Sodium dihydrogenorthophosphate

Endpoint summary

Description of key information

Acute oral toxicity: Three studies are available to assess the acute oral toxicity of sodium dihydrogenorthophosphate. All studies indicate that sodium dihydrogenorthophosphate has a low potential for systemic toxicity following acute administration via the oral route. 
The key study (Bradshaw  J , 2009) has been conducted according to a current guideline (OECD 420) according to the principles of GLP. The acute oral median dose (LD50) of sodium dihydrogenorthophosphate in the female Wistar strain rat was estimated to be > 2000 mg/kg bw and is therefore not classified according to Regulation (EC) No 1272/2008 (EU CLP). Additional supporting data (Birch MD, 1973 and Bullock CH, 1972) are considered to be sufficient to support the overall classification; however these studies are not sufficient as stand-alone data sources for this endpoint.
Acute inhalation toxicity: One key study is available to assess the acute inhalation toxicity of sodium dihydrogenorthophosphate. Sodium dihydrogenorthophosphate is considered to exhibit a low potential toxicity via the inhalation route and is not expected to be of significant concern. 
The key study (Signorin J, 1993) has been conducted according to the relevant guidelines (EU and US) and according to the principles of GLP. The acute inhalation median concentration (LC50) of sodium dihydrogenorthophosphate in male and female rats was estimated to be > 0.83 mg/L (the maximum attainable concentration). 
Acute dermal toxicity: One key study and a number of supporting studies are provided. All studies support no classification. The key study (Moore, 2006) details the acute dermal toxicity of the analogue substance potassium pentahydrogen bis(phosphate) which has an LD50 of >2,000 mg /kg bw and is therefore no classified according to Regulation (EC) No 1272/2008 (EU CLP). This classification can be read across to sodium dihydrogenorthophosphate on the basis of the argumentation provided below (see discussion box).

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 14 October 2009 and 10 November 2009.

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: 31 March 2010 Date of Signature on GLP certificate: 04 March 2009

Test type:

fixed dose procedure

Limit test:

yes

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

Animals and Animal Husbandry
Female Wistar ( HsdRccHan®™:WIST®™) strain rats were supplied by Harlan Laboratories UK Limited, Bicester, Oxon, UK. On receipt the animals were randomly allocated to cages. The females were nulliparous and non-pregnant. 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. At the start of the study the animals were eight to twelve weeks of age. The bodyweight variation did not exceed ± 20% of the initial/mean bodyweight of any previously dosed animal(s).
The animals were housed in groups of up to four in suspended solid floor polypropylene cages furnished with woodflakes. With the exception of an overnight fast immediately before dosing and for approximately three to four hours after dosing, free access to mains drinking water and food (2014 Teklad Global Rodent diet supplied by Harlan Teklad, Blackthorn, Bicester, Oxon, UK) was allowed throughout the study. The diet, drinking water and bedding were routinely analysed and were considered not to contain any contaminants that would reasonably be expected to affect the purpose or integrity of the study.
The temperature and relative humidity were set to achieve limits of 19 to 25°C and 30 to 70% respectively. Any occasional deviations from these targets were considered not to have affected the purpose or integrity of the study. 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.

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

Procedure
Using available information on the toxicity of the test material, 2000 mg/kg was chosen as the starting dose.

Dose Level Concentration Dose Volume Number of Rats
(mg/kg) (mg/ml) (ml/kg) Female
2000 200 10 1


In the absence of toxicity at a dose level of 2000 mg/kg, an additional group of animals was treated as follows:
Dose Level Concentration Dose Volume Number of Rats
(mg/kg) (mg/ml) (ml/kg) Female
2000 200 10 4

A total of five animals were therefore treated at a dose level of 2000 mg/kg in the study.
All animals were dosed once only by gavage using a metal cannula attached to a graduated syringe. The volume administered to each animal was calculated according to its fasted bodyweight at the time of dosing.
Clinical observations were made ½, 1, 2, and 4 hours after dosing and subsequently once 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.
At the end of the observation period 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.

Doses:

Following a sighting test at a dose level of 2000 mg/kg, an additional four fasted female animals were given a single oral dose of test material, as a suspension in distilled water, 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.

