Chromium (III) oxide

Carcinogenicity

Description of key information

A number of published carcinogenicity studies have been performed with chromium (III) oxide. Studies are largely non-standard, use different routes of administration but are consistently negative. Similarly, a number of studies performed using other chromium (III) compounds are consistently negative.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-07-29 to 2004-08-02

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published peer reviewed study, conducted by the NTP.

Remarks:

Minor restrictions: haematology, clinical biochemistry and urinalysis missing (not mandatory), histopathology was not performed on the following organs/tissues: aorta, caecum, cervix, colon, lacrimal gland (exorbital), peripheral nerve, rectum, skeletal muscle, spinal cord, vagina. Homogeneity studies were not performed with all dose formulations (highest dose formulation only). Raw data are not available for all reported endpoints.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

Principles of method if other than guideline:

Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 0, 2000, 10000 or 50000 ppm chromium picolinate monohydrate for 105 weeks. Mice were approx. 5 to 6 weeks old at the beginning of the study and housed individually (males) or in groups of three (females) per cage. Feed consumption was measured weekly for the first 13 weeks of the study and approx. montly thereafter. The following parameters were investigated/recorded: clinical signs, survival, body weight, food consumption, necrospy with microscopic examination and complete histopathology.

GLP compliance:

yes

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: to ensure stability, the bulk chemical was stored at room temperature, protected from light, in sealed plastic buckets

The bulk material was analysed for stability using ICP-AES and HPLC-UV. The results indicated the stability of chromium picolinate monohydrate as a bulk chemical for at least 2 weeks when stored in sealed amber glass containers at temperature up to 60°C. Periodic reanalyses of the bulk chemical were performed during the 2-year study using HPLC-UV, and no degradation of the bulk chemical was detected.

Species:

mouse

Strain:

B6C3F1

Details on species / strain selection:

not applicable

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms, Inc. (Germantown, NY)
- Age at study initiation: 5 to 6 weeks
- Weight at study initiation: mean body weight in g at study day 1
0 ppm group: 20.3 (males); 16.6 (females)
2000 ppm group: 20.5 (males); 16.6 (females)
10000 ppm group: 20.4 (males); 16.6 (females)
50000 ppm group: 20.5 (males); 16.5 (females)
- Housing: mice were housed individually (males) or in groups of five (females) per cage in polycarbonate cages (Lab Products, Inc., Maywood, NJ, changed weekyl (males) twice weekly (females)), bedding material: Irradiated, heat-treated hardwood bedding chips (P.J. Murphy Forest Products, Inc., Montville, NJ, changed weekly (males) or twice weekly (females)), Rack filters: Reemay spun-bonded polyester (Andico, Birmingham, AL, changed once every 2 weeks), Racks: stainless steel (Lab Products, Maywood, NJ, changed once every two weeks)
- Diet (ad libitum): Irradiated NTP-2000 open formula meal diet (Zeigler Brothers, Inc., Gardners, PA)
- Water (ad libitum): tap water (Brimingham, AL, municipal supply) via automatic watering system (Edstrom Industries, Waterford, WI)
- Acclimation period: 12 days

Mice were quarantined for 12 days before the beginning of the studies. Five male and five female mice were randomly selected for parasite evaluation and gross observation of disease.

ENVIRONMENTAL CONDITIONS
- Temperature: 72° ± 3° F
- Humidity: 50% ± 15%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: To: 2002-07-29 to 2004-08-02

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

DIET PREPARATION
A premix of feed and chromium picolinate monohydrate was prepared, then layered into the remaining feed and blended in a Patterson-Kelly twin-shell blender for 30 minutes using an intensifier bar (until June 16, 2003). Later dose formulations were mixed for only 15 minutes with the intensifier bar on.
- Rate of preparation of diet (frequency): monthly
- Storage temperature/time of food: formulations were stored in sealed double-thick plastic bags, protected from light at 5°C for up to 42 days (maximum storage time)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Periodic analyses of the dose formulations of chromium picolinate monohydrate were conducted by the study laboratory using HPLC-UV. During the 2-year study, the dose formulations were analyzed approx. every 12 weeks. Of the dose formulations analyzed, all 167 were within 10% of the target concentrations, all 12 animal room samples were within 10% of the target concentrations.

