Tetrasodium pyrophosphate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

There were no studies available on tetrasodium pyrophosphate. The reproductive toxicity endpoint has been addressed with the following data adaptations:

Section 8.7.1. Adaptation

According to Annex VIII, Section 8.7.1, Column 2 of Regulation (EC) No. 1907/2006, a screening for reproductive/developmental toxicity study does not need to be conducted if a prenatal development toxicity study is available. A developmental toxicity study on tetrasodium pyrophosphate and the analogue substance disodium dihydrogenpyrophosphate is included in IUCLID Section 7.8.2 of this dossier and therefore a screening study is not considered to be scientifically justified.

Section 8.7.2. Adaptation

The standard requirement for chemicals manufactured or imported into the EU in quantities of >1,000 an extended one generation reproductive toxicity test (EOGRTS). According to the Integrated Testing Strategy (ITS) proposed in the ECHA guidance document on the information requirements and chemical safety assessment, Chapter R. 7a: Endpoint specific guidance, Section 7.6.6, if there is sufficient data to permit a robust conclusion on reproductive toxicity testing then no further testing will be required. The justification for not conducting a two-generation study is based on the evaluation of existing data in laboratory animals, available data on similar or parent compounds, historical data and general characteristics of the test material.

 

For the purpose of assessing the risk of reprotoxicity the following substances are considered to be similar enough to facilitate read across:

 

- disodium dihydrogenpyrophosphate (EC No. 231-835-0)

- trisodium hydrogen diphosphate (EC No. 238-735-6)

- tetrasodium pyrophosphate (EC No. 231-767-1)

- tetrapotassium pyrophosphate (EC No. 230-785-7)

 

LABORATORY STUDIES

- Negative In vitro mutagenicity and genotoxicity evidence suggests a low potential for germ cell mutagenicity. The following studies have been conducted on Na, and K pyrophosphates: Bacterial Reverse Mutation Assay; AMES (OECD 471) and In vitro cytogenicity study in mammalian cells (OECD 473). Whilst these studies look specifically at the effects in somatic cell lines the results are still relevant to the potential of the test material to induce mutagenicity in germ cell lines.

- Negative in vivo genotoxicity data. The results of a dominant lethal assay conducted on disodium dihydrogenpyrophosphate are presented in Section 7.8.2 of this dossier. This study looks at the potential of a chemical substance to induce chromosomal aberrations in the germ cells of rats. As no effects are noted this can be used as part of the evidence against performing studies to investigate the effects on reprotoxicity.

-Developmental toxicity / teratogenicity studies similar to OECD 414 have been conducted on the following substances on behalf of the United States Food and Drug Administration; disodium dihydrogenpyrophosphate (sodium acid pyrophosphate) and tetrasodium pyrophosphate. The studies were conducted in four laboratory animal models; rat, mouse, hamster and rabbit. A range of dose levels up to a high dose of 335 mg/kg bw (mouse, disodium dihydrogenpyrophosphate), 169 mg/kg bw (rat, disodium dihydrogenpyrophosphate), 166 mg/kg bw (hamster, disodium dihydrogenpyrophosphate), 128 mg/kg bw (rabbit, disodium dihydrogenpyrophosphate), 130 mg/kg bw (mouse, tetrasodium pyrophosphate) and 138 mg/kg bw (rat, tetrasodium pyrophosphate) were used. The material was administered by oral intubation for ten consecutive days for rats and mice covering the gestation days 6 to 15. Although the studies were conducted prior to the implementation of Good Laboratory Practice, the study design and content were of sufficient standard to allow meaningful evaluation. The results showed no evidence of developmental toxicity to the foetus of any species or any other adverse effects to the foetus or mother at any dose level. It can therefore be concluded that sodium and potassium orthophosphates are not developmental toxicants at relatively high levels.

The lack of effects on maternal toxicity or offspring development at dose levels well in excess of normal human exposure suggests that sodium and potassium pyrophosphates are not a significant risk to the reproductive process and further studies are unlikely to show any significant effects.

