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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to OECD guideline study with acceptable restrictions
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2001

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
other: NTP standard protocol
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)
Deviations:
not applicable
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Bis(4-chlorophenyl) sulphone
EC Number:
201-247-9
EC Name:
Bis(4-chlorophenyl) sulphone
Cas Number:
80-07-9
Molecular formula:
C12H8Cl2O2S
IUPAC Name:
1-chloro-4-(4-chlorobenzenesulfonyl)benzene
Details on test material:
- Name of test material: p,p'-Dichlorodiphenyl sulfone (DCDPS)
- Physical state: white powder
- Lot Nos.: AX01 (TCI America, Portland, OR, USA), P02300 (Lancaster Synthesis Inc., Windham, NH, USA)
- Analytical purity: >9 9% for both lots (GC analysis)
- Impurities: no impurities with areas greater than 0.1 % of the major peak area (HPLC), less than 0.04 % water
- Stability: stable for at least 14 days in sealed vials at temperatures up to 62 °C

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Taconic Laboratory Animals and Services (Germantown, NY, USA)
- Age at study initiation: 8-9 weeks old
- Housing: 5 rats/cage, in polycarbonate cages
- Diet: NIH-07 open formula meal diet (Zeigler Brothers Inc., Gardners, PA, USA), ad libitum
- Water: tap water (Columbus municipal supply), ad libitum
- Acclimation period: 14 days (males), 15 days (females)

ENVIRONMENTAL CONDITIONS
- Temperature: 72 ± 3 °F (approx. 22.2 °C)
- Humidity: 50 ± 15 %
- Air changes: 10 changes/hour
- Photoperiod: 12 hours dark/12 hours light

IN-LIFE DATES: From: 14 January 1993 To: 30 April 1993

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
DIET PREPARATION
- Rate of preparation of diet: every 5-9 days
- Mixing appropriate amounts with: NIH-07 feed
- Storage temperature of food: diet formulations were stored in plastic buckets at approximately -20 °C for up to 14 days.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The dose formulations were analysed three times during the study using HPLC.
Duration of treatment / exposure:
14 weeks
Frequency of treatment:
Feed mixed with the test substance was available ad libitum throughout the treatment period.
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0, 30, 100, 300, 1000, or 3000 ppm
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0, 2, 6, 19, 65, or 200 mg/kg bw/day
Basis:
actual ingested
No. of animals per sex per dose:
10 animals
Control animals:
yes, plain diet
Positive control:
none

Examinations

Observations and examinations performed and frequency:
DETAILED CLINICAL OBSERVATIONS:
- Time schedule: observed twice daily, clinical findings recorded at study initiation, weekly and at the end of the study

BODY WEIGHT:
- Time schedule: at study initiation, weekly, and at the end of the study

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Time schedule: weekly
- Food consumption for each animal determined: yes
- Compound intake calculated: yes

HAEMATOLOGY:
- Time schedule for collection of blood: at the end of the study
- Anaesthetic used for blood collection: carbon dioxide
- How many animals: all surviving animals
- Parameters checked: haematocrit; haemoglobin concentration; erythrocyte, reticulocyte, and platelet counts; erythrocyte morphology; mean cell volume; mean cell haemoglobin; mean cell haemoglobin concentration and leukocyte count and differentials

CLINICAL CHEMISTRY:
- Time schedule for collection of blood: at the end of the study
- Anaesthetic used for blood collection: carbon dioxide
- How many animals: all surviving animals
- Parameters checked: urea nitrogen, creatinine, total protein, albumin and bile salt concentration; alanine aminotransferase, alkaline phosphatase, creatine kinase and sorbitol dehydrogenase activities

NEUROBEHAVIOURAL EXAMINATION:
- Time schedule: during week 12
- Dose groups that were examined: all rats exposed to 0, 100, 300, or 1000 ppm
- Battery of functions tested: autonomic, convulsive, excitability, neuromuscular, sensorimotor, and general motor activity domains

