Strontium bis[2-chloro-5-[(2-hydroxy-1-naphthyl)azo]toluene-4-sulphonate]

Carcinogenicity

Description of key information

Studies on carcinogenicity of the test item (Sr salt) were not performed. Since both substances are salts with similar structur and similar solubility, information on the carcinogenic potential were derived from experimental data of a structural analogue (Ba salt). In a longterm 2-year feeding study with Osborne-Mendel rats there was no increase in tumour incidence up to the highest feeding level. ICR mice with demal exposure for 18 months showed no increased evidence of neoplasms. In the course of a NTP bioassay conducted with rats and mice, no findings were seen in mice or female rats. Fibrosarcomas in spleen were found in high dose male rats. With regard to the absence of genotoxicity and cytotoxicity and the presence of hematotoxicity, fibrosarcoma formation in spleen in cosidered to be a secondary effect due to methemoglobin formation and excessive erythrocyte damaging. No indication of carcinogenic properties was observed upon drinking water application at 2500 ppm.

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 based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

1977-1979

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: well documented and NTP protocol conform study; animals were in the same room as animals of the same species on other feeding studies; organ weight data are not given

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 451 (Carcinogenicity Studies)

GLP compliance:

no

Remarks:

conducted before introduction of GLP

Species:

other: rats and mice

Strain:

other: F344 rats and B6C3F1 mice

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: NCI Frederick Cancer Research Center (Frederick, MD)
- Age at study initiation: 4 weeks
- Weight at study initiation: no data
- Housing: 5 per cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 12-16d

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-23
- Humidity (%): 40-60
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12

The start dates were March 10, and March 23, 1977 for male and female rats and April 8, and April 17, 1977 for male and female mice.

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Remarks:

mixed with diet

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: formulated by mixing weighed-amounts of Purina® Laboratory Chow and the test chemical for 15 minutes in
a Patterson-Kelly® twin-shell blender equipped with an intensifier bar

DIET PREPARATION
- Rate of preparation of diet (frequency): 10d
- Storage temperature of food: 23°C

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Formulated diets containing 100,000 ppm D & C Red No. 9 were analyzed at Midwest Research Institute and were found to be stable for 2 weeks at temperatures up to 45 C. Every 8 to 10 weeks, analytical concentrations of D & C Red No. 9 were determined in blindly selected batches of formulated diets and were within +10% of the desired concentration.

Duration of treatment / exposure:

2 years / 103 weeks

Frequency of treatment:

daily

Post exposure period:

1 weeks (rats)
2 weeks (mice)

Remarks:

Doses / Concentrations:
0, 1000 and 3000 ppm (rats)
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
0, 1000 and 2000 ppm (mice)
Basis:
nominal in diet

No. of animals per sex per dose:

50

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: dosel level rationale bases on effects observed in the 91 day study

Positive control:

no

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: each month

BODY WEIGHT: Yes
- Time schedule for examinations: every 4 weeks

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

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

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Statistics:

Animals were statistically censored as of the time that they died of other than natural causes or were found to be missing; animals dying from natural causes were not statistically censored. Statistical analyses for a possible dose-related effect on survival used the method of Cox (1972) for testing two groups for equality and Tarone's (1975) extensions of Cox's methods for testing for a dose-related trend. One-tailed P values have been reported for all tests except the departure from linearity test, which is reported only when its two-tailed P value is less than 0.05.
The purpose of the statistical analyses of tumor incidence is to determine whether animals receiving the test chemical developed a significantly higher proportion of tumors than did the control animals. As a part of these analyses, the one-tailed Fisher exact test (Cox, 1970) was used to compare the tumor incidence of a control group with that of a group of dosed animals at each dose level. When the results from two dosed groups are compared simultaneously with that for a control group, a correction to ensure an overall significance level of 0.05 may be made. The Bonferroni inequality criterion (Miller, 1966) requires that the P values for any comparison be less than or equal to 0.025. When this correction was used, it is discussed in the narrative section. It is not presented in the tables, where the Fisher exact P values are shown.
Furthermore: Cochran-Armitage test for linear trend in proportions, time-adjusted analysis was applied when numerous early deaths resulted from causes that were not associated with the formation of tumors, life table methods were used to analyze the incidence of tumors,

