[[(phosphonomethyl)imino]bis[ethane-2,1-diylnitrilobis(methylene)]]tetrakisphosphonic acid

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

31.10.1978 to 03.11.1978

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Objective of study:

other: absorption, distribution and excretion

Qualifier:

no guideline followed

Principles of method if other than guideline:

To provide preliminary information about the absorption, distribution and excretion of a compound after its administration to animals.

GLP compliance:

no

Radiolabelling:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River
- Age at study initiation: No data
- Weight at study initiation: 196 to 203 g
- Fasting period before study: yes, overnight and four hours after dosing
- Housing: Metabolism cages
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): No data
- Acclimation period: At least four days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): No data
- Humidity (%): No data
- Air changes (per hr): No data
- Photoperiod (hrs dark / hrs light): No data

IN-LIFE DATES: 31.10.1978 to 03.11.1978

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Not reported

HOMOGENEITY AND STABILITY OF TEST MATERIAL: No details

Duration and frequency of treatment / exposure:

Single dose

Dose / conc.:

47 mg/kg bw/day

Remarks:

1 ml (10 mg TS/ml) - dose of active 47±2 mg/kg

No. of animals per sex per dose / concentration:

Three males in total

Control animals:

no

Positive control reference chemical:

None

Details on study design:

- Dose selection rationale: None given

Details on dosing and sampling:

For 72 hours after dosing the animals were housed in metabolism cages designed to seperate urine, feces and expired CO2. The rats were fitted with fecal cups. Accumulated urine and feces was collected at 24, 48 and 72 hours after application of the test substance. CO2 was collected from the rats at 8 hour intervals for 72 hours (3 samples/day/rat).

SAMPLE COLLECTION
- Collection of blood: Blood samples taken at terminal sacrifice at 72 hours.
- Collection of urine and faeces: metabolism cages and fecal cups.
- Collection of expired air: metabolism cages
- Terminal procedure: Ether
- Analysis of organs: All organs and tissues removed for analysis.

SAMPLE PREPARATION
- Storage procedure: Samples frozen until analysis.
- Preparation details: Organs and tissues rinsed with water and blotted with paper towel. Fat or connective tissue from the organs removed and placed in sample jars. Organs that have internal cavities (heart, gall and urinary bladders) cut open and rinsed with water. If the urinary bladder contained urine, this urine was rinsed into the urine 48-72 hour collection. Skin samples were taken from the back of the animals. Bone samples were taken from the femur after the bone marrow had been removed. Muscle samples were taken from the hind limb. Adipose tissue samples were taken from the area of the psoas muscle. Carcasses were then frozen with dry ice before grinding in a Wiley mill.

ANALYSIS
- Method type(s) for identification: Liquid scintillation counting
- Liquid scintillation counting results (cpm) converted to dpm as follows: No details
- Validation of analytical procedure: No details
- Limits of detection and quantification: No details

Type:

absorption

Results:

2%

Type:

distribution

Results:

Affinity for bone (concentration of radioactivity in bone was 9 x greater than any other tissue)

Type:

excretion

Results:

98% excreted in feces by 72 hours, 1.3% in urine and 0.4% in CO2.

Details on absorption:

98% of the dose was excreted into feces, leaving 2% that was absorbed.
Total recovery: 100.6 ± 3.3%

Details on distribution in tissues:

Liver: 0.01± 0.00%
Kidneys: 0.004 ± 0.001%
Testes: 0.001± 0.000%
Carcass: 0.6 ± 0.2%
Cage wash: 0.0± 0.0%
GI tract: 0.005± 0.003%
GI wash: 0.0 ± 0.0%
Lung: 0.0009 ± 0.0001%
Spleen: 0.0002± 0.0002%
Pancreas: 0.0 ± 0.0%
Brain: 0.0 ± 0.0%
Muscle: 0.0 ± 0.0%
Bone: 2.9 ± 0.79 µg/g
Bone Marrow: 0.0 ± 0.0 µg/g
Blood: 0.05 ± 0.05 µg/g
Plasma: 0.03 ± 0.02 µg/g
Adipose: 0.0 ± 0.0 µg/g

Details on excretion:

See Table 1

Metabolites identified:

not measured

Table 1 Average excretion (% of dose ± SD) of neutralised DTPMP following oral ingestion.

	0 -24 h	24 -48 h	48 -72 h	Total
Urine	1.2 ± 0.2	0.06 ± 0.009	0.03 ± 0.01	1.3± 0.2
Feces	94 ± 5.2	4.3 ± 1.5	0.1 ± 0.005	98 ± 4
CO2	0.4 ± 0.0 (0 -8 h); Not detected (8 -24 h)	Not detected	Not detected	0.4 ± 0.0

Conclusions:

In an oral toxicokinetics study in rats, conducted prior to GLP (reliability score 2), 98% of the dose (oral gavage) of neutralised DTPMP was excreted in feces within 72 hours. Of the remaining dose 1.3% was found in urine and 0.4% in expired CO2. Minor quantities were found in various tissues, but the bone was found to have nine times more (2.9 ± 0.79 µg/g) than any other organ or tissue.