ORGAN WEIGHTS
At necropsy, the heart, right kidney, liver, ovary, right testis, thymus and uterus were weighed.
Sacrifice and pathology:
GROSS PATHOLOGY: yes
HISTOPATHOLOGY:
Complete histopathological examination was performed on all 0 and 3000 ppm rats. Target tissues were examined in animals of all groups. In addition to gross lesions and tissue masses, the following tissues were examined: adrenal gland, blood vessel, bone with marrow, brain, clitoral gland, esophagus, heart, large intestine (cecum, colon, rectum), small intestine (duodenum, jejunum, ileum), kidney, liver, lung, lymph nodes (mandibular and mesenteric), mammary gland with adjacent skin, skeletal muscle, nose, ovary, pancreas, pancreatic islets, parathyroid gland, pituitary gland, preputial gland, prostate gland, salivary gland, spleen, stomach (forestomach and glandular), testis (with epididymis and seminal vesicle), thymus, thyroid gland, trachea, urinary bladder, and uterus. The liver and kidneys were examined in all groups.
Statistics:
Dunn’s or Shirley’s test for haematology and clinical chemistry prameters, Williams's or Dunnett's test for weights and weight ratios, Fisher exact test for incidences of non-neoplastic lesions.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
not examined
Behaviour (functional findings):
no effects observed
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Details on results:
GENERAL:
Relevant changes of selected endpoints are summarized in tabular form in section "Any other information on results incl. tables".

CLINICAL SIGNS AND MORTALITY:
No exposure related clinical signs were observed. All rats survived to the end of the study.

BODY WEIGHT AND WEIGHT GAIN:
Final mean body weights and body weight gains of male and female rats exposed to 300 ppm or greater were statstically significantly less than those of the respective controls indicating a treatment related effect.

FOOD CONSUMPTION AND COMPOUND INTAKE:
During the first week of the study, feed consumption by male and female rats exposed to 3000 ppm was 23 % and 39 % less than that by the controls, respectively. However, feed consumption by exposed groups was generally similar to that by the controls at week 13. Dietary concentrations of 30, 100, 300, 1000 and 3000 ppm resulted in average doses of approximately 2, 6, 19, 65 and 200 mg/kg bw/day to males and females.

HAEMATOLOGY:
Minimal decreases in haemoglobin concentrations were noted at 1000 and 3000 ppm. Erythrocyte counts were minimally decreased in the 1000 ppm male group. Minimal decreases in mean cell volume (1000 and 3000 ppm females), mean cell haemoglobin and mean cell haemoglobin concentration (300 and 1000 ppm females and 3000 ppm males and females) were observed. A mild increase in reticulocyte counts was observed in 3000 ppm males. A minimal to mild increase in platelet counts occurred at 1000 and 3000 ppm.

CLINICAL CHEMISTRY:
Slightly increased albumin and total protein concentrations were noted in groups exposed to 300 ppm or greater. Alkaline phosphatase activity decreased in an exposure-related manner. There was evidence of a hepatocellular effect demonstrated by increased sorbitol dehydrogenase activity in the 3000 ppm groups. Alanine aminotransferase activity was not affected similarly. Bile acid concentrations were increased in 3000 ppm males supporting the possibility of a hepatic effect. Minimal increases in urea nitrogen and creatinine concentrations were noted at 3000 ppm.

NEUROBEHAVIOUR:
No adverse neurological effects were observed.

ORGAN WEIGHTS:
Absolute and relative liver weights of male and female rats exposed to 100 ppm or greater were significantly increased compared to the controls. Absolute kidney and testis weights of male rats at 1000 and 3000 ppm were also significantly increased. The absolute and relative thymus weights of male rats exposed to 300 ppm or greater were significantly less when compared to controls. The testis and thymus weight changes were without microscopical correlate.

