2-methyl-2H-isothiazol-3-one

Acute Toxicity: dermal

Administrative data

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP/Guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

not specified

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1200 (Acute Dermal Toxicity)

Deviations:

not specified

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: Japan 59 NohSan Notification No. 4200, Acute Dermal Toxicity Study

Deviations:

not specified

Test guideline 4

Qualifier:

according to guideline

Guideline:

EU Method B.3 (Acute Toxicity (Dermal))

Deviations:

not specified

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Test material form:

other: yellow/brown semi-solid

Details on test material:

The test substance, identified as Kordek 573T (Lot No. B-1103), was used. Kordek 573T was a yellow/brown semi-solid containing 97.5% 2-methyl-4-isothiazolin-3-one as the active ingredient.

Test animals

Species:

rat

Strain:

other: Crl:CD®BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

Adult male and female Crl:CD®BR rats were obtained from Charles River Laboratories, Raleigh, NC. Upon arrival, all animals were examined for physical abnormalities and quarantined/acclimated for approximately one week. The animals were individually housed in suspended stainless steel cages (18x34x20 cm) with wire mesh fronts and bottoms. Cages were suspended above absorbent-paper pan liners which were changed 3 times a week. Throughout the test period, all rats had free access to water (via automatic watering) purified by reverse osmosis and PMI Certified Rodent Diet 5002(C) (Purina Mills Inc., Richmond, IN). The animal room was environmentally controlled with controls set to maintain a temperature of approximately 23°C and a relative humidity range of 30-70%. The temperature and relative humidity were monitored 24 hrs a day. During the study, the average daily temperature ranged from 22 to 23°C and average daily relative humidity ranged from 43 to 52%. Any excursions beyond these ranges were minimal and did not affect the integrity of the study. Temperature and relative humidity remained in compliance with acceptable ranges defined in the "Guide for the Care and Use of Laboratory Animals" ISBN No. 0-309-05377-3, Revised 1996. The light cycle was automatically controlled, 12 hrs on and 12 hrs off.

On the day prior to treatment, rats were selected from a healthy stock population, assigned to the study group using a computer-generated sequence of random numbers and identified by uniquely numbered ear tags. At the time they were dosed, the males were approximately 8 weeks old and the females were approximately 9 weeks old. The body weights ranged from 252 to 309 g for males and from 191 to 235 g for females.

Administration / exposure

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

Approximately 24 hrs prior to the application of the test substance, the hair around the entire trunk between the flank and shoulders was shaved closely with electric clippers. The solid test substance was heated in an oven at approximately 45°C and applied topically to the shaved intact skin of male and female rats at 100, 200, 400 and/or 300 mg/kg body weight. Dose was calculated on an "as is" basis; no adjustment was made for percent active ingredient. The entire trunk of each animal was wrapped in a polyethylene sheet covered with Elastoplast® (Beiersdorf, Inc., Norwalk, CT) and PEG®(Becton-Dickinson Co., Franklin Lakes, NJ) elastic bandages and secured in place with adhesive tape.

The test substance remained in contact with the skin of each animal for 24 hrs. Each cuff was removed after the 24-hr exposure period, and the application site was wiped with paper towels saturated with tap water. The application site was blotted dry with paper towels, and the approximate dimensions of the contact area of the test substance were determined.

Each animal was fitted with a cardboard collar to prevent preening of the application site. The collar was worn throughout the 14 day observation period.

Duration of exposure:

24 hours

Doses:

100, 200, 300 and 400 mg/kg

No. of animals per sex per dose:

6 males and 6 females at 100, 200 and 400 mg/kg and 6 males at 300 mg/kg.

Control animals:

not specified

Details on study design:

The test substance was heated in an oven, dosed and occluded for 24 hrs on the back of rabbits. Test material was removed with a damp towel and a collar remained to keep the animal from licking the test material.

All animals were observed for signs of ill health, or reaction to treatment at approximately 1, 2 and 4 hrs after dosing and once daily thereafter for 14 days. Body weights were recorded on days 0 (prior to dosing), 7 and 14.

Decedents were necropsied as they were found. Surviving rats were killed on day 14 and necropsied. Necropsy consisted of a gross examination of organs in situ.

