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

Carcinogenicity

Description of key information

Carcinogenicity (oral route) - Kathon Biocide (Toxicology Department (TD) Sample No. 90-105; Lot No 48014; ~14.2% active ingredient) was administered in the drinking water to 5 groups (90 males/group; 80 females/group) of Crl:CD BR rats for up to 24 months at concentrations of 0 (tap water control), 0 (inorganic 'salt' control)

30, 100 or 300 ppm of active ingredient (a.i.). Administration of Kathon biocide to male and female rats in the drinking water for 24 months at concentrations up to and including 300 ppm active ingredient (a.i.) (17.2 mg a.i./kg of body weight/day in males and 25.7 mg a.i./kg of body weight/day in females) showed no effects on the type or incidence of neoplasms in any group. No treatment-related signs of toxicity were seen at 30 ppm active ingredient (a.i.)(2.0 mg a.i./kg of body weight/day in males and 3.1 mg a.i./kg of body weight/day in females), the No-Observed Effect Level (NOEL) in this study

Carcinogenicity (dermal route) - Kathon CG, when applied to the closely clipped dorsal skin of male mice at a concentration of 400 ppm and at a dose of 25 microliters three times a week for 30 months showed no tumorigenic potential either locally or systemically

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

other: read across from supporting study which contains this test material

Adequacy of study:

key study

Study period:

12 September 1990 - 18 September 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to test guidelines and in accordance with GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPP 83-5 (Combined Chronic Toxicity / Carcinogenicity)

Deviations:

no

GLP compliance:

yes

Species:

rat

Strain:

other: Crl:CD BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

Animal Husbandry
On 23 Aug 90 one thousand and ninety eight (624 male and 474 female) approximately 3 week old, non-littermate, Crl:CD BR rats were received from Charles River Laboratories, Portage Facility, Portage. MI. Upon receipt, all animals were placed directly into 1 of 2 study rooms and were weighed and examined for physical abnormalities. The animals were acclimated to the study room for approximately 3 weeks prior to the initiation of treatment. Standard quarantine procedures of the Laboratory Animal Services Unit were in effect for the first two weeks of acclimation.

During the first 7 days of the acclimation period, animals were housed 2 per cage. For the remainder of the acclimation period and throughout the testing period, each rat was housed individually. Animals were housed in stainless steel cages (7" x 13.5" x 7"; 17.8 cm x 34.3 cm 17.8 cm) with mesh floors and fronts, suspended over absorbent paper liners. The cages were changed approximately once every 2 weeks and the absorbent paper liners were changed 3 times each week. All rats were identified by a unique number tattooed on their tails using an Animal Identification and Marking Systems (AIMS) tattoo machine.

The animals were housed in environmentally controlled rooms, with controls set to maintain a temperature of approximately 73°F (22.8%) with a relative humidity of 30-70%. Temperature and relative humidity were monitored 24 hours a day. The light cycle of each room was automatically controlled to maintain 12 hours light, 12 hours dark. The temperature in the study rooms ranged from 70-75°F (21 .I -23.9%) over the duration of the study and the relative humidity was generally maintained at 30-70s. Excursions beyond these ranges did occur, however they were minimal andlor brief in duration and did not affect the integrity of the study.

During the acclimation period, all rats had free access to filtered tap water. Similarly, during the testing period, control and treated dosing solutions were available ad libitum. During pretest and throughout the testing period, all solutions were administered in glass water bottles, equipped with rubber stoppers and metal sipper tubes, that were fastened to the front of each animal's cage. During the acclimation and test periods, all rats had free access to certified laboratory feed (Purina Certified Rodent Chow #5002-(meal); Purina Mills, Inc., St. Louis, MO).

Groups and Dosages
One week prior to the initiation of treatment, all rats were weighed and given a physical examination and those in apparent poor health were excluded from use in the study. The remaining animals were then randomly assigned to one of two control groups (Groups 1 and 2; 90 males and 80 females per group), one of three Kathon biocide-treated groups (Groups 3, 4 and 5; 90 males and 80 females per group) or to the sentinel group (40 males and 40 females) based on a computer-generated randomization.

Rats in Group 1 were given untreated filtered tap water while those in Group 2 were given tap water containing the same concentration of inorganic stabilizer salts found in the high dose (300 ppm) Kathon biocide dosing solution (0.05%). Animals in Groups 3. 4 and 5 were given tap water solutions containing Kathon biocide at 30. 100 and 300 ppm. respectively. Sentinels were given untreated filtered tap water.

Health Monitoring (Sentinel Animal Program)
Prior to group assignment, 12 rats (6/sex) were randomly selected from the animals specifically ordered for use in this study and sent live to Charles River Laboratories, Wilmington, MA, for comprehensive health monitoring including serology, bacteriology, parasitology and pathology. No adverse findings were seen in these animals. In addition, 100 male rats were randomly selected, euthanized and necropsied to determine the incidence of renal pelvic dilation in this lot of males. A previous chronic study (Quinn and Kyle, 1992) was terminated after approximately 6 months due to a high incidence (~30%) of hydronephrosis (i.e., renal pelvic dilation) in males across the control and treatment groups. The incidence in the lot of males purchased specifically for use in this current study was found to be acceptable at 3%. Eighty rats (40/sex) were randomly assigned to be sentinel animals to monitor intercurrent disease and the health status of the rats throughout the course of the study. The sentinel rats were housed in the same study rooms (20/sex/room) as the animals on test.

At the 6 and 18 month study intervals, 20 randomly selected sentinel animals (5/sexhoom) were euthanized and tissues and blood samples collected for standard health monitoring. Serum from the blood samples collected was shipped frozen to Charles River Laboratories for analysis. No adverse finding were seen in these samples. Since there were no serum abnormalities, the tissues collected were not processed further but retained in formalin until the end of the study.

At the 12 month study interval, 20 sentinel animals (5/sex/room) were sent live to Charles River Laboratories for comprehensive health monitoring as indicated above. During the 24th month of the study, all surviving sentinel rats were shipped live to Charles River Laboratories for comprehensive health monitoring. There were no indications of any intercurrent disease or change of health status in the sentinel animals that would compromise the results of this study.