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

low dose rats had a greater rate of survival than other groups or females

Mortality:

mortality observed, treatment-related

Description (incidence):

low dose rats had a greater rate of survival than other groups or females

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

mean body weight of high-dose female mice was slightly lower than that of the controls

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

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 specified

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

non-neoplastic nodules of the liver in male rats

Histopathological findings: neoplastic:

effects observed, treatment-related

Description (incidence and severity):

fibrosarcomas in male rats

Details on results:

Rats:
Fibrosarcomas, apparently arising from the red pulp or capsule of the spleen, were found in 17 of 48 high-dose (3,000 ppm) male rats. In high-dose male rats, one animal had a leiomyosarcoma and five had splenic osteosarcoma. A fibroma was found in one low-dose male rat. Eleven of the splenic tumors metastasized to peritoneal tissues. The two sarcomas of multiple organs in high-dose males may have originated in the spleen.
Fourteen of, 48 males had congestion of the splenic parenchyma, 23 had focal or multifocal areas of fibrosis, 3 had diffuse fibrosis, and 13 had areas of fatty metamorphosis in the spleen. Twenty-five high-dose females had multifocal, diffuse, or focal fibrosis. Areas of fibrosis were present in two
control male rats.
The splenic lesions in dosed male and female rats ranged from multifocal areas of fibroblastic proliferation in the red pulp to areas of proliferation of pleomorphic spindle cells with an oval to round, open-faced nucleus, and generally, an indistinct nucleolus.
Large areas of pigment were occasionally seen in the fibrous areas in the splenic capsule and parenchyma. The pigment appeared different from the hemosiderin seen in spleens of aging F344 rats.
Hepatic neoplastic nodules were seen in 0/50 control males, 6/50 low-dose males, and 7/49 high dose males. Almost all of these nodules were relatively small and composed of hepatocytes with basophilic or eosinophilic cytoplasm. Hepatocellular carcinoma was seen in 1/50 control males.

Mice:
Histopathologic examination provided no evidence for the carcinogenicity of D & C Red No. 9 in B6C3F1 mice.

Relevance of carcinogenic effects / potential:

Under the conditions of this bioassay, D & C Red No. 9 was carcinogenic for male F344 rats causing an increased incidence of sarcomas of the spleen and a dose-related increase in neoplastic nodules of the liver. D & C Red No. 9 was not considered to be carcinogenic to female F344 rats, although the increased incidence of neoplastic nodules of the liver may have been associated with administration of the test chemical. D & C Red No. 9 was not carcinogenic for B6C3F1 mice of either sex.

Dose descriptor:

NOAEL

Sex:

male

Basis for effect level:

other: carcinogenic for male F344 rats causing an increased incidence of sarcomas of the spleen and a dose-related increase in neoplastic nodules of the liver

Remarks on result:

not determinable

Remarks:

no NOAEL identified. Effect type:carcinogenicity (migrated information)

Dose descriptor:

NOAEL

Sex:

male/female

Basis for effect level:

other: see 'Remark'

Remarks on result:

not determinable

Remarks:

no NOAEL identified. Effect type:carcinogenicity (migrated information)

food (mean) and compound intake

rats		0 ppm	1000 ppm	3000 ppm
male	feed (g/day)	20	20.5	20.3
male	dose (mg/kg bw/day)	0	50 - 162	150 - 470
female	feed (g/day	13.9	14.8	14.5
female	dose (mg/kg bw/day)	0	51 - 146	150 - 427
mice		0 ppm	1000 ppm	2000 ppm
male	feed (g/day)	8.3	8.2	8.3
male	dose (mg/kg bw/day)	0	216 - 410	421 - 830
female	feed (g/day)	8.1	8.2	7.8
female	dose (mg/kg bw/day)	0	234 - 432	446 - 821

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

chronic

Species:

mouse

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

Dangerous Substance Directive (67/548/EEC)

The available studies are considered reliable and suitable for classification purposes under 67/548/EEC. As a result the substance is not considered to be classified for carcinogenicity under Directive 67/548/EEC, as amended for the 28th time in Directive 2001/59/EC.