GROSS PATHOLOGY:
No exposure-related gross lesions were observed.

HISTOPATHOLOGY:
Incidences of centrilobular hepatocyte hypertrophy in male rats exposed to 100 ppm or greater and in female rats exposed to 300 ppm or greater were significantly increased compared to the controls. Hypertrophy consisted of minimal to mild increases in the size of hepatocytes surrounding the central veins and was more readily apparent in exposed males than females. The severity of hypertrophy was minimal in 100 ppm males and 300 ppm females and mild in 300, 1000, and 3000 ppm males and in 1000 and 3000 ppm females. Both cytomegaly and karyomegaly were evident. Affected hepatocytes had a lightly stained, ground-glass appearance due to numerous intracytoplasmic, small, clear vacuoles. There were significant increases in the incidences of nephropathy in the 1000 and 3000 ppm female rats. Nephropathy was mild in 300 ppm males, moderate in 1000 ppm males, and marked in 3000 ppm males. All lesions in females were of minimal severity. Nephropathy was characterised by foci of regenerating renal tubules with associated peritubular fibrosis and mononuclear inflammatory cell infiltration into the adjacent interstitium.

Effect levels

open allclose all
Dose descriptor:
NOEL
Effect level:
2 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: Based on liver weight increase associated by centrilobular hepatocyte hypertrophy noted at 6 mg/kg bw/day.
Dose descriptor:
NOAEL
Remarks on result:
not determinable
Remarks:
no NOAEL identified

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

ANALYSIS OF DOSE FORMULATIONS:

Of the dose formulations analysed, 12/13 were within 10% of the target concentrations. In addition, 6/8 animal room samples were within 10 % of the target concentrations.

14-WEEK FEED STUDY IN RATS: EFFECTS OF DCDPS EXPOSURE

 

MALE

Dose

(ppm)

0

30

100

300

1000

3000

Intake

(mg/kg bw/day)

0

2

6

19

65

200

 

Body Weight

Final BW

(g)

369 ± 4

378 ± 7

366 ± 4

350 ± 4*

340 ± 6**

304 ± 8**

 

(% change)

0

+2

-1

-5

-8

-18

Haematology

Haemoglobin

(g/dL)

16.5 ± 0.2

16.6 ± 0.1

16.2 ± 0.2

16.3 ± 0.2

15.6 ± 0.1**

15.8 ± 0.2**

 

(% change)

0

+1

-2

-1

-5

-4

Erythrocytes

(106/µL)

9.48 ± 0.10

9.33 ± 0.09

9.19 ± 0.15

9.28 ± 0.16

9.03 ± 0.10*

9.36 ± 0.17

 

(% change)

0

-2

-3

-2

-5

-1

Reticulocytes

(106/µL)

0.11 ± 0.01

0.11 ± 0.01

0.12 ± 0.01

0.13 ± 0.01

0.14 ± 0.01

0.15 ± 0.02*

 

(% change)

0

0

+9

+18

+27

+36

MCV

(fL)

51.3 ± 0.3

52.3 ± 0.1**

51.9 ± 0.3

51.6 ± 0.2

51.6 ± 0.2

51.8 ± 0.2

 

(% change)

0

+2

+1

+1

+1

+1

MCH

(pg)

17.4 ± 0.1

17.8 ± 0.1

17.6 ± 0.1

17.6 ± 0.1

17.3 ± 0.1

16.9 ± 0.3*

 

(% change)

0

+2

+1

+1

-1

-3

MCHC

(g/dL)

34.0 ± 0.2

34.0 ± 0.1

33.9 ± 0.2

34.0 ± 0.2

33.5 ± 0.2

32.6 ± 0.3**

 

(% change)

0

0

0

0

-1

-4

Platelets

(10³/µL)

754.7 ± 15.0

793.6 ± 56.5

769.1 ± 22.8

761.1 ± 13.3

837.8± 20.4**

948.8 ± 21.0**

 

