Decahydronaphthalene

Carcinogenicity

Description of key information

NTP studies with rats and mice with two years inhalation exposure have been conducted. No increased incidence of neoplastic effects was noted in male mice or in female rats at dose levels up to 400 ppm. Increased incidence of renal carcinoma or adenoma at 50 ppm or greater was observed in male rats. The identified mechanism (renal toxicity by accumulation of hyaline droplets, a2u-globulin accumulation) is considered to be species and sex specific with no relevance to human health risk. Some minor increases of neoplastic effects in liver and uterus of female mice could not unequivocally attributed to decahydronaphthalene with the data available.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

carcinogenicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997-08-14 to 1999-08-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to Guideline study

Principles of method if other than guideline:

NTP Carcinogenicity Study

GLP compliance:

yes

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ORGANISMS
- Source: Taconic Laboratory Animals and Services, Germantown (NY, USA)
- Age: 7 weeks at study initiation
- Weight at study initiation: males mean 120 g, females mean 96 g
- Number of animals: 50 per concentration level and sex (400 ppm males:  20 animals)
- Housing: individually, Stainless steel wire-bottom (Lab Products, Inc., Seaford, DE)
- Food (ad libitum except during exposure): NTP-2000 open formula pelleted diet (Zeigler Brothers, Inc., Gardners, PA), irradiated
- Water (ad libitum): tap water

ENVIRONMENTAL CONDITIONS (CHAMBER)
- Temperature: 72° ± 3° F
- Relative humidity: 50% ± 15%
- Room fluorescent light: 12 hours/day
- Chamber air changes: 15/hour

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

other: clean air

Details on exposure:

ADMINISTRATION / EXPOSURE
- Type of exposure:  whole-body inhalation
- Vehicle: clean air
- Concentrations: established within 12 minutes, monitored every 24  minutes   
males: 0, 25, 50; 100 ppm; additional 400 ppm group with only 20 animals   At 72 +- 3 °F (22.2 °C) these ppm concentrations correspond 
to: 0, 143,  285, 570; 2282 mg/m3   
females: 0, 25, 100, 400 ppm (0, 143, 570, 2282 mg/m3)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentrations in the exposure chambers were monitored every 24  minutes by an on-line gas chromatograph

Duration of treatment / exposure:

105 weeks

Frequency of treatment:

6 hours (+ 12 minutes concentration buildup)/day, 5 days/week

Post exposure period:

Post-exposure period: none

Remarks:

Doses / Concentrations:
25, 100, or 400 ppm; male rats also 50 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

 50 per concentration level and sex (400 ppm males:  20 animals)

Control animals:

yes, concurrent vehicle

Details on study design:

no data

Observations and examinations performed and frequency:

CLINICAL OBSERVATIONS AND FREQUENCY
- Clinical signs: observed twice daily
- Mortality: observed twice daily
- Clinical findings: every 4 weeks (weeks 5-89), every 2 weeks beginning  week 92
- Body weight: initially every 4 weeks (weeks 5-89), every 2 weeks  beginning week 92
- Hematology: none
- Clinical chemistry: none
- Urinalysis: none

Sacrifice and pathology:

SACRIFICE
Carbon dioxide asphyxiation

PATHOLOGY
Necropsy was performed on all animals.
ORGANS EXAMINED AT NECROPSY (MACROSCOPIC AND MICROSCOPIC):
- Macroscopic: "complete", no details reported
- Microscopic: all animals: gross lesions, adrenal gland, bone with marrow, brain, clitoral gland, esophagus, heart, large intestine (cecum, colon, rectum), small intestine (duodenum, jejunum, ileum), kidney, larynx, liver, lung, lymph nodes (mandibular, mesenteric, bronchial, and mediastinal), mammary gland, nose, ovary, pancreas, parathyroid gland, pituitary gland, preputial gland, prostate gland, salivary gland, skin, spleen, stomach (forestomach and glandular), testis with epididymis and seminal vesicle, thymus, thyroid gland, trachea, urinary bladder, and uterus.
OTHER EXAMINATIONS: Independent review of slides, individual animal data records, and pathology tables followed by clarification of any inconsistencies.

