm. Food and water consumption were significantly reduced at 3000 ppm, 1000 and 300 ppm. Males receiving 3000 ppm displayed significant reductions in total protein and globulin levels in the blood, possibly caused by mucosal hyperplasia occurring in the duodenum of these animals. Necropsy revealed no treatment-related gross lesions. Tissue slides indicated an increase in the cross sectional diameter and wall thickness of the duodenum. Subsequent microscopic evaluations revealed mild mucosal hyperplasia in eight of nine males receiving 3000 ppm and in seven of ten males receiving 1000 ppm. Minimal mucosal hyperplasia was noted in one of ten males receiving 300 ppm. Minimal to mild mucosal hyperplasia was also seen in ten of ten females receiving 3000 ppm and in eight of ten females receiving 1000 ppm. No other areas of the gastrointestinal tract were affected. No evidence of cellular atypia or architectual disruptions nor any other indications of neoplastic changes were observed; therefore, the treatment-related mucosal hyperplasia noted was not considered as a neoplastic lesion.

Effect levels

Key result

Dose descriptor:

NOEL

Effect level:

100 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

food consumption and compound intake

histopathology: non-neoplastic

water consumption and compound intake

Remarks on result:

other: 26 and 37 mg/kg bw/day for males and females, respectively

Target system / organ toxicity

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

300 ppm

System:

gastrointestinal tract

Organ:

duodenum

Treatment related:

yes

Dose response relationship:

yes

Applicant's summary and conclusion

Conclusions:

Under the study conditions, the sub-chronic NOEL of the substance in mice was determined to be 100 ppm (equivalent to 26 and 37 mg/kg/day for males and females, respectively).

Executive summary:

A study was conducted to determine the repeated dose oral toxicity of the substance according to OECD Guideline 408, in compliance with GLP. This subchronic toxicity study was conducted with a 35% aqueous solution of the test substance dissolved in drinking water to produce concentrations ranging from 100 to 3000 ppm. Groups of 15 male and 15 female C57BL/6NCrlBR mice was administered the test substance dissolved in their drinking water for 90 d. After the 90 -day exposure, 10 animals/sex of each dose group were sacrificed, while the remaining five animals/sex were kept for a six week recovery period. No treatment-related mortality or clinical signs were noted throughout the study. No other treatment-related effects were observed at the 100 ppm dose level. At 300 ppm, the consumption of food and water was reduced. Microscopic examination indicated an increase in the cross sectional diameter and wall thickness of the duodenum which corresponded to mild mucosal hyperplasia in eight of nine males and ten of ten females receiving 3000 ppm and in seven of ten males and eight of ten females receiving 1000 ppm. No other areas of the gastrointestinal tract were affected. During microscopical evaluation no evidence of cellular atypia or architectural disruptions nor any other indications of neoplastic changes were observed. Therefore, the treatment-related mucosal hyperplasia noted in the study was not considered as neoplastic lesion. Clinical pathologic effects (decreased total protein and globulin blood levels) were limited to the 3000 ppm level. All effects noted during the treatment period were reversible; animals sacrificed following the recovery period were considered biologically normal. Under the study conditions, the sub-chronic NOEL of the substance in mice was determined to be 100 ppm (equivalent to 26 and 37 mg/kg bw/day for males and females, respectively) (Weiner, 2000).