Ammonium undecafluorohexanoate

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

23 Dec 2009 - 20 Jun 2011

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Reason / purpose for cross-reference:

reference to same study

Objective of study:

toxicokinetics

Qualifier:

no guideline followed

Principles of method if other than guideline:

In a developmental toxicity study, dams were exposed to the test substance at dosages of 7, 35 and 175 mg/kg bw/day from Day 6 to Day 18 of gestation. Subsequently, F0 generation mice were scrificed on postpartum day (PPD) 20 and serum samples were collected. F1 generation mice were sacrificed on PPD 41 and serum and liver samples were collected. The concentrations of perfluorohexanoic acid (PFHxA) in mouse serum samples and mouse liver homogenates were determined using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.

GLP compliance:

yes

Radiolabelling:

no

Species:

mouse

Strain:

other: Crl:CD1(ICR)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., St Constant, Canada
- Age at study initiation: Approx. 63 days at day of arrival
- Weight at study initiation: 25.8-31.7 g (range)
- Housing: F0 was housed individually in stainless steel, wire bottom cages, except during the cohabitation and postpartum periods. During cohabitation, each pair of male and female mice was housed in the male mouse’s cage. Each dam and delivered litter was housed in a common nesting box with nesting material (Bed-o´cobs bedding) during the postpartum period. F1 was housed paired in nesting boxes until PND 27, afterwards individually.
- Diet (e.g. ad libitum): Certified Rodent Diet #5002 (PMI Nutrition International, Inc., St. Louis, MO, USA), ad libitum
- Water (e.g. ad libitum): Local water processed by passage through a reverse osmosis membrane (R.O. water), chlorine added as a bacteriostat, ad libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-26
- Humidity (%): 30-70
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: Reverse osmosis deionized water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Solutions of the test substance at concentrations of 1.4, 7 and 35 mg/mL were prepared once weekly at the Testing Facility and stirred continuously for at least 24 hours prior to dosage administration, and stored at room temperature.

VEHICLE
- Amount of vehicle: 5mL/kg bw

Duration and frequency of treatment / exposure:

daily, 7 days/weeks; from Day 6 - 18 of gestation

Dose / conc.:

7 mg/kg bw/day (actual dose received)

Dose / conc.:

35 mg/kg bw/day (actual dose received)

Dose / conc.:

175 mg/kg bw/day (actual dose received)

No. of animals per sex per dose / concentration:

F0: 80 females
F1: 80 males and females

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on adverse results in previous developmental toxicity studies of other perfluoroalkyl acids (PFAA), dosages of 7, 35 and 175 mg/kg bw/day were selected for this study.

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Liver, serum
- Time and frequency of sampling: liver samples: PPD (postpartum day) 21 (females F0); blood and liver samples: PPD 41 (F1 generation)
- From how many animals: 5 mice per group (40 mice in total)
- Other: Blood samples of F1 generation mice were collected via the vena cava after sacrifice. The blood samples were transferred into uncoated (red top) tubes and spun in a refrigerated (4°C) centrifuge for 10 minutes at 3500 rpm. The resulting serum was transferred into appropriately labeled polypropylene tubes. Livers of dams (F0) and pups (F1) were excised and weighed. All samples were frozen on dry ice as soon as possible and maintained frozen (≤ -70°C) until shipment for analysis to PCS-MTL.

- Reference substance: The test substance perfluorohexanoic acid (PFHxA equivalent to PFH ammonium salt) was used as reference material for pharmacokinetic analysis.

- Method type for identification: LC-MS/MS
- Limits of detection and quantification: Lower limit of detection (LLOQ; theoretical concentration 1.00 and 0.002 μg/mL for serum and liver samples, respectively)

Statistics:

Statistical analyses included quadratic regression with 1/concentration² weighting and descriptive statistics such as arithmetic means and standard deviations, accuracy and precision using Watson Laboratory Information Management System (LIMS) (Version 7.2.0.02) and Microsoft Excel (Version 2000/2003).

Type:

other: serum concentration

Results:

All F1 generation serum concentrations of Perfluorohexanoic Acid (PFHxA) were below the lower limit of detection (LLOQ; theoretical concentration 1.00 μg/mL).

Type:

other: concentration in liver samples

Results:

All F0 and F1 generation liver concentrations of Perfluorohexanoic Acid (PFHxA) were below the lower limit of detection (LLOQ; theoretical concentration 0.02 μg/mL)

Metabolites identified:

not measured

Conclusions:

Concentrations of perfluorohexanoic acid (PFHxA; equivalent to administered PFH ammonium salt) in serum of F1 generation mice and in liver samples of F0 and F1 generation mice at day of sacrifice were below lower limit of detection (LLOQ; theoretical concentrations of 1.00 μg/mL (serum) and 0.02 (liver)). Thus, distribution of the test substance into liver is assumed to be low.