GENERAL DISCUSSION

The pyrophosphate ion is the simplest form of a condensed phosphate group. A condensed phosphate anion has one or several P-O-P bonds. As the pyrophosphate only contains two phosphate groups, both of the phosphorus ions are classed as terminal phosphorus. The pyrophosphate can undergo ionisation with loss of H+ from each of the two –OH group groups on each P and can therefore occur in the -1, -2, -3 or -4 state. The degree of ionisation is dependent on upon the associated cations and the ambient pH (if in solution). As pyrophosphates are ionic in nature they will readily dissociate into their cations and anions in solution.

Sodium and potassium cations are not considered to pose a risk of reprotoxicity as they are essential micronutrients that are well regulated by the homeostatic mechanisms in the body. In addition, the recommended daily intakes of sodium and potassium for young adults are 1500 mg/day/person and 4700 mg/day/person respectively (1). These levels are well above the levels that would be expected in a reprotoxicity study and therefore the sodium or potassium cation can be discounted from further discussion.

The pyrophosphate anion is hydrolysed to orthophosphate by ubiquitous alkaline phosphatase activity. Orthophosphate then goes on to take part in various physiological processes. The World Health Organisation, reports that the maximum tolerable daily intake (MTDI) of phosphates is 70 mg/kg bw (2), this value is considered to be well below that observed for developmental toxicity and as such human exposure is likely to be considerably less that the level required for reprotoxicity testing.

 

Sodium and potassium pyrophosphates are frequently used as food additives (the EU food reference / INS number for tetrasodium pyrophosphate is E450 ii). The contribution of food supplements to phosphorus intake is low. No evidence exists to show that sodium or potassium pyrophosphates are likely to pose a risk of reproductive or developmental toxicity. The main toxicological finding in feeding studies with high levels of phosphates is nephrocalcinosis (the rat is known to be more susceptible to these effects (2, see also IUCLID section 7.5.), these effects are not considered to be relevant to reproductive toxicity.

In conclusion, an additional in vivo reproduction study in the rat is unlikely to result in providing further evidence of reproductive toxicity as the existing studies have demonstrated a lack of effect at dose levels well in excess of expected human exposure. A study would therefore be scientifically and ethically unjustified.

(1) Dietary Reference Intakes for Water, Potassium, Sodium, Chloride and sulphate. www.nap.edu. The National Academies. U.S.A.

(2)Evaluation of certain food additives and contaminants. Twenty-sixth report of the joint FAO/WHO expert committee of food additives. World Health Organisation. Technical Report Series 683. 1982. ISBN92 4 120683 7

Effects on developmental toxicity

Description of key information

Under the conditions of the study on tetrasodium pyrophosphate, administered to pregnant mice for 10 days up to a dose level of 130 mg/kg bw showed no maternal or developmental toxicity. The NOAEL for both maternal and fetotoxicity is > 130 mg/kg bw. 
Tetrasodium pyrophosphate was also administered to pregnant rats for 10 days up to a dose level of 138 mg/kg bw showed no maternal or developmental toxicity. The NOAEL for both maternal and fetotoxicity is > 138 mg/kg bw. 

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3/9/74 - 2/10/74

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Remarks:

Meets generally accepted scientific standards with acceptable restrictions. Deficiencies: Food consumption not reported Uterine weights not determined One third used for visceral examination; should be 50% Test substance identification (Batch etc) missing No details on housing conditions/source of animals Administration only during periods of organogenesis, not until day before pregnancy

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: no data

Deviations:

not specified

Principles of method if other than guideline:

