Reaction mass of chromium (+ 3) hydroxide sulfate and sodium sulfate

Carcinogenicity

Description of key information

No evidence of respiratory tract carcinogenicity was seen in an implantation study using basic chromium sulphate (Levy and Venitt, 1986).

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

GLP compliance:

yes

Species:

other: Rat and Mouse

Strain:

other: F344/N rats and B6C3F1 mice

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female F344/N rats and B6C3F1 mice were obtained from Taconic Farms. They were quarantined for 12 days, and were approximately 5-6 weeks old at study initiation. Animals were distributed randomly into groups of approximately equal initial mean body weights and idenitified by tail tattoo. Male mice were housed singly, male rats were housed in groups of 3, female rats and mice were housed in groups of 5. The animal room was maintained at a temperature of 72±3°F, a relative humidity of 50±15%, a 12 hour light-dark cycle, and 10 air changes per hour. Irradiated NTP-2000 open formula meal diet (Zeigler Brothers, Inc.) was available ad libitum and changed weekly. Tap water was available ad libitum via automatic watering system.

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on exposure:

CPM was fed in the diet. The dose formulations were prepared monthly by mixing CPM with the feed. The formulations were stored at room temperature in double-thick sealed plastic bags, protected from light.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

HPLC with UV detection was used to analyse the diet preparations. Homogeneity of the high dose formulation was confirmed. The stability of this formulation was confirmed for at least 42 days at room temperature when stored in double-thick sealed plastic bags, protected from light. Periodic analysis confirmed that all 167 dose formulations for rats and all 99 for mice were within 10% of the target concentrations.

Duration of treatment / exposure:

105 weeks

Frequency of treatment:

Daily

Post exposure period:

No post exposure period

Dose / conc.:

0 ppm (nominal)

Dose / conc.:

2 000 ppm (nominal)

Dose / conc.:

10 000 ppm (nominal)

Dose / conc.:

50 000 ppm (nominal)

No. of animals per sex per dose:

50 male and 50 female rats and mice per group.

Control animals:

yes, concurrent no treatment

Details on study design:

Groups of 50 male and 50 female rats and mice were fed diets containing 0, 2000, 10000 or 50000 ppm CPM for 105 weeks. Animals were randomly distributed into groups of approximately equal initial mean body weights. Dose levels were selected based on previous 3 month subchronic toxicity studies. Dosing in feed was chosen as this is the primary route for human exposure (in the diet and in supplements).

Positive control:

Not examined.

Observations and examinations performed and frequency:

All animals were observed twice daily. Animals were weighed initially, once a week for the first 13 weeks, once a month thereafter, and at the end of the studies. Feed consumption was measured weekly for the first 13 weeks of the study and monthly thereafter. Clinical findings were recorded monthly.

Sacrifice and pathology:

Complete necropsies and microscopic examinations were performed on all rats and mice at study termination. At necropsy, all organs and tissues were examined for grossly visible lesions, and all major tissues were fixed and preserved in 10% neutral buffered formalin (eyes were initially fixed in Davidson’s solution), processed and trimmed, embedded in paraffin, sectioned to a thickness of 4–6 lm, and stained with hematoxylin and eosin for microscopic examination. For all paired organs (e.g. adrenal gland, kidney, ovary), samples from each organ were examined.

Other examinations:

No further information available.

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. All reported P values for the survival analyses are two sided. The Poly-k test (Bailer and Portier, 1988; Portier and Bailer, 1989; Piegorsch and Bailer, 1997) was used to assess neoplasm and non-neoplastic lesion prevalence. This test is a survival-adjusted quantal-response procedure that modifies the Cochran–Armitage linear trend test to take survival differences into account. Unless otherwise specified, a value of k = 3 was used in the
analysis of site-specific lesions. Tests of significance included pairwise comparisons of each exposed group with controls and a test for an overall exposure-related trend. Continuity-corrected Poly-3 tests were used in the analysis of lesion incidence, and reported P values are one sided.