Homogeneity studies of 50000 ppm dose formulations were performed by the analytical chemistry using ICP-AES. Additional homogeneity studies of 50000 ppm dose formulation were performed using HPLC-UV. Homogeneity was confirmed.

Duration of treatment / exposure:

105 weeks

Frequency of treatment:

daily, ad libitum

Post exposure period:

not applicable

Dose / conc.:

0 ppm (nominal)

Remarks:

actually ingested: males and females: 0 mg/kg bw/day

Dose / conc.:

2 000 ppm (nominal)

Remarks:

actually ingested: males approx. 250 mg/kg bw/day; females: approx. 240 mg/kg bw/day

Dose / conc.:

10 000 ppm (nominal)

Remarks:

acutally ingested: males and females approx. 1200 mg/kg bw/day

Dose / conc.:

50 000 ppm (nominal)

Remarks:

actually ingested: males: approx. 6565 mg/kg bw/day; females: approx. 6100 mg/kg bw/day

No. of animals per sex per dose:

50 males/ 50 females

Control animals:

yes, plain diet

Positive control:

not applicable

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes (core study animals)
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes (core study animals)
- Time schedule for examinations: animals were weighed initially, weekly for 13 weeks, monthly thereafter and at the end of the study

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: Yes, feed consumption was recorded weekly for 13 weeks, monthly thereafter
- Compound intake calculated: Yes

FOOD EFFICIENCY: no data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS Necropsy: Yes
Gross necropsies were performed on all animals.


HISTOPATHOLOGY: Yes
Complete histopathology was performed on all animals. In addition to gross lesions and tissue masses, the following tissues were examined: adrenal gland, bone with marrow, brain, clitoral gland, esophagus, eyes, harderian gland, heart, large intestine (cecum, colon, rectum), small intestine (duodenum, jejunum, ileum), kidney, liver, lung, lymph nodes (mandibular and mesenteric), 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.

Statistics:

Survival analyses: Kaplan-Meier surivival curves, means, life table trend test, & life table pairwise comparisons. P values were two-sided.
Neoplasm and nonneoplastic lesions: Poly-k test, continuity-corrected Poly-3 test. P values were one-sided.
Body weight data: parametric multiple comparison procedures of Dunnett (1955) and Williams (1971, 1972).

Jonckheere’s test was used to assess the significance of the dose-related trends and to determine whether a trend-sensitive test (Williams’ or Shirley’s test) was more appropriate for pairwise comparisons than a test that does not assume a monotonic dose-related trend (Dunnett’s or Dunn’s test). Prior to statistical analysis, extreme values identified by the outlier test of Dixon and Massey (1957) were examined, and implausible values were eliminated from the analysis. Because vaginal cytology data are proportions, an arcsine transformation was used to bring the data into closer conformance with a normality assumption. Treatment effects were investigated by applying a multivariate analysis of variance (Morrison, 1976) to the transformed data to test for simultaneous equality of measurements across exposure concentrations. Proportions of regular cycling females in each exposed group were compared to the control group using the Fisher exact test. Tests for extended periods of estrus and diestrus were constructed based on a Markov chain model proposed by Girard and Sager (1987). For each exposure group, a transition probability matrix was estimated for transitions among the proestrus, estrus, metestrus, and diestrus stages, with provision for extended stays within estrus and diestrus. Equality of transition matrices among exposure groups and between the control group and each exposed group was tested using chi-square statistics.

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Please refer to attached background material below

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

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

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

not specified

Details on results:

MORTALITY:
Survival of exposed groups of males (0 ppm, 46/50; 2000 ppm, 43/50; 10,000 ppm, 38/50; 50,000 ppm, 45/50) and females (0 ppm, 45/50; 2000 ppm, 44/50; 10,000 ppm, 44/50; 50,000 ppm, 39/50) was similar to that of the control groups (see attached background material).

BODY WEIGHT:
Mean body weights of exposed groups of males were generally similar to those of the controls throughout the study. In females, decreases in mean body weights of up to 10% compared to controls were observed during the middle of the study in exposed animals; however, mean body weights recovered to control values by the end of the study.