Route of administration:

oral: drinking water

Vehicle:

water

Details on exposure:

Dosing Solution Preparation
Salt control and Kathon biocide-treated dosing solutions were prepared once a week for each week of the study. The appropriate amount of Kathon biocide (~14.2% a.i.) or aqueous inorganic stabilizer salt solution for each dosing solution was weighed and dissolved in an appropriate amount of filtered tap water contained in a high density polyethylene carboy. Each dosing solution was then stirred for 5 minutes using a Dyna-Mix stirrer to ensure homogeneity of the dosing solution. All animals (including tap water controls (Group 1) and sentinel animals) were given fresh solutions once every 7 days or as needed. Unused treated dosing solutions were discarded as hazardous waste at the end of each week of the study.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The first time dosing solutions were prepared (Week 1 of the study), top, middle, and bottom samples of each dosing solution (Groups 2-5) were submitted and analyzed for homogeneity and proximity to target concentrations. A single tap water control (Group 1) sample was also submitted and analyzed to assure that there was no cross-contamination with Kathon biocide. A single sample from each dose level was submitted and analyzed for proximity to target concentration the day after preparation for Weeks 2-4 of the study. At the end of each of the first four weeks of the study, an additional sample from each dose group was submitted and analyzed to assure that the test substance was stable in tap water over the treatment period. Samples of each dosing solution were collected weekly thereafter and one set of samples per month were submitted and analyzed for proximity to target concentrations. When the volume of dosing solutions prepared during the study was changed, top, middle and bottom samples were reanalyzed to assure the mixtures were homogeneous.

Duration of treatment / exposure:

Continuous for up to 2 years.

Frequency of treatment:

Continuous for up to 2 years.

Post exposure period:

Not applicable.

Remarks:

Doses / Concentrations:
30, 100 and 300 ppm Kathon
Basis:
nominal in water

No. of animals per sex per dose:

90 males and 80 females/dose level.

Control animals:

yes, concurrent no treatment

other: inorganic salt stabilizer solution

Details on study design:

Groups of 90 male and 80 female rats were administered 0 (water), 0 (inorganic stabilizer salt solution at same concentration as found in the high dose solution), 30, 100 or 300 ppm Active Ingredient of Kathon biocide in the drinking water for up to 2 years. Ten males and ten females were sacrificed at scheduled necropsies at 12 and 18 months. All survivors were necropsied after 24 months. Animals that died during the study, became moribund during the study and accidental deaths were subjected to a gross necropsy. At all necropsies, tissues were saved for histopathologic examination. At scheduled necropsies, selected organs were weighed.

Positive control:

No data.

Observations and examinations performed and frequency:

Clinical observation
Each animal was observed daily for signs of ill health or reaction to treatment. Cage liners were inspected daily for abnormal appearance of urine or feces and excessive spillage of dosing solutions. Physical examinations were performed weekly beginning one week prior to the start of dosing. The physical examination included evaluation of external structures, posture, gait and behavior, and abnormalities in respiration or body temperature. The animals were thoroughly palpated for tissue masses.

Bodv Welght Water Consumption and Feed Consumptlon
The weight of each rat and the quantity of water/dosing solution and feed consumed were determined weekly beginning one week prior to the initiation of dosing and continuing through the 13th week of treatment; body weight, water consumption and feed consumption were measured once every 4th week thereafter through Week 101. Group mean body weights, water consumption and feed consumption were calculated weekly for the first 13 weeks, and once every 4th week thereafter.

Sacrifice and pathology:

Clinical Patholoay
After 3, 6, 12, 18 and 24 months of treatment, blood samples were collected from 20 rats/sex/group for hematology and clinical chemistry evaluations. The same animals were examined at each interval when possible. Rats were anesthetized with an intraperitoneal injection of sodium pentobarbital (Nembutal Sodium Solution, Abbott Laboratories, North Chicago, Il.) prior to blood collection. Blood was collected via an orbital sinus. The parameters monitored are indicated on the next page:

Hematology
a. Hematocrit (HCT)
b. Red Blood Cell Count (RBC)
c. Red Blood Cell Morphology
d. Hemoglobin (HGB)
e. Total Whiie Blood Cell Count (WBC)
f. Differential White Blood Cell Count
g. Platelet Count (PLAT)
h. Mean Corpuscular Volume (MCV)
i. Mean Corpuscular Hemoglobin (MCH)
j. Mean Corpuscular Hemoglobin Concentration (MCHC)

Clinical Chemistry
a. Glutamic Pyruvic Transaminase (SGPT)
b. Glutamic Oxaloacetic Transaminase (SGOT)
c. Cholesterol (CHOL)
d. Alkaline Phosphatase (ALK)
e: Gamma Glutamyl Transpeptidase (GGT)
f. Urea Nitrogen (BUN)
g. Glucose (GLU)
h. Creatinine (CREAT)
i. Total Protein (TPRO)
j. Total Bilirubin (TBILI)
k. Albumin (ALE)
l. Calcium (CA++)
m. Globulin (GLOB)
n. A/G ratio
o. Inorganic Phosphorus (PHOS)
p. Triglycerides (TRIG)
q. Sodium (Na)
r. Potassium (K)
s. Chloride (CI)
t. Creatine Phosphokinase (CPK)

All hematology parameters excluding white blood cell differential and red blood cell morphology were determined using an Ortho ELT-8/ds Hematology Analyzer (Becton Dickinson. Braintree, MA). White blood cell differential counts and red blood cell morphology were determined by microscopic examination. White blood cell differentials were only performed on samples from the high dose (Group 5) animals and the controls (Groups 1 and 2) at the 12 and 24 month intervals. All clinical chemistry parameters were analyzed using a BMD Hitachi 704 analyzer (Boehringer Mannheim Diagnostics, Indianapolis, IN).

Clinical Patholoay
During the pretest period, freshly voided urine samples were collected from all males and females (where possible) intended for use in this study. At the end of the 3rd and 6th months of the study, urine was collected from all males (where possible) in the study and from 10 females/group. At the end of the 12th, 18th and 24th months of treatment, freshly voided urine samples were collected from 10 ratslsexlgroup. The urine samples were collected from the same animals scheduled for hematology and clinical chemistry analyses at 3, 6, 12, 18 and 24 months. The urinalysis parameters evaluated are listed below:

Urinalysis
a. Specific Gravity
b. pH
c. Protein
d. Glucose
e. Ketones
f. Bilirubin
g. Occult Blood
h. Color
i. Clarity
j. Microscopy of Sediment
Specific gravity was determined by refractometer, appearance (i.e.. color and clarity) by inspection, sediment by light microscopy, and other parameters by Bili-Labstix (Ames Division, Miles Laboratories, Inc., Elkhart, IN).