Adult female albino (Wistar derived stock) rats were mated with young adult males. Observation of a vaginal sperm plug was considered as Day 0 of gestation. Dosing by oral intubation with a control (Vehicle at level equivalent to group receiving the highest dose or aspirin at 250 mg/kg) or test article in a water suspension at 1.38, 6.41, 29.7 and 138.0 mg/kg was carried out daily on Days 6 to 15 of gestation. Observations of body weight, appearence, behaviour, and food consumption were performed. Daily room temperature was recorded. On Day 20 of gestation all dams underwent Caesarean section. Sex, number of corpora lutea, implantation sites, resorption sites and live/dead foetuses recorded. Body weights of live pups recorded. Urogenital tract of each dam examined for anatomical normality. All foetuses examined grossly for presence of external congenital abnormalities. One third foetuses of each litter underwent detailed visceral examination and the remaining two thirds were cleared in potassium hydroxide, stained with alizarin red S dye and examined for skeletal defects.

GLP compliance:

no

Remarks:

Study predates GLP

Limit test:

no

Species:

rat

Strain:

Wistar

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Outbred
- Age at study initiation: No data
- Weight at study initiation: 215 - 221 g
- Fasting period before study: No data
- Housing: Individual housing in mesh bottom cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: No data


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 - 26.7
- Humidity (%): 62 - 76

IN-LIFE DATES: 3/9/74 - 2/10/74

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
VEHICLE: Water
- Amount of vehicle (if gavage): 1 mL/kg bw at doses equal to or below 250 mg/kg bw and 2 mL/kg at doses up to 500 mg/kg bw

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- Impregnation procedure: No data
- Proof of pregnancy: vaginal plug referred to as day 0 of pregnancy

Duration of treatment / exposure:

10 days (Day 6 to Day 15 of gestation)

Frequency of treatment:

Daily

Duration of test:

20 days

No. of animals per sex per dose:

Table 1 Number of animals dosed
Material Dose (mg/kg) Total
Mated Pregnant
Sham 0.0 25 20
Aspirin 250.0 25 19
FDA 73-1 1.38 23 21
6.41 24 20
29.7 25 20
138.0 25 19

Control animals:

yes, sham-exposed

other: positive control: 250 mg/kg aspirin

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Appearence, behaviour, food consumption and weight observed daily.
DETAILED CLINICAL OBSERVATIONS: No
BODY WEIGHT: Yes
- Time schedule for examinations: Body weights recorded on days 0, 6, 11, 15 and 20.
POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: uterus and urogenital tract

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of resorptions: Yes

Fetal examinations:

- External examinations: Yes: one third per litter
- Soft tissue examinations: Yes: one third per litter
- Skeletal examinations: Yes: two thirds per litter
- Head examinations: Yes: two thirds per litter

Statistics:

No data

Indices:

No data

Historical control data:

No

Details on maternal toxic effects:

Maternal toxic effects:no effects

Dose descriptor:

NOAEL

Effect level:

> 138 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: no effects observed

Abnormalities:

no effects observed

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Dose descriptor:

NOAEL

Effect level:

> 138 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects observed

Abnormalities:

not specified

Developmental effects observed:

no

Table 2 Reproduction data

Dose (mg/kg)	Sham	Aspirin	1.38	6.41	29.7	138.0
Pregnancies
Total No.	20	19	21	20	20	19
Died or aborted (before Day 20)	0	0	0	0	0	0
To term (on Day 20)	20	19	21	20	20	19
Corpora Lutea
Total no.	244	258	267	263	249	248
Average/dam mated	9.76	10.3	11.6	11.0	9.96	9.92
Live litters
Total No.*	20	19	21	20	20	19
Implant Sites
Total No.	228	225	240	249	237	232
Average/dam*	11.4	11.8	11.4	12.5	11.9	12.2
Resorptions
Total No*	4	17	1	5	8	1
Dams with 1 or more sites resorbed	2	8	1	4	6	1
Dams with all sites resorbed	--	--	--	--	--	--
Per cent partial resorptions	10.0	42.1	4.76	20.0	30.0	5.26
Per cent complete resorptions	--	--	--	--	--	--
Live foetuses
Total No	224	208	239	244	229	231
Average/dam*	11.2	11.0	11.4	12.2	11.5	12.2
Sex ratio (M/F)	0.96	1.04	0.98	0.95	1.14	0.94
Dead Foetuses
Total No.*	--	--	--	--	--	--
Dams with 1 or more dead	--	--	--	--	--	--
Dams with all dead	--	--	--	--	--	--
Per cent partial dead	--	--	--	--	--	--
Per cent all dead	--	--	--	--	--	--
Average foetus weight (g)	3.90	2.97	4.01	4.01	3.95	4.09

