Synthetic wollastonite

Endpoint summary

Description of key information

Skin sensitistion information on Synthetic Wollastonite is not available. A Skin sensitisation study (OECD 429) on the analogue substance Kieselguhr soda ash flux calcined concluded that it was not a skin sensitizer in accordance with the local lymph node assay.  

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

The study was performed between 01 June 2010 and 24 June 2010

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

The use of data derived for Soda-ash flux calcined kieselghur are justified for read-across to
synthetic wollastonite. Justification for read-across is warranted given the similarities in toxicity profile and physico-chemical properties for Soda-ash flux calcined kieselghur and synthetic wollastonite.
Considering the available data:
The source substance show no concerns for the environment.
The source substance has low acute toxicity and low toxicity in repeated dose studies, is non-irritant (skin and eye), non-sensitizing, non-mutagenic to bacteria, non-cytogenic and has low toxicity for reproductive and developmental toxicity.
Please see RAAF attached in Section 13. for further details.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories UK Ltd, Bicester, Oxon, UK
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: 15 to 23 g
- Housing: Individually housed in suspended solid-floor polypropylene cages furnished with softwood woodflakes
- Diet: 2014 Tekland Global Rodent diet ad libitum
- Water: ad libitum


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

Vehicle:

propylene glycol

Concentration:

Groups of four mice were treated with the test material at concentrations of 10%, 5% or 2.5% w/w in propylene glycol

No. of animals per dose:

4 mice per dose

Details on study design:

PRELIMINARY SCREENING TEST:
Using available information regarding the systemic toxicity/irritancy potential of the test material, a preliminary screening test was performed using one mouse. The mouse was treated by daily application of 25 µl of the test material at a concentration of 10% w/w 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. Any signs of toxicity or excessive local irritation noted during this period were recorded. The bodyweight was recorded on Day 1 (prior to dosing) and on Day 6

MAIN STUDY:
Groups of four mice were treated with the test material at concentrations of 10%, 5% or 2.5% w/w in propylene glycol. The preliminary screening test suggested that the test material would not produce systemic toxicity or excessive local irritation at the highest suitable concentration. The mice were treated by daily application of 25 µl of the appropriate concentration of the test material to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The test material 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 material 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

Positive control substance(s):

other: Phenylacetaldehyde (90%)

Positive control results:

A group of five animals was treated with 50 µl (25 µl per ear) of Phenylacetaldehyde (90%) as a solution in propylene glycol at a concentration of 2.5% v/v. A further control group of five animals was treated with propylene glycol alone

The Stimulation Index expressed as the mean radioactive incorporation for the treatment group divided by the mean radioactive incorporation of the vehicle control group was 18.43.

Phenylacetaldehyde (90%) was considered to be a sensitiser under the conditions of the test

Key result

Parameter:

SI

Value:

1.13

Test group / Remarks:

4 animals: 2.5 % in propylene glycol

Key result

Parameter:

SI

Value:

0.97

Test group / Remarks:

4 animals: 5 % in propylene glycol

Key result

Parameter:

SI

Value:

0.99

Test group / Remarks:

4 animals: 10 % in propylene glycol

Table 1: Clinical Observations, Bodyweight and Mortality Data – Preliminary Screening Test

Concentration (%w/w) in propylene glycol	Animal Number	Bodyweight (g)		Day
				1		2		3		4	5	6
		Day 1	Day 6	Pre-Dose	Post Dose	Pre-Dose	Post Dose	Pre-Dose	Post Dose
10	S-1	19	20	0	0	0	0	0	0	0	0	0

0=      No signs of systemic toxicity

Table 2: Disintegrations per Minute, Disintegrations per Minute/Node and Stimulation Index

