Sodium metaphosphate

Repeated dose toxicity: oral

Administrative data

Endpoint:

chronic toxicity: oral

Remarks:

combined repeated dose and carcinogenicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Study not performed to GLP or guideline. But has been reviewed by an expert assessor (see expert report attached) and determined to be suitable for use for the purposes of REACH registration.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1960

Report date:

1960

Reference 2

Reference Type:

publication

Title:

Summaries of toxicological data

Author:

Summaries published by BIBRA

Year:

1964

Bibliographic source:

Fd Cosmet. Toxicol. Vol. 2 pp. 147-154. Pergamon Press 1964.

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

Deviations:

yes

Remarks:

Please see additional comments on materials and methods.

GLP compliance:

no

Remarks:

study predates GLP

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Sodium metaphosphate

EC Number:

233-343-1

EC Name:

Sodium metaphosphate

Cas Number:

10124-56-8

Molecular formula:

H6O18P6.6Na

IUPAC Name:

Sodium metaphosphate

Details on test material:

- Name of test material (as cited in study report): Sodium Hexametaphosphate
- Substance type: Granular
- Physical state: Solid
- Analytical purity: no data
- Lot/batch No.: # 195001-8
- Storage condition of test material: Test material is considered stable at room temperature.

Test animals

Species:

rat

Strain:

other: Rochester strain (ex-Wistar)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source:
- Age at study initiation: 21 days
- Weight at study initiation: 88-90g for male rats and 78-80g for female rats.
- Fasting period before study:
- Housing: In groups of 5 the rats were housed in galvanized iron cages with wire screen doors. The bottom of the cage was a pan containing wood shavings.
- Diet (e.g. ad libitum): ad libitum, Purina Fox Chow Meal,
- Water (e.g. ad libitum): ad libitum, Rochester tap water.
- Acclimation period: no data

ENVIRONMENTAL CONDITIONS
no data

IN-LIFE DATES: From: 13/08/1957 To: 12/08/1959

Administration / exposure

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION
Diet mixtures were prepared using a basal ration of Purina Fox Chow Meal into which the appropriate amounts of sodium hexametaphosphate were mixed by a mechanical mixer. At weekly intervals. Diets were stored during the week in galvanized iron pails with covers.

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

not applicable

Duration of treatment / exposure:

104 weeks

Frequency of treatment:

daily, in feed.

Doses / concentrations

Remarks:

Doses / Concentrations:
0.0% (controls), 0.05%, 0.5%, 5.0%
Basis:
nominal in diet

No. of animals per sex per dose:

50/sex/dose

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale:
The acute oral toxicity of the test material was determined in a group of 81 female albino rats. The LD50 was estimated to be 2900 mg/kg ± 258 mg/kg.
In a pilot study of 1 month duration, groups of 5 male rats each were maintained on diets containing: 0.2%, 2.0% and 10%.
The 10% group showed showed growth retardation, the 2% group grew in the same manner as the controls. For unknown reasons the group given the 0.2% diet grew less well than the 2% group. None of the rats died during the 30 day study. A serial sacrifice program was instituted where rats from each group were terminated on the 3rd, 7th, 15th and 28th days. Increased kidney weights were observed in the 10% group. Normal kidney weights were recorded in the 2% group. Kidney injury characterized by tubular degeneration and necrosis ("phosphate nephritis") was seen in the sections taken from the rats maintained on the 10% diet. Some kidney damage was seen in the 2% group but none in the 0.2% group.

Positive control:

no positive controls

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: weekly for the first twelve weeks, biweekly thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE:
- Food consumption was evaluated after 90 and 210 days on study on 5/sex/group from the control and high dose groups daily for 3 consecutive days. Each animal was provided with a set amount of basal or treated diet for the daily recording of food consumption for the 90 day measurement. For the 210 day measurement, control animals were provided with the amount of diet consumed by the treated animal on the preceding day. Body weights were also monitored during this measurement period.

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

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Pre-study and on days 23, 76, 94, 118, 153, 183, 247, 295, 379, 447, 546, 631, 713 and at termination (day 728) on all surviving rats.
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: 5 animals/ sex/ group
- Parameters examined: Haematocrit, haemoglobin concentration, erythrocyte count, erythrocyte characteristics, total and differential leukocyte count, plasma cell.
- Parameters not evaluated: platelet count, prothrombin time, activated partial thromboplastin time, mean corpuscular volume, mean corpuscular haemoglobin and haemoglobin concentration.

CLINICAL CHEMISTRY: No

URINALYSIS: Yes
- Time schedule for collection of urine: Pre-test and After 2, 5, 8, 11, 14, 17, 20 and 23 months on study.
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters checked: Protein % and Sugar %.


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see table in attachments)
HISTOPATHOLOGY: Yes (see table in attachments)

Other examinations:

no data

Statistics:

no data

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

no effects observed

Clinical biochemistry findings:

not specified

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

MORTALITY
Mortality was due primarily to respiratory infections and other causes. Deaths related to tumours did not show a relationship to treatment. There was no increase in mortality with increasing dose of test material. There was a small decrease, probably insignificant, in the median survival time with increasing dose of the test material in the female rats.

BODY WEIGHT AND WEIGHT GAIN
Growth retardation was observed in rats of both sexes at the high dose (5.0% in the diet). Among males the growth retardation was considered detectable, but not marked. Among females the growth retardation was considered only slight. There were no effects on body weight in the medium and low dose groups.

