Calcium dihydroxide precipitated with carbon dioxide during sugar juice purification

Endpoint summary

Description of key information

Repeat dose oral toxicity: A 14 day range finder study and a 28 day repeat dose oral toxicity study in rats are available that have evaluated the repeated dose toxicity of calcium carbonate (nano). These studies are directly applicable to SFL. A 28 day study in the mouse and a number of human studies are also available. None of the studies described any severe or adverse toxicological effects following oral administration of the test material.
Repeat dose dermal toxicity: No studies on the repeated dose dermal toxicity of SFL are available.
Repeat dose inhalation toxicity: No studies on the repeated dose inhalation toxicity of SFL are  available.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

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

Adequacy of study:

key study

Study period:

26 February 2010 to 02 June 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP guideline study As this study is being used for read-across, the reliability has been amended to reflect this. Read-across from calcium carbonate to sugar factory lime (SFL) is justified on the following basis. SFL is primarily composed of inorganic substances. The major constituent is calcium carbonate, along with sand and a small amount of other inorganic salts (including calcium salts) and the remainder is composed of organic plant material. SFL is not classified for human health. Of its components, only calcium oxalate is classified as acutely toxic via the oral and dermal routes (category 4); however, this does not affect the overall classification of SFL. As a result, it is considered that the properties of SFL are governed by those of calcium carbonate. It is therefore considered appropriate for this data to be used for read-across purposes and any further testing would be scientifically unjustified.

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories U.K. Ltd., Blackthorn, Bicester, Oxon, UK
- Age at study initiation: approximately 12 weeks old
- Weight at study initiation: Males: 299 - 376 g; Females: 191 - 227 g
- Housing: Initially, all animals were housed in groups of five in solid floor polypropylene cages with stainless steel mesh lids and softwood flake bedding (Datesand Ltd., Cheshire, UK). During the mating phase, animals were transferred to polypropylene grid floor cages suspended over trays lined with absorbent paper on a one male: one female basis within each dose group. Following evidence of successful mating, the males were returned to their original cages. Mated females were housed individually during gestation and lactation, in solid floor polypropylene cages with stainless steel mesh lids and softwood flakes. Environmental enrichment was provided in the form of wooden chew blocks and cardboard fun tunnels (Datesand Ltd., Cheshire, UK) except for mated females during gestation and lactation.
- Diet: A pelleted diet (Rodent 2018C Teklad Global Certified Diet, Harlan Laboratories U.K. Ltd., Oxon, UK) was used and was available ad libitum.
- Water: Mains drinking water was supplied from polycarbonate bottles attached to the cage and was available ad libitum.
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 2 °C
- Humidity (%): 55± 15%
- Air changes: at least fifteen air changes per hour
- Photoperiod: low intensity fluorescent lighting was controlled to give twelve hours continuous light and twelve hours darkness

IN-LIFE DATES: From: 02 March 2010 (first day of treatment) To: 18 April 2010 (final necropsy)

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: For the purpose of this study the test material was prepared at the appropriate concentrations as a suspension in Distilled water. The stability and homogeneity of the test material formulations were previously determined by Harlan Laboratories Ltd. (Harlan Laboratories Ltd. Project Number: 2974-0011). Results from the previous study showed the formulations to be stable for at least fourteen days. Formulations were therefore prepared weekly and stored at 4 ºC in the dark.
The treatment volume for each animal was 5 mL/kg.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of each test material formulation were taken and analysed for concentration of Calcium carbonate (nano).

Due to the complex nature of the test material and its limited solubility in organic and aqueous media, a substance specific quantitative method of analysis could not be developed. The concentration of Calcium Carbonate (nano) in the test material formulations was determined using a gravimetric technique.

The results indicate that the prepared formulations were within ± 6% of the nominal concentration.

Duration of treatment / exposure:

Up to 48 consecutive days (including a two week maturation phase, pairing, gestation and early lactation for females).