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

26 May 2009 - 05 Mar 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Objective of study:

toxicokinetics

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of test: Parmacokinetics were evaluated as part of an acute oral toxicity test.
- Short description of test conditions: The test substance was administered once by oral gavage to female Crl:CD1(ICR) mice at dose levels of 35, 175 and 350 mg/kg bw. The control substance used for this study was reverse osmosis deionized water. Blood samples from 3 mice per group were obtained prior to dosing and at 0.5, 2, 4, 6, 8 and 24 h after dosing and evaluated for serum concentration levels.
- Parameters analysed / observed: maximal serum concentration (Cmax), AUC, half-life time

GLP compliance:

yes

Radiolabelling:

no

Species:

mouse

Strain:

other: Crl:CD1(ICR)

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Kingston, NY, USA
- Age at arrival: approx. 62 days
- Weight at study initiation: 32.3 - 37.0 g (range)
- Housing: Individually in stainless steel, wire-bottomed cages
- Diet: Certified Rodent Diet® #5002 checkers (PMI® Nutrition International, St. Louis, MO, USA), ad libitum
- Water: reverse osmosis water, chlorine added
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-26
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

other: reverse osmosis water

Details on exposure:

Dosage volume: 5 mL/kg bw
Concentration in vehicle: 7, 35 and 70 mg/mL

Duration and frequency of treatment / exposure:

single administration

Dose / conc.:

35 mg/kg bw (total dose)

Dose / conc.:

175 mg/kg bw (total dose)

Dose / conc.:

350 mg/kg bw (total dose)

No. of animals per sex per dose / concentration:

21 females

Control animals:

yes, concurrent vehicle

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: serum
- Time and frequency of sampling: prior to dosing and 0.5, 2, 4, 6, 8 and 24 h after dosing
- From how many animals: three per group
- Method type for identification: LC-MS/MS
- Limits of detection and quantification: lower limit of quantitation (LLOQ) 1 µg/mL

ANIMAL OBSERVATIONS
Checks for viability were made at least twice daily. Clinical observations were recorded prior to dosage administration and prior to sacrifice. Body weights were recorded weekly during the acclimation period and once on the day of dosage administration (for main study mice only).

Statistics:

Mean and standard deviation (SD) was calculated.

Details on absorption:

Serum concentrations:
The serum concentrations of PFHxA were not quantifiable in predose samples in any of the groups. In the 35 mg/kg bw dose group, PFHxA could be quantified at sampling time points of 0.5, 2 and 4 h. No PFHxA could be quantified after 6 h. In the 175 and 350 mg/kg bw dose groups, PFHxA could be quantified at sampling points of 0.5, 2, 4, 6 and 8 h. The mean concentration of PFHxA was below the LLOQ at 24 h post-dose, but one individual animal in each group had quantifiable levels at 24 h.
Toxicokinetics:
The maximal serum concentrations (Cmax) of PFHxA were observed at the first sampling time point (30 minutes post dose), indicating that the compound was rapidly absorbed after oral administration. After Cmax was reached, serum concentrations of PFHxA decreased rapidly. At the 35 mg/kg bw dose level, the decline in PFHxA serum concentration was mono-exponential. At the 175 mg/kg bw and 350 mg/kg bw dose levels, the decline was multi-exponential, with a plateau in concentrations occurring between 0.5 and 2 hours in the 175 mg/kg bw dose group and between 2 and 4 hours in the 350 mg/kg bw dose group. The terminal elimination phases were nonetheless similar among the three dose groups, with terminal elimination half-lives ranging from 0.889 to 1.24 hours. Exposure increased with increase in dose level. The increase in Cmax (from 96.6 to 454 µg/mL) was lower than proportional, whereas the increase in AUC(0-inf) (from 178 to 1893 h*µg/mL) was proportional to the increase in dose from 35 to 350 mg/kg bw.

Key result

Test no.:

#1

Toxicokinetic parameters:

Cmax: 96.6, 330 and 454 µg/mL at dose levels of 35, 175 and 350 mg/kg bw, respectively

Key result

Test no.:

#2

Toxicokinetic parameters:

AUC: (t0-infinity)

Remarks:

178, 1144 and 1893 µg*h/mL at dose levels of 35, 175 and 350 mg/kg bw, respectively

Key result

Test no.:

#3

Toxicokinetic parameters:

half-life 1st: 0.889, 1.24 and 0.924 h at dose levels of 35, 175 and 350 mg/kg bw, respectively

Metabolites identified:

not measured

ANIMAL OBSERVATIONS:

No mortality and no clinical observations occured during the study period.