(% change)

0

+5

+2

+1

+11

+26

Clinical Chemistry

Urea nitrogen

(mg/dL)

20.5 ± 0.3

18.2 ± 0.5

19.8 ± 0.4

21.0 ± 0.3

21.0 ± 0.3

24.0 ± 0.3**

 

(% change)

0

-11

-3

+2

+2

+17

Creatinine

(mg/dL)

0.68 ± 0.01

0.70 ± 0.02

0.69 ± 0.01

0.69 ± 0.01

0.71 ± 0.02

0.76 ± 0.02**

 

(% change)

0

+3

+1

+1

+4

+12

Total protein

(g/dL)

7.4 ± 0.1

7.4 ± 0.2

7.7 ± 0.1

8.2 ± 0.1**

8.2 ± 0.1**

8.6 ± 0.1**

 

(% change)

0

0

+4

+11

+11

+16

Albumin

(g/dL)

4.9 ± 0.1

4.9 ± 0.1

5.1 ± 0.1

5.4 ± 0.1**

5.1 ± 0.0**

5.3 ± 0.1**

 

(% change)

0

0

+4

+10

+4

+8

ALP

(IU/L)

602 ± 11

509 ± 27**

460 ± 7**

474 ± 9**

402 ± 8**

421 ± 8**

 

(% change)

0

-15

-24

-21

-33

-30

SDH

(IU/L)

23 ± 2

24 ± 2

20 ± 1

23 ± 3

27 ± 2

42 ± 4**

 

(% change)

0

+4

-13

0

+17

+83

Bile salts

(µmol/L)

25.2 ± 2.4

23.6 ± 1.4

27.8 ± 2.9

25.0 ± 0.8

26.2 ± 0.5

32.0 ± 1.3**

 

(% change)

0

-6

+10

0

+4

+27

Necropsy Body Weight and Organ Weights

Necropsy BW

(g)

391 ± 4

387 ± 8

381 ± 5

366 ± 4**

353 ± 6**

313 ± 8**

 

Liver

(% bw)

3.960 ± 0.081

4.029 ± 0.070

4.768 ± 0.119**

5.481 ± 0.063**

7.082 ± 0.093**

8.471 ± 0.159**

 

(% change)

0

+2

+20

+38

+79

+114

Kidney (right)

(% bw)

0.352 ± 0.005

0.353 ± 0.005

0.374 ± 0.006*

0.389 ± 0.007**

0.462 ± 0.007**

0.500 ± 0.005**

 

(% change)

0

0

+6

+11

+31

+42

Testis (right)

(% bw)

0.380 ± 0.005

0.384 ± 0.006

0.398 ± 0.008

0.410 ± 0.005**

0.445 ± 0.009**

0.494 ± 0.011**

 

(% change)

0

+1

+5

+8

+17

+30

Thymus

(% bw)

0.088 ± 0.005

0.078 ± 0.003

0.081 ± 0.005

0.075 ± 0.003*

0.070 ± 0.003**

0.072 ± 0.004**

 

(% change)

0

-11

-8

-15

-20

-18

Histopathology

Liver

 

 

 

 

 

 

 

Hypertrophya

(incidence)

0/10

0/10

7/10**

10/10**

10/10**

10/10**

 

(severity grade)b

-

-

1.1

2.0

2.0

2.0

Kidney

 

 

 

 

 

 

 

Nephropathy

(incidence)

9/10

10/10

10/10

10/10

10/10

10/10

 

(severity grade)

1.0

1.0

1.0

1.8

2.9

3.8

 

 

FEMALE

Dose

(ppm)

0

30

100

300

1000

3000

Intake

(mg/kg bw/day)

0

2

6

19

65

200

 

Body Weight

Final BW

(g)

204 ± 2

201 ± 2

200 ± 2

196 ± 3*

185 ± 2**

174 ± 3**

 