Frequency of treatment:

Daily

Remarks:

Doses / Concentrations:
0, 100, 300 and 1000 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

10 animals/sex/group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dose levels were chosen based on the results of previous toxicity work (Harlan Project Number: 2974-0011).
- Rationale for animal assignment: The animals were allocated to dose groups using a randomisation procedure based on stratified bodyweights and the group mean bodyweights were then determined to ensure similarity between the dose groups.

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animals were examined for overt signs of toxicity, ill-health and behavioural change immediately before dosing, up to thirty minutes after dosing, and one and five hours after dosing, during the working week. Animals were observed immediately before dosing, soon after dosing, and one hour after dosing at weekends and public holidays (except for females during parturition where applicable). All observations were recorded.
Prior to the start of treatment and at weekly intervals thereafter, all animals were observed for signs of functional/behavioural toxicity. Functional performance tests were also performed on five selected males and females from each dose level, prior to termination, together with an assessment of sensory reactivity to various stimuli.
Detailed individual clinical observations were performed for each animal using a purpose built arena. The following parameters were observed: gait, hyper/hypothermia, tremors, skin colour, twitches, respiration, convulsions, palpebral closure, bizarre/abnormal/stereotypic behaviour, urination, salivation, defecation, pilo-erection, transfer arousal, exophthalmia, tail elevation, lachrymation

BODY WEIGHT: Yes
- Time schedule for examinations: Individual bodyweights were recorded on Day 1 (prior to dosing) and then weekly for males until termination and weekly for females until mating was evident. Bodyweights were then recorded for females on Days 0, 7, 14 and 20 post coitum, and on Days 1 and 4 post partum.

FOOD CONSUMPTION:
- During the maturation period, weekly food consumption was recorded for each cage of non-recovery adults. This was continued for males after the mating phase. For females showing evidence of mating, food consumption was recorded for the periods covering post coitum Days 0-7, 7-14 and 14-20. For females with live litters, food consumption was recorded on Days 1 and 4 post partum.

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 - Food efficiency was calculated retrospectively for males throughout the study period and for females during the premating phase. Due to offspring growth and milk production, food efficiency could not be accurately calculated during gestation and lactation.

WATER CONSUMPTION: Yes
- Time schedule for examinations: Water intake was observed daily by visual inspection of water bottles for any overt changes.

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Day 42 for males and Day 4 post partum for females
- How many animals: five males and five females selected from each test and control group
- Parameters examined:
* Haemoglobin (Hb)
* Erythrocyte count (RBC)
* Haematocrit (Hct)
* Erythrocyte indices - mean corpuscular haemoglobin (MCH)
- mean corpuscular volume (MCV)
- mean corpuscular haemoglobin concentration (MCHC)
* Total leucocyte count (WBC)
* Differential leucocyte count - neutrophils (Neut)
- lymphocytes (Lymph)
- monocytes (Mono)
- eosinophils (Eos)
- basophils (Bas)
* Platelet count (PLT)
* Reticulocyte count (Retic) - Methylene blue stained slides were prepared but reticulocytes were not assessed
* Prothrombin time (CT) was assessed by ‘Innovin’ and Activated partial thromboplastin time (APTT) was assessed by ‘Actin FS’ using samples collected into sodium citrate solution (0.11 mol/L).

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Day 42 for males and Day 4 post partum for females
- How many animals: five males and five females selected from each test and control group
- Parameters examined:
* Urea
* Inorganic phosphorus (P)
* Glucose
* Aspartate aminotransferase (ASAT)
* Total protein (Tot.Prot.)
* Alanine aminotransferase (ALAT)
* Albumin
* Alkaline phosphatase (AP)
* Albumin/Globulin (A/G) ratio (by calculation)
* Creatinine (Creat)
* Sodium (Na+)
* Total cholesterol (Chol)
* Potassium (K+)
* Total bilirubin (Bili)
* Chloride (Cl-)
* Bile acids (Bile)
* Calcium (Ca++)

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Prior to the start of treatment and at weekly intervals thereafter, all animals were observed for signs of functional/behavioural toxicity. Functional performance tests were also performed on five selected males and females from each dose level, prior to termination, together with an assessment of sensory reactivity to various stimuli.
- Dose groups that were examined: All animals in all dose groups and five selected males and females from each dose level, prior to termination.
- Battery of functions tested: sensory reactivity (grasp response, touch escape, vocalisation, pupil reflex, toe pinch, blink reflex, tail pinch, startle reflex, finger approach) grip strength, motor activity