Conclusions:

PFHxA was rapidly absorbed (Cmax reached within 30 minutes) and was not quantifiable at 24 hours after dose administration. The terminal elimination half-life of PFHxA ranged from 0.889 to 1.24 hours, and was dose-independent. The increase in Cmax (from 96.6 to 454 µg/mL) was lower than proportional, whereas the increase in AUC(t0-infinity) (from 178 to 1893 h*µg/mL) was proportional, to the increase in dose from 35 to 350 mg/kg bw.

Reference 3

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12 Jun - 21 Sep 2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Objective of study:

distribution

excretion

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.7485 (Metabolism and Pharmacokinetics)

GLP compliance:

yes

Radiolabelling:

yes

Species:

other: rat and mouse

Strain:

other: rat: Crl:CD[SD]; mouse: CD-1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Limited, UK
- Age at study initiation: 7 -10 weeks
- Weight at study initiation: 182-362 g (range for rats), 23 - 34 g (range for mice)
- Fasting period: 4 h before dosing and approx. 2 h after dosing
- Housing: Individually in glass metabolism cages; Rats not used for collection of excreta samples were housed in pairs by sex in suitable polycarbonate and stainless steel caging with raised wire mesh floors. Male mice were housed singly and females in pairs in polypropylene and stainless steel caging with raised wire mesh floors.
- Diet: SDS Rat and Mouse Diet No. 1 (Special diets Services, Stepfield, Witham, UK), ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Unlabeled test item: 10.55 mL (equivalent to 5000.23 mg) of ammonium perfluorohexanoate were mixed with 990 mL destilled water to give a solution. The final concentration was 5.02 mg/mL, with a final formulation weight of 995.41 g.
Radio-labelled test item: 1.74 mL( equivalent to 4.86 mg and 32.03 MBq) of [14C]-ammonium perfluorohexanoate prepared stock solution and 834 μl (equivalent to 395.32 mg) of ammonium perfluorohexanoate were mixed in a dose jar. The required volume (ca 77.4 mL) of sterile water was then added and mixed to give a solution. The final concentration was 5.06 mg/mL and 0.440 MBq/mL, with a final formulation weight of 79.15 g.

DOSE VOLUME: 10 mL/kg

Duration and frequency of treatment / exposure:

13 days, daily (ammonium perfluorohexanoate), followed by a single dose of radiolabelled [14C]-ammonium perfluorohexanoate on Day 14

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Remarks:

(target radioactive dose level: 3-5 MBq/kg)

No. of animals per sex per dose / concentration:

8 (rats) and 13 (mice)

Control animals:

no

Details on study design:

- Dose selection rationale: Dose level of 50 mg/kg bw/day was chosen to reach a target radioactive dose level of 3-5 MBq/kg.

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Urine, faeces, cage washes, blood (plasma), white adipose tissue, kidneys, liver, spleen, gastrointestinal tract, residual carcass
- Time and frequency of sampling: Blood:12 h pre-dose and 24 h post-dose; urine: for periods 0-6, 6-24 h then at 24 h intervals to 168 h post dose; faeces: 24 h intervals to 168 h post-dose. Cages were washed with water at the time of each faeces collection. Terminal blood and tissue collection: after termination following 168 h collection period.

Statistics:

Group mean values and standard deviations were calculated from the examined parameters.

Details on absorption:

Rats:
Following a multiple (13 daily doses) oral administration of ammonium perfluorohexanoate followed by a single oral administration of [14C]-Ammonium Perfluorohexanoate to male and female rats, at the 2 time points examined, the mean concentrations of radioactivity in plasma at 12 h post dose were 0.8 and 0.4 μg/mL in males and females respectively. Thereafter, plasma concentrations declined to 0.5 and 0.3 μg/mL in males and females, respectively at 24 h post dose. Analysis of the predose plasma confirmed the radioactive levels were at background level.

Mice:
Following a multiple (13 daily doses) oral administration of ammonium perfluorohexanoate followed by a single oral administration of [14C]-ammonium perfluorohexanoate to male and female mice, the mean concentrations of radioactivity in plasma at 12 h post dose were 1.3 and 1.0 μg/mL in males and females respectively. Thereafter, mean plasma concentrations declined to 1.0 and 0.5 μg/mL in males and females, respectively at 24 h post radiolabelled dose. Analysis of the predose (control mice) plasma confirmed the radioactive levels were at background level.

Details on distribution in tissues:

Rats:
At 168 h post dose, the mean blood concentrations of radioactivity were 0.15 and 0.16 μg equiv/g, in males and females, respectively. The only tissue concentration above circulating blood level was noted in the liver, with values of 1.16 and 0.85 μg equiv/g in males and females, respectively. All other tissue values (white fat, kidney, spleen, gastrointestinal tract and carcass) were lower than the blood level or below the limit of quantification, with mean concentrations above the limit of quantification ranging from 0.10-0.13 μg equiv/g.