FEED CONSUMPTION:
Feed consumption by exposed groups of males and females was similar to that by the controls throughout the study.

CLINICAL FINDINGS:
No clinical findings were attributed to chromium picolinate monohydrate exposure

NECROPSY:
No clinical findings or neoplastic or non-neoplastic lesions were attributed to chromoium picolinate monohydrate exposure.

Liver: In males, the incidences of hepatoblastoma occurred with a positive trend (P#0.05) (0 ppm, 0/50; 2,000 ppm, 1/50; 10,000 ppm, 0/50; 50,000 ppm, 3/50. Hepatoblastoma is considered a variant of hepatocellular carcinoma. The incidences of hepatocellular adenoma (21/50, 22/50, 21/50, 22/50), hepatocellular carcinoma (15/50, 18/50, 20/50, 16/50), and hepatocellular adenoma, hepatocellular carcinoma, or hepatoblastoma (combined) (32/50, 32/50, 33/50, 33/50) were similar between control and exposed males. Because of the lack of an increase in the incidences of all these neoplasms combined and the low incidences of hepatoblastoma in exposed animals, the incidences of hepatoblastoma were not considered to be related to chromium picolinate monohydrate exposure. There were no treatment-related effects in females.

Lung: In males, the incidences of alveolar/bronchiolar carcinoma occurred with a positive trend (P#0.05) (3/50, 2/50, 5/50, 8/50; Table C2). The incidences of alveolar/bronchiolar adenoma (13/50, 10/50, 7/50, 8/50) and alveolar/bronchiolar adenoma or carcinoma (combined) (16/50, 12/50, 12/50, 12/50) were decreased in exposed males. Because of the decreases in alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined), the increased incidences of alveolar/bronchiolar carcinoma were not considered related to chromium picolinate monohydrate exposure. There were no treatment-related effects in females.

ADDITIONAL RESULTS:
As part of the 2-year studies, total chromium content in excreta and selected tissues was determined in additional groups of male rats and female mice following 4, 11 or 180 days of exposure and a two day washout. These data will be reported in detail elsewhere; however, the primary findings of the tissue concentration studies aid in the interpretation of the bioassay results and will be discussed briefly here. Accumulation of total chromium with exposure concentration and duration was observed in the liver and kidney of rats and mice, suggesting that Cr(III) is taken up by these tissues; this pattern was less apparent in erythrocytes, forestomach, and glandular stomach. In both rats and mice, chromium tissue concentrations were generally not proportional to exposure concentration. As a result, tissue chromium concentrations in animals exposed to 50,000 ppm chromium picolinate monohydrate were similar to those in animals exposed to lower concentrations. These data suggest that the maximum achievable tissue chromium concentrations were reached in these studies and may offer a partial explanation for the lack of a higher preputial gland neoplasm incidence in male rats exposed to 50,000 ppm than was observed at 10,000 ppm.

Relevance of carcinogenic effects / potential:

Chromium picolinate monohydrate was not carcinogenic to male and female mice.

Key result

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Remarks:

absence of toxic effects in the highest dose tested

Critical effects observed:

not specified

Conclusions:

Chromium picolinate monohydrate was fed to male and female B6C3F1 mice in the diet for 2 years, in order to investigate the potential for chromium picolinate monohydrate to induce chronic toxicity and carcinogenicity. Concentrations of 0, 2000, 10000 or 50000 ppm were fed to groups of 50 male and female mice for 2 years. Exposure to chromium picolinate monohydrate did not induce biologically significant changes in survival, body weight, feed consumption, or non-neoplastic lesions in rats. Chromium picolinate monohydrate was not carcinogenic to male and female mice.

Since no biologically relevant toxic effects in any of the endpoints and no carcinogenic activity could be observed, the NOAEL for chromium picolinate monohydrate for male and female mice is greater than 50000 ppm, which is equivalent to 6565 mg/kg bw in males and 6100 mg/kg bw in females. Considering the chromium content of 11.9 % in chromium picolinate monohydrate, the calculated NOAEL for chromium is 781 mg Cr/kg bw for males and 726 mg Cr/kg bw for females.

Reference 2

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-08-12 to 2004-08-17

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Published peer reviewed study, conducted by the NTP.