Reference 2

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

31.10.1978 to 03.11.1978

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Qualifier:

no guideline followed

Principles of method if other than guideline:

To provide preliminary information about the absorption, distribution and excretion of a compound after its administration to animals.

GLP compliance:

no

Radiolabelling:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River
- Age at study initiation: No data
- Weight at study initiation: 175 to 225 g
- Fasting period before study: yes, overnight and four hours after dosing
- Housing: Metabolism cages
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): No data
- Acclimation period: At least four days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): No data
- Humidity (%): No data
- Air changes (per hr): No data
- Photoperiod (hrs dark / hrs light): No data

IN-LIFE DATES: 31.10.1978 to 03.11.1978

Type of coverage:

semiocclusive

Vehicle:

water

Duration of exposure:

72 hours

Doses:

- Concentration: 6.1 mg/ml
- Dose volume: 0.1 ml, which contained 2.31 microCi.
- Rationale for dose selection: None given

No. of animals per group:

Three male animals in total

Control animals:

no

Details on study design:

DOSE PREPARATION
- Method for preparation of dose suspensions: No data
- Method of storage: No data

APPLICATION OF DOSE: Using Eastman 910 adhesive, a contoured glass ring was glued to the middle of the back of each animal. The ring was 3.6 cm diameter.

TEST SITE
- Preparation of test site: Shaved
- Area of exposure: back
- % coverage: No data
- Time intervals for shavings or clipplings: No data

SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: yes: A porous glass disk was fitted over the skin inside the glass ring. This permited air circulation over the test site, but prevented loss of the test substance by flaking or ingestion.

REMOVAL OF TEST SUBSTANCE
- Removal of protecting device: After 72 hours
- Washing procedures and type of cleansing agent: No

For 72 hours after dosing the animals were housed in metabolism cages designed to seperate urine, feces and expired CO2. The rats were fitted with fecal cups. Accumulated urine and feces was collected at 24, 48 and 72 hours after application of the test substance. CO2 was collected from the rats at 8 hour intervals for 72 hours (3 samples/day/rat).

SAMPLE COLLECTION
- Collection of blood: Blood samples taken at terminal sacrifice at 72 hours.
- Collection of urine and faeces: metabolism cages and fecal cups.
- Collection of expired air: metabolism cages
- Terminal procedure: Ether
- Analysis of organs: All organs and tissues removed for analysis.

SAMPLE PREPARATION
- Storage procedure: Samples frozen until analysis.
- Preparation details: Organs and tissues rinsed with water and blotted with paper towel. Fat or connective tissue from the organs removed and placed in sample jars. Organs that have internal cavities (heart, gall and urinary bladders) cut open and rinsed with water. If the urinary bladder contained urine, this urine was rinsed into the urine 48-72 hour collection. Skin samples were taken from the back of the animals. Bone samples were taken from the femur after the bone marrow had been removed. Muscle samples were taken from the hind limb. Adipose tissue samples were taken from the area of the psoas muscle. Carcasses were then frozen with dry ice before grinding in a Wiley mill.

ANALYSIS
- Method type(s) for identification: Liquid scintillation counting
- Liquid scintillation counting results (cpm) converted to dpm as follows: No details
- Validation of analytical procedure: No details
- Limits of detection and quantification: No details

Signs and symptoms of toxicity:

no effects

Dermal irritation:

no effects

Absorption in different matrices:

- Non-occlusive cover + enclosure rinse: None reported
- Skin wash: None reported
- Skin adjacent to test site: 0.007 ± 0.002 (mean and SD)
- Skin test site: 89 ± 2% (mean and SD)
- Blood: 0.01 ± 0.01µg/g (mean and SD)
- Carcass: 0.5 ± 0.5% (mean and SD)
- Urine: 0.02 to 2% (mean 0.8%)
- Cage wash + cage wipe: 0.1 ±0.1 (mean and SD)
- Faeces: <=0.01%
- Expired air (if applicable): None reported
- Serial non-detects in excreta at termination: No

- Liver: none detected
- Kidneys: 0.01 ± 0.01% (mean SD)
- Gonads: none detected
- Plasma: none detected
- Muscle: 0.01 ±0.01 µg/g

Total recovery:

- Total recovery: 90%
- Recovery of applied dose acceptable: Accepted as low, but reasonable
- Results adjusted for incomplete recovery of the applied dose: Apparently not
- Limit of detection (LOD): No details
- Quantification of values below LOD or LOQ: No details

Dose:

0.1 ml

Parameter:

percentage

Absorption:

< 1 %

Remarks on result:

other: 72 hours

Conversion factor human vs. animal skin:

None

Table 1 Average excretion (% of dose ± SD)

	0 -24 h	24 -48 h	48 -72 h	Total
Urine	0.7 ± 0.6	0.02  ± 0.01	0.01 ±0.01	0.8  ± 0.7
Feces	0.003  ± 0.003	None detected	None detected	0.0 ± 0.0

Total recovery: 90 ± 3%

Conclusions:

In a dermal metabolism study (pre-GLP; reliability score 2), less than 1% of a dermally applied dose (0.1 ml) of neutralised DTPMP was absorbed over a 72 hour exposure period. Most (89 %) of the applied dose was recovered from test site. Total recovery was 90%.