 

 

Classification, Labeling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is not considered to be classified for genotoxicity under Regulation (EC) No. 1272/2008, as amended for the second time in Directive (EC 286/2011).

Additional information

Read across justification

Carcinogenicity of the test substance was not examined. The test item shares high structural similarity to an analogue substance, since both are salts which differ in the respective metal cation only. Both substances are poor soluble in water and octanol and dissolve most likely in an acidic environment (e.g. stomach). Therefore, it is acceptable to derive information on the carcinogenic potential from experimental data of the analogue substance.

Procedure and observations

100 ICR mice received pigment red 53:1 two times per week for 18 months at the shaven back (Carson et al 1974). Dosage levels were based on lipstick use determinations made in a group of human female volunteers. Twice each week a 0.1 ml dose containing 1 mg of the dye was applied to the dorsal skin of each mouse. All animals were necropsied; after termination of the study, tissues were selected for histopathology, sectioned, stained and examined by a pathologist. The repeated application of 0.1 ml containing 1 % dye did not increase the incidence of neoplasms when compared to the vehicle controls.

Groups of 50 B6C3F1 mice received diets containing 1,000 or 2,000 ppm of test substance for 103 weeks (NTP 1982). After week 50, the mean body weight of high-dose female mice was lower than that of the controls. No compound-related effect on survival or clinical signs were observed for mice of either sex. Under the conditions of this bioassay, D & C Red No. 9 was not carcinogenic for B6C3F1 mice of either sex.

Fisher 344 rats received 0, 1000 or 3000 ppm pigment red 53:1/kg bw for 103 weeks with the daily feed (NTP 1982). In males and females of the 3000 mg group non-neoplastic damage to the spleen (focal and diffuse fibrosis, lesions and splenic capsule) occured. There were no splenic sarcomas in low dose males or any of the female groups. There were small increases in neoplastic nodules of the liver in male rats.

Osborne-Mendel rats received 0, 0.01, 0.05, 0.25 and 1% pigment red 53:1 of the daily feed for two years (David and Fitzhugh 1962). Growth and mortality was unaffected. In the two highest dosage groups depressed haemoglobin levels, abnormal shape of erythrocytes and slight hyperplasia of bone marrow occurred. In the highest dosage group moderately to strong splenomegaly as well as haemosiderosis and partial infarction of the spleen was seen. Compared to the untreated control animals there was no increase in tumour incidence.

Regarding strontium, limited investigations on carcinogenic properties are available. Absence of carcinogenicity was reported in a 3 -year drinking water study with strontium chloride hexahydrate (Skoryna 1981), but insufficient details are available to conclude on the reliability of this data.

Discussion

The substance was tested for its carcinogenic potential in several studies. In one study with rats, high dose male animals developed splenic sarcomas and neoplastic nodules of the liver. Whereas, female animals and mice had no tumors. The neoplastic nodules in male high dose rats were not malignant and represent an early stage in the development of liver tumors in rats. It is not clear that any of them would have progressed to hepatocellular carinomas even if the rats had been allowed to live longer. Oral or dermal application of the test item to mice for 2 years gave no hints for a carcinogenic potential. Also oral administration to Osborne-Mendel rats for 2 years did not result in tumor formation. However, splenomegaly, hemosiderosis and splenic infarcts were seen at the high dose group.

Taken together, the substance has no genotoxic potential and does not interact with DNA or genetic material. Most likely, metabolites of the test article (1-amino-2-naphtol) cause methemoglobinamia leading to disturbances of iron metabolism and subsequently increased iron deposition in liver and spleen (hemosiderosis). Moreover, the substance or metabolites are attached at methemoglobin and transported via red blood cells into the spleen which acts as a filter for old or damaged erythrocytes. During degradation of methemoglobin, the substance or metabolite is released and affects spleenic mesenchymal tissue leading to fibrosis and promotion of tumor formation (sarcomas). Finally, the substance acts as a secondary carcinogen.