Disodium hydrogenorthophosphate

Endpoint summary

Description of key information

The key information has been provided on the analogous substance sodium aluminium phosphate. The key study (Matalski K, 1972b) has been selected as the most reliable or appropriate study for use in the derivation of DNELS. 
In addition a reliable 28 day study (OECD 422) exists for the analogous substance dipotassium hydrogenorthophosphate (Shim, 2005), 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.
Additional supporting data provided on sodium dihydrogenorthophosphate are not considered to fulfil the guideline requirements for repeated dose toxicity (sub-chronic or chronic). Full justification for the choice of data and the rationale for read-across can be found below.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
See read-across justification report under Section 13 ‘Assessment Reports’.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
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 source substance and the target substance are considered to be similar enough to facilitate read-across for the following reasons:
1. Both substances are similar inorganic ionic compounds. In aqueous solutions they will dissociate to their cationic and anionic forms and therefore these can be viewed as separate moieties with regards to toxicity
2. Both substances will ultimately dissociate into the common breakdown products of the Na+ cations and the PO43- anion. The Al3+is present in the substance tested in the studies from which the values for risk assessment are derived and therefore no further consideration of the toxicity of the aluminium cation is required as this is already taken into account
3. The Na+ cations are naturally occurring essential minerals that are highly regulated by homeostatic mechanisms. As such recommended intake values for all exist and are about the key NOAEL taken from the data and therefore no further assessment of their contribution to the toxicity of the materials is necessary. The phosphate moiety is not considered to differ to that from any other inorganic orthophosphate from a toxicological point of view for the purpose of risk assessment/

The main toxicological finding in repeated dose studies with most inorganic phosphates is nephrocalcinosis (calcification of the kidneys). It is noted by JEFCA that rats are particularly susceptible to these effects and these effects were taken into account when deriving the MTDI value.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See read-across justification report under Section 13 ‘Assessment Reports’.

3. ANALOGUE APPROACH JUSTIFICATION
See read-across justification report under Section 13 ‘Assessment Reports’.

4. DATA MATRIX
See read-across justification report under Section 13 ‘Assessment Reports’.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

no guideline followed

Principles of method if other than guideline:

A 90 day oral toxicity study was conducted with purebred beagle dogs fed KASAL at dietary levels of 0.3, 1.0 and 3.0%.

GLP compliance:

no

Remarks:

Study predates GLP

Limit test:

no

Species:

dog

Strain:

Beagle

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Laboratory's own IBTL colony
- Age at study initiation: See Table 1
- Weight at study initiation: See Table 1
- Fasting period before study: No data
- Housing: Animals were housed in kennels equipped with outside runs. Four dogs of the same sex and group were accommodated in a single kennel.
- Diet (e.g. ad libitum): Stock diet (Golden Choice Meals, Adolph Coors Company, Denver, Colorado) available ad libitum
- Water: available ad libitum
- Acclimation period: The dogs were observed for two weeks prior to the start of the investigation during which time they were reimmunised against rabies, distemper, infectious canine hepatitis and leptospirosis and rendered clinically free of any existing parasitic infestation.


ENVIRONMENTAL CONDITIONS
No data


IN-LIFE DATES: No data

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: No data


DIET PREPARATION
- Rate of preparation of diet (frequency): At the beginning of each week
- Mixing appropriate amounts with (Type of food): The appropriate dietary constituents for each group were thoroughly blended in a Hobart mixer. Preweighed amounts were distributed into self-feeding units and maintained in excess of the animals' consumption. One such unit was available to the dogs in each kennel on an ad libitum basis 24 hours per day.
- Storage temperature of food: No data


VEHICLE
Not applicable

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

Not applicable

Duration of treatment / exposure:

90 days

Frequency of treatment:

Continuous exposure in feed

Remarks:

Doses / Concentrations:
0.3, 1.0 and 3.0%
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
Male: 94.23, 322.88 and 1107.12 mg/kg bw/day Female: 129.31, 492.77 and 1433.56 mg/kg bw/day
Basis:
other: Calculated using the mean of the weekly body weight and food consumption (Week 5 has been discounted from the 492.77 mg/kg bw/day femal group due to illegible figures in the report)

No. of animals per sex per dose:

4 animals/sex/dose

Control animals:

yes, plain diet

Details on study design:

No data

Positive control:

Not used

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Daily


BODY WEIGHT: Yes
- Time schedule for examinations: The body weight of each dog in every group was determined and recorded at the start of the study and weekly thereafter.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): At the end of each 7 day period, all unconsumed food was collected and weighed. Food consumption was calculated and recorded.


