Boron orthophosphate

Endpoint summary

Description of key information

LLNA (according to OECD 429): not sensitising

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16 - 31 October 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

The department of health of the government of the United Kingdom

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

other: CBA/Ca (CBA/CaOlaHsd)

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories UK Ltd., Oxon, UK
- Age at study initiation: Animals were eight to twelve weeks old.
- Weight at study initiation: Animals were in the weight range of 15 to 23g.
- Housing: The animals were individually housed in suspended solid-floor polypropylene cages furnished with softwood woodflakes.
- Diet: ad libitum, 2014C Teklad Global Rodent diet supplied by Harlan Laboratories UK Ltd., Oxon, UK
- Water: ad libitum, drinking water
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-25
- Humidity (%): 30-70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: Day 1 to: Day 6

Vehicle:

propylene glycol

Concentration:

For the purpose of the study, the test item was freshly prepared as a suspension in propylene glycol. This vehicle was chosen as it produced the highest concentration that was suitable for dosing.
Each group was exposed to concentrations of 50%, 25% or 10% w/w (suspended in propylene glycol)

No. of animals per dose:

4

Details on study design:

Preliminary Screening Test
Using available information regarding the systemic toxicity/irritancy potential of the test item, a preliminary screening test was performed using one mouse. The mouse was treated by daily application of 25 μL of the test item at a concentration of 50% w/w suspended in propylene glycol, to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The mouse was observed twice daily on Days 1, 2 and 3 and once daily on Days 4, 5 and 6. Local skin irritation was scored daily. Any clinical signs of toxicity, if present, were also recorded. The bodyweight was recorded on Day 1 (prior to dosing) and Day 6 (prior to termination).

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
-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

- Name of test method:
Local Lymph Node Assay in the Mouse. The assay has undergone extensive inter-laboratory validation and has been shown to reliably detect test materials that are moderate to strong sensitisers.

- Criteria used to consider a positive response:
The proliferation response of lymph node cells was expressed as the number of radioactive disintegrations per minute per lymph node(dpm/node) and as the ratio of 3HTdR incorporation in lymph node cells of test nodes relative to that recorded for the control nodes (stimulation index).

The test material will be regarded as a sensitiser if at least one concentration of the test material results in a threefold or greater increase in 3HTdR incorporation compared to control values. Any test material failing to produce a threefold or greater increase in 3HTdR incorporation will be classified as a "non-sensitier".

TREATMENT PREPARATION AND ADMINISTRATION:
For the purpose of the study, the test material was freshly prepared in propylene glycol.

Determination, by analysis, of the concentration, homogeneity and stability of the test material preparations was not appropriate because it was not specified in the study plan and is not a requirement of OECD 429.

Test Material Administration
Groups of four mice were treated with the test item at concentrations of 50%, 25% or 10% w/w suspended in propylene glycol. The preliminary screening test suggested that the test item would not produce systemic toxicity or excessive local skin irritation at the highest suitable concentration. The mice were treated by daily application of 25 μL of the appropriate concentration of the test item to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The test item formulation was administered using an automatic micropipette and spread over the dorsal surface of the ear using the tip of the pipette. A further group of four mice received the vehicle alone in the same manner.

3H-Methyl Thymidine Administration:
Five days following the first topical application of the test item or vehicle (Day 6) all mice were injected via the tail vein with 250 μL of phosphate buffered saline (PBS) containing 3H-methyl thymidine (3HTdR: 80 μCi/mL, specific activity 2.0 Ci/mmol, ARC UK Ltd) giving a total of 20 μCi to each mouse.

OBSERVATIONS
Clinical Observations: All animals were observed twice daily on Days 1, 2 and 3 and on a daily basis on Days 4, 5 and 6. Any signs of toxicity or signs of ill health during the test were recorded.
Bodyweights: The bodyweight of each mouse was recorded on Day 1 (prior to dosing) and Day 6 (prior to termination).

TERMINAL PROCEDURES
Termination: Five hours following the administration of 3HTdR all mice were sacrificed by carbon dioxide asphyxiation. The draining auricular lymph nodes from the four mice were excised and pooled for each experimental group. For each group 1 mL of PBS was added to the pooled lymph nodes.

Preparation of Single Cell Suspension: A single cell suspension of pooled lymph node cells was prepared by gentle mechanical disaggregation through a 200-mesh stainless steel gauze. The lymph node cells were rinsed through the gauze with 4 mL of PBS into a petri dish labelled with the project number and dose concentration. The lymph node cell suspension was transferred to a centrifuge tube. The petri dish was washed with an additional 5 mL of PBS to remove all remaining lymph node cells and these were added to the centrifuge tube. The pooled lymph node cells were pelleted at 1400 rpm (approximately 190 g) for ten minutes. The pellet was resuspended in 10 mL of PBS and re-pelleted. To precipitate out the radioactive material, the pellet was resuspended in 3 mL of 5% trichloroacetic acid (TCA).

