Sodium dihydrogenorthophosphate

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Link to relevant study records

Reference

Endpoint:

extended one-generation reproductive toxicity - basic test design (Cohorts 1A, and 1B without extension)

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Effect on fertility: via oral route

Endpoint conclusion:

no study available (further information necessary)

Effect on fertility: via inhalation route

Endpoint conclusion:

no study available

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Effects on developmental toxicity

Description of key information

One reliable study is supplied for the endpoint ‘8.7.1 Screening for reproductive / developmental toxicity’. This study has been conducted according to an appropriate method (OECD guideline 422) and under the conditions of GLP.  However as the study is only a 28-day study and in accordance with Annex XI, Section 3.2 (a.ii) of Regulation (EC) N0. 1907/2006 (REACH) the data are not considered to be suitable for derivation of a DNEL as subchronic data are available. Furthermore, full access to the data has not been granted to all registrants.
In addition a key study is available for the endpoint '8.7.2. Developmental toxicity study'. This study assesses the teratogenic potential of sodium dihydrogenorthophosphate (Bailey, 1975) in rats and mice. This study is considered to be adequate to fulfil this endpoint. In addition, supporting data on the analogous substance monopotassium phosphate is also provided to support the lack of developmental toxicity potential of sodium and potassium orthophosphates as a group of chemicals. Studies on additional test species are not considered to be scientifically necessary due to the lack of toxicity of the substance to be registered. 

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06/10/1974 - 02/11/1974

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

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 CD-1 mice 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 150 mg/kg) or test article in a water suspension (10 mL/kg bw) at 3.7, 17.2, 79.7 or 370.0 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 and humidity were recorded. On Day 17 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:

mouse

Strain:

other: albino CD-1

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Outbred
- Age at study initiation: No data
- Weight at study initiation: 29 - 31 g
- Fasting period before study: No data
- Housing: Gang housing in disposable plastic cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: No data


ENVIRONMENTAL CONDITIONS
- Temperature (°C): ave 21 - 26
- Humidity (%): 42 - 74%

IN-LIFE DATES: From: 06/10/1974 To: 02/11/1974

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
VEHICLE: Water
- Amount of vehicle (if gavage): 10 mL/kg bodyweight

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

- Impregnation procedure: cohoused
- 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:

17 days

No. of animals per sex per dose:

Test material and vehicle control: 25 females / dose level
Positive control: 27 females
Table 1 Number of animals dosed
Material Dose (mg/kg) Total
Mated Pregnant
Sham 0.0 25 21
Aspirin 150.0 27 20
FDA 73-2 3.7 25 22
17.2 25 19
79.7 25 20
370.0 25 22

Control animals:

yes, sham-exposed

other: positive control: 150 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 17.
POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 17
- 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:

> 370 mg/kg bw/day

Based on:

test mat.

Basis for effect level:

other: no effects noted

Abnormalities:

no effects observed

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Dose descriptor:

NOAEL

Effect level:

> 370 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects noted

Abnormalities:

no effects observed

Developmental effects observed:

no

Table 2 Reproduction data

Dose (mg/kg)	Sham	Aspirin	3.7	17.2	79.7	370.0
Pregnancies
Total No.	21	20	22	19	20	22
Died or aborted (before Day 17)	0	0	0	0	0	0
To term (on Day 17)	21	20	22	19	20	22
Corpora Lutea
Total no.	275	233	255	233	251	279
Average/dam mated	11.0	8.63	10.2	9.32	10.0	11.2
Live litters
Total No.*	21	20	22	19	20	22
Implant Sites
Total No.	259	218	240	224	236	255
Average/dam*	12.3	10.9	10.9	11.8	11.8	11.6
Resorptions
Total No*	8	8	5	9	10	13
Dams with 1 or more sites resorbed	8	6	5	4	9	11
Dams with all sites resorbed	--	--	--	--	--	--
Per cent partial resorptions	38.1	30.0	22.7	21.1	45.0	50.0
Per cent complete resorptions	--	--	--	--	--	--
Live foetuses				215
Total No	248	208	233	11.3	224	240
Average/dam*	11.8	10.4	10.6	1.01	11.2	10.9
Sex ratio (M/F)	1.04	0.84	0.82		0.84	1.07
Dead Foetuses				--
Total No.*	3	2	2	--	2	2
Dams with 1 or more dead	3	1	2	--	2	2
Dams with all dead	--	--	--	--	--	--
Per cent partial dead	14.3	5.00	9.09	--	10.0	9.09
Per cent all dead	--	--	--	--	--	--
Average foetus weight (g)	0.8	0.85	0.85	0.92	0.93	0.86