No. of animals per sex per dose:

1 female at 2000 mg/kg
4 females at 2000 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.

Statistics:

The test material will be classified according to Annex 3 of the OECD Guidelines for Testing of Chemicals No. 420 "Acute Oral Toxicity - Fixed Dose Method" (adopted 17 December 2001).

Evaluation of data included identification of the number of animals that died during the study (or that were killed for humane reasons), and determination of the nature, severity, onset and duration of the toxic effects. If possible, the signs of evident toxicity were described. Evident toxicity refers to the toxic effects of sufficient severity that administration of the next higher dose level could result in development of severe signs of toxicity and probable mortality. Effects on bodyweights and abnormalities noted at necropsy were also identified.
Using the mortality data obtained, an estimate of the acute oral median lethal dose (LD50) of the test material was made.

Preliminary study:

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

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

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

Mortality:

There were no deaths.

Clinical signs:

other: No signs of systemic toxicity were noted.

Gross pathology:

No abnormalities were noted at necropsy.
Individual necropsy findings are given in Table 3.

Other findings:

- Organ weights:
Not recorded

- Histopathology:
Not recorded

- Potential target organs:
Not recorded

- Other observations:
None

Table1              Individual Clinical Observations and Mortality Data

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	1-0 Female	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

0= No signs of systemic toxicity

Table2              Individual Bodyweights and Bodyweight Changes

Dose Level mg/kg	Animal Number and Sex	Bodyweight (g) at Day			Bodyweight Gain (g) During Week
		0	7	14	1	2
2000	1-0 Female	194	202	209	8	7
	2-0 Female	161	177	187	16	10
	2-1 Female	176	186	199	10	13
	2-2 Female	189	202	222	13	20
	2-3 Female	182	202	210	20	8

 

Table3              Individual Necropsy Findings

Dose Level mg/kg	Animal Number and Sex	Time of Death	Macroscopic Observations
2000	1-0 Female	Killed Day 14	No abnormalities detected
	2-0 Female	Killed Day 14	No abnormalities detected
	2-1 Female	Killed Day 14	No abnormalities detected
	2-2 Female	Killed Day 14	No abnormalities detected
	2-3 Female	Killed Day 14	No abnormalities detected

Interpretation of results:

GHS criteria not met

Conclusions:

The acute oral median lethal dose (LD50) of the test material in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bodyweight (Globally Harmonised Classification System - Unclassified).
This study is conducted according to an appropriate guideline and under the conditions of GLP and therefore the study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement as a key study for this endpoint. In addition, the study is considered to be acceptable and reliable for the classification and labelling of sodium dihydrogenorthophosphate in accordance with Regulation (EC) No. 1272/2008 (EU CLP).

Executive summary:

Introduction. 

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

• OECD Guidelines for Testing of Chemicals No 420 "Acute Oral Toxicity - Fixed Dose Method" (adopted 17 December 2001).
•   Method B1 bis Acute Toxicity (Oral) of Commission Regulation (EC) No. 440/2008

       

Method. 

Following a sighting test at a dose level of 2000 mg/kg, an additional four fasted female animals were given a single oral dose of test material, as a solution in distilled water, 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.

Bodyweight. 

All animals showed expected gains in bodyweight.

Necropsy. 

No abnormalities were noted at necropsy.

Conclusion. 

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

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

LD50 > 2000 mg/kg bw
The study is compliant with GLP and has a Klimisch score of 1.
In addition, supporting data are included on a number of similar substances for the purpose of supporting the read-across argumentation applied for other acute endpoints. These studies have various Klimisch scores.