Remarks:

Minor restrictions: haematology, clinical biochemistry and urinalysis missing (not mandatory), histopathology was not performed on the following organs/tissues: aorta, caecum, cervix, colon, lacrimal gland (exorbital), peripheral nerve, rectum, skeletal muscle, spinal cord, vagina. Homogeneity studies were not performed with all dose formulations (highest dose formulation only). Raw data are not available for all reported endpoints.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

Principles of method if other than guideline:

Groups of 50 male and 50 female F344/N rats were fed diets containing 0, 2000, 10000 or 50000 ppm chromium picolinate monohydrate for 105 weeks. rats were approx. 5 to 6 weeks old at the beginning of the study and housed in groups of three to five per cage. feed consumption was measured weekly for the first 13 weeks of the study and approx. montly thereafter. The following parameters were investigated/recorded: clinical signs, survival, body weight, food consumption, necrospy with microscopic examination and complete histopathology.

GLP compliance:

yes

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: to ensure stability, the bulk chemical was stored at room temperature, protected from light, in sealed plastic buckets

The bulk material was analysed for stability using ICP-AES and HPLC-UV. The results indicated the stability of chromium picolinate monohydrate as a bulk chemical for at least 2 weeks when stored in sealed amber glass containers at temperature up to 60°C. Periodic reanalyses of the bulk chemical were performed during the 2-year study using HPLC-UV, and no degradation of the bulk chemical was detected.

Species:

rat

Strain:

other: F344/N

Details on species / strain selection:

not applicable

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms, Inc. (Germantown, NY)
- Age at study initiation: 5 to 6 weeks
- Weight at study initiation: mean body weight in g at study day 1
0 ppm group: 114 (males); 95 (females)
2000 ppm group: 114 (males); 95 (females)
10000 ppm group: 113 (males); 95 (females)
50000 ppm group: 113 (males); 96 (females)
- Housing: rats were housed three (males) or five (females) per cage in polycarbonate cages (Lab Products, Inc., Maywood, NJ, changed twice weekly), bedding material: Irradiated, heat-treated hardwood bedding chips (P.J. Murphy Forest Products, Inc., Montville, NJ, changed twice weekly), Rack filters: Reemay spun-bonded polyester (Andico, Birmingham, AL, changed once every 2 weeks), Racks: stainless steel (Lab Products, Maywood, NJ, changed once every two weeks)
- Diet (ad libitum): Irradiated NTP-2000 open formula meal diet (Zeigler Brothers, Inc., Gardners, PA)
- Water (ad libitum): tap water (Brimingham, AL, municipal supply) via automatic watering system (Edstrom Industries, Waterford, WI)
- Acclimation period: 12 days

Rats were quarantined for 12 days before the beginning of the studies. Five male and five female rats were randomly selected for parasite evaluation and gross observation of disease.

ENVIRONMENTAL CONDITIONS
- Temperature: 72° ± 3° F
- Humidity: 50% ± 15%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: To: 2002-08-12 to 2004-08-17

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

DIET PREPARATION
A premix of feed and chromium picolinate monohydrate was prepared, then layered into the remaining feed and blended in a Patterson-Kelly twin-shell blender for 30 minutes using an intensifier bar (until June 16, 2003). Later dose formulations were mixed for only 15 minutes with the intensifier bar on.
- Rate of preparation of diet (frequency): monthly
- Storage temperature/time of food: formulations were stored in sealed double-thick plastic bags, protected from light at 5°C for up to 42 days (maximum storage time)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Periodic analyses of the dose formulations of chromium picolinate monohydrate were conducted by the study laboratory using HPLC-UV. During the 2-year study, the dose formulations were analyzed approx. every 12 weeks. Of the dose formulations analyzed, all 167 were within 10% of the target concentrations, all 12 animal room samples were within 10% of the target concentrations.

Homogeneity studies of 50000 ppm dose formulations were performed by the analytical chemistry using ICP-AES. Additional homogeneity studies of 50000 ppm dose formulation were performed using HPLC-UV. Homogeneity was confirmed.