* Includes only those dams examined at term

** Positive control: 150 mg/kg

 

Table 3 Summary of skeletal findings

Findings	Dose (mg/kg)
	Sham	Aspirin	3.7	17.2	79.7	370.0
Live foetuses examined (at term)	173/21	144/20	165/22	148/149	156/20	167/22
Sternebrae
Incomplete oss.	60/19	65/19	32/14	51/16	13/5	81/19
Scrambled
Bipartite		1/1		3/2		3/2
Fused
Extra
Missing	39/12	36/11	19/9	13/7	2/2	20/12
Other
Ribs
Incomplete oss.
Fused/split				1/1
Wavy
Less than 12
More than 13	23/10	32/14	23/12	25/10	30/16	25/15
Other
Vertebrae
Incomplete oss.	4/2	11/5	4/3	1/1
Scrambled
Fused
Extra ctrs. oss.
Scoliosis
Tail defects
Other
Skull
Incomplete closure	2/2
Missing
Craniostosis
Other
Extremities
Incomplete oss.	6/4	15/5	2/2	1/1		1/1
Missing
Extra
Miscellaneous
Hyoid; missing	30/12	60/16	24/12	26/11	27/11	43/15
Hyoid; reduced	26/12	18/13	22/13	26/16	19/10	22/14

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

** Positive control: 150 mg/kg

Summary of soft tissue abnormalities: 1 pup from a litter where the dam was dosed with 3.7 mg/kg test material showed exophthalmos and encephalmeningocele.

Conclusions:

Under the conditions of the study, the test material administered to pregnant mice for 10 days up to a dose level of 370 mg/kg bw showed no maternal or developmental toxicity. The NOAEL for both maternal and fetoxicity is > 370 mg/kg bw.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

370 mg/kg bw/day

Study duration:

subchronic

Species:

mouse

Quality of whole database:

One key study exists - both mice and rats are investigated. In addition, supporting evidence on an analogous substance is also submitted. Both studies are Klimisch reliability 2.

Additional information

Justification for read-across

In accordance with REACH Annex XI, Section 1.5, of Regulation (EC) No. 1907/2006 (REACH) the standard testing regime may be adapted in cases where a grouping or read-across approach has been applied.

The similarities may be based on:

1. A common functional group

2. The common precursors and/or the likelihood of common breakdown products via physical or biological processes, which result in structurally similar chemicals; or

3. A constant pattern in the changing of the potency of the properties across the category

The following substances are considered to be similar enough to facilitate read across for systemic toxicity endpoints:

Sodium dihydrogenorthophosphate, CAS: 7558-80-7

Disodium hydrogenorthophosphate, CAS: 7558-79-4

Trisodium orthophosphate, CAS: 7601-54-9

Potassium dihydrogenorthophosphate, CAS: 7778-77-0

Dipotassium hydrogenorthophosphate, CAS: 7758-11-4

Tripotassium orthophosphate, CAS: 7778-53-2

Potassium pentahydrogen bis(phosphate), CAS: 14887-42-4

The source chemicals and the target chemical have the following similar properties:

1. All members of the group are structurally similar ionic inorganic compounds with the anion only changing by the number of hydrogen atoms to account for changes in charge due to increase in cation numbers.

Progression through the group sees an increase in cation number from one to three followed by a change in cation from sodium to potassium and again an increase in number from one to three. Both cations are group 1 alkali metals with the same ionic charge, similar chemical behaviour and both sodium and potassium are essential biological elements. Both the Na+ and the K+ cation have a similar biological function and therefore orthophosphate salts of these types are not considered to differ in their systemic toxicity profile.

2. All members of the group will ultimately dissociate into the common breakdown products of the Na+ or K+ cations and the PO43- anion.

3. All substances have been shown to have a similar systemic toxicological profile and predictable physicochemical nature.

No members of the group are classified for acute toxicity and generally exhibited no mortalities at the classification limit. Two members of the group are classified for local effects only (i.e. skin/eye irritation) which will not have an impact on the systemic toxicity of the compounds. Irritation effects are considered to be predictable based on structural similarities. All are highly water soluble.

Justification for selection of Effect on developmental toxicity: via oral route:
One key study exists. Selection is made on the basis that the mouse study had a slightly lower NOAEL (although this was still a greater than value).

Justification for classification or non-classification

Under the conditions of the study, the test material administered to pregnant mice for 10 days up to a dose level of 370 mg/kg bw showed no maternal or developmental toxicity. The NOAEL for both maternal and fetotoxicity in mice is > 370 mg/kg bw.

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