Ophthalmology
Prior to the initiation of treatment, the eyes of all animals were examined by a Board Certified Veterinary Ophthalmologist. During the 24th month of treatment, the eyes of all the surviving rats in the study were reexamined by a Board Certified Veterinary Ophthalmologist.

Kidnev UIltaswoaranhy
The kidneys of all male animals in the study were examined during the 6th and 12th months of the study via ultrasound by a Board
Certified Veterinary Radiologist. This was done to evaluate the incidence of dilated renal pelves since high incidences had been seen in a previous study (Quinn and Kyle, 1992) with the same strain of rat and there was a concern that a naturally occurring high incidence of this finding could compromise the integrity of the study.

Gross Pathology
Following 12 and 18 months of treatment, 10 rats/sex/group were anesthetized with an intraperitoneal injection of sodium pentobarbital (Nembutal Sodium Solution, Abbott Laboratories, North Chicago, II.), killed by exsanguination and necropsied. After 24 months of treatment, all surviving rats in each group were anesthetized with an intraperitoneal injection of sodium pentobarbital (Nembutal Sodium Solution, Abbott Laboratories, North
Chicago, II.), killed by exsanguination and necropsied. All organs, tissues, and body cavities of the animals killed during scheduled necropsies, as well as those found dead or euthanized moribund during the course of the study, were examined and gross abnormalities recorded.

The following organs were collected from each rat killed during a scheduled necropsy (i.e., interim or terminal) and weighed:
adrenals (2)
brain
kidneys (2)
liver
spleen
testes (2)

Gross Pathology
Organ to body weight ratios were calculated using each animal's terminal body weight (recorded just prior to necropsy).

The following tissues from all rats killed during scheduled necropsies, euthanized moribund or found dead during the course of the study were collected and preserved in 10% neutral buffered formalin:
Adrenals (2)
Aorta
Bone with Marrow (sternum and femur)
Bone Marrow Smear
Brain (medulla/pons, cerebellar cortex, cerebral cortex)
Epididymides (2)
Esophagus
Eye and Harderian gland (2)
Gross lesions (to include a border of apparently normal tissue)
Heart (with coronary vessels)
Intestine (colon, cecum, duodenum, rectum, ileum and jejunum)
Kidney (2)
Liver (2 lobes, median and left lateral)
Lung
Lymph node (mesenteric and mandibular)
Mammary gland (females)
Masses
Muscle, skeletal
Nerve, peripheral
Ovaries (2)
Pancreas
Pituitary
Prostate
Salivary gland
Seminal vesicles/coagulating gland
Skin
Spinal cord (cervical, mid-thoracic, lumbar)
Spleen
Stomach
Testes (2)
Tongue
Trachea
Thymus/remnant
Thyroid/parathyroid
Urinary bladder
Uterus and cervix
Vagina
Zymbal's gland

Histopathology
Postmortem studies were performed on 90 male and 80 female Crl:CD BR rats in each of 5 groups used in a 24-month drinking water chronic/oncogenic study on Kathon biocide. Gross and microscopic examinations were made of ten male and ten female rats of each group that were selected for necropsy for each of the 12- and 18-month interim necropsies and of all surviving rats of all groups killed at the 24-month terminal necropsy. Similar examinations were performed on all rats that died or were sacrificed in a moribund condition throughout the study. The number of rats included in the tabulations for the three intervals of the study are listed Table 1 below.

The tissues specified for microscopic examination were routinely processed, embedded in paraffin, sectioned and stained with hematoxylin and eosin. For all rats of both sexes of Groups 1, 2 and 5 and nonsurviving male and female rats of Groups 3 and 4, microscopic examination was performed on the following tissues: adrenal glands, aorta, bone and bone marrow (sternum and femur), brain, cecum, cervix, coagulating gland, colon, duodenum, epididymides, esophagus, eyes, Harderian glands, heart, ileum, jejunum, kidneys, liver, lung, mandibular and mesenteric lymph nodes, mammary glands (female rats only), skeletal muscle, peripheral nerve, ovaries, pancreas, parathyroid, pituitary, prostate, rectum, salivary gland, seminal vesicles, skin, spinal cord (cervical, lumbar and midthoracic), spleen, stomach, testes, thymus, thyroid, tongue, trachea, urinary bladder, uterus, vagina, Zymbal's gland and other tissues with gross lesions or masses. Microscopic examination of the rats of Groups 3 and 4 scheduled to be necropsied at each interval was limited to the kidneys, liver, lung, spleen, stomach and tissues with gross lesions or masses.

All histopathological examinations were performed by a Board Certified Veterinary Pathologist of Research Pathology Services, Inc.

Other examinations:

No additional information available.

Statistics:

See below.

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:

no effects observed

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

Test Substance and Dosing Solution Analvses
Samples of tap water containing Kathon biocide were analyzed for homogeneity and stability. In addition, throughout the 24 months of dosing, samples of dosing solutions at each Kathon biocide concentration (i.e., 30, 100 or 300 ppm) were analyzed for active ingredient (a.i.) content to determine proximity to target concentrations. The analytical results confirm that:
1) The mixing procedure provided homogeneous mixtures of Kathon biocide in tap water.
2) Kathon biocide was stable in the carrier for at least 9 days when stored at room temperature (at approximately 73°F).
3) Chemical analyses confirmed that the nominal concentrations were a satisfactory reflection of the concentrations administered to the animals (average proximity to target concentration was greater than 92% throughout the study).

Mortalitv and Clinical Observations
There were no effects on the survival of males or females in any dose group following chronic administration of Kathon biocide or stabilizer salts in the drinking water for 24 months. The 24-month survival (adjusted for scheduled interim necropsies) for the controls and Kathon biocide-treated groups was as follows in Table 2.

No treatment-related clinical signs of toxicity were evident in treated animals. Clinical signs were noted throughout the study in both the controls and Kathon biocide-treated animals, with no apparent difference between the controls and treated animals.