Statistics:

The mortality incidences of males and females were compared across doses with a categorical data modeling procedure using SAS CATMOD (SAS Institute Inc. SAS User's Guide: Statistics, Version 6 Edition, p 405-517. Cary, NC: SAS Institute Inc., 1990). The criterion of statistical significance was 0.05. Since the results did not indicate a significant difference between the mortality responses across dose groups for males and females, the LD50 was calculated on the pooled mortality incidences at each dose.

The LD50, 95% confidence limits, and slope were calculated from the logarithm of the doses and the incidences of mortality using a SAS PROBIT procedure (SAS Institute Inc. SAS User's Guide: Statistics, Version 6 Edition, p 1324-1350. Cary, NC: SAS Institute Inc., 1990) based on the method of D.J. Finney (Probit Analysis, Third Edition, London: Cambridge University Press, 1971).

Results and discussion

Effect levels

Sex:

male/female

Dose descriptor:

LD50

Effect level:

242 mg/kg bw

Based on:

test mat.

95% CL:

192 - 294

Mortality:

Dose-related mortality occurred in this study at 200 mg/kg and above (Table 1).

Clinical signs:

other: Clinical signs of toxicity were noted at all dose levels in both sexes. These clinical signs were noted beginning on day 1 and included: scant and/or no feces, passiveness and ataxia. Surviving rats recovered from these signs by day 5. Labored breathing

Gross pathology:

Necropsy of the decedents revealed gastrointestinal changes which included: reddened and/or blackened intestines; red/black and/or yellow material in the intestines; reddened glandular portion of the stomach; and black material in the stomach. Necropsy of the survivors revealed no gross changes

Other findings:

After dermal application, the test substance covered an area approximately 3-4 cm x 4-5 cm.

Any other information on results incl. tables

The LD₅₀ value was calculated from the combined male and female mortality incidence data. The acute dermal LD₅₀ for Kordek 573T in male and female rats was 242 mg/kg with 95% confidence limits of 192 to 294 mg/kg. The log probit slope of the dose- mortality data (probit incidence versus log dose) was 6.79 in this study.

Table 1 Mortality data

Dose (mg/kg)	100	200	300	400
Males	0/6	0/6	5/6	5/6
Females	0/6	3/6	--	6/6
Combined Sexes	0/12	3/12	5/6	11/12

Applicant's summary and conclusion

Interpretation of results:

Category 3 based on GHS criteria

Remarks:

Migrated information

Conclusions:

The LD50 value was calculated from the combined male and female mortality incidence data. The acute dermal LD50 for Kordek 573T in male and female rats was 242 mg/kg with 95% confidence limits of 192 to 294 mg/kg. The log probit slope of the dose-mortality data (probit incidence versus log dose) was 6.79 in this study.

Executive summary:

The acute dermal toxicity of Kordek 573T (Lot No. B-1103, Toxicology Department Sample No. 99-019, 97.5% active ingredient) was assessed in Crl:CD^®BR rats. The test substance was heated in an oven and applied to the shaved intact skin to three groups of six male and six female rats at 100, 200 and 400 mg/kg body weight. An additional group of six males were dosed at 300 mg/kg in order to determine the LD₅₀ for male rats. The application sites were occluded for 24 hrs. After the 24-hr exposure, the application sites were wiped with paper towels saturated with tap water and blotted dry with paper towels.

Dose-related mortality occurred in this study at 200 mg/kg and above. The total mortality incidences (no. deaths/no. treated) for males and females in this study were:

Dose (mg/kg)	100	200	300	400
Males	0/6	0/6	5/6	5/6
Females	0/6	3/6	--	6/6
Combined Sexes	0/12	3/12	5/6	11/12

Clinical signs of toxicity were noted at all dose levels in both sexes. These clinical signs were noted beginning on day 1 and included: scant and/or no feces, passiveness and ataxia. Surviving rats recovered from these signs by day 5.

Body weight gain in surviving rats was decreased (29-48%) among both sexes at 200 mg/kg and above when compared to historical control values. Skin effects were observed in both sexes at all levels beginning on day 1 and continuing through day 14. These effects included: blanching, edema, darkened areas, eschar, sloughing, scabbed areas and desiccation.

Necropsy of the decedents revealed gastrointestinal changes. Necropsy of the survivors revealed no gross changes. The LD₅₀ value was calculated from the combined male and female mortality incidence data. The acute dermal LD₅₀ for Kordek 573T in male and female rats was 242 mg/kg with 95% confidence limits of 192 to 294 mg/kg.