Chromium (III) hydroxide

Carcinogenicity

Description of key information

Review documents confirm absence of carcinogenic effects at high dose levels for a number of Chromium III salts.

It needs noting that Chromium III is an essential element found in food and natural water sources. It is readily eliminated from the body and does not accumulate.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

As with all inorganic salts, the significance for toxicity or environmental assessment is the presence of specific ions that will form when in solution or when in biological systems.In the case of Cr III salts, the counter ion will have an effect on solubility and this is itself dependant on the type of media being used and in particular the pH of that media. It is generally accepted that in the case of metal salts, testing with salts that are soluble in the respective test media will ensure maximum exposure of the metal ions. This will include chlorides and nitrates as being more soluble and will indeed have relevance when dissolved in acid media, such as if ingested.Read-across to other chromium III salts is therefore considered valid as long as the exposure in the test system is greater than wold be expected for the substance under review for registration

Principles of method if other than guideline:

Male and female F344/N rats and B6C3F1 mice were exposed to chromium picolinate monohydrate (95% to 96% pure) in feed for 3 months or 2 years. Genetic toxicology studies with chromium picolinate monohydrate were conducted in Salmonella typhimurium and mouse peripheral blood erythrocytes. Genetic toxicology studies with chromium picolinate were conducted in S. typhimurium and rat bone marrow cells.

GLP compliance:

yes

Remarks:

The 3-month and 2-year studies were conducted in compliance with Food and Drug Administration Good Laboratory Practice Regulations (21 CFR, Part 58).

Species:

other: rats and mice

Strain:

other: F344/N rats and B6C3F1 mice

Sex:

male/female

Details on test animals or test system and environmental conditions:

TABLE 1Experimental Design and Materials and Methods in the Feed Studies of Chromium Picolinate Monohydrate3-Month Studies 2-Year StudiesStudy LaboratorySouthern Research Institute (Birmingham, AL) Southern Research Institute (Birmingham, AL)Strain and SpeciesF344/N rats F344/N ratsB6C3F1 mice B6C3F1 miceAnimal SourceTaconic Farms, Inc. (Germantown, NY) Taconic Farms, Inc. (Germantown, NY)Time Held Before StudiesRats: 13 (males) or 14 (females) days 12 daysMice: 12 (males) or 11 (females) daysAverage Age When Studies Began5 to 6 weeks 5 to 6 weeks Date of First ExposureRats: October 16 (males) or 17 (females), 2001 Rats: August 12, 2002Mice: October 15 (males) or 14 (females), 2001 Mice: July 29, 2002Duration of ExposureCore studies: 14 weeks 105 weeksClinical pathology study: 3 weeks (rats)Date of Last ExposureCore studies: Rats: January 16 (males) or 17 (females), 2002 Rats: August 9-17, 2004Mice: January 15 (males) or 14 (females), 2002 Mice: July 26 to August 2, 2004Clinical pathology study:November 5 (males) or 6 (females), 2001Necropsy DatesRats: January 16 (males) or 17 (females), 2002 Rats: August 9-17, 2004Mice: January 15 (males) or 14 (females), 2002 Mice: July 26 to August 2, 2004Average Age at Necropsy18 to 20 weeks Rats: 109 to 111 weeks Mice: 110 to 112 weeks Size of Study GroupsCore studies: 10 males and 10 females 50 males and 50 femalesClinical pathology study: 10 male and 10 female ratsMethod of DistributionAnimals were distributed randomly into groups of approximately Same as 3-month studiesequal initial mean body weights.Animals per CageRats: 5 Rats: 3 (males) or 5 (females)Mice: 1 (males) or 5 (females) Mice: 1 (males) or 5 (females)Method of Animal IdentificationTail tattoo Tail tattooDietIrradiated NTP-2000 open formula meal diet (Zeigler Brothers, Inc., Same as 3-month studiesGardners, PA), available ad libitum, changed weeklyWaterTap water (Birmingham, AL, municipal supply) via automatic Same as 3-month studieswatering system (Edstrom Industries, Waterford, WI), availablead libitumCagesPolycarbonate (Lab Products, Inc., Maywood, NJ); changed weekly Same as 3-month studies(male mice) or twice weekly (rats and female mice)BeddingIrradiated, heat-treated hardwood bedding chips (P.J. Murphy Forest Same as 3-month studiesProducts, Inc., Montville, NJ); changed weekly (male mice) or twiceweeklyRack FiltersReemay® spun-bonded polyester (Andico, Birmingham, AL); Same as 3-month studiesRacksStainless steel (Lab Products, Maywood, NJ); changed once every Same as 3-month studies2 weeks Animal Room EnvironmentTemperature: 72° ± 3° F Temperature: 72° ± 3° FRelative humidity: 50% ± 15% Relative humidity: 50% ± 15%Room fluorescent light: 12 hours/day Room fluorescent light: 12 hours/dayRoom air changes: 10/hour Room air changes: 10/hour