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

Qualifier:

according to guideline

Guideline:

EPA OPP 81-3 (Acute inhalation toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: U.S. Environmental Protection Agency Toxic Substances Health Effects Test Guidelines, October 1984 (PB82-232984) Acute Inhalation Toxicity Study

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: FMC Acute Inhalation Toxicity Protocol Number 27

Deviations:

no

GLP compliance:

yes

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: young adult
- Weight at study initiation: males: 274 ± 9.1; females 217 ± 7.3
- Fasting period before study: not reported
- Housing: Individually housed in stainless steel suspended rat cages. Desorb bedding was used in the litter pans.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: a minimum of 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 69 - 73ºF
- Humidity (%): 41 - 70 %
- Photoperiod (hrs dark / hrs light): 12 h dark/ 12 h light

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: Rochester type exposure chamber
- Exposure chamber volume: 150 L
- Method of holding animals in test chamber: 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. The cage position assignment ensured equal distribution of both sexes throughout the cage bank.
- Source and rate of air: breathing grade compressed air
- System of generating particulates/aerosols: a BGI Wright dust feeder II was used to generate the test atmosphere. The test material was desiccated and packed into large dust cups. Breathing grade compressed air was metered to the Wright dust feeder through 1/4 inch teflon tubing by a Matheson® 605 rotameter with metal float. Rotameter back pressure was controlled using a Matheson®3104-C regulator. The dust feeder back pressure was controlled using a Marshalltown® back pressure gauge. The test material was made airborne by compressed air dispersing the material into the exposure chamber. The concentration of the test atmostphere was controlled by the delivery rate setting of the wright dust feeder.
- Method of particle size determination: the aerodynamic particle size distribution was determined by gravimetric analysis of the test material collected on the impactor stages and subsequent determination of the MMAD, geometric SD and other particule size parameters by logarithmic-probability plotting.
- Temperature, humidity, pressure in air chamber: Chamber and room air temperature and relative humidity were monitored continuously during the exposure with FMC wet/dry bulb hygrometers. Measurements were recorded at 30 min intervals.
At the end of the exposure, the chamber was cleared for 30 min by drawing room air through it at the same flow rate (31.9 L/min) prior to removing the animals.

TEST ATMOSPHERE
- Brief description of analytical method used: chamber air samples were taken on Gelman® Type A/E 47 mm glass fibre filters held in cassettes at approximately 1 h intervals during 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 concentration was calculated by dividing filter weight gain by the sample volume. The samples were taken from the centre of the chamber directly over the animal exposure caging.
Atmospheric monitoring:
The chamber homogeneity determination showed that the test atmosphere was homogeneously distributed throughout the test chamber (cv = 7.10 %).
The dust feeder was operated at what was considered a maximum setting which would allow reliable operation. At this setting the delivery rate required the dust feeder to be manually assisted during the exposure. The chamber airflow was operated at as low flow rate which would allow timely chamber equilibrium and maintain a slight negative pressure in the chamber. 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.


- Samples taken from breathing zone: yes
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): The MMADs ranged from 5.87 to 6.82 μm with geometric standard deviations ranging from 2.55 to 2.92. The fraction of particles less than or equal to 1 μm in mass aerodynamic diameter, based on the log probability graphs, ranged from 0 to 3.6 %. The fraction of particles less than or equal to 10 μm in mass aerodynamic diameter, based on the log probability graphs, ranged from 65.9 to 69.1 %. These results indicated the test material was respirable in size to the rat. The MMAD represents the smallest size that could be acheived in this study. The material had a static electric charge when generated causing the particles to agglomerate and / or adhere to surfaces inside the chamber.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

chamber air samples were taken on Gelman® Type A/E 47 mm glass fibre filters held in cassettes at approximately 1 h intervals during exposure to determine the airborne concentration of test material

Duration of exposure:

4 h

Concentrations:

Nominal concentration: 37.35 mg/L
Mean analytical data ±SD (Gravimetric concentration): 0.83 ± 0.065 mg/L

No. of animals per sex per dose:

5/sex/dose

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: the animals were observed for signs of toxicity and mortality at 15 min intervals during the first h of exposure , hourly for the remainder of the exposure, upon removal from the chamber, at 1 h post-exposure, twice daily thereafter for 13 days and once on day 14.
- Necropsy of survivors performed: yes, all animals were sacrificed and submitetd to gross necroscopy.
- Other examinations performed: body weights were recorded on days 0, 1, 2, 4, 7 and 14.

Statistics:

None reported

Preliminary study:

No data

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 0.83 mg/L air (analytical)

Exp. duration:

4 h

Mortality:

There were no deaths during the study.