Sacrifice and pathology:

GROSS PATHOLOGY: Yes: Adult males were killed by intravenous overdose of a suitable barbiturate agent followed by exsanguination on Day 43. Adult females were killed by intravenous overdose of a suitable barbiturate agent followed by exsanguination on Day 5 post partum. All adult animals and offspring, including those dying during the study, were subjected to a full external and internal examination, and any macroscopic abnormalities were recorded.
The following organs, removed from animals that were killed at the end of the study, were dissected free from fat and weighed before fixation:
* Adrenals
* Pituitary (post fixation)
* Brain
* Seminal vesicles
* Epididymides
* Spleen
* Heart
* Testes
* Kidneys
* Thymus
* Liver
* Thyroid (weighed post-fixation with Parathyroid)
* Ovaries
* Uterus (weighed with Cervix)
* Prostate

HISTOPATHOLOGY: Yes: Samples of the following tissues were removed from all animals and preserved:
* Adrenals
* Muscle (skeletal)
* Aorta (thoracic)
* Oesophagus
* Bone & bone marrow (femur including stifle joint)
* OVARIES
* Bone & bone marrow (sternum)
* Pancreas
* Brain (including cerebrum, cerebellum, medulla oblongata and pons)
* PITUITARY
* PROSTATE
* Caecum
* Rectum
* CERVIX
* Salivary glands (submaxillary)
* COAGULATION GLAND
* Sciatic nerve
* Colon
* SEMINAL VESICLES
* Duodenum
* Skin (hind limb)
* EPIDIDYMIDES
* Spinal cord (cervical, mid-thoracic and lumbar)
* Eyes
* Gross lesions
* Spleen
* Heart
* Stomach
* Ileum
* TESTES
* Jejunum
* Thymus
* Kidneys
* Thyroid/parathyroid
* Liver
* Trachea
* Lungs (with bronchi)
* Urinary bladder
* Lymph nodes (cervical and mesenteric)
* UTERUS
* MAMMARY TISSUE
* VAGINA

The tissues from five selected control and 1000 mg/kg bodyweight/day dose group animals, any animals dying during the study were prepared as paraffin blocks, sectioned at nominal thickness of 5 μm and stained with haematoxylin and eosin for subsequent microscopic examination. The tissues shown in capital letters from the remaining control and 1000 mg/kg bodyweight/day were also processed. In addition, sections of testes and epididymides from all control and 1500 mg/kg bodyweight/day males were also stained with Periodic Acid-Schiff (PAS) stain and examined.

Statistics:

Data for males and females prior to pairing, and functional performance test data, where appropriate, quantitative data were analysed by the Provantis™ Tables and Statistics Module. For each variable, the most suitable transformation of the data was found, the use of possible covariates checked and the homogeneity of means assessed using ANOVA and ANCOVA and Barletts’s test. The transformed data were analysed to find the lowest treatment level that showed a significant effect, using the Williams Test for parametric data or the Shirley Test for non-parametric data. If no dose response was found, but the data showed non-homogeneity of means, the data were analysed by a stepwise Dunnett (parametric) or Steel (non-parametric) test to determine significant differences from the control group. Finally, if required, pair-wise tests were performed using the Student t-test (parametric) or the Mann-Whitney U test (non-parametric).

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:

no effects observed

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

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

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:

not examined

Details on results:

MORTALITY
There were no unscheduled deaths that were considered to be related to test material toxicity.
One male treated with 1000 mg/kg bodyweight/day was killed in extremis on Day 39. Histopathological examinations of this animal revealed the cause of death to be due to a misplaced gavage with perforation leading to necrotizing inflammation around the trachea, oesophagus, lungs and thymus. This was therefore considered to be unrelated to test material toxicity.