Mice:
At 168 h post dose, the mean blood concentrations of radioactivity were 0.17 μg equiv/g, in both males and females. The only tissue concentration above circulating blood level was noted in the liver, with values of 0.70 and 0.61 μg equiv/g in males and females, respectively. All other tissue values (white fat, kidney, spleen, gastrointestinal tract and carcass) were lower than the circulating blood level and below the limit of quantification.

Observation:

not determined

Details on excretion:

Rats:
Following the radiolabelled dose administration, the major route of elimination of radioactivity was via the urine with means of 80.7% and 77.8% of the dose in males and females ,respectively. Faecal elimination accounted for 12.9% in males and 12.6% in females. Excretion of total radioactivity was rapid with means of 93.7% and 90.4% recovered by 24 h post dose (equivalent to 98.5% and 96.5% of the ultimately recovered material). By 168 h post dose, approximately 0.2% of the dose remained in the gastrointestinal tract and carcass, indicating that excretion was almost complete. Mean recoveries of total radioactivity (including residual radioactivity in the gastrointestinal tract and carcass) were 95.1% and 93.7% of the dose administered in males and females, respectively.

Mice:
Following the radiolabelled dose administration, the major route of elimination was via the urine with means of 81.1% and 83.4% of the dose in males and females, respectively. Faecal elimination accounted for 10.6% in males and 9.6% in females. Excretion of total radioactivity was rapid with means of 93.5% and 92.2% recovered by 24 hours post dose (equivalent to 96.4% and 95.6 % of the ultimately recovered material). By 168 h post dose, approximately 0.1% of the dose remained in the gastrointestinal tract and carcass, indicating that excretion was almost complete. Mean recoveries of total radioactivity (including residual radioactivity in the gastrointestinal tract and carcass) were 97.0% and 96.4% of the dose administered in males and females, respectively.

Metabolites identified:

not measured

Conclusions:

After a multiple (13 daily doses) oral administration of ammonium perfluorohexanoate in rats and mice followed by a single oral administration of [14C]-ammonium perfluorohexanoate absorption of the test substance was rapid with mean plasma concentrations of 0.8 and 0.4 μg/mL in male and female rats, respectively, and 1.3 and 1.0 μg/mL in male and female mice, respectively.
Tissue distribution measured at 168 h post dose in rats and mice, below the limit of detection or below blood concentration in most tissues (white fat, kidneys, spleen, gastrointestinal tract and carcas) with the exception of liver, which was approximately 4-8 times higher than the circulating blood level. Elevated levels of measurable radioactivity in the liver are consistent with its role in metabolism and excretion. There was no indication for bioaccumulation of the test substance.
Irrespective of sex or species, mean recoveries were of over 90% of the dose administered (and with mean values >95% of the ultimately recovered material) at 24 h post dose. The major route of elimination was via the urine (means of 77.8-83.4% of the dose), followed by the faeces (mean of 9.6-12.9%), indicating that the majority of the administered dose had been absorbed.

Reference 4

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 Mar - 27 Nov 2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Objective of study:

excretion

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.7485 (Metabolism and Pharmacokinetics)

GLP compliance:

yes

Radiolabelling:

yes

Species:

other: rat and mouse

Strain:

other: rat: Crl:CD[SD]; mouse: CD-1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Limited, UK
- Age at study initiation: 7 weeks
- Weight at study initiation: 172-253 g (range for rats) and 26-36 g (range for mice)
- Fasting period: 10-12 h before dosing and approx. 3-4 h after dosing
- Housing: During the pre-trial holding period, rats were multiply housed by sex in suitable polycarbonate and stainless steel caging with bedding and chewsticks. Male mice were housed singly and females multiply in solid floored polypropylene and stainless steel caging. During on-study periods, rats and mice were housed singly in glass metabolism cages.
- Diet: SDS Rat and Mouse Diet No. 1 (Special diets Services, Stepfield, Witham, UK), ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Rat: 0.73 mg of [14C]-ammonium perfluorohexanoate and 156 μL (equivalent to 73.94 mg) of ammonium perfluorohexanoate were weighed into a glass vial. The required volume of sterile water was then added to the vial and mixed to give a solution. The final concentration was 4.90 mg/mL, with a final formulation weight of 15.23 g.
Mouse: 1.69 mg of [14C]-ammonium perfluorohexanoate and 246 μL (equivalent to 123.1 mg) of ammonium perfluorohexanoate were weighed into a glass vial. The required volume of sterile water was then added to the vial and mixed to give a solution. The final concentration was 4.74 mg/mL, with a final formulation weight of 24.58 g.