Duration of treatment / exposure:

105 weeks

Frequency of treatment:

daily, ad libitum

Post exposure period:

not applicable

Dose / conc.:

0 ppm (nominal)

Remarks:

actually ingested: males and females: 0 mg/kg bw/day

Dose / conc.:

2 000 ppm (nominal)

Remarks:

actually ingested: males approx. 90 mg/kg bw/day; females: approx. 100 mg/kg bw/day

Dose / conc.:

10 000 ppm (nominal)

Remarks:

acutally ingested: males approx. 460 mg/kg bw/day; females: approx. 510 mg/kg bw/day

Dose / conc.:

50 000 ppm (nominal)

Remarks:

actually ingested: males: approx. 2400 mg/kg bw/day; females: approx. 2630 mg/kg bw/day

No. of animals per sex per dose:

50 males/ 50 females

Control animals:

yes, plain diet

Positive control:

not applicable

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes (core study animals)
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes (core study animals)
- Time schedule for examinations: animals were weighed initially, weekly for 13 weeks, monthly thereafter and at the end of the study

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: Yes, feed consumption was recorded weekly for 13 weeks, monthly thereafter
- Compound intake calculated: Yes

FOOD EFFICIENCY: no data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS Necropsy: Yes
Gross necropsies were performed on all animals.


HISTOPATHOLOGY: Yes
Complete histopathology was performed on all animals. In addition to gross lesions and tissue masses, the following tissues were examined: adrenal gland, bone with marrow, brain, clitoral gland, esophagus, eyes, harderian gland, heart, large intestine (cecum, colon, rectum), small intestine (duodenum, jejunum, ileum), kidney, liver, lung, lymph nodes (mandibular and mesenteric), 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.

Statistics:

Survival analyses: Kaplan-Meier surivival curves, means, life table trend test, & life table pairwise comparisons. P values were two-sided.
Neoplasm and nonneoplastic lesions: Poly-k test, continuity-corrected Poly-3 test. P values were one-sided.
Body weight data: parametric multiple comparison procedures of Dunnett (1955) and Williams (1971, 1972).

Jonckheere’s test was used to assess the significance of the dose-related trends and to determine whether a trend-sensitive test (Williams’ or Shirley’s test) was more appropriate for pairwise comparisons than a test that does not assume a monotonic dose-related trend (Dunnett’s or Dunn’s test). Prior to statistical analysis, extreme values identified by the outlier test of Dixon and Massey (1957) were examined, and implausible values were eliminated from the analysis. Treatment effects were investigated by applying a multivariate analysis of variance (Morrison, 1976) to the transformed data to test for simultaneous equality of measurements across exposure concentrations. Equality of transition matrices among exposure groups and between the control group and each exposed group was tested using chi-square statistics.

Clinical signs:

no effects observed

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Please refer to attached background material below

Although there was a significant trend for decreases in survival in male rats, the decreases were not significant at any exposure concentration and were not considered related to chromium picolinate monohydrate exposure.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

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

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

effects observed, treatment-related

Description (incidence and severity):

For incidences of neoplasms and nonneoplastic lesions ot the preputial gland in male rats and clitorial gland in female rats please refer to attached background material below

The incidence of preputial gland adenoma was significantly increased in 10000 ppm males compared to that in the control group and exceeded the historical control ranges for feed studies and for all routes combined. The incidence of clitorial gland adenoma was significantly decreased in 2000 ppm females. There was no incidence of preputial gland or clitorial gland carcinoma. There were no differences in the incidences of prepeutial gland hyperplasia or clitorial gland hyperplasia between exposed and control groups of rats.
Preputial gland hyperplasia was focal, characterized either by an increase in stratified squamous epithelium of the ducts or by increased numbers of sebaceous cells and possibly basal cells. Preputial gland adenomas were well-circumscribed masses that grew by expansion with compression of the surrounding parenchyma. The neoplastic glands retained some resemblance of acinar structure, although there was some fusion of the acini to form solid clusters of cells (Copeland-Haines and Eustis, 1990)*.
The female counterpart gland of the preputial gland in males is the clitoral gland. Proliferative lesions of the preputial and clitoral gland comprise a morphological continuum, and separation of these into categories of hyperplasia, adenoma, and carcinoma is based largely on cytological features and degree of altered growth pattern. Lesions classified as hyperplasia are considered to be preneoplastic (Copeland-Haines and Eustis, 1990)*.