CLINICAL OBSERVATIONS
There were no toxicologically significant changes detected.
Episodes of generalised fur loss were evident in three females treated with 1000 mg/kg bodyweight/day and two females treated with 100 mg/kg bodyweight/day. One female treated with 300 mg/kg bodyweight/day had a missing upper front tooth between Days 31 and 35. These incidences in isolation were considered not to be of toxicological significance. Two control females also had fur loss between Day 32 and Day 45. One male treated with 300 mg/kg bodyweight/day had an open wound from Day 27 onwards, followed by scab formation and fur loss from Day 28. Observations of this nature are commonly observed in group housed animals and are not considered to be related to treatment.
The male that was killed in extremis on Day 39 had noisy respiration on Days 36 and 39 and pilo erection, a decreased respiration rate, lethargy and hunched posture prior to termination.

BODY WEIGHT AND WEIGHT GAIN
There were no treatment related effects detected in bodyweight development.
Statistical analysis of the data did not reveal any significant intergroup differences.

FOOD CONSUMPTION
No adverse effect on food consumption was detected for males during the treatment period, or for females during the pre-mating, gestation or lactation phases of the study.

FOOD EFFICIENCY
Food efficiency (the ratio of bodyweight gain to dietary intake) was not affected for males throughout the treatment period, or for females during the pre-mating phase.

WATER CONSUMPTION
No treatment-related intergroup differences in water intake were detected for treated animals when compared to controls.

HAEMATOLOGY
No toxicologically significant effects were detected.
Males treated with 1000 mg/kg bodyweight/day showed a statistically significant reduction in mean corpuscular haemoglobin and mean corpuscular volume. All individual values were within the normal ranges for rats of the strain and age used and in isolation were considered not to be of toxicological importance.

CLINICAL CHEMISTRY
No toxicologically significant effects were detected.
Males treated with 1000 mg/kg bodyweight/day showed a statistically significant reduction in total protein and a statistically significant increase in chloride concentration. Males from all treatment groups also showed statistically significant reductions in phosphorus. All individual values were within the normal ranges for rats of the strain and age used and in isolation were considered not to be of toxicological importance.

NEUROBEHAVIOUR
- Behavioural Assessments: Weekly open field arena observations did not reveal any treatment-related effects for treated animals when compared to controls.
- Functional Performance Tests: There were no treatment related changes in functional performance.
- Sensory Reactivity Assessments: There were no treatment-related changes in sensory reactivity.

ORGAN WEIGHTS
No toxicologically significant effects were detected in the organ weights measured.
Males treated with 100 mg/kg bodyweight/day showed a statistically significant reduction in spleen weight both absolute and relative to terminal bodyweight. Females treated with 300 mg/kg bodyweight/day showed a statistically significant increase in relative brain weight. In the absence of a true dose related response or any associated histology correlates the intergroup differences were considered not to be of toxicological significance.

GROSS PATHOLOGY
Adults: There were no toxicologically significant macroscopic abnormalities detected in terminal kill animals.
Three males treated with 300 mg/kg bodyweight/day had red lungs at necropsy. A further male from this treatment group had pale lungs and dark cervical lymph nodes. One male treated with 100 mg/kg bodyweight/day also had dark cervical lymph nodes and hydronephrosis in the right kidney. In the absence of a true dose related response or any associated histology correlates the intergroup differences were considered not to be of toxicological importance. One female treated with 1000 mg/kg bodyweight/day, two females treated with 100 mg/kg bodyweight/day and two control females showed fur loss at necropsy. Observations of this nature are commonly observed following lactation and in conjunction with the observation also being present in control females the intergroup differences were considered unrelated to treatment.
The male that was killed in extremis on Day 39 showed thickening in the stomach, white fluid in the thoracic cavity, dark kidneys, red lungs and flaccid testes.

HISTOPATHOLOGY: NON-NEOPLASTIC
There were no treatment related microscopic abnormalities detected in terminal kill animals.
All findings noted in this study were considered to be incidental findings commonly noted in rats of this strain and age or findings associated with the status post partum.
The cause of death in the male that was killed in extremis was considered to be due to a misplaced gavage with perforation leading to necrotizing inflammation around the trachea, oesophagus, lungs and thymus. This was therefore considered to be unrelated to test material toxicity.