Statistics:

STATISTICAL METHODS:
- probability of survival: procedure of Kaplan and Meier (1950)
- possible dose-related effects on survival: method of Cox (1972) and  life table text of Tarone (1975)
- incidences of neoplasms or nonneoplastic lesions, also adjusted for  survival: Poly-k test with k = 3
- organ and body weights: procedures of Dunnett (1955) and Williams  (1971, 1972)
- hematology, clinical chemistry, urinalysis, renal toxicity, and  spermatid and epididymal spermatozoal data: methods of Shirley (1977) and 
 Dunn (1964)
- selection of trend-sensitive vs. non-trend-sensitive statistical test:  Jonckheere's test (1954)
- identification of outliers: test of Dixon and Massey (1951)
- average severity values: Mann-Whitney U test
- vaginal cytology data: arcsine transformation followed by multivariate  analysis of variance

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

reduced for 400 ppm males

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

male rats kidney effects

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

male rats kidney effects (chronic nephropathy, renal tubule hyperplasia, hyaline droplet accumulation, renal papilla mineralization, pelvic transitional epithelium hyperplasia)

Histopathological findings: neoplastic:

effects observed, treatment-related

Description (incidence and severity):

males rats kidney (renal tubule adenoma, renal tubule adenoma or carcinoma), male rats adrenal medulla (benign or malignant pheochromocytoma)

Details on results:

Result (carcinogenicity): ambiguous
CLINICAL SIGNS: There were no exposure-related clinical findings.
BODY WEIGHT GAIN: Mean body weights of 400 ppm males were slightly less than those of the control group during the second year of the study
(initial +2 %, minimum -7 %, final -2 % from control).
PATHOLOGY: Statistically significant observations in females (sorted by increasing exposure concentrations):
- Interstitial fibrosis (16/50; 24/50;,23/49; 28/50**)
- Histiocytic infiltration (21/50; 26/50; 29/49; 29/50*)
- Aleolar proteinosis (11/50; 16/50; 15/49; 23/50**)
- Chronic inflammation of visceral pleura (15/50; 17/50; 23/49; 27/50*)
These changes are all components of a focal lesion that appears to be a common incidental finding in aged F344/N rats. They were not considered to be clinically significant
Nonneoplastic effects in kidneys of males (sorted by increasing exposure concentrations):
- Severity of chronic nephropathy (1.4; 2.3; 2.6; 2.3; 3.0)
- Renal tubule hyperplasia (0/50; 11/50**; 11/49**; 15/50**; 5/20**)
- Hyaline droplet accumulation (2/50; 9/50*; 7/49; 11/50**; 2/20)
-Renal papilla mineralization (1/50; 34/50**; 41/49**; 43/50**; 17/20**)
- Pelvic transitional epithelium hyperplasia (1/50; 8/50*; 8/49*; 10/50**; 5/20**)
Neoplastic effects in males (sorted by increasing exposure concentrations):
- Renal tubule adenoma (1/50; 2/50; 6/49; 9/50**; 5/20**).
- Renal tubule adenoma or carcinoma (1/50; 3/50; 7/49*; 12/50***; 6/20***)
- Adrenal medulla: benign or malignant pheochromocytoma (8/49; 9/49; 13/49; 16/49*; 8/20*)
SIGNIFICANCE: * p <= 0.05; ** p <= 0.01; *** p <= 0.001
OTHER: There was a significant association between nephropathy severity and adrenal pheochromocytoma incidence.
TIME TO TUMOURS: Renal tubule adenoma or carcinoma first observed after
0 ppm: 733 days = terminal necropsy;
25 ppm: 644 days
50 ppm: 680 days
100 ppm: 617 days
400 ppm: 708 days

Dose descriptor:

NOAEC

Effect level:

> 400 ppm

Based on:

test mat.

Sex:

female

Dose descriptor:

NOAEC

Effect level:

25 ppm

Based on:

act. ingr.