(% change)

0

-1

-2

-4

-9

-15

Haematology

Haemoglobin

(g/dL)

15.8 ± 0.2

16.1 ± 0.1

15.7 ± 0.1

15.6 ± 0.2

15.0 ± 0.2**

14.8 ± 0.2**

 

(% change)

0

+2

-1

-1

-5

-6

Erythrocytes

(106/µL)

8.23 ± 0.12

8.33 ± 0.08

8.19 ± 0.09

8.36 ± 0.14

8.36 ± 0.13

8.32 ± 0.11

 

(% change)

0

+1

0

+2

+2

+1

Reticulocytes

(106/µL)

0.09 ± 0.01

0.10 ± 0.01

0.11 ± 0.02

0.10 ± 0.01

0.11 ± 0.01

0.12 ± 0.01

 

(% change)

0

+11

+22

+11

+22

+33

MCV

(fL)

55.2 ± 0.2

55.9 ± 0.2

55.6 ± 0.2

55.1 ± 0.2

54.4 ± 0.2*

54.1 ± 0.4**

 

(% change)

0

+1

+1

0

-1

-2

MCH

(pg)

19.2 ± 0.1

19.4 ± 0.1

19.2 ± 0.1

18.7 ± 0.1**

17.9 ± 0.1**

17.8 ± 0.1**

 

(% change)

0

+1

0

-3

-7

-7

MCHC

(g/dL)

34.9 ± 0.2

34.6 ± 0.2

34.5 ± 0.3

33.9 ± 0.3*

32.9 ± 0.2**

32.8 ± 0.2**

 

(% change)

0

-1

-1

-3

-6

-6

Platelets

(10³/µL)

736.4 ± 11.5

783.9 ± 14.9*

772.7 ± 23.2

790.4 ± 12.4*

843.9 ± 14.3**

826.9 ± 16.8**

 

(% change)

0

+6

+5

+7

+15

+12

Clinical Chemistry

Urea nitrogen

(mg/dL)

19.3 ± 0.6

18.7 ± 0.8

18.2 ± 0.5

19.6 ± 1.0

18.6 ± 0.5

21.8 ± 0.6

 

(% change)

0

-3

-6

+2

-4

+13

Creatinine

(mg/dL)

0.67 ± 0.02

0.71 ± 0.02

0.68 ± 0.01

0.68 ± 0.01

0.68 ± 0.01

0.73 ± 0.02*

 

(% change)

0

+6

+1

+1

+1

+9

Total protein

(g/dL)

7.2 ± 0.1

7.6 ± 0.1**

7.5 ± 0.1**

8.0 ± 0.1**

9.1 ± 0.1**

9.5 ± 0.2**

 

(% change)

0

+6

+4

+11

+26

+32

Albumin

(g/dL)

5.1 ± 0.1

5.3 ± 0.1*

5.1 ± 0.1

5.4 ± 0.1**

6.0 ± 0.1**

6.1 ± 0.1**

 

(% change)

0

+4

0

+6

+18

+20

ALP

(IU/L)

447 ± 16

432 ± 125

368 ± 14**

339 ± 15**

225 ± 8**

243 ± 9**

 

(% change)

0

-3

-18

-24

-50

-46

SDH

(IU/L)

20 ± 2

20 ± 1

20 ± 2

21 ± 1

27 ± 4

29 ± 4*

 

(% change)

0

0

0

+5

+35

+45

Bile salts

(µmol/L)

48.5 ± 5.3

54.2 ± 6.1

59.1 ± 5.1

72.0 ± 10.3

42.2 ± 2.4

49.4 ± 5.8

 

(% change)

0

+12

+22

+48

-13

+2

Necropsy Body Weight and Organ Weights

Necropsy BW

(g)

213 ± 3

206 ± 2*

206 ± 2*

201 ± 3**

189 ± 2**

177 ± 3**

 

Liver

(% bw)