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Critical effects observed:

not specified

Conclusions:

The oral administration of Calcium Carbonate (nano) to rats by gavage, at dose levels of 100, 300 and 1000 mg/kg bodyweight/day, resulted in treatment-related effects at all dose levels. These effects were considered not to represent an adverse effect of treatment, hence the 'No Observed Adverse Effect Level' (NOAEL) for systemic toxicity was considered to be 1000 mg/kg bodyweight/day.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

1 000 mg/kg bw/day

Study duration:

subacute

Species:

rat

Quality of whole database:

A number of studies or reviews are available for the majority of the constituents of SFL.

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Repeat dose oral toxicity:

No repeat dose oral toxicity studies are available for SFL. Data are available for a number of the main constituents, however.

Calcium carbonate (61.8 – 95.6 %w/w of SFL)

A 28 day repeat dose oral toxicity study combined with a reproduction/ developmental toxicity screening test was performed in the rat in accordance with OECD TG 422 [Dunster (2010)]. Calcium carbonate (nano) was administered by gavage to three groups, each of ten male and ten female Wistar rats, for up to forty-eight consecutive days (including a two week maturation phase, pairing, gestation and early lactation for females), at dose levels of 0, 100, 300 and 1000 mg/kg bodyweight/day. Clinical signs, behavioural assessments, bodyweight change, food and water consumption were monitored during the study. Haematology and blood chemistry were evaluated prior to termination on five selected males and females from each dose group. All animals were subjected to a gross necropsy examination and histopathological evaluation of selected tissues was performed. Although administration of the test material resulted in treatment-related effects at all dose levels, these effects were considered not to represent an adverse effect of treatment. Hence, the NOAEL for systemic toxicity was considered to be 1000 mg/kg bodyweight/day.

The daily oral administration of calcium carbonate (nano) to mice over a period of 28 days at dose levels of 0, 13, 130 and 1300 mg/kg bw/day, did not produce any obvious symptoms of toxicity or mortality even at the highest dose administered [Huang et al, 2009]. The NOAEL was therefore reported to be 1300 mg/kg bw/day.

Calcium carbonate occurs in the natural environment and humans are widely exposed to naturally occurring calcium carbonate, e. g. via drinking water on a day to day basis. Calcium carbonate is also a food additive approved by the Council Directive 95/2/EC on food additives (the substance has the acronym E 170). Ingested calcium and carbonate ions are actively regulated by the body.

The European Commission Scientific Committee on Food has produced a report on the Tolerable Upper Intake Level of Calcium (2003). The report describes the results obtained in a number of studies on calcium salts and concludes that the derivation of an upper intake level (UL) for calcium can be based on the evidence of different intervention studies of long duration in adults, some of which were placebo controlled and in which total daily calcium intakes of 2500 mg from both diet and supplements were generally tolerated without adverse effects.

The document prepared by the Scientific Committee on Food describes a number of potential adverse effects following calcium supplementation. These might include the following:

 1). Kidney function: Some studies have indicated that perimenopausal women with total calcium intakes between 2 and 3 g/day may show a tendency for compromised glomerular function as indicated by increases in serum creatinine. However, no such effect was observed in another study with women receiving comparable calcium amounts. Therefore, it is not clear whether this finding can be attributed to the ingestion of calcium.

 2). Milk-alkali syndrome: Manifestation of the milk-alkali syndrome through the combined intake of calcium both from food and especially from supplements and of absorbable alkalinising substances is facilitated by renal insufficiency, alkalosis and dehydration due to vomiting and anorexia and/or the use of thiazide diuretics, which increase renal tubular calcium reabsorption. All reported cases of milk-alkali syndrome in association with the prolonged or acute ingestion of calcium supplements used calcium carbonate as the nutrient source. In these reports the supplemental calcium intakes were reported as between 1.0 and 23 g/day. These patients also differ in their medical history, use and duration of use of drugs and alkali consumption, and their diets. Their dietary calcium intakes are often not known.

