Barium chromate

Carcinogenicity

Administrative data

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Test procedure in accordance with generally accepted scientific standard and described in sufficient detail.

Data source

Reference

Reference Type:

publication

Title:

Toxicology and Carcinogenesis Studies of Barium Chloride Dihydrate in F344/N rats and B6C3F mice

Author:

U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health

Year:

1994

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The toxicology study was conducted by administering barium chloride dihydrate (99% pure) in drinking water to F344/N rats for 2 years. Groups of 60 mlaes and 60 females received barium chloride dihydrate in the drinking water at concentrations of 0, 500, 1250, or 2500 ppm for 104 (males) or 105 weeks (females, corresponding to average daily doses of 15, 30, or 60 mg barium/kg body weight for males and 15, 45, or 75 mg barium/kg body weight for females.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

barium chloride dihydrate

IUPAC Name:

barium chloride dihydrate

Specific details on test material used for the study:

Name of test material (as cited in study report): Barium chloride dihydrate
EC number: 233-788-1
Physical state: white, crystalline solid
Analytical purity: > 99 %
Lot No.: 423103
Stability: The chemical should be stable over a wide range of temperatures.
Purity and water content: The purity and water content of the bulk chemical were reanalyzed every 4 months during the 2-year studies at the study laboratory by complexometric titration and weight loss on drying. The results indicated that the purity and moisture content of the barium chloride dihydrate did not change during the 2-year studies.
No further information on test material was stated.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Frederick Cancer Research Facility (Frederick, MD)
- Age at study initiation: 6 weeks
- Housing: five per cage; Cages: Polycarbonate (Lab Products, Inc., Rochelle Park, NJ), changed twice weekly; Bedding: BetaChips, hardwood laboratory bedding (Northeastern Products, Corp., Warrensburg, NY), changed twice weekly; Cage filters: Nonwoven polyester (Snow Filtration, Cincinnati, OH), changed once every 2 weeks; Racks: Stainless steel (Lab Products, Inc., Rochelle Park, NJ), changed once every 2 weeks; Cages were rotated every 2 weeks.
- Diet (ad libitum): NIH-07 open stock mash diet (Zeigler Brothers, Inc., Gardners, PA) The diet used contained less than 20 ppm barium.
- Water (ad libitum)
- Acclimation period: Rats were quarantined for 12 (males) or 14 (females) days before the beginning of the studies. Five rats of each sex were randomly selected and evaluated for evidence of disease. Serology samples were collected for viral screening. The health of the animals was monitored during the studies according to the NTP Sentinel Animal Program.

ENVIRONMENTAL CONDITIONS
- Temperature: 21°C - 23°C
- Relative humidity: 45%- 54%
- Air changes: 10/hour
- Photoperiod (hrs dark / hrs light): Fluorescent light: 12 hours/day
No further information on test animals was stated.

Administration / exposure

Route of administration:

oral: drinking water

Type of inhalation exposure (if applicable):

other: not applicable

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The dose formulations were prepared by mixing barium chloride dihydrate and water in a volumetric flask and stirring mechanically for 1 minute. Dose formulations were prepared weekly during the 2-year study
Stability studies of the 500 ppm dosed water solutions were performed using ultraviolet spectroscopy. Stability of the dose formulations was confirmed for at least 3 weeks when stored in the dark at 25 °C and for at least 3 days when stored exposed to air and light. No special handling was required during dosing.
No further information was stated on oral exposure.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Analyses of the dose formulations of barium chloride dihydrate were conducted at the study laboratory and the analytical chemistry laboratory using complexometric titration. During the 2-year studies, the dose formulations were analysed at least once every 8 weeks. The dose formulations were within 10 % of the target concentrations. Results of analyses performed by the analytical chemistry laboratory were in good agreement with the results obtained by the study laboratory.

Duration of treatment / exposure:

104 weeks (males)
105 weeks (females)

Frequency of treatment:

The distilled water containing the barium chloride dihydrate was available ad libitum (7 days per week).

Post exposure period:

none

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm

Remarks:

Basis:
nominal in water

Doses / concentrations 2

Dose / conc.:

500 ppm

Remarks:

Basis:
nominal in water

Doses / concentrations 3

Dose / conc.:

1 250 ppm

Remarks:

Basis:
nominal in water

Doses / concentrations 4

Dose / conc.:

2 500 ppm

Remarks:

Basis:
nominal in water

No. of animals per sex per dose:

60 males / 60 females

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale: Because of mortality, lower final mean body weights, decreased water consumption, and the presence of kidney lesions in male and female rats receiving 4,000 ppm in a 13 week study(subchronic study), the high dose selected for the 2-year study was 2,500 ppm.
No further information on study design was stated.