DOSE VOLUME: 10 mL/kg bw

Duration and frequency of treatment / exposure:

single administration

Dose / conc.:

50 mg/kg bw (total dose)

Remarks:

(target radioactive dose level: 3-5 MBq/kg)

No. of animals per sex per dose / concentration:

2

Control animals:

no

Details on study design:

- Dose selection rationale: Dose level of 50 mg/kg bw was chosen to reach a target radioactive dose level of 3-5 MBq/kg.

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Urine, faeces, cage washes, gastrointestinal tract, residual carcass
- Time and frequency of sampling: Urine and faeces: for periods 0-6, 6-24 h, then at 24 h intervals to 72 h post dose; cages were washed with water at the time of each faeces collection. Expired air was collected over 0-24 and 24-48 h post dose. At the end of the 72 h collection period, each animal was humanely killed by CO2 narcosis and the gastrointestinal tract and residual carcass from each rat was retained.

Statistics:

Group mean values and standard deviations were calculated from the examined parameters.

Observation:

not determined

Details on excretion:

Rats: Following a single oral administration, the major route of elimination was via the urine with means of 73.0% and 90.2% of the dose in males and females, respectively. Faecal elimination accounted for 15.5% in males and 7.3% in females. Elimination via expired air was minimal accounting for only 0.04% of the dose in both sexes 0-48 h after administration. Excretion of total radioactivity was rapid with means of 95.6% and 99.2% recovered by 24 hours post dose. By 72 h post dose, approximately 0.2% of the dose remained in the gastrointestinal tract and carcass, indicating that excretion was almost complete. Mean recoveries of total radioactivity (including residual radioactivity in the gastrointestinal tract and carcass) were 97.4% and 100.8% of the dose administered in males and females respectively.

Mice: One female animal had to be prematurely terminated at 48 h post dose due to poor wellbeing of the animal. This was considered not to be a result of the test item administration. This is not considered to have significant impact on the results of this study, as the majority of the radioactivity was excreted by this endpoint. Following a single oral administration, the major route of elimination was via the urine with means of 80.3% and 84.0% of the dose in males and females, respectively. Faecal elimination accounted for 10.5% in males and 7.0% in females. Elimination via expired air was minimal accounting for only 0.07-0.08% of the dose 0-48 h after administration. Excretion of total radioactivity was rapid with means of 90.9% and 94.1% recovered by 24 hours post dose. By 72 h post dose, approximately 0.6-0.9% of the dose remained in the gastrointestinal tract and carcass, indicating that excretion was almost complete. Mean recoveries of total radioactivity (including residual radioactivity in the gastrointestinal tract and carcass) were 95.4% and 97.3% of the dose administered in males and females respectively.

Metabolites identified:

not measured

Conclusions:

For the male and female rats and mice, following a single oral administration of [14C]-ammonium perfluorohexanoate, total radioactivity excretion was rapid, with mean recoveries of over 90% of the dose at 24 h post dose. The major route of elimination was via the urine (means of 73.0-90.2% of the dose), followed by the faeces (mean of 7.0-15.5%). Elimination via expired air was negligible. In rats, 72 hours post dose, mean recoveries of total radioactivity were 97.4% and 100.8% in males and females, respectively, with approximately 0.2% remaining in the gastrointestinal tract and carcass.
In mice, 72 hours post dose, mean recoveries of total radioactivity were 95.4% and 97.3% in males and females respectively, with approximately 0.6-0.9% remaining in the gastrointestinal tract and carcass.

Description of key information

Ammonium undecafluorohexanoate is assumed to dissociate to undecafluorohexanoic acid and its ammonium cation in aqueous solutions. Toxicokinetic data on the substance have shown that it is rapidly absorbed after oral exposure and distributed throughout the body to tissues and organs. The highest tissue concentrations were observed in the liver. Undecafluorohexanoic acid is rapidly eliminated via urine. There is no evidence of bioaccumulation. The molecular weight, physicochemical properties incl. water solubility and octanol-water partition coefficient of the substance suggest that dermal absorption is high and inhalative absorption negligible.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

In accordance with Annex VIII, Column 1, Item 8.8 of Regulation (EC) 1907/2006 and with Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2017), and assessment of the toxicokinetic behaviour of the test substance ammonium undecafluorohexanoate (also called ammonium salt of perfluorohexanoic acid; APFHx) was conducted to the extent that can be derived from the relevant available information on basic toxicokinetics, physicochemical and toxicological characteristics. There are 4 in vivo studies available evaluating the toxicokinetic properties of the test substance.

 

The test substance is a white powder but is marketed or used in a non-solid or granular form. It has a molecular weight of 331.08 g/mol and a water solubility of 57.61 g/L at 20 °C. The substance has a vapour pressure of 4.47E-03 Pa at 20 °C and the log Pow is 2.06 at pH4.