The use of calcium carbonate supplements in doses up to 2000 mg/day, and thereby achieving total daily calcium intakes up to more than 3000 mg/day, for preventive purposes in presumably healthy subjects, has not provoked the development of the milk-alkali syndrome, whereas the administration of large amounts (11.2 g calcium/day) of calcium carbonate in addition to large amounts of milk (1.8 g calcium/day) over 7 days to 20 gastric/duodenal ulcer patients resulted in reversible hypercalcaemia (2.8 mmol/L) in nine patients and renal insufficiency in all.

In conclusion, on the basis of the available evidence, a calcium dose which by itself might cause milk-alkali syndrome cannot be identified. The primary cause of milk-alkali syndrome appears to be when significantly large doses of calcium are ingested and is more prevalent in those people suffering from renal insufficiency.

 3). Kidney stones: Observational studies on the relationship between total calcium intake and kidney stone incidence and interventional studies with calcium supplements do not allow definition of a calcium intake on a population basis which promotes kidney stone formation. On dietary calcium intakes in the range of the recommended dietary intake the risk of nephrolithiasis is determined by other dietary components and by genetic factors.

 4). Interaction with minerals: Single-dose experiments demonstrate interference of both dietary and supplemental calcium with the absorption of other minerals. However, this effect is not demonstrable in long-term observational and interventional studies at dietary calcium intakes in the range of recommended intakes and at supplemental calcium of up to 2000 mg/day in adults and up to 1200 mg/day in one study with infants.

 In conclusion, calcium carbonate ingestion in humans up to the tolerable upper intake level of 2500 mg calcium per day (equivalent to a dose of calcium carbonate of 104 mg/kg bw/day for a 60 kg person) does not cause any adverse effects. Effects are only seen when this dose is significantly exceeded. Furthermore, as calcium carbonate is used as a food additive with an ADI not allocated, it can be concluded that intake of calcium carbonate should not pose a need for concern regarding its toxicity via the oral route.

European Commission (2003) Opinion of the Scientific Committee on Food on the Tolerable Upper Intake Level of Calcium, SCF/CS/NUT/UPPLEV/64 Final.

Silicon dioxide (0.50 – 22.0 %w/w of SFL)

A chronic study is available in the literature [Takizawa et al (1988) ]. In this study groups of 40 Fischer rats were fed 0, 12,500, 25,000 or 50,000 ppm silicon dioxide in the diet (equivalent to 0, 1.25, 2.5 or 5 g SiO2/ kg bw/day) for up to 24 months. The silicon content of the basal diet was not stated. No significant dose-related effects on food consumption, growth rate, survival, haematology or microscopic pathology were observed. Mineral levels in the tissues were not measured. Liver weights were reduced (by up to 15%) in the 2.5 and 5% females from 12-24 months; a clear dose related trend was not apparent. No dose related pathological changes were observed. No dose related increases in tumours were apparent but a relatively small number of animals were used in the study. The few effects identified may have resulted from a nutritional imbalance and therefore may not be relevant to humans. The top dose (equivalent to 2,500 mg/kg bw/day silicon dioxide, or 1,165 mg silicon/kg bw/day) was regarded as a NOAEL.

Based on this study, the Expert Group on Vitamins and Minerals (2003) applied uncertainty factors of 10 for inter-species and 10 for intra-species variation to derive a safe upper level for supplemental silicon dioxide of 25 mg/kg bw/day.

EVM (2003) Safe Upper Levels for Vitamins and Minerals, Silicon, 306-312 http: //cot. food. gov. uk/pdfs/vitmin2003. pdf

Tricalcium phosphate (0.08 – 2.4 %w/w of SFL)

The results of an OECD 422 study are available in the secondary literature [OECD (2009) ]. Tricalcium phosphate was administered via gavage at dose levels of 0, 250, 500 and 1,000 mg/kg bw/day to male rats from 2 weeks before mating to the end of the mating period, for at least 28 days, and to females from 2 weeks before mating to day 4 of lactation including the mating and gestation periods. Ten animals/sex/dose were assigned to the main group and 6 animals/sex/dose were used in the recovery group. No death was observed in either sex. There were no treatment-related changes in clinical signs, body weight, food consumption, urinalysis, hematology, serum biochemistry, necropsy finding and organ weights. At histopathological examination, slight tubulardegeneration/regeneration was observed in kidney in males and mineralization in kidney in females at 1,000 mg/kg bw/day. However, these findings were not considered to be toxicologically significant, since no treatment-related changes were observed in serum biochemistry due to kidney dysfunction. Based on these results, the NOAEL for repeated dose oral toxicity was considered to be 1,000 mg/kg bw/day in both sexes (the highest dose tested).