Route of administration:

oral: feed

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The dose formulations were prepared by mixing chromium picolinate monohydrate with feed.Homogeneity studies of 82 and 50,000 ppm dose formulations and stability studies of the 82 ppm dose formulation were performed by the analytical chemistry laboratory using ICP-AES. Additional homogeneity studies of 80 and 50,000 ppm dose formulations were performed by the study laboratory using HPLC-UV. Homogeneity was confirmed, and the stability of the dose formulations was confirmed for at least 42 days at room temperature when stored in double-thick sealed plastic bags, protected from light.Periodic analyses of the dose formulations of chromium picolinate monohydrate were conducted by the study laboratory using HPLC-UV. For the 3-month studies, the dose formulations were analyzed at the beginning, midpoint, and end of the studies; all 35 dose formulations analyzed for rats and mice were within 10% of the target concentrations (Table I3). During the 2-year studies, the dose formulations were analyzed approximatelyevery 12 weeks (Table I4). Of the dose formulations analyzed, all 167 for rats and all 99 for mice were within 10% of the target concentrations.Samples of dosed feed taken from the animal rooms were analyzed periodically during the studies. During the 3-month studies, all 10 samples taken from the rat animal room and 8 of 10 samples from the mouse animal room were within 10% of target; all samples were within 13% of target. During the 2-year studies, all 12 samples from the rat animal room and 8 of 15 samples from the mouse animal room were within 10% of target; all sampleswere within at least 27% of target. Low results in the mouse samples were attributed to contamination by urine, feces, and bedding during the study period when animals were small enough to get into the feeders.

Duration of treatment / exposure:

Uo to 105 weeks

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations: 0, 80, 240, 2,000, 10,000, or 50,000 ppmBasis:nominal in diet

No. of animals per sex per dose:

3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 80, 240, 2,000, 10,000, or 50,000 ppm chromium picolinate monohydrate (equivalent to average daily doses of approximately 7, 20, 160, 800, and 4,240 mg chromium picolinate monohydrate/kg body weight to males and 6, 20, 160, 780, and 4,250 mg/kg to females) for 14 weeks.3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were fed diets containing 0, 80, 240, 2,000, 10,000, or 50,000 ppm chromium picolinate monohydrate (equivalent to average daily doses of approximately 17, 50, 450, 2,300, and 11,900 mg chromium picolinate monohydrate/kg body weight to males and 14, 40, 370, 1,775, and 9,140 mg/kg to females) for 14 weeks.2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 2,000, 10,000, or 50,000 ppm chromium picolinate monohydrate (equivalent to average daily doses of approximately 90, 460, and 2,400 mg/kg to males and 100, 510, and 2,630 mg/kg to females) for 105 weeks. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 2,000, 10,000, or 50,000 ppm chromium picolinate monohydrate (equivalent to average daily doses of approximately 250, 1,200, and 6,565 mg/kg to males and 240, 1,200, and 6,100 mg/kg to females) for 105 weeks.

Control animals:

yes, plain diet

Details on study design:

The concentrations of chromium picolinate in the feed selected for the 3-month studies (80, 240, 2,000, 10,000 and 50,000 ppm) were widely spaced to extend the exposure-response curve. The three highest exposure concentrations used in the 3-month studies (2,000, 10,000 and 50,000 ppm) were selected for testing in the 2-year studies because of the lack of chemical-related toxic effects at any exposure concentration in the 3-monthstudies. The highest exposure concentration of 50,000 ppm (5%) used in these studies is considered to be a limit dose in feed studies because higher concentrations would alter the nutritional content of the diet.

Observations and examinations performed and frequency:

3-Month Studies 2-Year StudiesType and Frequency of ObservationObserved twice daily; core study animals were weighed initially, Observed twice daily; animals were weighed and feed consumptionweekly, and at the end of the studies; clinical findings were recorded was recorded initially, weekly for 13 weeks, monthly thereafter, andweekly. Feed consumption by core study animals was recorded at the . Clinical findings were recorded monthly for core study animals. end of the studies weekly by cage.