FOOD EFFICIENCY: No


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: Prior to inception of the study and after 42 and 84 days of testing
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: all animals
- Parameters: Total leukocyte count, erythrocyte count, haemoglobin, haematocrit, differential leukocyte count


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Prior to inception of the study and after 42 and 84 days of testing
- Animals fasted: No data
- How many animals: all animals
- Parameters: Blood urea nitrogen, serum glucose, serum alkaline phosphatase, serum glutamic-oxalacetic transaminase, serum glutamic-pyruvic transaminase


URINALYSIS: Yes
- Time schedule for collection of urine: Prior to inception of the study and after 42 and 84 days of testing
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters: Albumin, glucose, pH, microscopic elements (leukocytes, erythrocytes, crystals)


NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
All major tissues and organs were examined grossly. The weights of the following organs were obtained: liver, kidneys, heart, brain, spleen, gonads, adrenal glands, thyroid gland and pituitary gland.

HISTOPATHOLOGY: Yes (see table)

Other examinations:

None

Statistics:

No data

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:

not examined

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

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:

CLINICAL SIGNS AND MORTALITY: No untoward behavioural reactions were recorded during the investigation and no fatalities occurred.


BODY WEIGHT AND WEIGHT GAIN: No significant deviations from normally expected body weight gains for dogs of this age were noted (see Table 1).


FOOD CONSUMPTION AND COMPOUND INTAKE : There is no significant difference between the untreated control group and the three test groups (see Table 2).


HAEMATOLOGY: No significant abnormalities were noted at any level tested (see attached Tables 3-11).


CLINICAL CHEMISTRY: There is no significant difference between the untreated control group and the three test groups (see attached Tables 12-16).


URINALYSIS: Urinalysis revealed no significant abnormalities at any of the levels tested (see attached Tables 17-23).


ORGAN WEIGHTS: No significant abnormalities were noted among any levels tested (see attached Tables 24-32).


GROSS PATHOLOGY and HISTOPATHOLOGY: NON-NEOPLASTIC: There are no changes that can be attributed to the test material or the test procedure. All of the findings noted are attributed to spontaneous disease. (see Tables 33-36). All tissues and organs not mentioned were normal.

Dose descriptor:

NOAEL

Effect level:

322.88 mg/kg bw/day (nominal)

Based on:

other: test material, calculated based on food consumption

Sex:

male

Basis for effect level:

other: histopathology; specific to kidneys

Dose descriptor:

NOAEL

Effect level:

492.77 mg/kg bw/day (nominal)

Based on:

other: test material, calculated based on food consumption

Sex:

female

Basis for effect level:

other: histopathology; specific to kidneys

Critical effects observed:

not specified

Table 1: Mean body weight data and age for males and females

Group	Dietary level (%)	Males			Females
		Mean age at inception of test (months)	Mean body weight at week 0 (kg)	Overall weight gain (kg)	Mean age at inception of test (months)	Mean body weight at week 0 (kg)	Overall weight gain (kg)
UC	None	5.9	9.5	1.9	6.0	7.3	1.7
T-I	0.3%	5.9	8.2	1.8	5.6	7.6	1.4
T-II	1.0%	5.9	9.2	2.1	5.6	5.5	1.4
T-III	3.0%	6.0	7.6	2.0	5.5	7.1	1.4

 

Table 2: Mean food consumption data

Week	-	Mean food consumed during week indicated (g/day)
	Sex:	Males				Females
	Group:	UC	T-I	T-II	T-III	UC	T-I	T-II	T-III
	Dietary level (%):	None	0.3	1.0	3.0	None	0.3	1.0	3.0
1	-	352	375	388	401	380	451	436	385
2	-	361	381	385	430	417	407	458	418
3	-	366	362	359	392	397	378	410	386
4	-	338	371	353	342	366	382	407	375
5	-	356	358	336	363	399	359	391	369
6	-	348	335	332	366	375	352	394	351
7	-	319	347	328	364	343	369	398	352
8	-	285	305	277	323	323	331	358	346
9	-	315	335	268	325	321	361	377	363
10	-	333	303	274	328	362	370	361	356
11	-	300	336	321	317	341	332	334	330
12	-	286	268	261	287	298	302	279	288
13	-	281	338	304	346	285	344	423	350
Mean	-	326	340	322	353	354	364	387	359

 