Bodv Weight
There were no treatment-related effects on body weight or cumulative body weight change in males or females at doses up to and including 100 ppm Kathon biocide (Group 4). A treatment-related decrease in body weight and cumulative body weight change was seen in Group 5 males (300 ppm Kathon biocide) throughout the study. The change was considered treatment related, although the magnitude of the effect was not dramatic (body weight decrease generally in the 2-4% range; cumulative body weight gain decrease generally in the 6-12% range during the first 4 weeks of treatment and the 3-7% range for the remainder of the study). The body weight effects in males were consistent and statistically significant at the majority of time points.

An equivocal decrease in body weights and body weight gain was noted in Group 5 females (300 ppm Kathon biocide). This effect was judged equivocal for a number of reasons. Throughout most of the study, female body weight and cumulative body weight gain appear to be slightly decreased at both 100 (Group 4) and 300 (Group 5) ppm compared to the pooled control groups. For the first year of the study the effect was generally slight and more pronounced in the mid-dose group (100 ppm) than in the high dose group (300 ppm). The lack of a dose response is interpreted as normal variability and not indicative of a treatment-related effect. During the second year of treatment the effect was more pronounced in the high dose group (300 ppm) and does appear to be a treatment-related effect at that dose. Body weight and cumulative body weight change in the salt control group (Group 2) was consistently higher than that of the tap water control group (Group 1). Since pooled control values were used for comparison to the Kathon biocide treated groups, the higher salt control values may have contributed to the large number of statistically significant differences that were seen. In light of the conflicting data, a decrease in body weight and cumulative body weight change in females at 300 ppm was considered equivocal. There were no treatment-related effects at lower doses.

Water Consumption
A treatment-related and concentration-dependent decrease in water consumption was seen in both sexes in all Kathon biocide-treated groups (Groups 3, 4 and 5; 30, 100 and 300 ppm, respectively) throughout the study. These decreases ranged from 0-22% at 30 ppm, 3-30% at 100 ppm and 15-40% at 300 ppm a.i.. These decreases appear to be attributable to the unpalatability of the active ingredient in Kathon biocide and not its inorganic stabilizer salts, since the water consumption in Group 2 ( salt control) was comparable to the tap water control throughout the study. Based on the average daily water consumption, the 300 ppm dose was judged to be a maximum tolerated dose.

Feed Consumption
There were no treatment-related effects on feed consumption in males at doses up to and including 100 ppm Kathon biocide (Group 4). In the high dose (300 ppm) male group there was a slight (statistically significant at a number of time points) decrease in feed consumption throughout the study. The decrease was considered treatment related. In females, there were a number of statistically significant differences at all dose levels throughout the study, however in the majority of cases no dose response was evident and the magnitude of the response among the Kathon biocide treated groups varied only slightly. These changes were judged normal biologic variation and no treatment-related effects on feed consumption were seen in females.

Compound Intake
The mean compound intake of Kathon biocide over 24 months of dosing for each sex in Groups 3, 4 and 5 is summarized in Table 3 below:

Hematology
No treatment-related effects on hematology parameters were seen at any dose in either sex throughout the 24 months of treatment with Kathon biocide. Statistically significant differences were occasionally noted in some parameters throughout the 24 month study. These differences were considered random events and not related to treatment since the changes lacked a dose response relationship and/or were seen only sporadically over the time intervals when hematology parameters were evaluated.

Clinical Chemistry
No treatment-related effects on clinical chemistry parameters were seen in males or females at any dose throughout the 24-month treatment period.
Statistically significant differences were occasionally noted in various parameters throughout the 24 month study. These differences were considered random events and not related to treatment since the changes lacked a dose response relationship and/or were seen only sporadically over the time intervals when clinical chemistry parameters were evaluated.

Urinalysis
No changes in urinary parameters were seen which were considered indicative of treatment-related systemic toxicity. Statistically significant increases in urinary specific gravity were seen in males and females at 100 and 300 ppm after 3 and 6 months of treatment and in males at 30 ppm after 6 months of treatment. Other than a random occurrence of statistical significance, similar effects were not evident at any dose, in either sex, after 12, 18 or 24 months of treatment. Increases in urinary specific gravity are not unexpected in light of the decreased water consumption seen in this study and are most likely secondary to that effect and not considered indicative of systemic toxicity. The single occurrence in the 30 ppm (Group 3) males was considered incidental.

Qphthalmology
An indirect ophthalmoscopic examination at study termination (i.e., following 24 months of dosing) indicated there was no compound related ocular disease in any Kathon biocide-treated animals when compared to control animals. The abnormalities observed occur commonly in laboratory rats of this strain and age and were judged to be unrelated to treatment.

Kidney Ultrasonography
No treatment-related effects were seen via ultrasound in the renal pelves of any male rats at any dose up to and including 300 ppm Kathon biocide (Group 5) at 6 or 12 months of the study.

Organ Weights
There were no treatment-related effects on organ weights, in males or females, at any dose up to and including 300 ppm (Group 5) following 24 months of treatment with Kathon biocide. Statistically significant differences were occasionally noted in some absolute or relative organ weights throughout the 24 month study however none were considered treatment related. A statistically significant increase in relative kidney weights was seen in both sexes at 300 ppm after 12 months of treatment. This change was judged to be related to a decrease in terminal body weight seen in both sexes at this point. No changes in absolute kidney weights were seen at 12 months and no changes in absolute or relative kidney weights were seen at 18 or 24 months. No histopathologic changes were seen in the kidneys at any time point.

Other statistically significant differences occurred sporadically and were considered spurious and not related to treatment since the changes lacked a dose response relationship and were not observed consistently over several time intervals.

Gross and Microscopic P athology
The only treatment-related effects observed were indicative of gastric irritation.

The administration of Kathon biocide in the drinking water for up to 24 months had no effect on the type or incidence of any neoplasms that were observed in this study. There were no treatment-related gross or microscopic changes in any of the male or female rats given 30 ppm of Kathona biocide during the study. Treatment-related gross and microscopic changes were limited to the stomach and were seen in male and female rats of Group 4 (100 ppm) and 5 (300 ppm). The predominant change was an increased thickness or prominence of the mucosa, frequently at the limiting ridge of the forestomach which was due to hyperplasia and hyperkeratosis of the squamous mucosa. There were a few other changes which occurred sporadically in the stomach of these groups of rats but only focal necrosis of the superficial glandular mucosa and edema and inflammatory cell infiltration of the submucosa of the forestomach in the 300 ppm dosage group male rats were significantly increased when compared to both of the control groups. There were no significant differences in the incidence of these changes among the tap water control. "salt" control and 30 ppm dosage groups.