Although the increase in the incidence of preputial gland adenoma at 10,000 ppm appeared to be treatment-related, this increase was considered to be equivocal evidence of carcinogenic activity because of the lack of an exposure concentration-response, absence of increased incidences in neoplasms in the corresponding tissue in females, lack of progression to carcinoma, and lack of preneoplastic lesions.


References:
*Copeland-Haines, D., and Eustis, S.L. (1990). Specialized sebaceous glands. In Pathology of the Fischer Rat. Reference and Atlas (G.A. Boorman, S.L. Eustis, M.R. Elwell, C.A. Montgomery, Jr., and W.F. MacKenzie, Eds.), pp. 279–293. Academic Press, Inc., San Diego.

Other effects:

not specified

Details on results:

BODY WEIGHT:
Mean body weights of exposed groups of males and females were similar to those of the controls throughout the study

FEED CONSUMPTION:
Feed consumption by exposed groups of males and females was generally similar to that of the controls throughout the study

CLINICAL FINDINGS:
No clinical findings were attributed to chromium picolinate monohydrate exposure

ADDITIONAL RESULTS:
As part of the 2-year studies, total chromium content in excreta and selected tissues was determined in additional groups of male rats and female mice following 4, 11 or 180 days of exposure and a two day washout. These data will be reported in detail elsewhere; however, the primary findings of the tissue concentration studies aid in the interpretation of the bioassay results and will be discussed briefly here. Accumulation of total chromium with exposure concentration and duration was observed in the liver and kidney of rats and mice, suggesting that Cr(III) is taken up by these tissues; this pattern was less apparent in erythrocytes, forestomach, and glandular stomach. In both rats and mice, chromium tissue concentrations were generally not proportional to exposure concentration. As a result, tissue chromium concentrations in animals exposed to 50,000 ppm chromium picolinate monohydrate were similar to those in animals exposed to lower concentrations. These data suggest that the maximum achievable tissue chromium concentrations were reached in these studies and may offer a partial explanation for the lack of a higher preputial gland neoplasm incidence in male rats exposed to 50,000 ppm than was observed at 10,000 ppm.

Relevance of carcinogenic effects / potential:

The increased incidence of preputial gland adenomas in male rats at 10000ppm was considered equivocal. Chromium picolinate monohydrate was not carcinogenic to female rats.

Key result

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Remarks:

absence of toxic effects in the highest dose tested

Critical effects observed:

not specified

Conclusions:

Chromium picolinate monohydrate was fed to male and female F344/N rats in the diet for 2 years, in order to investigate the potential for chromium picolinate monohydrate to induce chronic toxicity and carcinogenicity. Concentrations of 0, 2000, 10000 or 50000 ppm were fed to groups of 50 male and female rats for 2 years. Exposure to chromium picolinate monohydrate did not induce biologically significant changes in survival, body weight, feed consumption, or non-neoplastic lesions in rats.
Exposure of male rats to chromium picolinate monohydrate for 2 years resulted in a significantly increased incidence of preputial gland adenoma over the control group at the mid dose; this incidence exceeded the historical control ranges for feed studies and for all routes of exposure. This increase appeared to be treatment-related; however, because of the lack of an exposure concentration response, the lack of progression to carcinoma, the lack of preneoplastic lesions, including hyperplasia, and the lack of a neoplastic response in the clitoral gland in females, this increase was considered to be equivocal evidence of carcinogenic activity in male rats. In female rats exposed to chromium picolinate monohydrate, there was no evidence of carcinogenic activity.
The assumption that the increase in preputial gland adenomas in male rats is considered to be equivocal is supported by the fact that a 2-year feeding study in mice, conducted at the same time and by the same laboratory, did not show any increase in adenomas or carcinomas in any tissue or organ.
Further, there is an ongoing debate about whether humans have functional homologues to preputial glands. This gland is located in the folds of skin front of the genitals of some mammals. They occur in several species, including mice, ferrets, rhinoceroses and even-toed ungulates and produce pheromones. They play a role in the urine-marking behaviour of canids. Since no functional homologues are known so far, the relevance of this finding is a matter of debate.