 

Absorption

The major routes by which the test substance can enter the body are via the lung, the gastrointestinal tract, and the skin. To be absorbed, the test substances must transverse across biological membranes either by active transport mechanisms or - as being the case for most compounds - by passive diffusion. The latter is dependent on compound properties such as molecular weight, lipophilicity and water solubility (ECHA, 2017).

 

Oral

In general, low molecular weight (MW ≤ 500) and moderate lipophilicity (log Pow values of -1 to +4) are favourable for gastrointestinal absorption. The molecular weight of the test substance is relatively low with 331.08 g/mol, favouring oral absorption of the compound. This is supported by the log Pow value of 2.1 and the water solubility, which both favour oral absorption. Since Ammonium undecafluorohexanoate is an ammonium salt it is assumed to dissociate to undecafluorohexanoic acid and its ammonium cation in aqueous solutions like in the gastrointestinal tract.

 

The pharmacokinetics of the dissociated form of ammonium undecafluorohexanoate also called perfluorohexanoic acid (PFHxA) were characterized in female Crl:CD1(ICR) mice (n = 21 /group) when administered once by oral gavage at dose levels of 35, 175 and 350 mg/kg bw of ammonium undecafluorohexanoate (Hoberman, 2011). The maximal serum concentrations (Cmax) of PFHxA were observed at the first sampling time point (30 minutes post-dose), indicating that the compound was rapidly absorbed after oral administration. After Cmax was reached, serum concentrations of PFHxA decreased rapidly. At the 35 mg/kg bw dose level, the decline in PFHxA serum concentration was mono-exponential. At the 175 mg/kg bw and 350 mg/kg bw dose levels, the decline was multi-exponential, with a plateau in concentrations occurring between 0.5 and 2 hours in the 175 mg/kg bw dose group and between 2 and 4 hours in the 350 mg/kg bw dose group. The terminal elimination phases were nonetheless similar among the three dose groups, with terminal elimination half-lives ranging from 0.889 to 1.24 hours. Measured concentration increased approximately with increase in dose level. The increase in Cmax (from 96.6 to 454 µg/mL) was lower than proportional, whereas the increase in AUC(0-inf) (from 178 to 1893 h*µg/mL) was proportional to the increase in dose from 35 to 350 mg/kg bw (Hoberman, 2010).

In conclusion, oral absorption of the test substance is assumed to be rapid.

 

The observation of systemic toxicity following exposure by any route is an indication for substance absorption; however, this will not provide any quantitative information.

In an acute oral toxicity study conducted with the test substance at 20% solution in rats, signs of systemic toxicity (hunched posture) were observed for all animals at 2000 and 3000 mg/kg bw (converted dose: 400 and 600 mg/kg bw, respectively) on Day 1 and 2 (Teunissen, 2004). No mortality occurred during the study period.

A repeated-dose oral toxicity study in rats was conducted with the source substance sodium perfluorohexanoate (CAS 2923-26-4) (Chemours, 2009). In a dose range-finding study, animals were treated at concentrations of 500 and 1000 mg/kg bw/day for 14 days. Test substance-related effects on hematology (decreased red cell mass, hemoglobin and hematrocrit; increased reticulocytes and platelets) and clinical chemistry (increased AST and ALT) occurred in male rats dosed with 500 or 1000 mg/kg bw/day. In addition, an increase in liver weights was observed in animals receiving 500 or 1000 mg/kg/day test substance. Animals dosed with 500 and 1000 mg/kg bw/day exhibited mildly decreased cholesterol and triglycerides and decreases in total protein due to decreases in globulin.

In the main 90 -day study , animals were treated with test substance at concentrations of 20, 100 and 500 mg/kg bw/day. Under the conditions of this study, the local NOAEL for subchronic toxicity was 20 mg/kg bw/day, based on microscopic pathology of the nasal tissue (olfactory epithelium degeneration and atrophy) observed at 100 and 500 mg/kg bw/day. Considering the irritant/corrosive properties of the test substance, local effects observed are assumed to result from errors during the gavage procedure leading to inhalation of small quantities of the test substance. The systemic NOAEL was 100 mg/kg bw/day based on decreased red blood cell parameters, splenic extramedullary hematopoiesis and erythroid hyperplasia in bone marrow and follicular cell hypertrophy in the thyroid gland observed at 500 mg/kg bw/day.

Based on available data from the acute oral and repeated dose toxicity study, oral toxicity was observed with the test substance and thus absorption of the test substance via the gastrointestinal tract has occurred.

 

Dermal

The dermal uptake of liquids and substances in solution is generally expected to be higher than that of dry particles. Molecular weights below 100 g/mol favour dermal uptake, while for those above 500 g/mol the molecule may be too large. Therefore, for this molecular weight level of the test substance dermal uptake can be seen to be moderate. The Log Pow value and the water solubility of the test substance is optimal for dermal absorption, as for dermal uptake sufficient water solubility is needed for the partitioning from the stratum corneum into the epidermis.