Clinical signs:

other: The incidence of clinical signs were highest at the removal from chamber observations. Clinical signs noted during the exposure included lacrimation and squinting eyes. Clinical signs noted following the exposure incuded chromodacryorrhea, lacrimation, n

Body weight:

Most animals lost weight through day 1 of the study and then began to gain weight in a normal pattern. At termination all animals had exhibited increases in body weight over their day 0 values.

Gross pathology:

There were no gross internal lesions observed in any animal necropsy.

Other findings:

no data

Table 4. The concentration presented should be considered the maximum available:

Exposure Date	Mean Analytical Data ± SD (mg/L)	Nominal Concentration (mg/L)	Mortality
	Gravimetric Concentration		# Dead / # Exposed
			Male	Female
1993-08-06	0.83 ± 0.065	37.35	0 / 5	0 / 5

Table 5. Mean body weights (g) ± SD:

	Study day
	0	1	2	4	7	14
Males	274 ± 9.1	270 ± 10.4	277 ± 11.1	293 ± 10.3	313 ± 10.6	348 ± 13.4
Females	217 ±7.3	218 ± 5.9	215 ± 6.1	222 ± 6.8	228 ± 9.9	238 ± 10.2

Table 6. Incidence of clinical signs: Male

Observation	Time after treatment
	Day 0										Day 1		Day 2		Day 3
	Hour
	PT	0.25	0.50	0.75	1	2	3	4	R	1PE	AM	PM	AM	PM	AM	PM
Chromodacryorrhea	0	0	0	0	0	0	0	0	1	0	0	0	0	0	0	0
Lacrimation	0	3	3	3	3	3	3	3	5	2	0	0	0	0	0	0
Material on fur	0	0	0	5	5	5	5	5	5	5	5	5	5	5	0	0
Nasal discharge	0	0	0	0	0	0	0	0	2	1	0	0	0	0	0	0
Squinting eyes	0	5	5	5	5	5	5	5	1	0	0	0	0	0	0	0
Death (cumulative)	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

Continued:

Observation	Day
	4		5		6		7		8		9		10		11		12		13		14
	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM
Chromodacryorrhea	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Lacrimation	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Material on fur	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Nasal discharge	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Squinting eyes	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Death (cumulative)	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

PE - Post exposure

PT - Prior to exposure

R - Removal from chamber

Incidence of clinical signs: Female

Observation	Day 0										Day 1		Day 2		Day 3
	Hour
	PT	0.25	0.50	0.75	1	2	3	4	R	1PE	AM	PM	AM	PM	AM	PM
Lacrimation	0	2	3	3	3	3	2	0	5	3	0	0	0	0	0	0
Material on fur	0	0	0	5	5	5	5	5	5	5	5	5	3	3	0	0
Nasal discharge	0	0	0	0	0	0	0	0	1	0	0	0	0	0	0	0
Squinting eyes	0	5	5	5	5	5	5	2	1	0	0	0	0	0	0	0
Death (cumulative)	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

Continued:

Observation	Day
	4		5		6		7		8		9		10		11		12		13		14
	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM	AM	PM
Lacrimation	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Material on fur	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Nasal discharge	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Squinting eyes	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Death (cumulative)	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

PE - Post exposure

PT - Prior to exposure

R - Removal from chamber

Table 7. Individual body weights:

Animal #	Day 0 (g)	Day 1 (g)	Day 2 (g)	Day 4 (g)	Day 7 (g)	Day 14 (g)
Male
AC8941M	262	260	266	280	299	330
AC8942M	277	268	277	292	311	351
AC8943M	281	683	293	307	327	365
AC8944M	282	279	283	298	319	354
AC8945M	266	261	268	287	309	340
Mean	274	270	277	293	313	348
SD	± 9.1	± 10.4	± 11.1	± 10.3	± 10.6	± 13.4
Female
AC8951F	209	212	212	216	223	228
AC8952F	227	223	222	231	242	251
AC8953F	221	223	216	223	225	238
AC8954F	217	220	220	224	232	245
AC8955F	211	211	207	214	216	228
Mean	217	218	215	222	228	238
SD	± 7.3	± 5.9	± 6.1	± 6.8	± 9.9	± 10.2

AC - rat

M - Male

F - Female

Table 8. Individual necropsy findings:

Animal	Type, Time of Death	Term Body Weight (g)	Body Weight Change (g)	Internal Findings
Male
AC8941M	S (14)	330	+ 68	No gross lesions
AC8942M	S (14)	351	+ 74	No gross lesions
AC8943M	S (14)	365	+ 84	No gross lesions
AC8944M	S (14)	354	+ 72	No gross lesions
AC8945M	S (14)	340	+ 74	No gross lesions
Female
AC8951F	S (14)	228	+ 19	No gross lesions
AC8952F	S (14)	251	+ 24	No gross lesions
AC8953F	S (14)	238	+ 17	No gross lesions
AC8954F	S (14)	245	+ 28	No gross lesions
AC8955F	S (14)	228	+ 17	No gross lesions

AC - Rat

M - Male

F - Female

S ( ) - Sacrificed (study day)

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Under the conditions of this study, the test material caused no mortality when administered for 4 h to Sprague Dawley rats at a mean, maximum attainable concentration of 0.83 mg/L. Based on this, the LC50 for monosodium phosphate is considered to be greater than 0.83 mg/L. This study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement for this endpoint.

As the study was conducted up to the maximum attainable concentration and in accordance with Regulation (EC) No. 1272/2008 (EU CLP) sodium dihydrogenorthophosphate is not considered to be classified.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

LC50 >830 mg/m3
Study is conducted according to the appropriate guidelines (EU AND US), under the conditions of GLP and has a Klimisch score of 1.

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:

2005-09-27 to 2006-07-07

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

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 monovalent inorganic salts containing an alkali metal cation and a phosphate anion.
(2) Both substances will ultimately dissociate into the similar breakdown products of the M+ cations and the PO43- anion.
(3) In general, independently of the cation under consideration, the water solubility of phosphates decreases with increasing degree of phosphate condensation (orthophosphate > diphosphate > triphosphate > polyphosphate).
In accordance with the provisions set out in Annex XI, Section 1.5, the results of the studies used for assessment and read-across are adequate for the purpose of classification and labelling and/or risk assessment; have adequate and reliable coverage of the key parameters addressed in the corresponding test method; cover an exposure duration comparable to or longer than the corresponding test method; and adequate and reliable documentation of the applied method is provided in the technical dossier. 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; differences arise in their local effects profile due to the increasing or decreasing acidity/alkalinity and buffering capacities of the substances. This has been shown not to have an effect on systemic toxicity. In addition, both salts have been shown to be of similar low toxicity in acute oral studies. These studies are supported by a number of acute oral studies on similar compounds which all show potassium and sodium orthophosphates to possess low systemic toxicity via the oral route (See section 7.2.1.) and therefore comparisons can be drawn to allow read-across for the acute dermal endpoint. Regarding the nature of the substances in question; inorganic, Molecular weight >100, the absorption through the dermal layer will be considerably less than via the gastro-intestinal tract (a route which has shown low systemic toxicity). This approach is considered to be reliable and justified and no further testing for sodium dihydrogenorthophosphate is required.


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:

not specified

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.1200 (Acute Dermal Toxicity)

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

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

Deviations:

not specified

GLP compliance:

yes

Test type:

fixed dose procedure

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Ace Animals, Inc., Boyertown, PA.
- Age at study initiation: 9 - 10 weeks (young adult)
- Weight at study initiation: Males 298 - 320 g; females 206 - 220 g.
- Housing: Singly housed in suspended stainless steel caging with mesh floors which conform to the size recommendations in the most recent guide for the care and use of laboratory animals DHEW (NIH). Litter paper was placed beneath the case and was changed at least three times per week.
- Diet: Purina rodent chow #5012
- Water: Filtered tap water supplied ad libitum by automatic water dispenser.
- Acclimation period: 15 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 - 23 ºC
- Photoperiod (hrs dark / hrs light): 12-h light/dark cycle

Type of coverage:

occlusive

Vehicle:

water

Details on dermal exposure:

TEST SITE
- Area of exposure: Dorsal area and trunk.
- % coverage: Approximately 10 % (2 inches by 3 inches)
- Type of wrap if used: A gauze pad and 3 inch Durapore tape.