Concentration (%w/w) in propylene glycol	dpm	dpm/Node^a	Stimulation Index^b	Result
Vehicle	6210.33	776.29	na	na
2.5	7020.81	877.60	1.13	Negative
5	6047.51	755.94	0.97	Negative
10	6135.29	766.91	0.99	Negative

dpm=  Disintegrations per minute

a=      Disintegrations per minute/node obtained by dividing the disintegrations per minute value by 8 (total number of lymph nodes)

b=      Stimulation Index of 3.0 or greater indicates a positive result

na =    Not applicable

Table 3: Individual Clinical Observations and Mortality Data

Concentration (% w/w) in propylene glycol	Animal Number	Day 1		Day 2		Day 3		Day 4	Day 5	Day 6
		Pre-Dose	Post Dose	Pre-Dose	Post Dose	Pre-Dose	Post Dose
Vehicle	1-1	0	0	0	0	0	0	0	0	0
	1-2	0	0	0	0	0	0	0	0	0
	1-3	0	0	0	0	0	0	0	0	0
	1-4	0	0	0	0	0	0	0	0	0
2.5	2-1	0	0	0	0	0	0	0	0	0
	2-2	0	0	0	0	0	0	0	0	0
	2-3	0	0	0	0	0	0	0	0	0
	2-4	0	0	0	0	0	0	0	0	0
5	3-1	0	0	0	0	0	0	0	0	0
	3-2	0	0	0	0	0	0	0	0	0
	3-3	0	0	0	0	0	0	0	0	0
	3-4	0	0	0	0	0	0	0	0	0
10	4-1	0	0	0	0	0	0	0	0	0
	4-2	0	0	0	0	0	0	0	0	0
	4-3	0	0	0	0	0	0	0	0	0
	4-4	0	0	0	0	0	0	0	0	0

0=      No signs of systemic toxicity

Table 4: Individual Bodyweights and Bodyweight Changes

Concentration (% w/w) in propylene glycol	Animal Number	Bodyweight (g)		Bodyweight Change (g)
		Day 1	Day 6
Vehicle	1-1	20	20	0
	1-2	20	21	1
	1-3	17	17	0
	1-4	18	17	-1
2.5	2-1	18	17	-1
	2-2	19	19	0
	2-3	19	19	0
	2-4	19	19	0
5	3-1	20	20	0
	3-2	20	19	-1
	3-3	18	18	0
	3-4	20	20	0
10	4-1	17	17	0
	4-2	21	20	-1
	4-3	18	18	0
	4-4	20	20	0

Interpretation of results:

not sensitising

Conclusions:

The analogue substance Kieselguhr soda ash flux calcined is not classified as a skin sensitiser in accordance with CLP Regulation (EC) no. 1272/2008

Reference 2

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

The study was performed between 01 June 2010 and 24 June 2010

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)

GLP compliance:

yes (incl. QA statement)

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories UK Ltd, Bicester, Oxon, UK
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: 15 to 23 g
- Housing: Individually housed in suspended solid-floor polypropylene cages furnished with softwood woodflakes
- Diet: 2014 Tekland Global Rodent diet ad libitum
- Water: ad libitum


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

Vehicle:

propylene glycol

Concentration:

Groups of four mice were treated with the test material at concentrations of 10%, 5% or 2.5% w/w in propylene glycol

No. of animals per dose:

4 mice per dose

Details on study design:

PRELIMINARY SCREENING TEST:
Using available information regarding the systemic toxicity/irritancy potential of the test material, a preliminary screening test was performed using one mouse. The mouse was treated by daily application of 25 µl of the test material at a concentration of 10% w/w 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. Any signs of toxicity or excessive local irritation noted during this period were recorded. The bodyweight was recorded on Day 1 (prior to dosing) and on Day 6

MAIN STUDY:
Groups of four mice were treated with the test material at concentrations of 10%, 5% or 2.5% w/w in propylene glycol. The preliminary screening test suggested that the test material would not produce systemic toxicity or excessive local irritation at the highest suitable concentration. The mice were treated by daily application of 25 µl of the appropriate concentration of the test material to the dorsal surface of each ear for three consecutive days (Days 1, 2, 3). The test material 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 material 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

Positive control substance(s):

other: Phenylacetaldehyde (90%)

Positive control results:

A group of five animals was treated with 50 µl (25 µl per ear) of Phenylacetaldehyde (90%) as a solution in propylene glycol at a concentration of 2.5% v/v. A further control group of five animals was treated with propylene glycol alone

The Stimulation Index expressed as the mean radioactive incorporation for the treatment group divided by the mean radioactive incorporation of the vehicle control group was 18.43.