The dermal permeability constant Kp of the substance was estimated to be 5.08E-04 cm/h using DermwinTM(v.2.02) (US EPA, 2012) and taking into account an estimated log Pow of 2.06 and the molecular weight of 331.08 g/mol. The dermal flux rate was calculated to be 0.029 mg/cm² per hour, indicating a high dermal absorption potential.

Data from an acute dermal toxicity study performed with a 20% solution of the test substance revealed no systemic effects of the test substance up to a dose of 2000 mg/kg bw (converted dose: 400 mg/kg bw) (Teunissen, 2004).

The skin corrosive properties of the test substance, shown in an in vitro test (Miyaura, 2018), may increase the potential for dermal absorption through the damaged skin. Moreover, the substance has been identified as a skin sensitiser in available in vitro test (Tsubokura, 2017; Maeda, 2017), showing that some uptake must have occurred although it may only have been a small fraction of the applied dose (ECHA, 2017).

In conclusion, taking a worst-case approach the dermal absorption potential of ammonium undecafluorohexanoate is expected to be high.

 

Inhalation

Although the substance is a solid, no data on particle size distribution is available since the substance is imported into the EU and marketed or used in a non-solid or granular form. Moderate log P values (between -1 and 4) are favourable for absorption directly across the respiratory tract epithelium by passive diffusion. However, the test substance has a low vapour pressure of 4.47E-03 Pa at 20 °C. Therefore, under normal use and handling conditions, inhalation exposure and thus availability for respiratory absorption of the pure test substance in the form of vapour can be considered negligible.

 

Distribution

Distribution of a compound within the body depends on the physicochemical properties of the substance; especially the molecular weight, the lipophilic character and the water solubility. In general, the smaller the molecule, the wider is the distribution. If the molecule is lipophilic, it is likely to distribute into cells and the intracellular concentration may be higher than extracellular concentration particularly in fatty tissues (ECHA, 2017).

Since the test substance is lipophilic (log Pow 2.1) the distribution into cells is likely and the intracellular concentration may be higher than extracellular concentration.

 

The tissue distribution of ammonium perfluorohexanoate (APFHx) was investigated after administration of a single and multiple (14 days) oral dose(s) of 50 mg/kg bw/day [14C]-labeled APFHx to male and female CD-1 mice and Sprague-Dawley (Crl:CD[SD]) rats (Shaw, 2009a and b).

In rats, following a single oral administration, the major route of elimination was via the urine with means of 73.0% and 90.2% of the dose in males and females, respectively (Shaw, 2009a). Faecal elimination accounted for 15.5% in males and 7.3% in females. Elimination via expired air was minimal accounting for only 0.04% of the dose in both sexes 0-48 h after administration. Excretion of total radioactivity was rapid with means of 95.6% and 99.2% recovered by 24 hours post dose. By 72 h post dose, approximately 0.2% of the dose remained in the gastrointestinal tract and carcass, indicating that excretion was almost complete. Mean recoveries of total radioactivity (including residual radioactivity in the gastrointestinal tract and carcass) were 97.4% and 100.8% of the dose administered in males and females respectively.

In mice, following a single oral administration, the major route of elimination was via the urine with means of 80.3% and 84.0% of the dose in males and females, respectively. Faecal elimination accounted for 10.5% in males and 7.0% in females. Elimination via expired air was minimal accounting for only 0.07-0.08% of the dose 0-48 h after administration. Excretion of total radioactivity was rapid with means of 90.9% and 94.1% recovered by 24 hours post dose. By 72 h post dose, approximately 0.6-0.9% of the dose remained in the gastrointestinal tract and carcass, indicating that excretion was almost complete. Mean recoveries of total radioactivity (including residual radioactivity in the gastrointestinal tract and carcass) were 95.4% and 97.3% of the dose administered in males and females respectively.

In rats, at 168 h after 14-days treatment period, the mean blood concentrations of radioactivity were 0.15 and 0.16 μg equiv/g, in males and females, respectively (Shaw, 2009b). The only tissue concentration above circulating blood level was noted in the liver, with values of 1.16 and 0.85 μg equiv/g in males and females, respectively. All other tissue values (white fat, kidney, spleen, gastrointestinal tract and carcass) were lower than the blood level or below the limit of quantification, with mean concentrations above the limit of quantification ranging from 0.10-0.13 μg equiv/g. In mice, at 168 h after 14-days treatment period, the mean blood concentrations of radioactivity were 0.17 μg equiv/g, in both males and females.