The chronic administration of Kathon biocide in the drinking water to rats at or above 100 ppm caused gastric irritation and the no-observed effect level in male and female rats was 30 ppm.

Relevance of carcinogenic effects / potential:

Administration of Kathon biocide to male and female rats in the drinking water for 24 months at concentrations up to and including 300 ppm active ingredient (a.i.) (17.2 mg a.i./kg of body weightlday in males and 25.7 mg a.i./kg of body weightlday in females) showed no effects on the type or incidence of neoplasms in any group.

Dose descriptor:

NOEL

Effect level:

>= 2 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: Dose level is for Active Ingredient.

Remarks on result:

other: Effect type: toxicity (migrated information)

Dose descriptor:

LOAEL

Effect level:

>= 6.6 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: Increased thickness of the forestomach mucosa due to hyperplasia and hyperkeratosis of the squamous mucosa (both sexes). Dose level is for Active Ingredient.

Remarks on result:

other: Effect type: toxicity (migrated information)

Dose descriptor:

NOEL

Effect level:

>= 17.2 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: Dose level is for Active Ingredient.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Table 2 Adjusted Survival

Group	Dose	Males	Females
1	Tap H20	36%	35%
2	'Salt'^a	41%	35%
3	30 ppm^b	30%	33%
4	100 ppm	37%	38%
5	300 ppm	46%	32%

^a inorganic stabilizer salt solution (0.05%)

^b ppm active ingredient (a.i.) Kathon biocide

Table 3 Mean compound intake of Kathon biocide over 24 months

Group	ppm A.I. Kathon	24 Month Mean Intake (mg A.I./kg/day) Males	24 Month Mean Intake(mg A.I./kg/day)Females
3	30 ppm	2.0 + 0.6	3.1 + 0.5
4	100 ppm	6.6 + 1.9	9.8 + 1.3
5	300 ppm	17.2 + 4.7	25.7 + 3.3

Conclusions:

Administration of Kathon biocide to male and female rats in the drinking water for 24 months at concentrations up to and including 300 ppm active ingredient (a.i.) (17.2 mg a.i.lkg of body weightlday in males and 25.7 mg a.i./kg of body weightlday in females) showed no effects on the type or incidence of neoplasms in any group.

No treatment-related signs of toxicity were seen at 30 ppm active ingredient (a.i.)(2.0 mg a.i./kg of body weight/day in males and 3.1 mg a.i./kg of body weight/day in females), the No-Observed Effect Level (NOEL) in this study.

Executive summary:

Kathon Biocide (Toxicology Department (TD) Sample No. 90-105; Lot No 48014; ~14.2% active ingredient) was administered in the drinking water to 5 groups (90 males/group; 80 females/group) of Crl:CD BR rats for up to 24 months at concentrations of 0 (tap water control), 0 (inorganic 'salt' control) 30, 100 or 300 ppm of active ingredient (a.i.). All rats were observed daily for signs of ill health or reaction to treatment. Physical examinations were performed weekly. Body weight, water consumption and feed consumption were monitored weekly for the first 13 weeks of dosing and once every fourth week thereafter through term.

Ophthalmoscopic examinations were performed on all rats during the pretest period, and on all surviving rats during the 24th month of treatment. Ultrasonographic examinations were performed on the kidneys of all males during the 6th and 12th months of treatment. Urinalysis parameters were evaluated for all animals (where possible) during the pretest period, and for all males during the third and sixth month of treatment. The urine of 10 females/group was evaluated during the third and sixth month of treatment, and 10 rats/sex/group following the 12th, 18th and 24th month of treatment. During the 3rd, 6th, 12th, 18th and 24th months of the study, 10 rats/sex/dose were bled for clinical chemistry and hematology analysis. At 12 and 18 month intervals. 10 rats/sex/group (selected from the pool of animals not designated for hematology, clinical chemistry or urinalysis) were euthanized, necropsied, organ weights recorded and tissues collected for histopathologic evaluation. All rats that died or were euthanized moribund during the study were necropsied and tissues were collected for histopathologic examination. Following 24 months on test, all surviving rats were euthanized, necropsied, organ weights recorded and tissues collected for histopathologic examination.

No effects on survival were observed in male or female rats treated with Kathon biocide for 24 months. No treatment-related clinical signs of toxicity were evident.

There was a treatment-related decrease in body weight and cumulative body weight gain in Group 5 (300 ppm Kathon biocide) males throughout the 24 month treatment period. Decreased body weight and cumulative body weight gain in Group 5 (300 ppm) females was judged to be equivocal because it occurred only sporadically and frequently lacked a dose response.

Treatment-related decreases in water consumption were observed in both sexes in all Kathon biocide-treated groups during the 24 month study. Water consumption was decreased in Group 3 (30 ppm) 0-22% Group 4 (100 ppm) 3 -30% and in Group 5 (300 ppm) 15-40%.

There was a treatment-related decrease in feed consumption in Group 5 (300 ppm) males throughout 24 months of treatment with Kathon biocide. This effect was not seen in the high dose (300 ppm) females.

There were no treatment-related changes in any hematology or clinical chemistry parameters at any time point during the 24 month study period.

Increases in urine specific gravity in both sexes were considered secondary to decreased water consumption.

No treatment-related ocular abnormalities were observed following 24 months of treatment with Kathon biocide, nor were there any treatment-related changes in the renal pelves of the males in this study as determined by ultrasonography during the 6th and 12th months of treatment.

No treatment-related effects on organ weights were seen at any dose throughout the study.

Kathon biocide administration had no effect on the type or incidence of neoplasms in rats in any group. Treatment-related morphologic changes were limited to the stomach and occurred in both sexes at 100 and 300 ppm. The primary effect noted was gastric irritation which was reflected by thickening of the forestomach mucosa due to hyperplasia and hyperkeratosis of the squamous mucosa. Focal necrosis of the superficial glandular mucosa and edema and inflammatory cell infiltration in the forestomach submucosa were seen in the 300 ppm males.

