2-Butanone, peroxide

Repeated dose toxicity: dermal

Administrative data

Endpoint:

sub-chronic toxicity: dermal

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

1987-07-06 to 1987-10-07

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

no positive control, no OECD and EU guideline was followed; no GLP stated

Data source

Reference

Reference Type:

secondary source

Title:

Unnamed

Year:

1993

Report date:

1993

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

NA

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2-[(2-hydroperoxybutan-2-yl)peroxy]butane-2-peroxol; butane-2,2-diperoxol

EC Number:

700-954-4

Cas Number:

1338-23-4

Molecular formula:

Mixture of C4H10O4 and C8H18O6

IUPAC Name:

2-[(2-hydroperoxybutan-2-yl)peroxy]butane-2-peroxol; butane-2,2-diperoxol

Test animals

Species:

rat

Strain:

other: F344/N

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic farms, Germantown, NY
- Age at study initiation: 6 weeks
- Housing: individually
- Diet (e.g. ad libitum): NIH-07 Open Formula Pellets (Zeigler Brothers, Inc, Gardners, PA) ad libitum
- Water (e.g. ad libitum): tap water ad libitum
- Acclimation period: 4 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 20 - 23.89 °C
- Humidity: 31 -72 %
- Air changes (per hr): 12 to more than 20 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours per day

Administration / exposure

Type of coverage:

not specified

Vehicle:

other: DMP

Details on exposure:

Methyl-ethylketone peroxide in DMP was diluted with DMP to achieve 0.3, 1.0, 3.0, 10.0, and 30.0% (w/w) solutions. Groups of 10 animals were dosed at a volume of 0.3 mL per rat.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

once a day for 5 days per week, except holidays, for a total of 13 weeks, plus 2 consecutive dose days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 other: mg/animal

Remarks:

untreated and DMP control

Doses / concentrations 2

Dose / conc.:

1.07 other: mg/animal

Doses / concentrations 3

Dose / conc.:

3.57 other: mg/animal

Doses / concentrations 4

Dose / conc.:

10.7 other: mg/animal

Doses / concentrations 5

Dose / conc.:

35.7 other: mg/animal

Doses / concentrations 6

Dose / conc.:

107 other: mg/animal

No. of animals per sex per dose:

10

Control animals:

yes

Details on study design:

Doses for the 13-week studies were based on the results of the 2-week studies (doses of 0, 50.6, 101.3, 202.5, 405 or 810 mg MEKP/kg body weight). In the 13-week studies, methyl-ethylketone peroxide in DMP was diluted with DMP to achieve 0.3, 1.0, 3.0, 10.0 and 30.0% (w/w) solutions. All groups were dosed at a volume of 0.3 mL per rat. Methyl-ethylketone peroxide was administered topically to the clipped dorsal skin of rats.

Positive control:

no positive control

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS:No data

DETAILED CLINICAL OBSERVATIONS:No data

DERMAL IRRITATION (if dermal study): Yes

BODY WEIGHT: Yes

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY:No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

- Vaginal cytology and sperm morphology evaluations were performed on rats during the 13-week studies.
- Sperm motility was evaluated at necropsy.

Statistics:

Two approaches were employed to assess the significance of pairwise comparisons between dosed and control groups in the analysis of continuous variables. Organ and body weight dat, which are approximately normally distributed, were analyzed using the parametric multiple comparisons procedures of Williams (1971, 1972) and Dunnett (1955). Data that typically have skewed distributions were analyzed using the nonparametric multiple comparisons methods of Shirley (1977) or Dunn (1964). Jonckheere`s test (Jonckheere,1954) used to assess the significance of dose-response trends and to determine whether a trend-sensitive test (Williams, Shirley) was more appropriate for pairwise comparisons than a test capable of detecting departures from monotonic dose response (Dunnett, Dunn). If the P-value from Jonckheere`s test was greater than or equal to 0.10, Dunn`s or Dunnett`s test was used rather than Shirley`s or Williams`test.
The outlier test of Dixon and Massey (1951) was employed to detect extreme values. No value selected by outlier test was eliminated unless it was at least twice the next largest value or at most half of the next smallest value. The extreme values chosen by the statistical test were subject to approval by NTP personnel. In addition, values indicated by the laboratory report as being inadequate due to technical problems were eliminated from the analysis.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Three females in the high-dose (107 mg/animal) group died or were killed moribund during week 1 of the study. All animals in the 35.7 mg/animal group and all remaining animals in the 107 mg/animal group were killed during week 8 due to the severity of the skin lesions at the site of methyl-ethylketone peroxide application.

Dermal irritation:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Description (incidence):

Three females in the high-dose (107 mg/animal) group died or were killed moribund during week 1 of the study. All animals in the 35.7 mg/animal group and all remaining animals in the 107 mg/animal group were killed during week 8 due to the severity of the skin lesions at the site of methyl-ethylketone peroxide application.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

The mean final body weight and mean body weight gain for untreated controls were greater than the corresponding values for DMP controls.

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

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

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

not specified

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

There were statistically significant increases in the relative weights of several organs, primarily in males in the 10.7 mg/animal group.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

Additional observations in many of the early-death rats receiving 107 mg/animal were "scar tissue" at the application site and enlarged spleens. In those animals that survived for 13 weeks, significant necropsy observations were limited to thick, crusty skin at the application site in serveral animals from the 10.7 mg/animal group. Necrosis varied in severity from diffuse involvement of both dermis and epidermis at higher concentrations to focal ulcerations of the epidermis, which occurred more frequently in the 10.7 mg/animal group. An associated inflammatory reaction consisted of both surface exudation and dermal inflammation. Typically, a coagulum of surface exudate containg serous fluid and neutrophils was seen overlying denuded or regenerative areas, with necrotic skin tissue admixed in more severe cases. The dermal reaction was subjacent to ulcerated, sloughed, or regenerateted epidermis and was collectively termed "chronic-active" to be inclusive of varied patterns, including primarily neutrophilic, fibrovascular, granulomatous, or fibrotic reactions.

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

< 1.07 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: local tissue damage

Target system / organ toxicity

Key result

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

None of those studies are suitable for risk assessment of systemic toxicity after dermal contact, as severe local tissue (skin) damage was noted due methyl-ethylketone peroxide`s corrosively.

Executive summary:

Methyl-ethylketone peroxide (in DMP) was tested in two dermal 90-day repeated dose toxicity studies to mice and rats (Reliability: 3). None of those studies are suitable for risk assessment of systemic toxicity after dermal contact, as severe local tissue (skin) damage was noted due methyl-ethylketone peroxide`s corrosively. Consequently, systemic toxicity after dermal application is extrapolated from oral studies by route to route extrapolation according to the guidance documents. Performing of repeated dermal toxicity studies is not in line with animal welfare ideas. Therefore a new 90 day oral toxicity study is proposed to gain more information on the repeated dose toxicity of methyl-ethylketone peroxide.