 

Overall, tissue concentrations were below those of blood concentrations, with the exception of the liver, in which the concentration was approximately 4–8 times higher than that of the circulating blood level. Elevated levels of measurable radioactivity in the liver were consistent with its role in metabolism and excretion. No tissue accumulation was observed (Shaw, 2009a and b).

 

In addition, the concentrations of APFHx in mouse serum samples of F1 generation were measured in support of an oral (gavage) combined developmental and perinatal/postnatal reproduction toxicity study of APFHx in mice (Hoberman, 2011). Dams were were orally treated by gavage from day 6 of presumed gestation (GD 6) through GD 18 at doses of 0 (Vehicle), 7, 35 and 175 mg/kg bw/day. For pharmacokinetic analysis liver samples were taken from dams when sacrificed on postpartum day 20, blood and liver samples were collected from pups when sacrificed on day 41 postpartum. Concentrations of the test substance in serum of F1 generation mice and in liver samples of F0 and F1 generation mice at day of sacrifice were below the lower limit of detection (LLOQ; theoretical concentrations of 1.00 μg/mL (serum) and 0.02 (liver)). The results indicate that there is no accumulation potential in the liver and rapid elimination of the test substance occurred.

 

In conclusion, it was shown that distribution of the test substance to tissues and organs in rats and mice occurred, and the highest tissue concentrations found in the liver. Rapid elimination of the substance occurred (see ‘Excretion’ below) and the bioaccumulation potential is expected to be low.

 

Metabolism

No metabolism studies are available with the test substance itself. Molecular structure information gives some indication of possible metabolic pathways, based on general biochemical information. The potential metabolites following enzymatic metabolism were predicted based on the molecular structure using the OECD QSAR toolbox (v4.1, OECD, 2017). This QSAR tool predicts which metabolites may result from enzymatic activity in the liver and in the skin, and by intestinal bacteria in the gastrointestinal tract. Hydrolysis to undecafluorohexanoic acid and ammonium hydroxide was predicted. No further hepatic and dermal metabolites were predicted, respectively, indicating that undecafluoxanoid acid will be metabolised by phase II enzymes to enable rapid excretion.

In the liver, ammonium is utilized to form amino acids and proteins. Further, it is metabolised either via the formation of urea (which is considered the main metabolic pathway) or via the formation of glutamine. While the metabolism to urea mainly occurs in the liver, formation of glutamine from ammonium is observed also in other tissues, notably in the brain (EFSA, 2012).

Four metabolites were predicted to result from all kinds of microbiological metabolism in the gastrointestinal tract. These metabolites were found to be a consequence of degradation of the molecule.

 

There was no evidence in in vitro genotoxicity tests for differences in genotoxic potencies due to metabolic activation. The studies performed on genotoxicity (Ames test and HPRT test and chromosome aberration test in mammalian cells in vitro) were all negative, with and without metabolic activation (Ogura, 2017; Ogura, 2017; Kovács, 2018).

 

 

Excretion

Excretion patterns and rates of ammonium perfluorohexanoate (APFHx) after administration of a single and multiple (14 days) oral dose(s) at 50 mg/kg bw/day to male and female CD-1 mice and Sprague-Dawley (Crl:CD[SD]) rats were examined. The test substance used was [14C]-labeled APFHx.

After a single oral administration, the excretion was rapid and extensive, with mean recoveries of over 90% of the dose 24 h after administration, irrespective of sex or species. The major route of elimination was via the urine (means of percentage recovery between 73.0 and 90.2% of the dose), followed by the feces (means of percentage recovery between 7.0 and 15.5% of the dose). The elimination rate via expired air was negligible (Shaw, 2009a).

For the multiple dose tests, multiple (13 daily doses) oral administration of APFHx was followed by a single oral administration of [14C]-APFHx. Excretion was rapid, with mean recoveries of over 90% of the administered dose (mean values >95% of the ultimately recovered material) at 24 h after dosing, irrespective of gender or species. The major route of elimination was via the urine (means of recovery between 77.8 and 83.4% of the dose), followed by the feces (means of recovery between 9.6 and 12.9% of the dose) (Shaw, 2009b).

In conclusion, investigation on rats and mice showed that APFHx administered as a single or multiple dose was rapidly eliminated; mainly via the urine.

 

 

 

References

ECHA (2017): Guidance on information requirements and chemical safety assessment – Chapter 7c: Endpoint specific guidance. European Chemicals Agency, Helsinki

 

EFSA (2012): Health risk of ammonium released from water filters. European Food Safety Authority, EFSA Journal 2012;10(10):2918

 

OECD (2017): QSAR Toolbox 4.1. Organisation for Economic Co-operation and Development, Paris, France

 

US EPA (2012). Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.1. United States Environmental Protection Agency, Washington, DC, USA.