Trisodium hydrogen diphosphate

Endpoint summary

Description of key information

Acute oral toxicity: One key study is available. The study is performed in accordance with OECD TG 420 and under the conditions of GLP. No dose descriptor is assigned as the LD50 was determined to be in the range of > 300 < 2000 mg/kg bw.

Acute inhalation toxicity: One key study is available. The study was performed on an analogous substance and in accordance an appropriate guideline and under the conditions of GLP. No dose descriptor is assigned as the LC50 was determined to be a greater than value.

Acute dermal toxicity: One key study is available. The study was performed on an analogous substance and in accordance with OECD TG 402 and under the conditions of GLP. No dose descriptor is assigned as the LD50 was determined to be a greater than value (>2,000 mg/kg bw).

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

The study was performed between 26 June 2012 and 2 August 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 420 (Acute Oral Toxicity - Fixed Dose Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.1 bis (Acute Oral Toxicity - Fixed Dose Procedure)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of GLP inspection: 19-21 July 2011 Date of Signature on GLP certificate: 31 August 2011

Test type:

fixed dose procedure

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories UK Limited, Bicester, Oxon, UK

- Age at study initiation: At the start of the study the animals were eight to twelve weeks of age.

- Weight at study initiation: The bodyweight variation did not exceed ± 20% of the initial/mean bodyweight of any previously dosed animal(s).

- Fasting period before study: overnight fast immediately before dosing

- Housing: The animals were housed in groups of up to four in suspended solid floor polypropylene cages furnished with woodflakes.

- Diet (e.g. ad libitum): 2014 Teklad Global Rodent diet supplied by Harlan Laboratories UK Limited, Bicester, Oxon, UK was allowed ad libitum throughout the study.

- Water (e.g. ad libitum): free access to mains drinking water.

- Acclimation period: at least five days.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25°C

- Humidity (%): 30 to 70%

- Air changes (per hr): The rate of air exchange was at least fifteen changes per hour.

- Photoperiod (hrs dark / hrs light): lighting was controlled by a time switch to give twelve hours continuous light (06:00 to 18:00) and twelve hours darkness.


IN-LIFE DATES: From: Day 1 To: Day 14

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

VEHICLE
- Concentration in vehicle: For the purpose of the study the test material was freshly prepared, as required, as a suspension in distilled water to give a dose levels of 300 mg/kg and 2000 mg/kg bodyweight.

- Amount of vehicle: Not stated

- Justification for choice of vehicle: Distilled water was the preferred vehicle of the test method.

- Lot/batch no.: Not applicable

- Purity: Not applicable


MAXIMUM DOSE VOLUME APPLIED: 10 ml/kg


DOSAGE PREPARATION: Not applicable

CLASS METHOD: Not applicable

- Rationale for the selection of the starting dose: In the absence of data regarding the toxicity of the test item, 300 mg/kg was chosen as the starting dose.

Doses:

Dosing regimen:
A single animal was treated with the starting dose of 300 mg/kg bw. In this absence of toxicity on this animal an additional animal was treated with 2000 mg/kg bw. As this animal exhibited no toxicity an additional 4 animals were treated with 2000 mg/kg be of the test material (a total of 5 animals were treated with 2000 mg/kg bw). Due to mortality and signs of systemic toxicity in the animals tested at 2000 mg/kg bw an additional group of 4 animals were treated with 300 mg/kg bw (a total of 5 animals were treated with 300 mg/kg bw).

No. of animals per sex per dose:

5 females at 2000 mg/kg
5 females at 300 mg/kg

Control animals:

no

Details on study design:

- Duration of observation period following administration:
14 days

- Frequency of observations and weighing:
Clinical observations were made ½, 1, 2, and 4 hours after dosing and then daily for fourteen days. Morbidity and mortality checks were made twice daily. Individual bodyweights were recorded on Day 0 (the day of dosing) and on Days 7 and 14.

- Necropsy of survivors performed:
Yes

- Other examinations performed:
Clinical signs, body weight.

Preliminary study:

A sighting test at a dose level of 300 mg/kg was performed and a sighting test at a dose level of 2000 mg/kg was performed.