Since no biologically relevant toxic effects in any of the endpoints and no carcinogenic activity could be observed, the NOAEL for chromium picolinate monohydrate for male and female rats is greater than 50000 ppm, which is equivalent to 2400 mg/kg bw in males and 2630 mg/kg bw in females. Considering the chromium content of 11.9 % in chromium picolinate monohydrate, the calculated NOAEL for chromium is 286 mg Cr/kg bw for males and 313 mg Cr/kg bw for females.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

Study duration:

chronic

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The results of the available studies do not trigger a classification according to Directive 67/548/EEC and according to CLP Regulation (EC) No. 1272/2008.

 

Additional information

Studies with chromium (III) oxide

No effects of treatment were seen in a 2 -year dietary study performed at levels of up to 5% chromium (III) oxide, equivalent to approximately 2000 mg/kg bw/d (Ivankovic & Preussmann, 1975). No evidence of carcinogenicity was seen in two inhalation studies performed in the rat (Hueper & Payne, 1961) and mouse (Nettesheim et al, 1970) although both studies have deficiencies in design and reporting. Some evidence of local inflammation of the respiratory tract was seen in the rat study. No evidence of carcinogenicity was seen in two studies using intratracheal or intrabronchial implantation (Levy & Venitt, 1986; Laskin et al, 1970). A poorly reported study (Dvizhkov & Fedorova, 1975) indicates local tumorigenicity follwoing administration of chromium (III) oxide by intratracheal, pleural interstitial or intraperitoneal administration.

 

Studies with other compounds

A number of (largely non-standard) studies performed with chromite ore, chromium acetate, chromium chloride and basic chromium sulphate have been performed. These studies and the chromium (III) oxide studies have been reviewed by the UK HSE (1989) and Finnish IOH (2006). Both of these reviews conclude that chromium (III) is not carcinogenic.

 

Chromium picolinate monohydrate was fed to male and female F344/N rats and B6C3F1 mice in the diet for 2 years, in order to investigate the potential for chromium picolinate monohydrate to induce chronic toxicity and carcinogenicity. Concentrations of 0, 2000, 10000 or 50000 ppm were fed to groups of 50 male and female animals for 2 years. Exposure to chromium picolinate monohydrate did not induce biologically significant changes in survival, body weight, feed consumption, or non-neoplastic lesions in rats.

Exposure of male rats to chromium picolinate monohydrate for 2 years resulted in a significantly increased incidence of preputial gland adenoma over the control group at the mid dose; this incidence exceeded the historical control ranges for feed studies and for all routes of exposure. This increase appeared to be treatment-related; however, because of the lack of an exposure concentration response, the lack of progression to carcinoma, the lack of preneoplastic lesions, including hyperplasia, and the lack of a neoplastic response in the clitoral gland in females, this increase was considered to be equivocal evidence of carcinogenic activity in male rats. In female rats exposed to chromium picolinate monohydrate, there was no evidence of carcinogenic activity.

The assumption that the increase in preputial gland adenomas in male rats is considered to be equivocal is supported by the fact that a 2-year feeding study in mice, conducted at the same time and by the same laboratory, did not show any increase in adenomas or carcinomas in any tissue or organ.

Further, there is an ongoing debate about whether humans have functional homologues to preputial glands. This gland is located in the folds of skin front of the genitals of some mammals. They occur in several species, including mice, ferrets, rhinoceroses and even-toed ungulates and produce pheromones. They play a role in the urine-marking behaviour of canids. Since no functional homologues are known in humans, the relevance of this finding for humans is called into question.

Since no biologically relevant toxic effects in any of the endpoints and no carcinogenic activity could be observed, the NOAEL for chromium picolinate monohydrate for male and female rats is greater than 50000 ppm, which is equivalent to 2400 mg/kg bw in males and 2630 mg/kg bw in females. Considering the chromium content of 11.9 % in chromium picolinate monohydrate, the calculated NOAEL for chromium is 286 mg Cr/kg bw for males and 313 mg Cr/kg bw for females.

 

Epidemiological data

Occupational exposure to chromium (III) compounds in tanneries has not been associated with an excess risk of cancer. It is noted that both IARC and EPA have classified chromium (III) as Group C and Group D, respectively, that is, not classifiable as to carcinogenic potential.