Description of key information

The available information suggests that only minor amounts of sodium DTPMP-H are absorbed after ingestion (limited by physicochemical interactions within the gut) or skin contact (limited by hydrophilic nature). There are also not expected to be any major differences between animals and humans for these parameters.

Key value for chemical safety assessment

Absorption rate - oral (%):

2

Additional information

Absorption

Oral

The physicochemical properties of phosphonic acid compounds, notably their high polarity, charge and complexing power, suggests that they will not be readily absorbed from the gastrointestinal tract. This is supported by experimental data which confirm that absorption after oral exposure is low, averaging 2-7% in animals and 2-10% in humans. In a study by Procter and Gamble (1978) approximately 2% of a dose of neutralised DTPMP-H was absorbed from a gavage dose, and 98% of the dose was excreted in feces within 72 hours of dosing.

Gastrointestinal pH is a major determinant influencing uptake, and is relatively acidic in the stomach (range: pH 1 - 4) and slightly more alkaline in the intestine (pH 4 - 7). The number of ionisations of the phosphonic acid moiety increases with increasing pH, rising from 1 - 2 at low pH (i.e. stomach) to 4 - 6 at more neutral pH (reflective of conditions in the intestine). The negative charge on each molecule also increases with each ionisation, further reducing the already low potential for uptake. Stability constants for the interaction of phosphonic acids with divalent metal ions are high, and indicate strong binding, especially at lower pHs. Complexation of a metal with a phosphonic acid would produce an ion pair of charge close to neutral which might favour absorption; however the overall polarity of the complex would remain high thereby counteracting this potential. Overall, these considerations indicate that ingested phosphonic acid compounds will be retained within the gut lumen.

Dermal

DTPMP-H is too hydrophilic to be absorbed through the skin. In a dermal absorption study (Procter and Gamble, 1978a, Reliability 2), 89% of the applied radioactivity (0.6 mg/kg bw) was recovered from the test site 72 hours after application to rat skin, with negligible amounts in faeces (< 0.01%) and minor amounts in urine (< 2% ) and carcass (<1.5%).

Inhalation

The vapour pressure of DTPMP-H is extremely low (<10E-08 Pa). Consequently, inhalation of DTPMP-H vapour is not possible. It is possible that aerosol (from aqueous solution) of DTPMP-H could be inhaled. The very high water solubility of this substance suggests that absorption would be low following inhalation exposure to aerosol.

 

Distribution

In oral and dermal studies conducted by Procter and Gamble (1978) the concentrations of DTPMP-H in all tissues was extremely low, due to the low overall absorption (Table 5.1.2). In the oral study it was shown that most test substance was distributed to the bone, and this tissue had nine times more DTPMP-H than any other organ or tissue.

Bone imaging following 2 and 4 hour intravenous administration of radiolabelled DTPMP-H in rabbits (Subramanian et al., 1975) and rats (Goeckeler et al., 1978) confirms that DTPMP is preferentially distributed to bone, but that concentrations in the bone marrow are low in comparison with the bone and comparable with other tissues such as muscle, kidney and liver (Table 1).

Table 1: Distribution of DTPMP in tissues

Tissue	Distribution following oral administration (μg/kg) Procter and Gamble (1978) (species: rat)	Distribution following 2h intravenous administration (% dose/g) (2h) Goeckeler (1987) (species: rat)	Distribution following 4h intravenous administration (% dose/1% body weight) Subramanian (1975) (species: rabbit)	Distribution following 4h intravenous administration (% dose/1% body weight) Subramanian (1975) (species: rabbit)
Radiolabel	14-C	153-Sm	85-Sr	113m-In
Blood	0.05 ± 0.05	74	0.7	0.4
Plasma	0.03 ± 0.02	Not determined	Not determined	Not determined
Average bone	2.9 ± 0.79	30	8.1	4.8
Marrow	Below limit of detection	Not determined	0.3	0.2
Muscle	Below limit of detection	0.9	0.2	0.04
Kidney	0.17 ± 0.03	0.4	0.9	2.3
Liver	0.11 ± 0.02	0.3	0.3	0.2
Testes	0.05 ± 0.007	Not determined	Not determined	Not determined

Metabolism

There are no data on the metabolism of DTPMP.

Excretion

Information is available on the elimination of¹⁴C-DTPMP (neutralised sodium salt) following oral or dermal administration to SD rats. In an oral toxicokinetics study using SD rats and with¹⁴C-DTPMP (neutralised sodium salt), 98% of a gavage dose (10 mg/kg bw, 7 μCi/kg bw), was excreted in the feces within 72 hours (Procter and Gamble, 1978). Of the remaining dose 1.3% was found in urine (the majority within 24 hours) and 0.4% in expired CO₂. Faecal elimination of unabsorbed material predominates after ingestion (up to 90% of dose). Following dermal application, the majority of the absorbed dose was excreted in urine within 24 hours of the start of exposure.