Sex:

female

Dose descriptor:

LD50

Effect level:

> 300 - < 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

other: 95% confidence limits not given in study report.

Mortality:

Dose Level - 2000 mg/kg: Two animals were found dead one or two days after dosing.

Dose Level - 300 mg/kg: There were no deaths.

Clinical signs:

other: Dose level - 2000mg/kg: Signs of systemic toxicity noted were hunched posture, pilo-erection, ptosis, lethargy and ataxia. Surviving animals appeared normal one, five or six days after dosing. Dose level - 300mg/kg: No signs of systemic toxicity were not

Gross pathology:

Dose level - 2000mg/kg: Abnormalities noted at necropsy of animals that died during the study were dark liver, dark spleen, dark kidneys and haemorrhagic gastric mucosa. A raised limiting ridge of the stomach and pale gastric mucosa were noted at necropsy of one animal that was killed at the end of the study. No abnormalities were noted at necropsy of the remaining animals that were killed at the end of the study.

Dose level - 300mg/kg: No abnormalities were noted at necropsy.

Other findings:

- Organ weights: Not recorded

- Histopathology: Not recorded

- Potential target organs: Not recorded

- Other observations: None

Table 1. Individual Clinical Observations and Mortality Data -2000mg/kg

 

Dose Level mg/kg	Animal Number and Sex	Effects Noted After Dosing (Hours)				Effects Noted During Period After Dosing (Days)
		½	1	2	4	1	2	3	4	5	6	7	8	9	10	11	12	13	14
2000	2-0 Female	0	0	0	H	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	3-0 Female	0	0	0	0	0	0	H	H	0	0	0	0	0	0	0	0	0	0
	3-1 Female	0	0	0	0	HP	H	H	HP	H	0	0	0	0	0	0	0	0	0
	3-2 Female	0	0	0	HAPPtL	X
	3-3 Female	0	0	0	HLP	HAP	X

 

0 = No signs of systemic toxicity

H = Hunched posture

P = Pilo-erection

Pt = Ptosis

L = Lethargy

A = Ataxia

X = Animal dead 

Table 2. Individual Bodyweights and Bodyweight Changes -2000mg/kg

 

Dose Level mg/kg	Animal Number and Sex	Bodyweight (g) at Day			Bodyweight (g) at Death	Bodyweight Gain (g) During Week
		0	7	14		1	2
2000	2-0 Female	162	179	187		17	8
	3-0 Female	186	202	217		16	15
	3-1 Female	180	174	213		- 6	39
	3-2 Female	165	-	-	160	-	-
	3-3 Female	166	-	-	153	-	-

 

Table 3.  Individual Necropsy Findings -2000 mg/kg

 

Dose Level mg/kg		Animal Number and Sex		Time of Death		Macroscopic Observations
2000		2-0 Female		Killed Day 14		Stomach: raised limiting ridge Gastric mucosa: pale
		3-0 Female		Killed Day 14		No abnormalities detected
		3-1 Female		Killed Day 14		No abnormalities detected
		3-2 Female		Animal found dead Day 1		Liver: dark Spleen: dark Kidneys: dark Gastric mucosa: haemorrhagic
		3-3 Female		Animal found dead Day 2		Liver: dark Spleen: dark Kidneys: dark Gastric mucosa: haemorrhagic

 

 

 

 

 

Table 4. Individual Clinical Observations and Mortality Data - 300mg/kg

 

Dose Level mg/kg	Animal Number and Sex	Effects Noted After Dosing (Hours)				Effects Noted During Period After Dosing (Days)
		½	1	2	4	1	2	3	4	5	6	7	8	9	10	11	12	13	14
300	2-0 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	3-0 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	3-1 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	3-2 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	3-3 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

 

0= No signs of systemic toxicity

Table 5. Individual Bodyweights and Bodyweight Changes - 300mg/kg

 

Dose Level mg/kg	Animal Number and Sex	Bodyweight (g) at Day			Bodyweight Gain (g) During Week
		0	7	14	1	2
300	2-0 Female	162	187	202	25	15
	3-0 Female	182	199	216	17	17
	3-1 Female	188	197	220	9	23
	3-2 Female	183	199	214	16	15
	3-3 Female	189	214	230	25	16

 