Sacrifice and pathology:

3-Month Studies 2-Year StudiesMethod of SacrificeCarbon dioxide asphyxiation Same as 3 month studiesNecropsyNecropsies were performed on all core study animals. Organs Necropsies were performed on all animals.weighed were heart, right kidney, liver, lung, right testis, and thymus.Clinical PathologyBlood was collected from the retroorbital sinus of clinical pathology Nonerats on days 3 and 21 and from core study animals at the end of thestudies for hematology or clinical chemistry (rats only). Hematology: hematocrit; hemoglobin; erythrocyte, reticulocyte, andplatelet counts; nucleated erythrocytes; mean cell volume; mean cellhemoglobin; mean cell hemoglobin concentration; and leukocytecount and differentialsClinical chemistry: urea nitrogen, creatinine, total protein, albumin,alanine aminotransferase, alkaline phosphatase, creatine kinase,sorbitol dehydrogenase, and bile acidsHistopathologyComplete histopathology was performed on 0 and 50,000 ppm core Complete histopathology was performed on all animals. In additionstudy rats and mice. In addition to gross lesions and tissue masses, to gross lesions and tissue masses, the following tissues werethe following tissues were examined: adrenal gland, bone with examined: adrenal gland, bone with marrow, brain, clitoral gland,marrow, brain, clitoral gland, esophagus, eyes, gallbladder (mice esophagus, eyes, gallbladder (mice only), harderian gland, heart,only), harderian gland, heart, large intestine (cecum, colon, rectum), large intestine (cecum, colon, rectum), small intestine (duodenum,small intestine (duodenum, jejunum, ileum), kidney, liver, lung, jejunum, ileum), kidney, liver, lung, lymph nodes (mandibular andlymph nodes (mandibular and mesenteric), mammary gland, nose, mesenteric), mammary gland, nose, ovary, pancreas, parathyroidovary, pancreas, parathyroid gland, pituitary gland, preputial gland, gland, pituitary gland, preputial gland, prostate gland, salivary gland,prostate gland, salivary gland, skin, spleen, stomach (forestomach skin, spleen, stomach (forestomach and glandular), testis withand glandular), testis with epididymis and seminal vesicle, thymus, epididymis and seminal vesicle, thymus, thyroid gland, trachea,thyroid gland, trachea, urinary bladder, and uterus. urinary bladder, and uterus.Sperm Motility and Vaginal CytologyAt the end of the studies, sperm samples were collected from male Noneanimals in the 0, 2,000, 10,000, and 50,000 ppm groups for spermmotility evaluations. The following parameters were evaluated:spermatid heads per testis and per gram testis, and epididymalspermatozoal motility and concentrations. The left cauda, leftepididymis, and left testis were weighed. Vaginal samples werecollected for up to 12 consecutive days prior to the end of the studiesfrom females exposed to 0, 2,000, 10,000, or 50,000 ppm for vaginalcytology evaluations. The percentage of time spent in the variousestrous cycle stages and estrous cycle length were evaluated.

Statistics:

The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958) Statistical analyses for possible dose-related effects on survival used Cox’s (1972) method for testing two groups for equality and Tarone’s (1975) life table test to identify dose-related trends.The Poly-k test was used to assess neoplasm and nonneoplastic lesion prevalence.

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):

no effects observed

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

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:

effects observed, treatment-related

Details on results:

3-MONTH STUDY IN RATS: All rats survived to the end of the study. Mean body weights and feed consumption of all exposed groups of males and females were similar to those of the control groups throughout the study. No exposure-related lesions occurred in males or females.3-MONTH STUDY IN MICE: All mice survived to the end of the study. Mean body weights and feed consumption of all exposed groups were similar to those of the control groups throughout the study. No exposure-related lesions occurred in male or female mice.2-YEAR STUDY IN RATS: Survival of all exposed groups of males and females was similar to that of the control groups. Mean body weights and feed consumption of exposed groups of males and females were generally similar to those of the controls throughout the study. The incidence of preputial gland adenoma was significantly increased in 10,000 ppm males compared to that in the control group and exceeded the historical control ranges for feed studies and for all routes combined. There was no incidence of preputial gland carcinoma. There were no differences in the incidence of preputial gland hyperplasia between exposed and control groups of rats. Preputial gland hyperplasia was focal, characterizedeither 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. Proliferative lesions of thepreputial comprise a morphological continuum, and separation of these into categories of hyperplasia, adenoma, and carcinoma is based largely oncytological features and degree of altered growth pattern. Lesions classified as hyperplasia are considered to be preneoplastic.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. 2-YEAR STUDY IN MICE: Survival of all exposed groups of males and females was similar to that of the control groups. Mean body weights of exposed groups of males were generally similar to those of the controls throughout the study; mean body weights of 50,000 ppm females was 10% less than the control group at 1 year. Feed consumption by exposed groups of males and females was similar to that by the controls throughout the study. No neoplasms or nonneoplastic lesions were attributed to exposure to chromium picolinate monohydrate.