Positive control:

No data

Examinations

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Animals were observed twice daily. The clinical observations were recorded initially, weekly for 13 weeks, then monthly and at inerim evaluations. The interim evaluation was conducted with 10 males and 10 females per group after 15 months of chemical administration.

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Recorded initially, weekly for 13 weeks, then monthly and at interim evaluations. The interim evaluation was conducted with 10 males and 10 females per group after 15 months of chemical administration.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study):: Yes
- Time schedule for examinations: weekly

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Blood was collected from the jugular vein of all rats at the 15 month interim evaluations.
- How many animals: Ten male and 10 female rats per group were randomly selected for interim evaluations after 15 months of chemical administration.
- Parameters examined: hemoglobin, hematocrit, erythrocytes, mean erythrocyte volume, mean erythrocyte hemoglobin, mean erythrocyte hemoglobin concentration, platelets, reticulocytes, nucleated erythrocytes, and leukocyte count and differential

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Blood was collected from the jugular vein of all rats at the 15 month interim evaluations.
- How many animals: Ten male and 10 female rats per group were randomly selected for interim evaluations after 15 months of chemical administration.
- Parameters examined: urea nitrogen, creatinine, calcium. phosphorus, alanine aminotransferase, creatine kinase, lactate dehydrogenase, sorbitol dehydrogenase, and γ -glutamyltransferase

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data


OTHER: Plasma and Bone Analyses
At the 15-month interim evaluations, plasma from blood collected for clinical pathology was analyzed to determine plasma barium concentrations in rats. In addition, the left femur from eight male and eight female rats in the control and 2 ,500 ppm groups were analyzed for barium, calcium, and phosphorus concentrations, and bone density.

Sacrifice and pathology:

Complete necropsy performed on all animals. The animals were anestetised by carbon dioxide asphyxiation. The adrenal gland, brain, heart, right kidney, liver, lung, ovary, spleen, right testis, uterus and thymus of rats were weighed at the 15-month interim evaluations. At necropsy, all organs and ti ssues were examined for gross lesions, and all major tissues were fixed and preserved in 10% neutral buffered formalin, processed and trimmed, embedded in paraffin, sectioned and stained with hematoxylin and eosin for microscopic examination. A complete histopathologic examination was performed on all rats. In addition to gross lesions, tissue masses, and associated lymph nodes, the tissues examined included: adrenal gland, brain, bone and marrow, clitoral gland, large, intestine (cecum, colon, rectum), epididymis, esophagus, heart, kidney, liver, lung, mammary gland, mandibular lymph node, mesenteric lymph node, nose, ovary, pancreas, parathyroid gland, pituitary gland,preputial gland, prostate gland, salivary gland, seminal vesicle, skin, small intestine (duodenum, jejunum, ileum), spleen, stomach (forestomach and glandular), testis, thyroid gland, trachea, thymus, urinary bladder, and uterus.

Other examinations:

none

Statistics:

The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958) and is presented in the form of graphs. Statistical analyses for possible dose-related effects on survival used Cox’s (1972) method for testing groups for equality and Tarone (1975) life table test to identify dose-related trends. All reported P values for the survival analyses are two sided.

Analysis of continuous variables:
Two approaches were employed to assess the significance of pair wise comparisons between exposed and control groups in the analysis of continuous variables. Organ and body weight data, which have approximately normal distributions, were analyzed using the parametric multiple comparison procedures of Dunnett (1955) and Williams (1971, 1972). Clinical chemistry, hematology, neurobehavioral, and cardiovascular data, which have typically skewed distributions, were analyzed using the nonparametric multiple comparison methods of Dunn (1964) and Shirley (1977). Jonckheere’s test (Jonckheere, 1954) was used to assess the significance of the dose response trends and to determine whether a trend sensitive test (Williams’ or Shirley’s test) was more appropriate for pair wise comparisons than a test that does not assume a monotonic dose-response trend (Dunnett’s or Dunn’s test). Average severity values were analyzed for significance using the Mann- Whitney U test (Hollander and Wolfe, 1973).

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):

not specified

Food efficiency:

not specified

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

effects observed, treatment-related

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY (see attchment "survival")
Survival of exposed female groups was similar to that of the controls. The marginally increased survival of exposed male groups was probably due to a decreased incidence of leukemia.
There were no chemical-related clinical findings noted in male or female rats.

