Hydrogen peroxide

Endpoint summary

Description of key information

The acute oral toxicity of a 70.1 % w/w (Finlay 1996) and a 35 % w/w (FMC 1983) solution of hydrogen peroxide was tested in two valid studies in male and female Crl:CD BR and Sprague-Dawley rats, respectively, establishing LD50 values of 1026 mg/kg in male rats and 694 mg/kg in female rats for the higher concentrated solution and 1193 mg/kg in male and 1270 mg/kg in female rats for the lower concentrated solution.

A valid guideline study on the acute inhalation toxicity of vapours of a 49.3 % w/w hydrogen peroxide solution was carried out (Hoffman 1990). No LC50 value was established but it was shown that the LC50 value must be greater than 170 mg/m3 as no mortality occurred at the highest achievable vapour concentration. A valid study on the acute dermal toxicity of a 35 % w/w solution of hydrogen peroxide is available (Geiger (1983) resulting in a LC50 value of greater 2000 mg/kg body weight/day.

Additional information

Oral studies

Two valid, guideline-conform studies on the acute oral toxicity of hydrogen peroxide were performed with solutions of 35% w/w (FMC 1983b) and 70% w/w (Finlay 1996). Oral LD50 values obtained with 35% solutions were 1193 mg/kg in male rats and 1270 mg/kg in female rats. Oral LD50 values of 1026 mg/kg in male rats and 694 mg/kg in female rats were obtained with 70% solutions.

Additional, less reliable studies on the acute oral toxicity of hydrogen peroxide were mentioned in the EU risk assessment report for hydrogen peroxide (European Commission 2003). An oral LD50 value of 75 mg/kg was established for a 70% solution administered to rats of unknown strain (FMC 1979). The oral LD50 values in male and female Wistar rats receiving a single dose of 60% solution were 872 mg/kg and 801 mg/kg, respectively (Mitsubishi 1981). In a limit test, Sprague-Dawley rats received a single oral dose of 10% solution of 5000 mg/kg (FMC 1990). One rat died on the first observation day, and no LD50 value was established. In another study, a 9.6% solution was administered to Wistar JCL rats at a series of concentrations. The oral LD50 value was 1518 mg/kg in male rats and 1617 mg/kg in female rats (Ito et al. 1976).

Inhalation studies

In a valid inhalation toxicity study according to OECD Guideline 403 with hydrogen peroxide vapours generated from a 49.3% w/w solution no mortality was observed even at the highest attainable vapour concentration of 170 mg/m3 in the Sprague-Dawley rat (Hoffman 1990), and therefore, the LD50 value was considered to be >170 mg/m3.

The EU risk assessment report for hydrogen peroxide (European Commission 2003) mentions a number of additional acute inhalation toxicity studies.

An acute inhalation toxicity study in accordance with the principles described by Zwart et al. (1992) was performed under GLP conditions with male Swiss mice (Solvay Duphar 1995). Four animals per exposure group were exposed nose-only to aerosols generated from a 70% solution of hydrogen peroxide. Exposure to 2,200, 3,430 and 4,960 mg/m3 occurred for 7.5 minutes, exposure to 880, 1,530, 1,720 and 3,590 mg/m3 occurred for 15 minutes, exposures to 960, 1,370, 2,050 and 3,220 mg/m3 occurred for 30 minutes, exposure to 910, 1,370, 2,170 and 3,130 mg/m3 occurred for 60 minutes and exposure to 920, 1,450 and 2,000 mg/m3 occurred for 120 minutes. Mortality was observed in all animals exposed for 120 minutes. None of the animals exposed for 60 minutes to 2,170 mg/m3 or lower died. However, surviving animals exhibited swelling of the skin on the head, ptosis or closed eyelids and noisy breathing. These effects disappeared within 3 to 6 days after cease of exposure.

An acute inhalation toxicity study was performed in which white mice of unknown strain were exposed for 5 to 15 minutes to aerosols of less than 4 micrometre diameter generated from a 90% solution (Punte et al. 1953). In a first series, ten animals per exposure group were exposed for 5 minutes to aerosol concentrations ranging from 3,600 to 5,200 mg/m3. None of the animals died. In a second series, exposure concentrations were increased and ranged from 5,200 to 19,000 mg/m3. Ten animals per exposure group were exposed for 5 to 15 minutes. One animal in the group receiving 9,400 mg/m3 died after six days. The mortality increased with increasing doses and nine out of ten animals exposed to 16,800 mg/m3 for 15 minutes died, of which eight died between 11 and 48 minutes after the start of exposure. A mild irritation of the nose, blinking of the eyes, slight gasping and loss of the muscular control were observed in surviving animals exposed to low concentrations. These symptoms disappeared within 30 minutes after removal from the exposure atmosphere. The irritation was more severe at higher exposure concentration. Burns of the nose and the paws tended to disappeared after approximately one week, whereas eye inflammation persisted for two weeks in most animals. Gross corneal opacities persisted for six weeks in two animals that were exposed to 19,000 mg/m3 for 10 minutes.

Dermal studies

A valid study on acute dermal toxicity of hydrogen peroxide was performed in accordance with criteria similar to those of OECD Guideline 402. The study showed that a solution of 35% w/w had a LD50 value of greater 2000 mg/kg and did not cause mortality in rabbits during the 24-hour exposure and the 14-day observation periods (FMC 1983). Another acute dermal toxicity study performed with 70% solutions of hydrogen peroxide in male rabbits resulted in no deaths at a dose of 6500 mg/kg and in four dead animals at a dose of 13000 mg/kg. The dermal LD50 value determined in this study was 9200 mg/kg (FMC 1979).