Administration of Kathon biocide to male and female rats in the drinking water for 24 months at concentrations up to and including 300 ppm active ingredient (a.i.)(17.2 mg a.i./kg of body weightlday in males and 25.7 mg a.i./kg of body weight/day in females) showed no effects on the type or incidence of neoplasms in any group.

No treatment-related signs of toxicity were seen at 30 ppm active ingredient (a.i.)(2.0 mg a.i./kg of body weight/day in males and 3.1 mg a.i./kg of body weight/day in females), the No-Observed Effect Level (NOEL) in this study.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

3.1 mg/kg bw/day

Study duration:

chronic

Species:

rat

Quality of whole database:

Klimisch 1

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not stated.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: This study was conducted prior to GLP and test guidelines, but sufficient data is available for interpretation of results

Principles of method if other than guideline:

Test material was applied to the skin 3 times/week for 30 months.

GLP compliance:

no

Species:

mouse

Strain:

CD-1

Sex:

male

Details on test animals or test system and environmental conditions:

One hundred and eighty three male CD-1 mice (21-28 days old) were obtained from Charles River Breeding Laboratories, Portage, Michigan, on October 16, 1979. Upon arrival all animals were examined for physical abnormalities, identified with unique numbers (ear tags) and acclimated for two weeks. Animal care quarantine procedures (SOP 10.11) were in effect for the first week of the acclimation period. Animals which appeared to be in poor health were excluded from the study.

Throughout the study, mice were individually housed in suspended stainless steel cages with wire mesh floors and fronts. The cages were assigned sequentially top to bottom and left to right in the cage bank. The animals were housed in an environmentally controlled room with controls set to maintain a temperature of approximately 22C and a relative humidity of 40-60%. The light cycle was automatically controlled 12 hr on and 12 hr off.

Throughout the acclimation period and for the duration of the study, all mice had free access to tap water (via automatic watering) and standard laboratory rodent food (Wayne Lab-Blox, Allied Mills, Inc., Chicago, IL, or Purina Rodent Laboratory Chow 5001C, Ralston Purina Co., St. Louis, MO).

Route of administration:

dermal

Vehicle:

water

Details on exposure:

The dosing solution of Kathon CG (400 ppm active ingredient) was prepared by weighing 0.667 g of the Kathon CG stock solution (1.5% active ingredient) into a 25 ml volumetric flask on a Sartorius model 82462 analytical balance. The content of the flask was then brought to volume (25 ml ) with distilled water and the flask was stoppered. The flask was inverted several times to insure adequate mixing. Five ml of this solution was pipetted into a glass screw-top vial and stored under refrigeration when not in use. The remaining 20 ml of the solution was used for analysis of active ingredient to verify concentration. The dosing solution of 3-MC was prepared by weighing 0.005 g of 3-MC powder (100% active ingredient) into a small screw-top glass vial on a Sartoruis model 82462 analytical balance. Five ml of acetone was added to the vial to dissolve the 3-MC. The 3-MC solution was stored in the hood when not in use. The 3-MC solutions were not analyzed. Weighing and dissolving of both compounds was done in a type 2 Class A ultra hazardous hood (Baker Co.). All dosing solutions were prepared fresh weekly (on the first day of dosing each week), and unused portions were
discarded as hazardous waste at the end of the week.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

No additional information available in report but was probably analyzed by HPLC.

Duration of treatment / exposure:

3 times a week for 30 months

Frequency of treatment:

3 times a week for 30 months

Post exposure period:

No data.

Remarks:

Doses / Concentrations:
400 ppm A.I.
Basis:
other: nominal concentration in solution and dosed at 25 ul/animal

No. of animals per sex per dose:

40 males/dose level

Control animals:

yes, concurrent vehicle

Details on study design:

Groups and Dosages
One week prior to the initiation of dosing, 167 apparently healthy mice, with ear tags, were weighed, and randomly assigned (computerized randomization by body weight) to either the control group or one of two treatment groups. Immediately afterward the 10 or 11 animals in each group whose body weights were furthest from the group mean were eliminated so that during the pretest week there were 45 animals per group. These animals were then identified by cage card and observed for five days. Three days prior to the initiation of dosing, 40 animals per group had the hair removed from their backs with electric clippers. The five extra animals in each group (those whose body weights were furthest from the group mean) were not shaved. On the two days just prior to dosing, only the shaved animals were observed. The five extra animals in each group were eliminated on the first day of treatment. Prior to each treatment, the application sites of animals in Groups 1 and 2 were moistened with distilled water using a 1/2 inch paintbrush. The application site on the back of each mouse was clipped weekly throughout the study, usually on Thursday ( a non-treatment day) .

The dose level of Kathon CG employed in this study was based on data obtained in a range-finding study with Kathon CG in mice. Animals in Group 2 were treated dermally with Kathon CG (400 ppm active ingredient in distilled water) at a dose of 25 microliters per animal (10 micrograms per animal). Animals in Group 3 were treated with 3-MC (1000 ppm active ingredient in acetone) at a dose of 25 microliters per animal (25 micrograms per animal). Animals in Group 1 were treated dermally with tap water at a dose of 25 microliters per animal. All doses were administered 3 times a week (usually on Monday, Wednesday, and Friday) to the clipped space on the back of each animal with a Centaur pipette (Centaur Sciences, Inc., Stamford, CT) and a 25 microliter disposable tip.

Positive control:

Three-methylcholanthrene (3-MC) was employed in this study as a positive control; a substance known to induce skin tumors in mice by dermal application.

Observations and examinations performed and frequency:

Individual body weights were recorded weekly beginning 1 week prior to initiation of dosing and for the first 13 weeks of treatment. For the last 27 months of the study, individual body weights were recorded monthly. Each mouse was observed daily for signs of ill health, reaction to treatment, morbidity, mortality, and tumor-like growths. The first time a tumor-like growth was detected, it's size and location and a description were recorded. The status of the growth and any additional growths subsequently detected were monitored and recorded until the growth(s) was no longer evident or until the animal died. Daily observations of tumor-like growths on animals in Group 3 (3-MC treated) were discontinued on April 28, 1980 (approximately 6 months after initiation of treatment). At that time, all animals in the group had detectable tumor-like growths at or near the application site. From that time on, only the presence or absence of tumor-like growths on animals in this group were recorded.