Sex:

male

Basis for effect level:

other: see 'Remark'

MORTALITY AND TIME TO DEATH: Survival of exposed groups was similar to  that of the control groups: 

	Survivors/total		Mean survival of deaths
Concentration	Males	Females	Males	Females
0 ppm	28/50	32/50	684 days	700 days
25 ppm	23/50	35/50	675 days	713 days
50 ppm	23/49	-	697 days	-
100 ppm	20/50	39/50	673 days	703 days
400 ppm	14/20	28/50	711 days	683 days

Conclusions:

Under the conditions of the study, there was clear evidence of carcinogenic activity of decahydronaphthalene in male F344/N rats based on
increased incidences of renal tubule neoplasms. The increased incidences of benign or malignant pheochromocytoma (combined) of the adrenal
medulla in male rats were also considered to be exposure related. There was no evidence of carcinogenic activity of decahydronaphthalene in
female F344/N rats.
Exposure of male rats to decahydronaphthalene resulted in nonneoplastic lesions of the kidney characteristic of a2u-globulin accumulation.

Executive summary:

Groups of 50 male and 50 female F344/N rats were exposed to 0, 25, 50 (male rats only), 100, or 400 ppm (female rats only) decalin vapor 6 hours per day, 5 days per week for 105 weeks. A group of 20 male rats was exposed to 400 ppm. Survival of exposed groups was similar to that of the chamber control groups. Mean body weights of 400 ppm males were slightly less than those of the chamber controls during the second year of the study. Incidences of renal tubule adenoma and adenoma or carcinoma (combined) and of benign or malignant pheochromocytoma (combined) of the adrenal medulla in 100 and 400 ppm males were significantly increased. There was a significant association between nephropathy severity and adrenal pheochromocytoma incidence. Nonneoplastic lesions related to decalin exposure occurred in the kidney of male rats.

Reference 2

Endpoint:

carcinogenicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997-08-28 to 1999-09-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Comparable to Guideline study

Principles of method if other than guideline:

Method: other: NTP Carcinogenicity Study

GLP compliance:

yes

Species:

mouse

Strain:

B6C3F1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ORGANISMS
- Source: Taconic Laboratory Animals and Services, Germantown (NY, USA)
- Age: 6 weeks at study initiation
- Weight at study initiation: males mean 24.1 g, females mean 19.7 g
- Number of animals: 50 per sex and exposure level
- Housing: individually, Stainless steel wire-bottom (Lab Products, Inc., Seaford, DE)
- Food (ad libitum except during exposure): NTP-2000 open formula pelleted diet (Zeigler Brothers, Inc., Gardners, PA), irradiated
- Water (ad libitum): tap water

ENVIRONMENTAL CONDITIONS (CHAMBER)
- Temperature: 72° ± 3° F
- Relative humidity: 50% ± 15%
- Room fluorescent light: 12 hours/day
- Chamber air changes: 15/hour

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

other: clean air

Details on exposure:

ADMINISTRATION / EXPOSURE
- Type of exposure:  whole-body inhalation
- Vehicle: clean air
- Concentrations: established within 12 minutes, monitored every 24  minutes   At 72 +- 3 °F (22.2 °C) the ppm concentrations correspond 
to: 143, 570,  2282 mg/m3

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentrations in the exposure chambers were monitored every 24  minutes by an on-line gas chromatograph

Duration of treatment / exposure:

105 weeks

Frequency of treatment:

6 hours (+ 12 minutes concentration buildup)/day, 5 days/week

Post exposure period:

none

Remarks:

Doses / Concentrations:
25, 100, or 400 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

50

Control animals:

yes, concurrent vehicle

Details on study design:

Post-exposure period: none

Positive control:

no

Observations and examinations performed and frequency:

CLINICAL OBSERVATIONS AND FREQUENCY
- Clinical signs: observed twice daily
- Mortality: observed twice daily
- Clinical findings: every 4 weeks (weeks 4-89), every 2 weeks beginning  week 92
- Body weight: initially, every 4 weeks (weeks 4-89), every 2 weeks  beginning week 92
- Hematology: none
- Clinical chemistry: none
- Urinalysis: none