Key result

Dose descriptor:

NOEL

Remarks:

rats

Effect level:

50 000 ppm (nominal)

Sex:

female

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOEL

Remarks:

rats

Effect level:

2 000 ppm (nominal)

Sex:

male

Basis for effect level:

other: An increase in preputial gland ademonas was seen at the 10 000 ppm dose, however the effects were considered equivocal due to lack of a dose-response and lack of tumours in corresponding tissues in females.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

TABLE6

Incidences of Neoplasms and Nonneoplastic Lesions of the Preputial Gland in Male Rats

and Clitoral Gland in Female Rats in the 2-Year Feed Study of Chromium Picolinate Monohydrate

	0 ppm	2,000 ppm	10,000 ppm	50,000 ppm
Male
Number Examined Microscopically	50	50	50	50
Hyperplasiaa	3 (2.7)b	1 (4.0)	0	2 (2.5)
Adenomac
Overall rated	1/50 (2%)	1/50 (2%)	7/50 (14%)	4/50 (8%)
Adjusted ratee	2.2%	2.3%	14.9%	9.3%
Terminal ratef	0/37 (0%)	1/36 (3%)	5/35 (14%)	2/28 (7%)
First incidence (days)	653	729 (T)	528	582
Poly-3 testg	P=0.206	P=0.750	P=0.031	P=0.158
Female
Number Examined Microscopically	50	50	50	50
Hyperplasia	8 (2.4)	10 (2.6)	11 (2.6)	4 (2.3)
Adenoma, Bilateral	0	0	0	1
Adenoma (includes bilateral)h
Overall rate	10/50 (20%)	2/50 (4%)	8/50 (16%)	11/50 (22%)
Adjusted rate	21.9%	4.4%	17.7%	23.4%
Terminal rate	9/36 (25%)	1/35 (3%)	6/36 (17%)	11/40 (28%)
First incidence (days)	666	698	647	729 (T)
Poly-3 test	P=0.109	P=0.013N	P=0.405N	P=0.534

 

(T)Terminal sacrifice

aNumber of animals with lesion

bAverage severity grade of lesions in affected animals: 1=minimal, 2=mild, 3=moderate, 4=marked

cHistorical incidence for 2-year feed studies with controls given NTP-2000 diet (mean ± standard deviation):

8/250 (3.2% ± 4.2%), range 0%-10%; all routes: 43/1,193 (3.6% ± 3.5%), range 0%-10%

dNumber of animals with neoplasm per number of animals with tissue examined microscopically

ePoly-3 estimated neoplasm incidence after adjustment for intercurrent mortality

fObserved incidence at terminal kill

gBeneath the control incidence is the P value associated with the trend test. Beneath the exposed group incidences are the P values

corresponding to pairwise comparisons between the controls and that exposed group. The Poly-3 test accounts for differential mortality

in animals that do not reach terminal sacrifice. A lower incidence in an exposed group is indicated byN.

hHistorical incidence for feed studies: 26/200 (13.0% ± 6.2%), range 6%-20%; all routes: 104/1,096 (9.5% ± 8.6%), range 0%-34%

Conclusions:

Under the conditions of these 2-year feed studies there was equivocal evidence of carcinogenic activity* of chromium picolinate monohydrate in male F344/N rats based on an increase in the incidence of preputial gland adenoma. There was no evidence of carcinogenic activity of chromium picolinate monohydrate in female F344/N rats or in male or female B6C3F1 mice exposed to 2,000, 10,000, or 50,000 ppm.

Executive summary:

Feed containing 2,000, 10,000, or 50,000 parts per million (ppm) of chromium picolinate was given to groups of 50 male and female rats and mice for two years. Similar groups of animals were given feed with no chemical added and served as the control groups. At the end of the study, tissues from more than 40 sites were examined for every animal. Survival of all exposed groups of animals was similar to their controls. The rate of adenomas of the preputial gland was greater in male rats receiving 10,000 ppm chromium picolinate than in the control group. The study concluded that the occurence of preputial gland adenomas in one group of male rats was possibly associated with exposure to chromium picolinate. Chromium picolinate did not cause cancer in female rats or in male or female mice.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

chronic

Species:

rat

Quality of whole database:

Several studies reviewed in Concise International Chemical Assessment Document 76