FOOD CONSUMPTION AND COMPOUND INTAKE
90-day evaluation: male and female rats in the high dose group consumed more food per day than controls: 14.8-18.3 g/day for control males and 18.8-19.5 g/day for high dose males; 7.2-13.4 g/day for control females and 13.9-15.1 g/day for high dose females. Body weight gains at 90 days and 210 days were slightly higher among treated animals, compared to control animals, used for the food consumption evaluations. These data are consistent with a mild cathartic action of the test material.

210-day evaluation in a paired-feeding design: 18.1-19.6 g/day for control males and 18.8-19.9 g/day for high dose males; 12.5-13.6 g/day for control females and 13.4-17.5 g/day for high dose females. There is an indication of a slight excess of eating by the high dose animals. Thus, the food consumption measurements showed that the general body weight growth retardation in the high dose group of both sexes was related to some interference with absorption or assimilation of food, but not due to reduced food intake.

HAEMATOLOGY
Periodic haematology evaluations found that all values in the treated groups were within the normal ranges. There was no indication of any effect from the addition of the test material to the diet.

URINALYSIS
Only the usual trace values of protein and sugars were found in all dose groups and at all timepoints. There was no indication of a toxic effect of the test material in these data.

ORGAN WEIGHTS
Kidney weights were increased among the high dose group animals at study termination. There were no other effects on organ weights in the other organs examined in any dose group. The fresh kidney weights for the male rats were about 3.5g for the control group contrasted with 4.1, 4.3, and 4.2 g for the 0.05%, 0.5% and 5.0% groups, respectively. Thus, there seems to be a distinction between the control and all experimental groups.

GROSS PATHOLOGY
There was an increase in calcification in the tubules of the kidneys of male and female rats in the 5.0% dose group. The calcification is believed to be an intensification of severity of naturally occurring processes of infection and degeneration. Some of the rats given the 5.0% diet had normal kidneys. No other changes were attributed to the adminstration of the test material.
That these calcifications were not simply or solely phosphate effects is shown by the fact that there were histologically normal kidneys in some of the rats given the 5.0% diet. That phosphates in quantity were a factor in the incidence rate of the calcifications is demonstrated by the fact that in the group of rats, 13 of 20 did exhibit calcification. With the exception of 1 female rat in the 0.5% group, these were the only rats that exhibited calcification.
None of the rats in any of the control groups exhibited any calcifications.

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
The incidence of tumours among survivors at terminal sacrifice did not show any significant increase in any particular tumour type related to treatment.

BONE ANALYSES:
Analyses of bones of the bones from all the rats showed normal compositions. Bone ash analyses on femurs of the rats given the 5% diet gave normal calcium phosphorus values.

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

ca. 250 mg/kg bw/day (nominal)

Based on:

not specified

Sex:

male/female

Basis for effect level:

other: overall effects Growth, mortality, food consumption, urine analyses, haematology, organ weights, bone analyses, gross and histo- pathology (5000 ppm is equivalent to 0.5% nominal in diet.)

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

NOAEL calculated in accorance with Appendix F, guidelines for the preparation of toxicological working papers for the joint FAO/WHO expert committee on food additives, December 2000.

See the attached file for tabulated data.

Applicant's summary and conclusion

Conclusions:

The test material showed no toxicity when administered in the diet of rats at a level of 5000 ppm for two years. The no-observed effect level for chronic toxicity in this study is 5000 ppm in the diet. At the high dose (50,000 ppm) there were effects on body weight gain and kidney weights. Histopathological evaluation indicated a treatment-related increase in calcification of the kidneys. There was no apparent increase in tumour incidence to suggest a carcinogenic effect, though the number of survivors at termination was generally low due to infections or other causes in all dose groups.

This study has been selected as the key study because the results are sufficient in order to derive a reliable conclusion on classification and labelling in accordance with Regulation EC (No.) 1272/2008 (EU CLP).

Executive summary:

The chronic toxicity/carcinogenicity study is a scientifically sound study that met the scientific standards at the time it was conducted. It included many parameters that meet the current OECD 453 guideline and one that exceeded it (bone physiology evaluation). Although it was not a GLP study, the report contains detailed information on the study conduct, individual animal data and summary tables.

 

The deficiencies included the following: inadequate test material characterization, incomplete food and water consumption, inadequate clinical observations and ophthalmology, lack of clinical chemistry, some haematological parameters not included, not all required organs were weighed and not all required tissues were evaluated for histopathology. Survival generally met the criteria for survival after 24 months, but did not meet the criteria for the percentages of deaths due to infections and other causes. Survival in the study was poor due to respiratory infections and pericarditis-peritonitis which were not treatment-related and occurred in all groups. Nevertheless, the Hodge study was able to adequately identify potential target organs, evaluate haematological effects, body weight gain, and, indirectly, food consumption, as well as to provide histopathological evaluation of many organs and tumours. The lack of purity analysis, while a clear deficiency, is not considered to affect the reliability because there were no unexpected toxic effects due to the test material at a high dose of 5% in the diet which would lead one to believe that the test material had toxic impurities. The results of the study are appropriate for those expected of an inorganic phosphate and similar to those observed with other inorganic phosphates.