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:

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:

Rat study: In males, there was a significant trend (P = 0.041) for decreased survival (0 ppm, 37/50; 2000 ppm, 36/50; 10,000 ppm, 35/50; 50,000 ppm, 28/50); however, because survival was not significantly different from the control group at any exposure concentration the decreases was not considered to be related to exposure. Survival in exposed females (0 ppm, 36/50; 2000 ppm, 35/50; 10,000 ppm, 36/50; 50,000 ppm, 40/50) was similar to that of the control group. Mean body weights of exposed groups of males and females were similar to those of the controls throughout the study. Feed consumption by exposed groups of males and females was generally similar to that of the controls throughout the study. Body weight and feed consumption data were used to calculate average daily doses of CPM resulting from each concentration (Table 1). Average daily doses were also calculated for Cr(III) and picolinic acid, the components of the CPM complex. Based on the body weight and feed consumption data, the increases in calculated ingested dose were proportional to the increases in exposure concentration. No clinical findings or non-neoplastic lesions were attributed to exposure. The incidence of preputial gland adenoma was significantly increased in males at 10,000 ppm compared to the control group (Table 2). This increase exceeded the historical control ranges for feed studies and for all routes of exposure. The incidence of preputial gland hyperplasia was not increased at any exposure concentration. Preputial gland carcinoma was not observed in control or exposed males. 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 of the preputial gland is the clitoral gland. There were no increases in the incidences of clitoral gland adenoma or hyperplasia over the control group (Table 2). Carcinomas of the clitoral gland were not observed in control or treated females. Proliferative lesions of the preputial and clitoral glands 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.

Mouse study: 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. 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 by exposed groups of males and females was similar to that by the controls throughout the study. Body weight and feed consumption data were used to calculate average daily doses of CPM resulting from each concentration (Table 1). Average daily doses were also calculated for Cr(III) and picolinic acid, the components of the CPM complex. Based on the body weight and feed consumption data, the increases in calculated
ingested dose were proportional to the increases in exposure concentration. No clinical findings or neoplastic or non-neoplastic lesions were attributed to CPM exposure.

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 CPM 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. CPM was not carcinogenic to female rats or male and female mice. The concentrations administered were very high relative to human exposures.

Dose descriptor:

NOEL

Effect level:

50 000 ppm (nominal)

Sex:

male/female

Basis for effect level:

other: B6C3F1 mice

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOEL

Effect level:

50 000 ppm (nominal)

Sex:

female

Basis for effect level:

other: F344/N female rats

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Dose descriptor:

NOEL

Effect level:

2 000 ppm (nominal)

Sex:

male

Basis for effect level:

other: F344/N male rats. An increase in the incidence of preputial gland adenomas was observed at the 10000 ppm dose but the finding was considered equivocal as a similar increase was not seen in the 50000 ppm group.

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

Table 1. Conversion of CPM exposure concentrations in feed to average daily doses (mg/kg/day) of CPM, Cr(III) and picolinic acid in rats and mice exposed for 2 years.

	Rats			Mice
CPM (ppm)	CPM^a(mg/kg/day)	Cr(III)^b(mg/kg/day)	Picolinic acid^c(mg/kg/day)	CPM^a(mg/kg/day)	Cr(III)^b(mg/kg/day)	Picolinic acid^c(mg/kg/day)
Males
0	-	-	-	-	-	-
2000	90	10.7	79.3	250	29.8	220.2
10000	460	54.9	405.1	1200	143.1	1056.9
50000	2400	286.2	2113.8	6565	783.0	5782.0
Females
0	-	-	-	-	-	-
2000	100	11.9	88.1	240	28.6	211.4
10000	510	60.8	449.2	1200	143.1	1056.9
50000	2630	313.7	2316.3	6100	727.5	5372.5

aCalculated using body weight and feed consumption data.

bCalculated using the average daily dose of CPM and the percent mass of Cr(III) in CPM.

cCalculated using the average daily dose of CPM and the percent mass of picolinic acid in CPM.

Table 2. Accessory sex gland neoplasms in male and female rats exposed to CPM for 2 years.

	Exposure concentration (ppm)
	0	2000	10000	50000
Males
Preputial gland
No. necropsied	50	50	50	50
Hyperplasia	3^a(2.7)^b	1(4.0)	0	2 (2.5)
Adenoma^c	1(2.2)^d	1(2.3)	7(14.9)^*	4 (9.3)
Females
Clitoral gland
No. necropsied	50	50	50	50
Hyperplasia	8^a(2.4)^b	10(2.6)	11 (2.6)	4(2.3)
Adenoma^c	10(21.9)^d	2(4.4)^*	8(17.7)	11(23.4)

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: 43/1193

(3.6% ± 3.5%), range 0–10%.

dSurvival adjusted incidence (%).

eHistorical incidence: 26/200 (13.0% ± 6.2%), range 6–20%; all routes: 104/1096

Conclusions:

There was very little evidence of adverse effect following dietary exposure of rats and mice to CPM for 2 years.