Table 33: Gross and histologicfindings – Untreated control group

Dog number and sex	Organ	Gross	Grade	Histologic	Grade
1-M	Liver	-	-	Focal lymphoid infiltration	+
	Lungs	-	-	Focal interstitial pneumonia	++
	Prostate	-	-	Chronic focalprostatitis	++
	Spleen	-	-	Haemosiderosis	+
2-M	Lungs	-	-	Chronic interstitial pneumonia	++
3-M	Heart	-	-	Congestion	+
	Liver	-	-	Focal lymphoid infiltration	+
	Lungs	-	-	Focal interstitial pneumonia	++
4-M	Liver	-	-	Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	++
	Spleen	-	-	Haemosiderosis	+
5-F	Liver	-	-	Congestion	++
				Focal lymphoid infiltration	+
	Lungs	-	-	Chronic interstitial pneumonia	+
		-	-	Hyperemia	+
6-F	Liver			Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	+
	Uterus	-	-	In estrus	-
7-F	Ovaries	-	-	Proestrus	-
	Liver	-	-	Congestion	++
8-F	Lungs	-	-	Chronic interstitial pneumonia	+

 

Table 34: Gross and histologic findings – Test group I: 0.3 percent

Dog number and sex	Organ	Gross	Grade	Histologic	Grade
9-M	Liver	-	-	Congestion	+
	Lungs	-	-	Hyperemia	+
10-M	Liver	-	-	Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	+
11-M	Kidneys	-	-	Focal lymphoid infiltration	+
	Lungs	-	-	Congestion Focal lymphoid infiltration	+ +
12 -M	Liver	-	-	Congestion	+
	Lung	-	-	Chronic interstitial pneumonia	++
13-F	Liver	-	-	Focal lymphoid infiltration	+
	Lungs	-	-	Chronic interstitial pneumonia	+
14-F	Liver	-	-	Congestion	++
	Lungs	-	-	Bronchopneumonia	++
15-F	Liver	-	-	Focal lymphoid infiltration	+
	Lungs	-	-	Chronic interstitial pneumonia	++
16 -F	Liver	-	-	Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	++

 

Table 35: Gross and histologic findings – Test group II: 1.0 percent

Dog number and sex	Organ	Gross	Grade	Histologic	Grade
17-M	Lungs	-	-	Hyperemia Chronic interstitial pneumonia	+ ++
18-M	Liver	-	-	Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	+
19 -M	-	-	-	-	-
20 -M	Lungs	-	-	Chronic interstitial pneumonia	+
21 -F	Liver	-	-	-Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia Bronchopneumonia	++ ++
22-F	Liver	-	-	Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	+
23 -F	Liver	-	-	Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	+
	Mesenteric lymph node	-	-	Hyperemia	+
	Pancreas	-	-	Hyperemia	+
24 -F	Lungs	-	-	Chronic interstitial pneumonia	+

 

Table 36: Gross and histologicfindings – Test group III: 3.0 percent

Dog number and sex	Organ	Gross	Grade	Histologic	Grade
25-M	Liver	-	-	Congestion	+
	Kidney	-	-	Tubular concretions	+++
26-M	Liver	-	-	Congestion	+
	Kidney	-	-	Tubular concretions	+++
27-M	Liver	-	-	Congestion	++
	Lung	-	-	Chronic interstitial pneumonia	+
	Prostate	-	-	Chronic focal prostatitis	+
28 -M	Kidneys	-	-	Focal lymphoid infiltration	+
	Lungs	-	-	Chronic interstitial pneumonia	++
29 -F	Liver	-	-	Congestion	++
	Lungs	-	-	Chronic interstitial pneumonia	++
30 -F	Liver	-	-	Congestion	+
	Lungs	-	-	Chronic interstitial pneumonia	+
31-F	Liver	-	-	Congestion	+
32 -F	Gonads	-	-	Calcified follicle	+
	Kidneys	-	-	Tubular concretions	+++
	Liver	-	-	Focal lymphoid infiltration	+
	Spinal cord	-	-	Calcified debris in central canal	+

 Grading system:

+ = minimal or slight

++ = mild

+++ = moderate

++++ = severe

Conclusions:

The 90-day oral administration of KASAL to purebred beagle dogs at dietary levels of 0.3, 1.0 and 3.0% revealed in three of the Group T-III animals renal concretions which were unusually large and more numerous than those normally observed in untreated dogs. The few other calcified microconcretions present in the lumen of renal tubules located at the corticomedullary junction and/or medulla of the kidney were attributed to normally occurring disease.
No significant other changes were noted. Thus the dieatry level of 1% can be considered as NOAEL (this is equivalent to 322.88 mg/kg bw/day).

This study is considered to satisfy the guideline requirements for this endpoint and also be adequate for the purposes of risk assessment. Therefore, the study is submitted as a key study and the NOAEL reported in this study is used to derive the inhalation and dermal DNELs. On consideration of all the available data, the ratio of sodium, aluminium and phosphate in the test material is not considered to be of key relevance in determining the derived no effect levels.