Determination of 3HTdR Incorporation: After approximately eighteen hours incubation at approximately 4°C, the precipitates were recover ed by centrifugation at 2100 rpm (approximately 450 g) for ten minutes, resuspended in 1 mL of TCA and transferred to 10 mL of scintillation fluid (Optiphase 'Trisafe'). 3HTdR incorporation was measured by b-scintillation counting. The "Poly QTM" vials containing the samples and scintillation fluid were placed in the sample changer of the scintillator and left for approximately twenty minutes. The purpose of this period of time in darkness was to reduce the risk of luminescence, which has been shown to affect the reliability of the results. After approximately twenty minutes, the vials were shaken vigorously. The number of radioactive disintegrations per minute was then measured using the Beckman LS6500 scintillation system (Beckman Instruments Inc, Fullerton, CA, USA).

Positive control substance(s):

other: Phenylacetaldehyde (90%)

Positive control results:

One group of five animals was treated with the positive control phenylacetaldehyde (2.5% v/v; dissolved in propylene glycol).
The stimulation index for the positive control expressed as the mean radioactive incorporation for the treatment group divided by the mean radioactive incorporation of the vehicle control group is as follows: 3.49
Phenylacetaldehyde is considered to be a skin sensitiser under the conditions of the test.

Parameter:

SI

Remarks:

see remarks

Value:

2.1

Test group / Remarks:

the test concentrations at 50% w/w (suspended in propylene glycol)

Parameter:

other: disintegrations per minute (DPM)

Test group / Remarks:

n.a.

Remarks on result:

other: The radioactive disintegrations per minute per lymph node and the stimulation index are given in Table 4.

Parameter:

SI

Value:

1.43

Test group / Remarks:

the test concentrations at 10% w/w (suspended in propylene glycol)

Parameter:

SI

Value:

1.39

Test group / Remarks:

the test concentrations at 25% w/w (suspended in propylene glycol)

Preliminary Screening Test

Clinical observations, bodyweight and mortality data are given in Table 1 and local skin irritation is given in Table 2. The ear thickness measurements and mean ear thickness changes are given in Table 3.

No signs of systemic toxicity, visual local skin irritation or irritation indicated by an equal to or greater than 25% increase in mean ear thickness were noted. Based on this information the dose levels selected for the main test were 50%, 25% and 10% w/w in propylene glycol.

Main Test

Estimation of the Proliferative Response of Lymph Node Cells

The radioactive disintegrations per minute per lymph node and the stimulation index are given in Table 4.

The Stimulation Index expressed as the mean radioactive incorporation for each treatment group divided by the mean radioactive incorporation of the vehicle control group are as follows:

Concentration (%w/w) in propylene glycol	Stimulation Index	Result
10	1.43	Negative
25	1.39	Negative
50	2.10	Negative

Clinical Observations and Mortality Data

Individual clinical observations and mortality data for test and control animals are given in Table 5.

There were no deaths. No signs of systemic toxicity were noted in the test or control animals during the test.

Bodyweight

Individual bodyweights and bodyweight changes for test and control animals are given in Table 6.

Bodyweight changes of the test animals between Day 1 and Day 6 were comparable to those observed in the corresponding control group animals over the same period.

Interpretation of results:

GHS criteria not met

Conclusions:

CLP: not classified

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The skin sensitisation potential of boron orthophosphate was assessed in a local lymph node assay (LLNA) according to OECD 429 and under GLP (Bradshaw, 2013). Following a preliminary screening test in which no clinical signs of toxicity were noted at a test concentration of 50% w/w (suspended in propylene glycol), this concentration was selected as the highest concentration in the main test. Three groups, each of four mice, were treated with the test substance at concentrations of 50%, 25% or 10% w/w to the dorsal surface of each ear for three consecutive days. A further group was treated with the vehicle control (propylene glycol). The thickness of each ear was measured pre-dose on Day 1, post- dose on Day 3 and on Day 6. Five days following the first application all mice were injected via the tail vein with 3H-methyl thymidine (3HTdR). Five hours later all mice were sacrificed and the draining lymph nodes were excised and pooled for each experimental group. 3HTdR incorporation was measured by beta-scintillation counting.

There were no deaths and no signs of systemic toxicity were noted during the test.

The stimulation indices (SI) expressed as the mean radioactive incorporation for each treatment group divided by the mean radioactive incorporation of the vehicle control group are as follows: 2.1, 1.39 and 1.43 at test concentrations of 50%, 25% and 10%, respectively. The decision process regards a result as positive when SI ≥ 3. Under the conditions of the test, the test substance was considered to be a non skin sensitiser.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

Study not required according to Annex VII-X of Regulation (EC) No 1907/2006.

Justification for classification or non-classification

The available data on skin sensitisation with boron orthophosphate (CAS 13308-51-5) do not meet the criteria for classification according to Regulation (EC) No 1272/2008, and are therefore conclusive but not sufficient for classification.