Acetic acid, chromium salt, basic

Carcinogenicity

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

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

Adequacy of study:

key study

Study period:

August 12, 2002 - August 17, 2004

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-compliant study conducted according to internationally accepted guidelines

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

GLP compliance:

yes

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms, Inc. (Germantown, NY, USA)
- Age at study initiation: 5 to 6 weeks
- Weight at study initiation: 114 / 95 g (m/f)
- Housing: three (males) or five (females) per cage,
- Diet (e.g. ad libitum): Irradiated NTP-2000 open formula meal diet (Zeigler Brothers, Inc., Gardners, PA), available ad libitum, changed weekly
- Water (e.g. ad libitum): Tap water (Birmingham, AL, municipal supply) via automatic watering system, available ad libitum
- Acclimation period: 12 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22± 2
- Humidity (%): 50% ± 15%
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12


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

Route of administration:

oral: feed

Details on exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): max. storage time 42 days
- Storage temperature of food: Stored in sealed double-thick plastic bags, protected from light at 5° C.

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.
The dose formulations were analyzed approximately every 12 weeks. Of the dose formulations analyzed, all 167 for rats and all 99 for mice were within 10% of the target concentrations.

Duration of treatment / exposure:

2 years

Frequency of treatment:

ad libitum

Post exposure period:

none

Remarks:

Doses / Concentrations:
0, 2,000, 10,000, or 50,000 ppm
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
90, 460, and 2,400 mg/kg bw/day (males); 100, 510, and 2,630 mg/kg bw/day (females)
Basis:
actual ingested

No. of animals per sex per dose:

50

Control animals:

yes, plain diet

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed twice daily. Clinical findings were recorded monthly.

BODY WEIGHT: Yes
- Time schedule for examinations: Rats were weighed initially, weekly for the first 13 weeks, monthly thereafter, and at the end of the studies


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
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes


FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / No data

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER:

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
Necropsies were performed on all animals.

HISTOPATHOLOGY: Yes (see table)
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, gallbladder (mice only), 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
The probability of survival was estimated by the product-limit procedure of Kaplan and Meier (1958) All reported P values for the survival analyses are two sided.

Analysis of Neoplasm and Nonneoplastic Lesion Incidences
The Poly-k test (Bailer and Portier, 1988; Portier and Bailer, 1989; Piegorsch and Bailer, 1997) was used to assess neoplasm and nonneoplastic lesion prevalence.

Analysis of Continuous Variables
Two approaches were employed to assess the significance of pairwise comparisons between exposed and control
groups in the analysis of continuous variables. Organ and body weight data were analyzed with the parametric multiple comparison procedures of Dunnett (1955) and Williams (1971, 1972). Hematology, clinical chemistry, spermatid, and epididymal spermatozoal data, were analyzed using the nonparametric multiple comparison methods of Shirley (1977).
Jonckheere’s test (Jonckheere, 1954) 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).

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

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:

not examined

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

effects observed, treatment-related

Details on results:

HISTOPATHOLOGY: NEOPLASTIC (see Table 1)
The incidence of preputial gland adenoma was significantly increased in 10,000 ppm males compared to that in the control and exceeded the historical control ranges for feed studies and for all routes combined.
The incidence of clitoral gland adenoma was significantly decreased in 2,000 ppm females. There was no incidence of preputial gland or clitoral gland carcinoma.
There were no differences in the incidences of preputial gland hyperplasia or clitoral gland hyperplasia between exposed and control groups of rats.

Relevance of carcinogenic effects / potential:

In male rats in the 2-year study, there was an exposure-related significant increase in the incidence of preputial gland adenoma at 10,000 ppm; the incidence exceeded the historical control ranges for feed studies and for all routes of exposure. Proliferative lesions of the preputial and clitoral glands (the clitoral gland is the corresponding accessory sex gland in females) constitute 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 (Copeland-Haines and Eustis, 1990). Lesions classified as hyperplasia are considered 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. There were no biologically significant increases in the incidences of neoplasms in any other tissue in male rats, or in any tissue in female rats or male or female mice.

Table 1: 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
Hyperplasia ^a	3 (2.7)^b	1 (4.0)	0 2 (2.5)
Adenoma
Overall rate ^d	1/50 (2%)	1/50 (2%)	7/50 (14%)	4/50 (8%)
Adjusted rate ^e	2.2%	2.3%	14.9%	9.3%
Terminal rate ^f	0/37 (0%)	1/36 (3%)	5/35 (14%) 2	2/28 (7%)
First incidence (days)	653	729 (T)	528	582
Poly-3 test^g	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%	7.7%	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 a Number of animals with lesion b Average severity grade of lesions in affected animals: 1=minimal, 2=mild, 3=moderate, 4=marked c Historical 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% d Number of animals with neoplasm per number of animals with tissue examined microscopically e Poly-3 estimated neoplasm incidence after adjustment for intercurrent mortality f Observed incidence at terminal kill g Beneath 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 by N. h Historical incidence: 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.

Executive summary:

Male and female F344/N rats were exposed to chromium picolinate monohydrate (95% to 96% pure) in feed for 2 years.

Groups of 50 male and 50 female rats were fed diets containing 0, 2000, 10,000, or 50,000 ppm chromium picolinate monohydrate (equivalent to average daily doses of approximately 90, 460, and 2400 mg/kg to males and 100, 510, and 2630 mg/kg to females) for 105 weeks.

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 males exposed to 10,000 ppm and exceeded the historical control ranges.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The available data on carcinogenicity do not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and is therefore conclusive but not sufficient for classification.

Additional information

Two studies are available which investigated carcinogenicity of the source substance chromium picolinate monohydrate in rats and mice similar to OECD 451 and GLP (NTP, 2008). In male rats in the 2-year study, there was an exposure-related significant increase in the incidence of preputial gland adenoma at 10,000 ppm; the incidence exceeded the historical control ranges for feed studies and for all routes of exposure.

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 pre-neoplastic lesions. There were no biologically significant increases in the incidences of neoplasms in any other tissue in male rats, or in any tissue in female rats or male or female mice.

Since basic Cr(III) acetate is not genotoxic in vivo and the long-term studies in rodents have only revealed marginal and probably irrelevant neoplastic effects, there is no concern for carcinogenic activity by basic Cr(III) acetate.

Justification for selection of carcinogenicity via oral route endpoint:
Hazard assessment is conducted by means of read-across from a structural analogue/surrogate. The selected study is the most adequate and reliable study based on the identified similarities in structure and intrinsic properties between source and target substance and overall assessment of quality, duration and dose descriptor level (refer to the endpoint discussion for further details).