Read across from sodium aluminium phosphate to the substance to be registered is justified on the following basis: Sodium aluminium phosphate is essentially a sodium orthophosphate that also contains an aluminium ion. Although aluminium is known to have toxic effects, the only systemic toxicity observed in the tests performed on sodium aluminium phosphate are not indicative of aluminium toxicity. The addition of aluminium in the phosphate compound is unlikely to have an impact on the use of this data for the sodium and potassium phosphates as any toxicity observed is due to the phosphate content of the test material. Therefore the results of the tests performed with sodium aluminium phosphate can reliably be read across to the phosphates detailed above (more detailed rationale is provided in the endpoint summary).

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

322.88 mg/kg bw/day

Study duration:

subchronic

Species:

dog

Quality of whole database:

11 reliability 2 repeated dose studies were available on sodium aluminium phosphate. These studies ranged in duration from 28 days to 6 months. The available toxicity studies have been predominantly been performed on variants of sodium aluminium phosphate referred to in the reports as KASAL, LEVN-LITE and LEVAIR. The ratios of sodium aluminium and phosphate in these materials is reported in the discussion.

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

Read across from sodium aluminium phosphate to sodium and potassium orthophosphates: Derivation of the long term DNELs is proposed based on a series of tests performed with sodium aluminium phosphate.

This read-across argument applies to the following substances;

-          Sodium dihydrogenorthophosphate

-          Disodium hydrogenorthophosphate

-          Trisodium orthophosphate

-          Potassium dihydrogenorthophosphate

-          Dipotassium hydrogenorthophosphate

-          Tripotassium orthophosphate

-          Potassium pentahydrogen bis(phosphate)

 

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

 

Read-across from sodium and potassium orthophosphates is considered appropriate for the repeated-dose endpoint based on the following similarities between substances:

 

(1)  All substances are ionic and share the PO43-anion as a common functional groups.

(2)  All members of the group will ultimately dissociate into the common breakdown products of the Na+ or K+ cations (for sodium and potassium orthophosphates respectively) and the PO43-anion (all).

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 calcium are essential biological elements.

 

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.

 

Sodium aluminium phosphate is essentially a sodium orthophosphate that also contains an aluminium ion. Although aluminium is known to have toxic effects, the only systemic toxicity observed in the tests performed on sodium aluminium phosphate are not indicative of aluminium toxicity. The addition of aluminium in the phosphate compound is unlikely to have an impact on the use of this data for the sodium and potassium phosphates as any toxicity observed is due to the phosphate content of the test material. Therefore the results of the tests performed with sodium aluminium phosphate can reliably be read across to the phosphates detailed above.

Choice of data:

The available studies are performed on sodium aluminium phosphate variants. These are referred to as KASAL, LEVN-LITE and LEVAIR are believed to have the following ratios (Kasal has been reported as having two different ratios and as such it is unclear as to which ratio is correct):

Test material name	Sodium	Aluminium	Phosphate
KASAL	15	3	8
KASAL	8	2	4
LEVAIR	1	3	8
LEVN-LITE	3	2	8

 

All available studies report the doses administered to the animals as either ppm or % in feed. As such and where the relevant information (e.g. bodyweights and food consumption) is available this has been converted to mg/kg bw/day.

11 reliability 2 repeated dose oral toxicity studies are available on sodium aluminium phosphate. One of these appears to be a literature paper based on a full report also presented in the dossier (Hicks JS et al, Food Chem Toxicol. 1987 Jul;25(7):533-8. PMID: 3623343. Sprague GL, T-12644) and two lacked data to convert the dose from % in feed to consumed dose (Reyna M, BTL-71-49D and Smith PS, BTL-71-49A). The latter study was a range finding study for a 90-day study also presented in the dossier.

All the available study reports list the doses administered to the animals in either ppm or % in feed. Where the information is available in the report (i.e. body weights and food consumption) this has been converted to mg/kg bw.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
The key study (Matalski K, 1972b) has been selected as the most reliable or appropriate study for use in the derivation of DNELS.

Repeated dose toxicity: via oral route - systemic effects (target organ) urogenital: kidneys

Justification for classification or non-classification

The only indication of systemic toxicity observed in the tests performed on sodium aluminium phosphate was nephrocalcinosis observed in the renal tubes. Rats generally and particularly female rats are known to be susceptible to nephrocalcinosis when administered high doses of phosphates (typically starting at about 0.5 – 1.0 % in the diet).The effects are only seen in high dose animals (well above the recommended classification limits for STOT RE as defined in the Guidance on the Application of Regulation (EC) No 1272/2008) and therefore classification for STOT RE is not justified and no classification is proposed.