Sacrifice and pathology:

SACRIFICE
Carbon dioxide asphyxiation

PATHOLOGY
Necropsy was performed on all animals.
ORGANS EXAMINED AT NECROPSY (MACROSCOPIC AND MICROSCOPIC):
- Macroscopic: "complete", no details reported
- Microscopic: all animals: gross lesions, adrenal gland, bone with marrow, brain, clitoral gland, esophagus, gall bladder, heart, large intestine (cecum, colon, rectum), small intestine (duodenum, jejunum, ileum), kidney, larynx, liver, lung, lymph nodes (mandibular, mesenteric, bronchial, and mediastinal), mammary gland (females only), nose, ovary, pancreas, parathyroid gland, pituitary gland, preputial gland, prostate gland, salivary gland, skin, spleen, stomach (forestomach and glandular), testis with epididymis and seminal vesicle, thymus, thyroid gland, trachea, urinary bladder and uterus.
OTHER EXAMINATIONS: independent review of slides, individual animal data records, and pathology tables followed by clarification of any inconsistencies

Statistics:

STATISTICAL METHODS:
- probability of survival: procedure of Kaplan and Meier (1950)
- possible dose-related effects on survival: method of Cox (1972) and  life table text of Tarone (1975)
- incidences of neoplasms or nonneoplastic lesions, also adjusted for  survival: Poly-k test with k = 3
- organ and body weights: procedures of Dunnett (1955) and Williams  (1971, 1972)
- hematology, clinical chemistry, urinalysis, renal toxicity, and  spermatid and epididymal spermatozoal data: methods of Shirley (1977) and Dunn (1964)
- selection of trend-sensitive vs. non-trend-sensitive statistical test:  Jonckheere's test (1954)
- identification of outliers: test of Dixon and Massey (1951)
- average severity values: Mann-Whitney U test
- vaginal cytology data: arcsine transformation followed by multivariate  analysis of variance

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Male mice, liver: eosinophilic focus, centrilobular hypertrophy, necrosis, syncytial alteration, erythrophagocytosis

Histopathological findings: neoplastic:

no effects observed

Details on results:

Result (carcinogenicity): ambiguous
CLINICAL SIGNS: There were no clinical findings related to exposure. 
BODY WEIGHT GAIN: Mean body weights of exposed groups were generally  similar to those of the control groups throughout the study. 
PATHOLOGY: 
- Males: Statistically significant findings (all in the liver)   
- eosinophilic focus (10/50; 9/50, 7/50; 19/50*)   
- centrilobular hypertrophy (2/50; 0/50; 4/50; 36/50**)   
- necrosis (0/50; 1/50; 3/50; 19/50**)   
- syncytial alteration (26/50; 28/50; 36/50*; 44/50**)   
- erythrophagocytosis (0/50; 0/50; 0/50; 9/50**)
- Males: not statistically significant   
- hepatocellular adenoma or carcinoma: 28/50; 26/50; 22/50; 34/50  (within historical control range)   
- interstitial cell adenoma in testis: 0/50; 0/50; 0/50; 3/50. 400 ppm  
incidence at upper end of historical control range, not considered to be  exposure related
- Females: Statistically significant or dose-related findings   
- liver hepatocellular adenoma (7/49; 13/50; 8/50; 17/50*)   
- liver hepatocellular carcinoma (4/49; 16/50**; 6/50; 5/50)   
- one of these two (11/49; 27/50***; 14/50; 20/50*): equivocal evidence   
- uterus stromal polyp (0/49; 0/50; 2/50; 3/50)   
- uterus stromal polyp or stromal sarcoma (0/49; 0/50; 2/50; 4/50): 400  ppm 
incidence exceeds historical control range, may have been exposure  related.  
SIGNIFICANCE: * p <= 0.05; ** p <= 0.01; *** p <= 0.001
TIME TO TUMORS: First incidence of (order of increasing exposure  concentration)
- hepatocellular adenoma or carcinoma in males: 384 / 495 / 448 / 552 days
- hepatocellular adenoma or carcinoma in females: 703 / 488 / 594 / 636  days

Dose descriptor:

NOAEC

Effect level:

> 400 ppm

Based on:

act. ingr.