3.526 ± 0.042

3.719 ± 0.057

3.968 ± 0.036**

4.609 ± 0.078**

6.471 ± 0.118**

8.316 ± 0.147**

 

(% change)

0

+5

+13

+31

+84

+136

Histopathology

Liver

 

 

 

 

 

 

 

Hypertrophya

(incidence)

0/10

0/10

0/10

10/10**

10/10**

10/10**

 

(severity grade)b

-

-

-

1.0

1.9

1.9

Kidney

 

 

 

 

 

 

 

Nephropathy

(incidence)

0/10

0/10

1/10

2/10

5/10*

10/10**

 

(severity grade)

-

-

1.0

1.0

1.0

1.2

 

Note: values are mean ± SD of 10 animals/group
* significantly different from control (p<0.05)

** significantly different from control (p<0.01)

MCV: mean cell volume

MCH: mean cell haemoglobin

MCHC: mean cell haemoglobin concentration

ALP: alkaline phosphatase

SDH: sorbitol dehydrogenase

a: centrilobular hypertrophy

b: 1 = minimal, 2 = mild, 3 = moderate, 4 = marked

-: not applicable

Applicant's summary and conclusion

Conclusions:
The NOEL for dietary administration of DCDPS to rats over a period of 14 weeks is 2 mg/kg bw/day.
Under the conditions of this study, treatment-related effects were noted in the liver and the kidneys.
The effects were identified as non-adverse since a clear correlation to an adaptive hepatic enzyme induction can be made.
Executive summary:

In a subchronic oral toxicity study (NIH, 2001), performed to select dose levels for a subsequent 2 -year study, DCDPS was administered via the diet to F344/N rats (10 animals/sex/dose) at dose levels of 0, 30, 100, 300, 1000 or 3000 ppm (corresponding to 0, 2, 6, 19, 65 and 200 mg/kg bw/day, respectively) for a period of 14 weeks. Clinical signs, body weights and food consumption were recorded periodically. In addition, neurobehavioural and clinical pathological endpoints were assessed. Following necropsy, selected organs were weighed and macroscopical as well as histopathological examinations were performed.

Feeding of DCDPS resulted in no mortality, no clinical signs, and no neurobehavioural or macroscopical findings. Mean body weights at 19 mg/kg bw/day or greater were significantly less than those of the controls. This was correlated to a transient reduction in food consumption (week1) which almost recovered to control levels (week13).

Minimal changes were noted in haematology and clinical chemistry parameters. Though treatment related, apart of an increased sorbitol dehydrogenase activity at 200 mg/kg bw/day (+83 %), all described effects weere within biological variance and can therefore not be considered as adverse.

Absolute liver weights of groups exposed to 6 mg/kg bw/day or greater and absolute kidney weights of 65 and 200 mg/kg bw/day male rats were significantly greater than those of the controls. Centrilobular hepatocyte hypertrophy of the liver was observed in male rats at 6 mg/kg bw/day or greater and in female rats at 19 mg/kg bw/day or greater, and the severities were increased in 19 mg/kg bw/day males, and 65 and 200 mg/kg bw/day males and females.

Dose related increases in severity of nephropathy were observed in male rats at 19 mg/kgbw/dayor greater with high incidences noted in both treatment and control group animals. Incidences of nephropathy in female rats were significantly increased at 65 and 200 mg/kgbw/day, though achieving minimal severity at the most.

Under the conditions of this study, the NOEL was established at 2 mg/kg bw/day. This NOEL is based on centrilobular hepatocyte hypertrophy accompanied by vacuolisation in affected cells and associated with increased liver weight. Treatment related effects were observed in both the liver and the kidneys, though none of them could be attributed as adverse or relevant to humans. Overall, males were more affected than females.

This subchronic toxicity study in the rat is acceptable as key study and satisfies the guideline requirement for a subchronic oral study according to test guideline OECD 408.