Table 6. Individual Necropsy Findings - 300mg/kg

 

Dose Level mg/kg	Animal Number and Sex	Time of Death	Macroscopic Observations
300	2-0 Female	Killed Day 14	No abnormalities detected
	3-0 Female	Killed Day 14	No abnormalities detected
	3-1 Female	Killed Day 14	No abnormalities detected
	3-2 Female	Killed Day 14	No abnormalities detected
	3-3 Female	Killed Day 14	No abnormalities detected

Interpretation of results:

Category 4 based on GHS criteria

Conclusions:

The acute oral median lethal dose (LD50) of the test material in the female Wistar strain rat was estimated to be in the range of 300 - 2000 mg/kg bodyweight (EU CLP - Category 4).

This study is considered to be reliable and acceptable for use as a key study in accordance with Regulation (EC) No. 1907/2006 (REACH) and for the purposes of classification and labelling in accordance with Regulation (EC) No. 1272/2008 (EU CLP).

Executive summary:

.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Quality of whole database:

LD50 > 2,000 mg/kg bw
The study is conducted under the conditions of GLP and in accordance with an appropriate guideline (OECD 420). This study has been assigned a Klimisch reliability of 1.

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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

(1) The source and target substances are both inorganic salts of a monovalent cation from Group 1A of the periodic table, sodium or potassium, and pyrophosphoric acid. Thus, they all share the Na+ or K+ cation and the P2O74- anion as common functional groups.
(2) All members of the group will ultimately dissociate into the common breakdown products of the Na+ or K+ cations and the P2O74- anion.
(3) 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 group contains only two phosphate groups, both of the phosphorus ions are classified as “terminal phosphorus”. The pyrophosphate can undergo ionisation with loss of H+ from each of the two –OH groups on each P and therefore can occur in the -1, -2 -3 or -4 state. The degree of ionisation is dependent upon the associated cations and the ambient pH (if in solution). Therefore the above substances have a pyrophosphate anion that is likely to behave in a similar way. In addition, the sodium and potassium cations are key elements in various cellular processes their import and export over cell membranes is regulated via pore systems and usually tightly regulated. As such, the presence of varying quantities of such cations is not expected to have an impact on the toxicity of the substances detailed above therefore as the both ionic components of the substance are common the results of toxicity studies can be reliably read-across within the group.


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:

according to guideline

Guideline:

EPA OPP 81-3 (Acute inhalation toxicity)

Deviations:

yes

Remarks:

- minor deviations: the chamber and room humidity was slightly higher than recommended in the guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

- minor deviations: the chamber and room humidity was slightly higher than recommended in the guideline

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

Deviations:

yes

Remarks:

- minor deviations: the chamber and room humidity was slightly higher than recommended in the guideline

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Kingston, NY
- Age at study initiation: The actual age of the rats was not specified, only that they were young adults.
- Weight at study initiation (± SD): Males: 318 ± 11.4 g; Females: 249 ± 12.6 g
- Fasting period before study: No data
- Housing: Animals were housed individually in stainless steel suspended rat cages. Deosorb bedding was used in the litter pans.
- Diet: Purina Laboratory Rodent Chow 5001 available ad libitum
- Water: Tap water available ad libitum
- Acclimation period: Minimum of 5 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 - 23 °C (quoted in the study as 69 - 74 °F)
- Humidity (%): 42 - 77%
- Air changes (per hr): 14.2 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 h fluorescent light and 12 h dark cycle

Route of administration:

inhalation: dust

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: The Rochester type exposure chamber was made of stainless steel and glass and was operated dynamically. The calculated 99% equilibrium time for the chamber at a flow rate of 35.6 L per minute was 19.4 minutes (equivalent to 14.2 "air changes per hour").
- Exposure chamber volume: 150 L
- Method of holding animals in test chamber: The test animals were assigned to and housed in individual compartments of a wire mesh cage bank (all on the same horizontal level) during the exposure.
- Source and rate of air: Breathing grade compressed air was used and the total chamber air flow rate was 35.6 L/minute.
- Method of conditioning air: No data
- System of generating particulates/aerosols: The test material was generated using a BGI Wright Dust Feeder II. The test material was desiccated and packed into large dust cups. Breathing Grade compressed air was metered to the Wright dust feeder through teflon tubing by a Matheson® 605 rotameter with a metal float. Rotameter back pressure was controlled using a Matheson® 3104C regulator. The dust feeder back pressure was monitored using a Marshalltown® back pressure gauge. The test material was made airborne by the compressed air dispersing the material into the exposure chamber. The concentration of the test atmosphere was controlled by the delivery rate setting of the Wright dust feeder.
- Method of particle size determination: The samples were drawn through a Sierra 218 cascade impactor at 2.78 liters per minute. The aerodynamic particle size distribution was determined by gravimetric analysis of the amount of test material collected on the impactor stages and subsequent determination of the mass median aerodynamic diameter (MMAD), geometric standard deviation and other particle size parameters by logarithmic-probability plotting.
- Treatment of exhaust air: The chamber air was exhausted from the bottom of the chamber and passed through an orifice tube system which continuously monitored airflow and then through a commercial filter box. The filter box was connected to a line leading to additional filters and an exhaust fan on the roof. The exhaust operated at a flow rate of 35.6 liters per minute, creating a slight negative pressure in the chamber, which was considered to be the total chamber air flow rate. The entire exposure system and primary exhaust filter were contained in a fume hood.
- Temperature, humidity, pressure in air chamber: The mean temperature and relative humidity in the chamber were 22 °C (71 °F) and 66%, respectively. The pressure in the air chamber was not measured.


TEST ATMOSPHERE
- Brief description of analytical method used: The airborne concentration of the test material was determined gravimetrically.
- Samples taken from breathing zone: Yes - Chamber air samples were taken on glass fiber filters held in cassettes at approximately one hour intervals during the exposure to determine the airborne concentration of test material. The airborne concentration of the test material was determined gravimetrically by drawing a known amount of chamber air through the filter. The samples were taken from the center of the chamber directly over the animal exposure caging.
The difference between gravimetric and nominal concentration was attributed to sedimentation of larger particles and/or adhesion of the test material to surfaces in the exposure chamber.


VEHICLE
- Not applicable: The test material was administered as received and a vehicle was not used.


TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: The fraction of particles less than or equal to 1 µm in mass aerodynamic diameter, based on the log-probability graphs, ranged from 7.6 to 9.4%. The fraction of particles less than or equal to 10 µm in mass aerodynamic diameter, based on the log probability graphs, ranged from 72.3 to 76.1%. These results indicated the test material was respirable in size to the rat.
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): The MMADs ranged from 4.61 to 4.87 micrometers (µm) with geometric standard deviations ranging from 2.98 to 3.39. The MMAD represents the smallest size that could be achieved in this study. The material is hygroscopic causing the particles to agglomerate and/or adhere to surfaces inside the chamber. Several trials were initially performed with various generation schemes and the system which was ultimately chosen provided the best performance.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

Nominal concentration: 35.14 mg/L (maximum attainable concentration)
Gravimetric concentration: 0.58 ± 0.103 mg/L

No. of animals per sex per dose:

5 animals/sex

Control animals:

no

Details on study design:

- Duration of observation period following administration: 28 days
- Frequency of observations and weighing: Animals were observed for signs of toxicity and mortality every 15 mins during the first hour of exposure, hourly for the remainder of the exposure, upon removal from the chamber, at 1 h post-exposure, twice daily thereafter for 27 days and once on day 28. Individual body weights were recorded on days 0, 1, 2, 4, 7, 14, 21 and 28.
- Necropsy of survivors performed: Yes
- Other examinations performed: No data

Statistics:

No data

Preliminary study:

Not applicable

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 0.58 mg/L air (analytical)

Exp. duration:

4 h

Mortality:

See Table 1.
One female died on day 1 and one male died on day 14 post-exposure.

Clinical signs:

other: See Table 1. Clinical signs noted during the exposure included lacrimation, material on fur, oral discharge and squinting eyes. Incidence of clinical signs was highest at the removal from chamber observation. Signs gradually resolved during the study, how

Body weight:

See Table 2.
Most animals lost weight through day 4 of the study, then began to gain weight in a normal pattern. At termination all surviving animals exhibited increases in body weight over their day 0 values.