Executive summary:

Chromium picolinate monohydrate (CPM) 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 CPM to induce chronic toxicity and carcinogenicity. Concentrations of 0, 2000, 10000 or 50000 ppm were fed to groups of 50 male and female mice and rats for 2 years. Exposure to CPM did not induce biologically significant changes in survival, body weight, feed consumption, or non-neoplastic lesions in rats or mice. In male rats, a statistically significant increase in the incidence of preputial gland adenoma at 10,000 ppm was considered an equivocal finding. CPM was not carcinogenic to female rats or to male or female mice.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Carcinogenicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

carcinogenicity, other

Remarks:

intrabronchial implantation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-standard published study

Qualifier:

no guideline followed

Principles of method if other than guideline:

Investigation of carcinogenicity following intrabronchial implantation

GLP compliance:

no

Remarks:

: older published study

Species:

rat

Strain:

other: Porton-Wistar

Sex:

male/female

Route of administration:

implantation

Vehicle:

other: cholesterol

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

Single implantation

Frequency of treatment:

Single implantation

Post exposure period:

2 years

Remarks:

Doses / Concentrations:
2 mg
Basis:
other: actual weight

No. of animals per sex per dose:

50

Control animals:

yes, concurrent vehicle

Details on results:

No evidence of carcinogenicity was seen in this study.

Relevance of carcinogenic effects / potential:

No evidence of carcinogenicity was seen in this study.

Basis for effect level:

other: No evidence of carcinogenicity was seen in this study.

Survival to 24 months exceeded 90% in both groups. Examination of the treated bronchus did not reveal any increase in teh incidence of squamous epithelial metaplasia compared to controls. No evidence of carcinogenicity was seen.

Conclusions:

Implantation of chromium (III) hydroxide sulphate into the lungs of rats did not cause any proliferative or carcinogenic effects.

Executive summary:

A group of 48 male and 52 female rats received a bronchial pellet in which cholesterol was mixed with an equal amount (2 mg) of chromium(III) hydroxide sulphate. The animals were kept for two years, and a post-mortem study was performed on the 94 remaining rats. None of them exhibited local squamous carcinomas, or carcinomas in situ, and the occurrence of squamous metaplasia was not increased compared with the stainless steel wire mesh controls.

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

There are no studies in animals showing clear evidence of carcinogenicity of water-soluble chromium (III) compounds, including chromium hydroxide sulphate. Studies of workers in tanneries reported no association between exposure to chromium (III) and excess risk of cancer. The results of the available studies do not trigger classification according to Regulation (EC) No 1272/2008.

Additional information

Study with chromium hydroxide sulphate

Groups of 48 male and 52 female rats received a pellet containing cholesterol mixed with an equal amount (2 mg) of chromium chloride hexahydrate or basic chromium sulphate via intrabronchial administration. None of the rats in either group exhibited local squamous carcinomas, or carcinomas in situ (Levy & Venitt, 1986).

Administration of water-soluble chromium (III) acetate (5 ppm) in drinking water of rats and mice for their lifetime produced no signs of toxicity and tumour incidence was similar to controls. The incidence of lung adenomas were similar between test and control groups following repeated ip injections of mice with 5-27 mg Cr (III) as chromium sulphate for 8 weeks. Studies in leather tanners, who are often exposed to chromium (III) hydroxide sulphate, were consistently negative. .

Studies with other Cr (III) compounds

A number of literature reviews have summarized information on the carcinogenicity of water-soluble chromium (III) compounds. A drinking water study in rats and mice showed no increase in tumour incidence compared to controls when administered low concentrations of chromium acetate for their lifetime (HSE review, 1989). Intraperitoneal injections of mice with water-soluble chromium (III) sulphate three times per week for eight weeks showed similar incidences of lung adenomas in test and control groups (HSE review, 1989). Occupational exposure to chromium (III) compounds in tanneries, usually to basic chromium sulphate, has not been associated with an excess risk of cancer (ATSDR review, 2000).

Carcinogenicity studies employing various water-soluble chromium (III) compounds and exposure routes have yielded negative results. Both IARC and EPA have classified chromium (III) as Group C and Group D, respectively, that is, not classifiable as to carcinogenic potential (ATSDR review, 2000).

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.

NTP carcinogenicity studies in the rat and mouse with the water-soluble complex chromium picolinate produced only equivocal evidence of carcinogenicity in the male rat. Rats (50/sex) were administered chromium picolinate in the diet at 0, 2000, 10000 and 50000 ppm; a slight and non dose-related increase in the incidence of preputial gland adenoma in males. No evidence of carcinogenicity was seen in mice (50/sex/group) administered the same dose levels. It is noted that this highly water-soluble complex is an extreme worst case as systemic absorption of Cr (III) is likely to be considerably higher than from the less soluble chromium (III) hydroxide sulphate.

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.