Magnesium carbonate (0.4 – 3.4 %w/w of SFL)

No repeated dose oral toxicity study is publicly available for magnesium carbonate. However, a study is available for magnesium chloride hexahydrate. Read across is justified as when magnesium carbonate is ingested orally it is converted into the chloride through reaction with stomach acid and in any case systemic toxicity is likely to be caused by absorption of the magnesium ion rather than the carbonate or chloride ions. In the available study [Takizawa T, et al (2000)] four groups of 10 male and 10 female F344 rats received magnesium chloride hexahydrate by dietary supplementation at 0, 0.1, 0.5 or 2.5 % (equivalent to 0, 62, 308 or 1600 mg MgCl2/kg bw/day (males) and 0, 59, 299 or 1531 mg MgCl2/kg bw/day (females)) for 90 days. No treatment-related death was observed during the study. Transient soft stool and sustained increase in water consumption were observed both in males and females of the 2.5% group and slight reduction in body weight gain was noted in the high-dose males. There were no toxic changes in food consumption, organ weights, hematology and biochemistry, and histopathological examinations in any treated-groups. Based on these results, the no-observed-adverse-effect-level was estimated to be 0.5% equivalent to 308 mg MgCl2/kg bw/day for males and 299 mg MgCl2/kg bw/day for females. Converting to MgCO3, this is equivalent to 127 mg/kg bw/day for males and 124 mg/kg bw/day for females.

Calcium oxalate (0-5.9 %w/w of SFL)

No repeated dose toxicity studies are available for calcium oxalate.

Oxalate salts are a natural part of the human diet and daily intake is very dependent on individual food composition.Daily adult oxalate intake is usually 80-120 mg/day; it can range from 44-1000 mg/d in individuals who eat a typical Western diet.

Dietary oxalate accounts for only a small part of the oxalate found in urine. The largest part of excreted oxalate is formed by the endogenous metabolism of carbohydrates.Oxalates themselves will be metabolised through the Formyl CoA Oxalate CoA transferase. Oxalate urinary excretion is in the range of 20 to 40 mg/day and is the result of dietary intake, endogenous metabolism and catabolism.

If we exclude the massive intoxications with oxalic acid leading to calcium chelation and then tetany and coagulation disorders, the main pathology associated with oxalate presence in the organism is the formation of calcium oxalate bladder stones. Only 20% of the cases of calcium oxalate bladder stones seem to be linked to clear increase in oxalate excretion and oxalic acid restriction is not always sufficient to reduce the risk of oxalate bladder stones formation. However, studies are available (for example) von Unruh, et al (2004) which demonstrate that when oxalic acid is ingested in combination with calcium then the absorption of oxalate is inversely related to the amount of calcium, i.e. increasing levels of calcium decrease the amount of absorption. In the case of SFL, the oxalate is already present as the calcium salt. In addition, due to the ratio of calcium oxalate to calcium carbonate, there is a large reservoir of calcium present which should ensure that the oxalate remains as the calcium salt and is excreted in faeces rather than being absorbed to any great extent.

von Unruh GE, Voss S, Sauerbruch T, Hesse A. Dependence of oxalate absorption on the daily calcium intake. J Am Soc Nephrol. 2004 Jun;15(6):1567-73

Aluminium oxide (0-2.5 % w/w)