Gross pathology:

See table 3.
There were no gross internal lesions observed in any animal which survived to study termination. One male which died on day 14 had discoloured lungs with many light red nodules. This animal was also observed to have a corneal opacity in one eye.

Other findings:

No data

See attached file for Tables 1, 2 and 3.

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of this study, the test material caused mortality in one male and one female Sprague Dawley rat when administered for four hours at a mean, maximum attainable chamber concentration of 0.58 mg/L. Based on this, the LC50 for sodium acid pyrophosphate is considered to be greater than 0.58 mg/L.
This study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement as a part of a weight of evidence for this endpoint. In addition the study is considered to be acceptable for classification and labelling in accordance with Regulation (EC) No 1272/2008 (EU CLP) and as such sodium acid pyrophosphate is not considered to be acutely toxic via the inhalation route (EU CLP).

Read-across between the following sodium and potassium pyrophosphates;

- disodium dihydrogenpyrophosphate
- trisodium hydrogen pyrophosphate
- tetrasodium pyrophosphate
- tetrapotassium pyrophosphate

Can be justified on the following basis; All substance contain a pyrophosphate anion and either a sodium or a potassium cation.

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 group contains only two phosphate groups, both of the phosphorus ions are classified as “terminal phosphorus”. The pyrophosphate can undergo ionisation with loss of H+ from each of the two –OH groups on each P and therefore can occur in the -1, -2 -3 or -4 state. The degree of ionisation is dependent upon the associated cations and the ambient pH (if in solution). Therefore the above substances have a pyrophosphate anion that is likely to behave in a similar way.

In addition, the sodium and potassium cations are key elements in various cellular processes their import and export over cell membranes is regulated via pore systems and usually tightly regulated. As such, the presence of varying quantities of such cations is not expected to have an impact on the toxicity of the substances detailed above therefore as the both ionic components of the substance are common the results of toxicity studies can be reliably read-across within the group.

This study is therefore deemed reliable for the classification and labelling of trisodium hydrogen diphosphate according to Regulation (EC) No 1272/2008 (EU CLP).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Two studies were available to assess the acute inhalation toxicity of trisodium hydrogen diphosphate. Studies were conducted on the analogous substances disodium dihydrogenpyrophosphate and tetrapotassium pyrophosphate. Both studies were conducted up to a mean, maximum attainable chamber concentration of 0.58 mg/L and 1.1 mg/L respectively. As the LC50 values have been determined to be greater than these concentrations neither substance is considered to be classified in accordance with Regulation (EC) No. 1272/2008 (EU CLP). Trisodium hydrogen diphosphate is considered to exhibit a low potential toxicity via the inhalation route and is not expected to be of significant concern.

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

The study was performed between 12 May 2010 and 26 May 2010.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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

(1) The source and target substances are both inorganic salts of a monovalent cation from Group 1A of the periodic table, sodium or potassium, and pyrophosphoric/phosphoric. Thus, they all share the Na+ or K+ cation and the P2O74- anion as common functional groups.
(2) All members of the group will ultimately dissociate into the common breakdown products of the Na+ or K+ cations and the P2O74- anion.
(3) 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 group contains only two phosphate groups, both of the phosphorus ions are classified as “terminal phosphorus”. The pyrophosphate can undergo ionisation with loss of H+ from each of the two –OH groups on each P and therefore can occur in the -1, -2 -3 or -4 state. The degree of ionisation is dependent upon the associated cations and the ambient pH (if in solution). Therefore the above substances have a pyrophosphate anion that is likely to behave in a similar way. In addition, the sodium and potassium cations are key elements in various cellular processes their import and export over cell membranes is regulated via pore systems and usually tightly regulated. As such, the presence of varying quantities of such cations is not expected to have an impact on the toxicity of the substances detailed above therefore as the both ionic components of the substance are common the results of toxicity studies can be reliably read-across within the group.


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:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.3 (Acute Toxicity (Dermal))

Deviations:

no

Principles of method if other than guideline:

The sequence of dosing may not always follow the Test Guideline as shown in the schematic diagram in attachment 1. It is Company Policy to minimisethe number of animals used on each study in accordance with UK Government Home Office guidelines.