* Includes only those dams examined at term

** Positive control: 250 mg/kg

 

Table 3 Summary of skeletal findings

Findings	Dose (mg/kg)
	Sham	Aspirin	4.1	19.0	88.3	410.0
Live foetuses examined (at term)	156/20	145/19	165/21	169/20	163/20	160/19
Sternebrae
Incomplete oss.	20/12	86/18	36/14	19/11	46/15	7/5
Scrambled
Bipartite		3/2	1/1
Fused
Extra
Missing	2/2	117/19	9/7	4/3	15/9
Other
Ribs
Incomplete oss.	3/2			2/1
Fused/split		1/1
Wavy	21/9	55/16	25/11	23/8	24/13	13/9
Less than 12	1/1
More than 13		110/17	5/1		1/1	1/1
Other
Vertebrae
Incomplete oss.	6/4	64/17	4/2	3/2	2/2
Scrambled
Fused
Extra ctrs. oss.
Scoliosis
Tail defects
Other
Skull
Incomplete closure	32/12	48/14	19/12	27/11	17/7	18/9
Missing
Craniostosis
Other
Extremities
Incomplete oss.	1/1	4/3
Missing
Extra
Miscellaneous
Hyoid; missing	16/8	45/15	10/8	17/9	17/7	10/9
Hyoid; reduced	29/14	9/6	19/10	19/9	13/7	28/10

* Numerator = Number of foetuses affected; Denominator = Number of litters affected

** Positive control: 250 mg/kg

 

Table 4 Summary of soft tissue abnormalities

Material	Dose level (mg/kg)	Dam	Number of pups	Description
Aspirin	250.0	43634	1	Encephalomeningocele; encephalomyelocele
		43639	1	Gastroschisis
		43645	1	Hydrocephalus
		43654	4	Encephalomyelocele
		43655	1	Encephalomyelocele
FDA 73-1	6.41	43707	1	Hydrocephalus; cleft palate

Conclusions:

Under the conditions of the study, the test material administered to pregnant rats for 10 days up to a dose level of 138 mg/kg bw showed no maternal or developmental toxicity. The NOAEL for both maternal and fetotoxicity is > 138 mg/kg bw.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

138 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

Two key studies (One study report, two different test animals) are available to assess the teratogenic potential of tetrasodium pyrophosphate (Bailey, 1974 ) in mice and rats. This study is considered to be adequate to fulfil this endpoint. In addition supporting data on the analogous substance disodium dihydrogenpyrophosphate is provided to support a lack of developmental toxicity potential for sodium and potassium pyrophosphates.

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

There are no structural alerts to suggest that tetrasodium pyrophosphate is a developmental toxicant. The data presented are considered to adequately address this endpoint for the purpose of human risk assessment.

Justification for classification or non-classification

Tetrasodium pyrophosphate is not known nor presumed to be a human reproductive toxicant. In addition, based on knowledge of the use of the substance reproductive toxicity is not suspected.

No maternal or developmental toxicity was observed in the teratogenicity studies performed on tetrasodium pyrophosphate and there is no evidence to suggest that tetrasodium pyrophosphate will have any effect on lactation.

It is not considered to be scientifically justified to further investigate the effects of tetrasodium pyrophosphate on reprotoxicity, developmental or maternal toxicity and as such no classification is proposed for this endpoint and no further studies are deemed necessary.