The toxicity of aluminium to humans has been evaluated by EFSA (2008). The Panel considered that all species of inorganic aluminium will equally contribute to aluminium body burden. Aluminium occurs naturally in the environment and is also released due to anthropogenic activities. A variety of aluminium compounds are produced and used for different purposes, such as in water treatment, papermaking, fire retardant, fillers, food additives, colours and pharmaceuticals. Aluminium metal, mainly in the form of alloys with other metals, has many uses including in consumer appliances, food packaging and cookware. The major route of exposure to aluminium for the general population is through food. Aluminium in drinking water represents another, minor, source of exposure. Additional exposures may arise from the use of aluminium compounds in pharmaceuticals and consumer products. Due to the design of the human dietary studies and the analytical methods used, which only determine the total aluminium content in food, and not the individual aluminium compounds or species present, it is not possible to conclude on the specific sources contributing to the aluminium content of a particular food, such as the amount inherently present, the contributions from use of food additives, and the amounts released to the food during processing and storage from aluminium-containing foils, containers, or utensils. Thus a detailed breakdown by exposure source is not possible.

The estimated daily dietary exposure to aluminium in the general population, assessed in several European countries, varied from 0.2 to 1.5 mg/kg bw/week at the mean and was up to 2.3 mg/kg bw/week in highly exposed consumers.

In view of the cumulative nature of aluminium in the organism after dietary exposure, the Panel considered it more appropriate to establish a tolerable weekly intake (TWI) for aluminium rather than a tolerable daily intake (TDI). Based on the combined evidence from the above-mentioned studies, the Panel established a TWI of 1 mg aluminium/kg bw/week. However, this is likely to be exceeded in a significant part of the European population.

 

EFSA (2008) Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Food Contact

Materials on a request from European Commission on Safety of aluminium from dietary intake.The EFSA Journal(2008) 754, 1-34

Organic matter derived from Sugar beet fragments (1.8-18.3 %w/w)

The organic matter present in SFL is derived from sugar beet fragments. Pulp fragments, including the polysaccharides araban and galactan make up the largest proportion, but saccharose, pectin, proteins and calcium maleate and citrate are also present in small percentages. All of these substances are naturally occurring in vegetable foodstuffs consumed by humans and are considered to be safe.

Repeat dose dermal toxicity:

Currently, no studies are available that have evaluated the repeated dose dermal toxicity of SFL. SFL is primarily composed of inorganic substances (the major constituent is calcium carbonate, along with silicon dioxide and a small amount of other inorganic salts) and the remainder is composed of organic plant material. It is expected that SFL will partition strongly to water rather than organic media. While it is not possible to measure or accurately predict an octanol/water partition coefficient for inorganic ionic or UVCB substances like SFL, such a value would be expected to be very low. Electrolytes are also known not to penetrate the skin in any significant quantity. Given the physico-chemical properties of SFL, it is not expected that the substance would penetrate the skin in any significant quantity and so would therefore not cause any toxic effects following repeated dermal exposure.

 Repeat dose inhalation toxicity:

Currently, no studies are available that have evaluated the repeated dose inhalation toxicity of SFL. Testing to determine the dust generation tendency ('dustiness') of SFL as manufactured and supplied (containing 27.75 %w/w water) has been performed according to DIN 55992 -1:2006 [Selck & Parr (2010)]. The results of the study were as follows: total dustiness = 7.85 mg/g (0.785 %w/w); inhalable fraction = 4.45 mg/g (0.445 %w/w); thoracic fraction = 0.20mg/g (0.02 % w/w); and respirable fraction = 0.01 mg/g (0.001 %w/w). Based on this study it is concluded that although the particle size distribution data indicates that SFL is potentially inhalable, exposure via this route during use of the substance in the form it is manufactured and supplied is unlikely as the inhalable fraction is expected to be < 0.5 %w/w.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Study performed on the main constituent of SFL

Justification for classification or non-classification

Studies on calcium carbonate can be read across to SFL. No systemic toxicological findings could be detected in rats after repeated administration of calcium carbonate by the oral route for a period of 28 days. A number of potential adverse effects have been reported following calcium supplementation e.g. effects on kidney function, milk-alkali syndrome, kidney stones and interactions with minerals. However, these effects are more prevalent in those people suffering from renal insufficiency and following the ingestion of high doses of calcium (well above the recommended classification limits for STOT RE as defined in the Guidance on the Application of Regulation (EC) No 1272/2008). Therefore, a classification as STOT RE for SFL is not justified and no classification is proposed.