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of Inspection: 15 September 2009 Date of signature: 26 November 2009

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

Test Animals:
Animals: Rat, HsdRccHan: WIST

Rationale: Recognized by international guidelines as a recommended test system.

Breeder: Harlan Laboratories UK Limited, Oxon, UK.

Number of Animals per Group: 5 males and 5 females

Total number of Animals: 5 males and 5 females

Age when treated: At the start of the study the animals weighed at least 200g, and were eight to twelve weeks of age. The weight variation did not exceed ± 20% of the mean weight for each sex.

Identification: After an acclimatisation period of at least five days the animals were selected at random and given a number unique within the study by indelible ink-marking on the tail and a number written on a cage card.

Acclimatization: At least 5 days under laboratory conditions, after health examination. Only animals without any visible signs of illness were used for the study.

Environmental Conditions:
Conditions:
The temperature and relative humidity were within the range of 19 to 21 cC and 45 to 56% respectively. The rate of air exchange was at least fifteen changes per hour and the lighting was controlled by a time switch to give twelve hours continuous light (06:00 to 18:00) and twelve hours darkness.

The animals were provided with environmental enrichment items which were considered not to contain any contaminant of a level that might have affected the purpose or integrity of the study.

Accommodation:
The animals were housed in suspended solid-floor polypropylene cages furnished with woodflakes. The animals were housed individually during the 24-hour exposure period and in groups of five, by sex, for the remainder of the study.

Diet:
Free access food (2014 Teklad Global Rodent diet supplied by Harlan Laboratories UK, Oxon, UK) was allowed throughout the study. The diet was routinely analysed and were considered not to contain any contaminants that could reasonably be expected to affect the purpose or integrity of the study.

Water:
Free access to mains drinking water was allowed throughout the study. The drinking
water was routinely analysed and were considered not to contain any contaminants that could reasonably be expected to affect the purpose or integrity of the study.

Type of coverage:

semiocclusive

Vehicle:

arachis oil

Details on dermal exposure:

On the day before treatment the back and flanks of each animal were clipped free of hair.

Using available information on the toxicity of the test material, a group of five male and five female rats was treated with the test material at a dose level of 2000 mg/kg.

The appropriate amount of test material, moistened with arachis oil, was applied as evenly as possible to an area of shorn skin (approximately 10% of the total body surface area). A piece of surgical gauze was placed over the treatment area and semi-occluded with a piece of self adhesive bandage. The animals were caged individually for the 24-Hour exposure period. Shortly after dosing the dressings were examined to ensure that they were securely in place.

Duration of exposure:

24 hours

Doses:

2000 mg /kg body weight

No. of animals per sex per dose:

5

Control animals:

not required

Details on study design:

After the 24-Hour contact period the bandage was carefully removed and the treated skin and surrounding hair wiped with cotton wool moistened with distilled water to remove any residual test material. The animals were returned to group housing for the remainder of the study period.

The animals were observed for deaths or overt signs of toxicity ½, 1, 2 and 4 hours after dosing and subsequently once daily for fourteen days.

After removal of the dressings and subsequently once daily for fourteen days, the test sites were examined for evidence of primary irritation and scored according to the following scale from Draize J H (1977) "Dermal and Eye Toxicity Tests" In: Principles and Procedures for Evaluating the Toxicity of Household Substances, National Academy of Sciences, Washington DC p.31:

EVALUATION OF SKIN REACTIONS
Erythema and Eschar Formation Value
No erythema 0
Very slight erythema (barely perceptible) 1
Well-defined erythema 2
Moderate to severe erythema 3
Severe erythema (beef redness) to slight eschar formation (injuries in depth) 4
Oedema Formation
No oedema 0
Very slight oedema (barely perceptible) 1
Slight oedema (edges of area well-defined by definite raising) 2
Moderate oedema (raised approximately 1 millimetre) 3
Severe oedema (raised more than 1 millimetre and extending beyond the area of exposure) 4

Any other skin reactions, if present were also recorded.

Individual bodyweights were recorded prior to application of the test material on Day 0 and on Days 7 and 14.