Sacrifice and pathology:

Post Mortem
Necropsies were performed on all mice found dead, killed moribund, or killed intentionally at the conclusion of the study. All organs, tissues, and body cavities were examined, and gross abnormalities were recorded. The thoracic and abdominal organs were removed and fixed in 10% neutral buffered formalin. The head of the animal was removed, the roof of the skull detached, the dorsal meninges incised, and the brain either removed and placed in 10% neutral buffered formalin or fixed in-situ in the same fixative. If the brain was removed, the remainder of the head was also placed in 10% neutral buffered formalin.

Histopatholoqic Evaluation
The following tissues were examined ftom all mice in Group 1 (water control) and Group 2 (Kathon CG): skin (treated and untreated), liver, lung, heart, kidneys, spleen, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, bone with marrow (femur), and all other tissues with gross lesions. Histopathologic evaluation of mice in Group 3 (3-MC) was limited to treated skin and tissues with gross lesions. The tissues were processed, embedded in paraffin, sectioned at 5 to 6 microns, and stained with hematoxylin and eosin.

Other examinations:

No additional information available.

Statistics:

No additional information available.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

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

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

Dosing Solution Analysis
The results of the weekly analyses of the Kathon CG dosing solution were in good approximation to the intended concentration of 400 ppm of active ingredient. Analyses of 123 weekly samples yielded a mean value of 372.3 ppm with a standard deviation of 58.0.

Clinical Observations
Mortality
One mouse in the Kathon CG-treated group was found dead on the tenth day of the study. Nothing remarkable was seen at necropsy or histopathologically. This death is not considered compound related. The next death in the Kathon CG-treated group occurred during the tenth month of treatment, and 1 death occurred during each of the next 3 months. Beginning with the 16 th month of treatment, deaths occurred on a more regular basis
(1 to 4 each month) until the study was terminated after 30 months of treatment with 7 surviving animals (17.5% survival). No deaths occurred during the 26th or 30 th months of treatment.

In the water control group, the first death occurred during the 9th month of treatment. No further deaths occurred in this group until the 14th month of treatment. From the 14th month until termination of the study, deaths occurred at regular intervals. During the last 16 months of treatment, deaths occurred at a fairly consistent rate of 1 to 3 per month except during the 16th and 18th months when no deaths occurred and the 27th month when 5 deaths occurred. After 30 months of treatment (termination of the study), there were 10 surviving animals in the water control group (25% survival).

In the 3-MC-treated group, the first death occurred during the 6th month of treatment. At that time, 39 of 40 animals including the animal that died had tumor-like growths at the application site. The single animal that did not have a tumorlike growth at the time of the first death had a detectable growth 4 days later; thus, all animals in this group had detectable tumor-like growths by the end of the 6th month of treatment. Between the 6th and 13th month of treatment (inclusive) 39 of 40 mice in this group died. The last mouse died during the 16th month of treatment.

A comparison of percent survivals at 4 month intervals throughout the treatment period is presented in Table 2 below:

Overall survival distributions, utilizing time to death or study termination in months for each animal, were analyzed by two separate methods. The first method (the generalized Wilcoxon test) gives more weight to earlier death times than does the second method (the log rank test). These tests utilize information from all animals including censored observations (i. e., those animals that survived to termination). Survival for the duration of the study (30 months) was compared by the chi-square test or Fishers exact test. When the survival data comparing the Kathon CG-treated group to the w ater control group were analyzed by the general Wilcoxon test, a significant difference was found (P < 0.05).

When the same data were analyzed by the log rank test, no significant difference was found (P = 0.079). When 30 month survival in these two groups was compared by the chi-square test, no significant difference was found (P > 0.7). When the 3-MC treated group was compared to either the water control group or the Kathon CG-treated (with regard to overall survival distribution or 30-month survival) survival in the 3-MC treated was significantly less than either of the other groups (P <0.01).

While the % survival in the Kathon CG-treated group was somewhat less than in the water control group for a period of time during the mid and latter stages of treatment, this is not considered a treatment-related effect since: 1) there was no difference at 30 months, 2) there was disagreement between the two statistical tests employed, and 3 ) histopathologically, no signs of systemic toxicity were evident in the Kathon CG-treated animals.

Signs
Only two signs were seen during the in-life portion of the study which were related to treatment with Kathon CG. Brown staining at the application site was seen in 9 of 40 animals at various times throughout the treatment period. Similar staining was not seen in the water control group. In addition , eschar and/or desiccation or flaking of the skin was seen in 10 of 40 Kathon CG-treated mice at various times during the treatment period.

All other signs are considered incidental or related to aging of the animals and not to Kathon CG treatment. Some of the more frequently occurring signs are discussed below.

Red ears were seen with similar frequency in all three groups of animals. Alopecia and reddened skin in the head and neck area were seen with equal frequency in the water control group and the Kathon CG group. Yellow staining of the anogenital area and a wet anogenital area and belly were seen with equal frequency in all groups.

Many observations were made regarding the eyes of the test animals. White foci in the eye(s), eyes with a red, dry, or irregular surface, and exophthalmos were seen with no apparent relationship to treatment. Pale, white, or opaque eyes were seen most commonly in the 3-MC-treated animals (19 of 40) and more commonly in the Kathon CG-treated animals (7 of 40) than in the water control animals (2 of 40). In the 3-MC-treated animals, the sign was seen most commonly preceding death. In the water control and Rathon CG groups, these observations were most commonly made in the latter stages of the study and are considered age-related, not treatment-related.

Apparent weight loss, ataxia, lethargy, and/or passiveness were seen in all three groups of animals, generally prior to the death of the animal. In addition, pale extremities, cyanosis, distended abdomens, prostration, tremors, and labored breathing were seen alone or in combination as ante-mortem signs in the water control and Rathon CG-treated animals.

All animals in Group 3 (3-MC) developed visually detectable masses at the application site. The first growth appeared on day 94 of the study, and by the 164th day of the study, all surviving animals (39 of 39) had masses at the application site. The animal that had died also had a mass at the application site. In the water control group, no masses were seen at the application site. Two animals in the water control group developed masses at locations other than the application site. Specifically, these masses were located at the base of the tail (diagnosed histologically as a hemangiosarcoma) and in the right axillary area (diagnosed histologically as a granular cell myoblastoma) and were first noticed on days 791 and 874, respectively. Two animals in the Kathon CG-treated group developed masses at the application site that were first noticed on days 758 and 632 of the study, respectively. These masses were histologically diagnosed as a hemangioma and a hemangiosarcoma, respectively.