Sex:

male/female

MORTALITY AND TIME TO DEATH: 

Survival of exposed mice was similar to that  of the controls:

	Survivors/total		Mean survival
Concentration	Males	Females	Males	Females
0 ppm	40/50	37/49	701 days	708 days
25 ppm	41/50	28/50	697 days	687 days
100 ppm	36/50	35/50	702 days	695 days
400 ppm	34/50	36/50	697 days	702 days

Conclusions:

There was no evidence of carcinogenic activity of decahydronaphthalene in male B6C3F1 mice. There was equivocal evidence of carcinogenic activity of decahydronaphthalene in female B6C3F1 mice based on marginally increased incidences of hepatocellular and uterine neoplasms.
Nonneoplastic lesions of the liver were observed in male mice exposed to decahydronaphthalene.

Executive summary:

Groups of 50 male and 50 female B6C3F1 mice were exposed to 0, 25, 100, or 400 ppm decalin vapor 6 hours per day, 5 days per week for 105 weeks. Survival of exposed mice was similar to that of the chamber controls. Mean body weights of exposed groups were generally similar to those of the chamber control groups throughout the study. Increased incidences of hepatocellular neoplasms occurred in 25 and 400 ppm female mice, and the incidences of centrilobular hypertrophy, necrosis, syncytial alteration, and erythrophagocytosis of the liver in 400 ppm males were significantly increased. The incidences of uterine stromal polyp and stromal polyp or stromal sarcoma (combined) occurred with positive trends in female mice.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

chronic

Species:

other: rat amd mouse

Quality of whole database:

Klimisch 1 (reliable without restrictions)

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

Method: other: Carcinogenicity test

GLP compliance:

no

Species:

mouse

Strain:

other: C3H/He

Sex:

not specified

Route of administration:

dermal

Duration of treatment / exposure:

50 weeks

Frequency of treatment:

3 times/week

Remarks:

Doses / Concentrations:
50 µL
Basis:
other: mixture (1:1) of decahydronaphthalene/dodecane

No. of animals per sex per dose:

50

Control animals:

no

Details on study design:

Post-exposure period: none

Relevance of carcinogenic effects / potential:

No carcinogenic effects noted upon dermal application.

Dose descriptor:

NOAEL

Effect level:

50 other: µL/animal/day

Based on:

other: 1:1 mixture of decahydronaphthalene: dodecane

Sex:

male/female

Basis for effect level:

other: No skin tumours were noted

Remarks on result:

other: Effect type: carcinogenicity

No tumours (benign or malignant) were found in any test substance preparation (up to 0.02% benzo[a]pyrene in  decahydronaphthalene). 

"Positive" control: application of 0.02 %  benzo[a]pyrene in decahydronaphthalene caused a tumour incidence of 50 %   (5 malignant, 1 benign); mortality: 8/20.

Conclusions:

Decahydronaphthlene did not induce tumors in mice following dermal application for 50 weeks.

Executive summary:

In a study on the carcinogenicty of benzo-a-pyrene in groups of 20 -30 mice upon dermal application decahydronaphthalene was used as solvent and applied at 50 µL three times a week for 50 weeks.

Groups of mice were treated topically with decahydronaphthalene containing different concentrations of benzo-a-pyrene. No tumours were noted up to 0.02% benzo-a-pyrene.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

chronic

Species:

mouse

Quality of whole database:

Klimisch 2 (reliable with restrictions)

Justification for classification or non-classification

No increase of neoplasm in male mice and female rats was noted. Effects noted in male rats are considered species and sex specific and are not relevant for humans.

Some minor increases of neoplastic effects in liver and uterus of female mice could not unequivocally attributed to decahydronaphthalene with the data available.

Therefore, no classification regarding carcinogenicity is required according to CLP Regulation 1272/2008.