REMOVAL OF TEST SUBSTANCE
- Washing: Test site was gently cleansed of any residual test substance.
- Time after start of exposure: After 24 h.

TEST MATERIAL
- Amount applied: 2000 mg/kg bw. Individual doese were calculated based on the initial body weights and concentration of the test mixture.
- Concentration: 90 % w/w
- For solids, paste formed: Yes the test substance was moistened with distiled water to acheive a dry paste.

Duration of exposure:

24 h

Doses:

2000 mg/kg bw

No. of animals per sex per dose:

5/sex/dose

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: body weights of the animals were recorded prior to test substance application (initial) and again on Days 7 and 14 (termination). Cage side observations for mortality, signs of gross toxicity and behavioural changes during the first several hours after application and at least once daily thereafter for 14 days. Observations included gross evaluation of skin and fur, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous systems, somatomotor activity and behaviour pattern. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhoea and coma.
- Necropsy of survivors performed: Yes gross necropsies were performed on all animals. Tissues and organs of the thoracic and abdominal cavities were examined.

Statistics:

No data

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Remarks on result:

other: The test substance was applied as a 90 % w/w mixture in distilled water.

Mortality:

All animals survived.

Clinical signs:

other: All animals appeared healthy and active during the study. There were no signs of gross toxicity, dermal irritation, adverse pharmacologic effects or abnormal behaviour.

Gross pathology:

No gross abnormalities were noted for any of the animals when necropsied at the conclusion of the 14-day observation period.

Other findings:

No data

Table 2. Individual body weights and doses:

Animal No.	Sex	Body weight			Dose*
		Initial	Day 7	Day 14
9342	M	307	363	400	0.68
9343	M	320	348	388	0.71
9344	M	312	338	376	0.69
9345	M	298	345	390	0.66
9346	M	307	369	416	0.68
9347	F	212	227	239	0.47
9348	F	215	239	248	0.48
9349	F	214	243	253	0.48
9350	F	220	236	254	0.49
9351	F	206	242	261	0.46

* The test substance was applied as a 90 % w/w mixture in distilled water.

Table 3. Individual cage-side observations:

Animal No.	Findings	Day of occurrence
Males
9342 – 9346	Active and healthy	0 - 14
Females
9347 - 9351	Active and healthy	0 - 14

Table 4. Individual necroscopy observations:

Animal No.	Tissue	Findings
Males
9342 – 9346	All tissues and organs	No gross abnormalities
Females
9347 - 9351	All tissues and organs	No gross abnormalities

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of the study, the single dose acute dermal LD50 of PeKacid is greater than 2000 mg/kg bw in male and female rats.
This study is conducted according to the appropriate guidelines (EU AND US) and under the conditions of GLP and therefore the study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement for this endpoint.
In addition, this study is suitable to fulfill the requirements for classification and labelling according to Regulation (EC) No 1272/2008 (EU CLP).

Read-across from potassium pentahydrogen bis(phosphate) to sodium dihydrogenorthophosphate is justified on the following basis.

Both salts are monovalent inorganic phosphates, composed of a phosphate anion and an alkali metal cation. 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; differences arise in their local effects profile due to the increasing or decreasing acidity/alkalinity and buffering capacities of the substances. This has been shown not to have an effect on systemic toxicity.
In addition, both salts have been shown to be of similar low toxicity in acute oral studies. These studies are supported by a number of acute oral studies on similar compounds which all show potassium and sodium orthophosphates to possess low systemic toxicity via the oral route (See section 7.2.1.) and therefore comparisons can be drawn to allow read-across for the acute dermal endpoint.
Regarding the nature of the substances in question; inorganic, Molecular weight >100, the absorption through the dermal layer will be considerably less than via the gastro-intestinal tract (a route which has shown low systemic toxicity).

This study is therefore deemed reliable for classification and labeling according to Regulation (EC) No 1272/2008 (EU CLP).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

LD50 > 2000 mg/kg bw
The study is compliant with GLP and has a Klimisch score of 2 (amended for read-across).
In addition, supporting data are included on a number of similar substances in order to support the read-across justification. These studies have various Klimisch scores.