BODY WEIGHT AND WEIGHT GAIN
Mean body weights of male rats receiving 2,500 ppm were slightly lower than controls from week 18 to the end of the study. Female rats that received 2,500 ppm had mean body weights 5% to 11% lower than the controls beginning at week 49. The final mean body weights of males receiving 500 and 1,250 ppm and females receiving 500 ppm were similar to those of the controls. The final mean body weight of males that received 2,500 ppm was 5% lower than that of the controls. The final mean body weights of females receiving 1,250 and 2,500 ppm were 6% and 11 % lower than the controls, respectively.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study):
Barium chloride dihydrate in drinking water caused a dose-related decrease in water consumption. Average water consumption (g/day) over the 2-year period for males was: 0 ppm, 21.2; 500 ppm, 20.2; 1,250 ppm, 18.7; 2,500 ppm, 16.5; and over the 2-year period for females was: 16.2, 15.6, 14.9, and 12.1. The greatest effect on water consumption was observed in rats receiving 2,500 ppm. Beginning as early as week 5, water consumption by these groups was substantially depressed (males: 11% to 30%; females: 19% to 33%). Based on the water consumption data the average daily dose of barium chloride dihydrate received by rats was 15, 30 , or 60 mg barium& body weight for males, and 15, 45, or 75 mg barium kg body weight for females.

HAEMATOLOGY
Hematologic parameters measured at the 15-month interim evaluation were considered to be within the range of normal values.

CLINICAL CHEMISTRY
Clinical chemistry parameters measured at the 15-month interim evaluation were considered to be within the range of normal values.

ORGAN WEIGHTS (at the 15-month interim evaluation)
Significantly different from the control group were: heart and right kidney (males; 1,250 and 2,500 ppm); liver (females; 500, 1250 and 2500 ppm)

HISTOPATHOLOGY:NONNEOPLASTIC
At the end , there was no increased incidences of nonneoplastic lesions that could be related to test substance.

HISTOPATHOLOGY: NEOPLASTIC
There were no increased incidences of neoplasms in rats receiving barium chloride.
Multiple organs: Mononuclear cell leukemia was not observed in males at 15 months. However, at 2 years, there was a significant negative trend in the incidence of mononuclear cell leukemia in males and the incidences in exposed male groups were significantly decreased. The decreased incidence of this lethal neoplasm may account for the marginal increase in survival of exposed males. The incidences of mononuclear cell leukemia in exposed females were similar to that in the controls (0 ppm, 15/50; 500 ppm, 13/50; 1,250 ppm, 9/50; 2,500 ppm, 9/50). Neoplasms occured with a dose-related decrease incidence of adrenal medulla pheochromocytomas in males.
Mammary gland: A significant negative trend in the incidence of mammary gland neoplasms (fibro-adenoma, adenoma, or carcinoma) was observed in female rats (17/50, 21/50, 13/50, 11/50)

OTHER FINDINGS: Plasma and Bone Analyses
Plasma barium levels were significantly increased in males receiving 2,500 ppm and all exposed groups of females. The density of femoral bone in rats that received 2,500 ppm was similar to that of the controls. Barium levels in all portions of femoral bone were approximately 400 times greater in males and females receiving 2,500 ppm than in controls. Calcium levels in the upper portion of the femoral bone of male and female rats receiving 2,500 ppm were slightly but significantly lower than those of the controls. Phosphorus levels in exposed males and females were similar to those in the controls.

Relevance of carcinogenic effects / potential:

There was no evidence of carcinogenic activity (showing no chemical related increase of malignant or benign neoplasms) of barium chloride dihydrate in both sexes of rats that received 500, 1250, and 2500 ppm. Thus, the concentration of 2500 ppm represents a NOAEL (corresponding to Ba doses of 60 and 75 mg/kg bw/d to male and female rats, respectively). The NOAEL was derived by an toxicologist that reviewed the article

Effect levels

1

Dose descriptor:

NOAEL

Effect level:

2 500 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: see 'remarks'

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

2

Dose descriptor:

NOAEL

Effect level:

60 mg/kg bw/day (nominal)

Based on:

other: barium

Sex:

male

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

3

Dose descriptor:

NOAEL

Effect level:

75 mg/kg bw/day (nominal)

Based on:

other: barium

Sex:

female

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Applicant's summary and conclusion

Conclusions:

In rats, there was no treatment-related effect on survival. At the end of 2 years, there were no increased incidences of neoplasms or nonneoplastic lesions in rats that could be related to the test substance. However, there was dose-related decreased incidence of adrenal medulla pheochromocytoma and mononuclear cell leukemia in male rats.