Studies via other routes

The toxicity of hydrogen peroxide to the Wistar rat following a single intravenous administration by infusion for about 30 minutes at a rate of 0.2 mL/minute was investigated in a study according to GLP (Cefic 1997). Animals receiving 0.5 and 1% solutions (corresponding to 55 and 65 mg/ kg body weight) died 15 and 6 minutes after dosing. Administration of a 0.2% solution (approximately 50 mg/kg body weight) resulted in clinical signs but not in mortality. It was concluded from the findings that the maximum tolerable dose in Wistar rats receiving hydrogen peroxide solutions via intravenous injection is 50 mg/kg body weight.

In a preliminary toxicity study performed in the course of a micronucleus study in OF1/ICO:OF1 mice via the intraperitoneal route (Molinier 1995), injection of 2000 mg/kg hydrogen peroxide (8% solution, 25 mL/kg) caused convulsion followed by death in 5/13 males and 7/13 females. The same dose given in two doses of 4 or 5 % solutions killed 2/2 or 4/6 males but none of the females, respectively.

Justification for classification or non-classification

Oral studies on the acute toxicity of hydrogen peroxide were performed with aqueous solutions of varying concentrations. The reliable, guideline-conform study in male and female Crl: CD BR rats exposed to a 70% solution of hydrogen peroxide (Finlay 1996) resulted in LC50 values slightly above 1000 mg/kg in male and below 700 mg/kg in female animals, which triggers the CLP classification with Acute Toxicity Hazard Category 4. The reliable, guideline-conform study performed in male and female Sprague-Dawley rats (FMC 1983) demonstrates that a similar classification is required for a 35% solution of hydrogen peroxide. The studies with less concentrated solutions of hydrogen peroxide are less reliable and the results are somewhat contradictory. An acute oral toxicity study in male and female Sprague-Dawley rats receiving a 10 % solution of hydrogen peroxide resulted in a LC50 value >5000 mg/kg (FMC 1990). Another acute oral toxicity study in male and female Wistar rats receiving a 9.6% solution of hydrogen peroxide produced LC50 values below 2000 mg/kg, which triggers the CLP classification with Acute Toxicity Hazard Category 4. No reliable information on the oral acute toxicity of hydrogen peroxide solutions containing less than 9.6% of the substance is available. The current concentration limit for the classification of hydrogen peroxide solutions as harmful if swallowed (R22) according to the Directive 67/548/EEC is ≥8% w/w. This concentration limit may be linked to the concentration limits established for eye irritation caused by aqueous hydrogen peroxide solutions. Hydrogen peroxide solutions containing between 5 to <8% are classified as eye irritant, category 2, whereas solution containing ≥8% hydrogen peroxide are classified as eye irritant, category 1 according to the CLP Regulation (EC) No 1272/2008, i.e. may cause serious damage to eyes. The significant irritating, potentially corrosive effects in the eye of solutions containing ≥8% may be seen as a suitable proxy setting a limit concentration for potential adverse local effects in the gastrointestinal tract and thus acute oral toxicity. In conclusion, the oral Acute Toxicity Hazard Category 4 is suggested for hydrogen peroxide solutions containing 8% or more of the substance.

The available studies on the acute inhalation toxicity were performed with aerosols generated from 50% and 70% hydrogen peroxide solutions. The experimental setup in the first study with 50% solution was such that no appreciable aerosol formation was achieved and the attainable vapour concentration of hydrogen peroxide in the study was 170 mg/m3 (Hoffman 1990). None of the male and female Sprague-Dawley rats died during the 4-hour exposure period or during the 14-day observation period following exposure and no LC50 value was established. The study with 70% solution of hydrogen peroxide was not performed in accordance with currently accepted guidelines. Male Swiss mice were exposed to aerosols for 7.5 to 120 minutes. Mortality was observed in all dose groups exposed for 120 minutes, which demonstrates the potential acute inhalation toxicity of 70% hydrogen peroxide solutions. The current concentration limit for the classification of hydrogen peroxide solutions as harmful by inhalation (R 20) according to the Directive 67/548/EEC is ≥50%. This concentration limit may be linked to the concentration limits established for skin irritation and skin corrosion. Hydrogen peroxide solutions containing between 35% and <50% w/w are classified as Skin irritant category 2, whereas solutions containing 50% to <70% w/w hydrogen peroxide are classified as Skin corrosion category 1B according to the CLP Regulation (EC) No 1272/2008, i.e. may cause burns to the skin. The significant irritating and corrosive effects on the skin of solutions containing ≥50% hydrogen peroxide may be seen as a suitable proxy setting a limit concentration for potential adverse local effects in the respiratory tract and thus acute inhalation toxicity. In conclusion, a classification with the inhalation Acute Toxicity Hazard Category 4 is suggested for hydrogen peroxide solutions containing 50% or more of the substance.

The available acute dermal toxicity studies performed with 35% and 70% solutions clearly demonstrate that no classification for acute dermal toxicity according to the CLP Regulation (EC) No 1272/2008 is required for hydrogen peroxide solutions.