Additional information

JUSTIFICATION FOR READ ACROSS; sodium and potassium orthophosphates.

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 chemical and sodium dihydrogenorthophosphate have the following similarities:

1. Both substances are inorganic salts of a monovalent cation from Group 1A of the periodic table, sodium or potassium, and phosphoric acid. Thus, they all share the Na+ or K+ cation and the PO43- 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 PO43- anion.

3. Sodium and potassium orthophosphates have been shown to have a similar toxicological profile and physicochemical nature and therefore this data is considered to be adequate and reliable for use in read-across.

The following substances are therefore 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 following endpoint(s) are considered to be suitable for read-across for the substance sodium dihydrogenorthophosphate.

-Acute toxicity: dermal.

Read across is justified on the following basis:

1. Low systemic toxicity in acute oral studies.

A number of studies are provided to show that monovalent potassium and/or sodium inorganic orthophosphates exhibit low acute oral toxicity. These data are provided in Section 7.2.1 of the dossier for sodium dihydrogenorthophosphate. The information provided in these records is considered to be of suitable relevance and reliability to underpin the read across for the acute dermal endpoint.

2. Substance similarities

Only one reliable study is available to assess the acute dermal toxicity; this study was conducted on potassium pentahydrogen bis(phosphate). This study has been used to provide the required data to assess the acute dermal toxicity endpoint for sodium dihydrogenorthophosphate. Supporting data are also provided for all the aforementioned substances. This data is not sufficient as stand-alone sources or information for this endpoint, however it does support the conclusion that sodium and potassium orthophosphates are of low acute toxicity via the dermal route.

The use of data relating to potassium pentahydrogen bis(phosphate) is justified on the following basis:

Both salts are monovalent inorganic phosphates, composed of a phosphate anion and an alkali metal cation. 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; differences arise in their local effects profile due to the increasing or decreasing acidity of the substances. This has been shown not to have an effect on systemic toxicity.

Regarding the nature of the substances in question; inorganic, Molecular weight >100, absorption through the dermal layer will be considerably less than via the gastro-intestinal tract (a route which has shown low systemic toxicity).

Justification for selection of acute toxicity – oral endpoint
One key study exists.

Justification for selection of acute toxicity – inhalation endpoint
One key study exists.

Justification for selection of acute toxicity – dermal endpoint
One key study and a number of supporting studies exists.

Justification for classification or non-classification

Acute toxicity: oral:The acute oral median dose (LD50) of sodium dihydrogenorthophosphate in the female Wistar strain rat was estimated to be greater than 2000 mg/kg bw and is therefore not classified according to Regulation (EC) No 1272/2008 (EU CLP).

Acute toxicity: inhalation:The acute inhalation median concentration (LC50) of sodium dihydrogenorthophosphate in male and female rats was estimated to be greater than 0.83 mg/L. The result was achieved at the maximum attainable concentration and is considered to be equivalent to a limit test conducted at 5 mg/L and therefore sodium dihydrogenorthophosphate is not considered to be classified according to Regulation (EC) No 1272/2008 (EU CLP). In addition the authors state that the particles of sodium dihydrogenorthophosphate were prone to agglomeration and / or adherence to the surfaces of the chamber and therefore it stands to reason that this study is acceptable for assessment and no further animal testing is justified and no classification according to Regulation (EC) No 1272/2008 (EU CLP) shall be proposed.

Acute toxicity: dermal:the acute dermal median dose (LD50) of the analogue substance potassium pentahydrogen bis(phosphate) in rabbits was estimated to be greater than 2000 mg /kg bw and is therefore not classified according to Regulation (EC) No 1272/2008 (EU CLP). This classification can be read across to sodium dihydrogenorthophosphate on the basis of the justifications provided above (see discussion box). As data (Birch MD, 1973, Reliability 4) was provided on sodium dihydrogenorthophosphate to support this conclusion and due to the overall low toxicity of potassium and sodium orthophosphate by this route it is deemed scientifically unjustified to repeat this study with sodium dihydrogenorthophosphate in vivo. Therefore, it can be reliably concluded that sodium dihydrogenorthophosphate does not exhibit dermal toxicity and should not be classified according to Regulation (EC) No 1272/2008 (EU CLP).