Body Weiqht
No treatment-related differences in mean body weight between Kathon CG-treated animals and water control animals were observed throughout the study. The group mean weight of the 3-MC-treated animals became greater than either of the other two groups as tumors developed, many of which were fairly large, relative to the size of the animal.

Necropsy Observations
A necropsy examination was performed on all animals, whether found dead, killed moribund, or killed at the termination of the study after 30 months of treatment. There were no treatment-related findings evident at necropsy in the Kathon CG treated animals relative to the water control animals. In the 3-MC-treated animals, an increased incidence of enlarged livers, white nodules on the lungs, enlarged spleens, and masses at the application site were evident.

In the water control group and the Kathon CG-treat'ed group, all findings were of a similar incidence with no indication of a treatment-related effect. Of these findings, many were related to the age of the animal; others were autolytic changes.

Histopathology
Histopathologic evaluation of the skin at the application site of mice treated with Kathon CG revealed treatment-related effects consisting of focal or multifocal epidermal necrosis, hyperplasia, hyperkeratosis, eschar, dermal inflammation, and increased dermal collagen. There were no indications of a treatment-related increased incidence of neoplasms of any type at the application site for mice treated with Kathon CG. Two mice treated with Kathon CG developed a hemangioma and a hemangiosarcoma, respectively, in the skin at the application site. The mouse with the hemangiosarcoma at the application site also had a hemangiosarcoma in the liver. These are not considered treatment-related since vascular tumors of a similar nature (hemangiosarcomas) were seen in the liver, spleen, and skin of the tail in 3 different water control animals. No signs of systemic toxicity were seen in any organs or tissues examined from mice treated with Kathon CG. The incidence of neoplasms seen in the Kathon CG-treated animals was similar to that seen in the water control animals. Liver tumors (hepatocellular adenomas or carcinomas) and lung tumors (alveolar/bronchiolar adenomas or adenocarcinomas) were seen in some animals in both the water control group and the Kathon CG-treated group in similar incidences. None of these tumors are considered treatment related. Other tumors seen in the water control and/or the Kathon CG treated group were of a low or single incidence with no indication of a treatment-related effect. Lesions of a nonneoplastic nature were seen in both the water control and Kathon CG-treated animals at a low or similar frequency. These lesions were of the type commonly seen in aged laboratory mice and are judged not to be treatment-related.

All Group 3 mice (3-MC-treated) developed squamous cell carcinomas at the application site. In many of the mice, the squamous cell carcinoma had metastasized to the lung. The same findings were seen in the kidneys or spleen but in single or low incidence. Stem cell proliferation, which had often proliferated into granulocytic type cells, was seen in the liver and spleen of many of the animals treated with methylcholanthrene. Similar stem cell proliferations (leukemia/leukemoid reaction) were seen in the lungs of many mice and the liver, kidneys, adrenal glands, stomach, or lymph nodes of several mice in that group. All of these findings are judged to be treatment-related.

Relevance of carcinogenic effects / potential:

Kathon CG, when applied to the closely clipped dorsal skin of male mice at a concentration of 400 ppm and at a dose of 25 microliters three times a week for 30 months showed no tumorigenic potential either locally or systemically.

Table 2 Survival

Treatment Month (numerically)	Group 1 Water Control (25 ul 3x week) survivors	Group 1 Water Control (25 ul 3x week) % survival	Group 2 Kathon CG 400 ppm (25 ul 3x week) survivors	Group 2 Kathon CG 400 ppm (25 ul 3x week) % survival	Group 3 3 -MC* 1000 ppm (25 ul 3x week) survivors	Group 3 3 -MC* 1000 ppm (25 ul 3x week) % survival
4	40/40	100.0	39/40	97.5	40/40	100.0
8	40/40	100.0	39/40	97.5	35/40	87.5
12	39/40	97.5	36/40	90.0	2/40	5.0
16	37/40	92.5	33/40	82.5	0/40	0.0
20	31/40	77.5	24/40	60.0	-	-
24	27/40	67.5	13/40	32.5	-	-
28	14/40	35.0	9/40	22.5	-	-
30^a	10/40	25.0	7/40	17.5	-	-

*3-MC = 3-Methylcholanthrene.

^a = Terminated at 30 months.

Conclusions:

Kathon CG, when applied to the closely clipped dorsal skin of male mice at a concentration of 400 ppm and at a dose of 25 microliters three times a week for 30 months showed no tumorigenic potential either locally or systemically.

Executive summary:

Dermal application of Kathon CG (400 ppm) did not affect 30-month survival of the animals. Although the percent survival in the water control group was greater than for the Kathon CG treated animals for a period of time during the mid and latter stages of treatment, the 30-month survival records showed no difference between groups (i. e., 10 of 40 in the water control group and 7 of 40 in the Kathon CG group). Thirty-seven of 40 3-MC-treated animals died during the first 11 months of treatment; all were dead by the end of the 16th month.

 

Only local signs of treatment were seen in the KathonCGtreated animals. Brown staining of the skin, eschar and/or desiccation, and flaking of the skin at the application site were the only treatment-related effects seen. Kathon CG produced no adverse effects on body weight, and no necropsy abnormalities were seen. Animals exposed to 3-MC developed increased body weights (from the masses present), enlarged livers, white nodules on the lungs, enlarged spleens, and a 100% incidence of masses at the application site.

 

Histopathologically, no indication of a treatment-related increased incidence of neoplasms of any type was seen either locally (at the application site) or systemically. No signs of systemic toxicity were seen in any of the organs or tissues examined from mice treated with Kathon CG. Irritation at the application site was evident in treated skin because of an increased incidence of focal or multifocal epidermal necrosis, hyperplasia, hyperkeratosis, eschar, dermal inflammation, and increased dermal collagen.

 

Kathon CG, when applied to the closely clipped dorsal skin of male mice at a concentration of 400 ppm and at a dose of 25 microliters three times a week for 30 months showed no tumorigenic potential either locally or systemically.

 

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

400 mg/kg bw/day

Study duration:

chronic

Species:

mouse

Quality of whole database:

Klimisch 1

Justification for classification or non-classification

Based on the results og both the dermal (mouse) study and oral (via drinking water) study in rats, this test material has no concern on the carginogenic endpoint.