At the end of the study the animals were killed by cervical dislocation. All animals were subjected to gross necropsy. This consisted of an external examination and opening of the abdominal and thoracic cavities. The appearance of any macroscopic abnormalities was recorded. No tissues were retained.

Statistics:

No statistical analysis was performed.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

other: 95% confidence limits not reported.

Mortality:

No deaths occurred during the study.

Clinical signs:

other: No clinical signs were observed during the course of the study. There were no signs of dermal irritation.

Gross pathology:

No macroscopic findings were recorded at necropsy.

Other findings:

None.

Table1              Individual Clinical Observations and Mortality Data

Dose Level mg/kg	Animal Number and Sex	Effects Noted After Initiation of Exposure (Hours)				Effects Noted After Initiation of Exposure (Days)
		½	1	2	4	1	2	3	4	5	6	7	8	9	10	11	12	13	14
2000	1-0 Male	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	1-1 Male	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	1-2 Male	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	1-3 Male	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	1-4 Male	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	2-0 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	2-1 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	2-2 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	2-3 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	2-4 Female	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

0= No signs of systemic toxicity

See attachment for Tables 2 - 4

Interpretation of results:

GHS criteria not met

Conclusions:

The acute dermal median lethal dose (LD50) of the test material in the Wistar strain rat was found to be greater than 2000 mg/kg bodyweight.
Disodium dihydrogenpyrophosphate is not considered to be classified according to Regulation (EC) No. 1272/2008 (EU CLP).

This study is considered to be adequate and reliable for the purposes of registration under REACH (Regulation (EC) No. 1907/2006) and classification and labelling in accordance with Regulation (EC) No. 1272/2008 (EU CLP) for the analogous substance trisodium hydrogen diphosphate.

Executive summary:

Introduction. The study was performed to assess the acute dermal toxicity of the test material in the Wistar strain rat. The method was designed to meet the requirements of the following

OECD Guidelines for the Testing of Chemicals No. 402 “Acute Dermal Toxicity” (adopted24 February 1987)

Method B3 Acute Toxicity (Dermal) of Commission Regulation (EC) No. 440/2008

Method. A group of ten animals (five males and five females) was given a single, 24-hour, semi‑occluded dermal application of the test material to intact skin at a dose level of 2000 mg/kg bodyweight. Clinical signs and bodyweight development were monitored during the study. All animals were subjected to gross necropsy.

Mortality. There were no deaths.

Clinical Observations. There were no signs of systemic toxicity.

Dermal Irritation. There were no signs of dermal irritation.

Bodyweight. All animals showed expected gains in bodyweight over the study period.

Necropsy. No abnormalities were noted at necropsy.

Conclusion. The acute dermal median lethal dose (LD₅₀) of the test material in the Wistar strain rat was found to be greater than 2000 mg/kg bodyweight.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

LD50 > 2,000 mg/kg bw
One key study is available to assess the acute dermal toxicity of trisodium hydrogen diphosphate. This study has been performed on an analogous substance and has been assigned a Klimisch reliability of 1.
In addition, a number of supporting studies on the analogous substances disodium dihydrogenpyrophosphate, tetrasodium pyrophosphate and tetrapotassium pyrophosphate are provided to support the conclusion that sodium and potassium pyrophosphates exhibit low systemic toxicity when administered via the dermal route.

Justification for classification or non-classification

Acute oral toxicity: The oral LD₅₀has been determined to be within the range 300 - 2000 mg/kg bw and therefore in accordance with Regulation (EC) No. 1272/2008 (EU CLP) trisodium hydrogen diphosphate is classified as acutely toxic via the oral route category 4.

Acute inhalation toxicity: The LC₅₀values for the inhalation of the analogous substances disodium dihydrogenpyrophosphate and tetrapotassium pyrophosphate were not classified at the greatest attainable concentration and therefore trisodium hydrogen diphosphate is not considered to be classified in accordance with Regulation (EC) No. 1272/2008 and no further testing is recommended.

Acute dermal toxicity: The dermal LD50 of the analogous substance disodium dihydrogenpyrophosphate in the rat was found to be > 2000 mg/kg bw and as such trisodium hydrogen diphosphate is not considered to be classified according to Regulation (EC) No. 1272/2008 (EU CLP).