Phenylacetaldehyde (90%) was considered to be a sensitiser under the conditions of the test

Key result

Parameter:

SI

Value:

1.13

Test group / Remarks:

4 animals: 2.5 % in propylene glycol

Key result

Parameter:

SI

Value:

0.97

Test group / Remarks:

4 animals: 5 % in propylene glycol

Key result

Parameter:

SI

Value:

0.99

Test group / Remarks:

4 animals: 10 % in propylene glycol

Table 1: Clinical Observations, Bodyweight and Mortality Data – Preliminary Screening Test

Concentration (%w/w) in propylene glycol	Animal Number	Bodyweight (g)		Day
				1		2		3		4	5	6
		Day 1	Day 6	Pre-Dose	Post Dose	Pre-Dose	Post Dose	Pre-Dose	Post Dose
10	S-1	19	20	0	0	0	0	0	0	0	0	0

0=      No signs of systemic toxicity

Table 2: Disintegrations per Minute, Disintegrations per Minute/Node and Stimulation Index

Concentration (%w/w) in propylene glycol	dpm	dpm/Node^a	Stimulation Index^b	Result
Vehicle	6210.33	776.29	na	na
2.5	7020.81	877.60	1.13	Negative
5	6047.51	755.94	0.97	Negative
10	6135.29	766.91	0.99	Negative

dpm=  Disintegrations per minute

a=      Disintegrations per minute/node obtained by dividing the disintegrations per minute value by 8 (total number of lymph nodes)

b=      Stimulation Index of 3.0 or greater indicates a positive result

na =    Not applicable

Table 3: Individual Clinical Observations and Mortality Data

Concentration (% w/w) in propylene glycol	Animal Number	Day 1		Day 2		Day 3		Day 4	Day 5	Day 6
		Pre-Dose	Post Dose	Pre-Dose	Post Dose	Pre-Dose	Post Dose
Vehicle	1-1	0	0	0	0	0	0	0	0	0
	1-2	0	0	0	0	0	0	0	0	0
	1-3	0	0	0	0	0	0	0	0	0
	1-4	0	0	0	0	0	0	0	0	0
2.5	2-1	0	0	0	0	0	0	0	0	0
	2-2	0	0	0	0	0	0	0	0	0
	2-3	0	0	0	0	0	0	0	0	0
	2-4	0	0	0	0	0	0	0	0	0
5	3-1	0	0	0	0	0	0	0	0	0
	3-2	0	0	0	0	0	0	0	0	0
	3-3	0	0	0	0	0	0	0	0	0
	3-4	0	0	0	0	0	0	0	0	0
10	4-1	0	0	0	0	0	0	0	0	0
	4-2	0	0	0	0	0	0	0	0	0
	4-3	0	0	0	0	0	0	0	0	0
	4-4	0	0	0	0	0	0	0	0	0

0=      No signs of systemic toxicity

Table 4: Individual Bodyweights and Bodyweight Changes

Concentration (% w/w) in propylene glycol	Animal Number	Bodyweight (g)		Bodyweight Change (g)
		Day 1	Day 6
Vehicle	1-1	20	20	0
	1-2	20	21	1
	1-3	17	17	0
	1-4	18	17	-1
2.5	2-1	18	17	-1
	2-2	19	19	0
	2-3	19	19	0
	2-4	19	19	0
5	3-1	20	20	0
	3-2	20	19	-1
	3-3	18	18	0
	3-4	20	20	0
10	4-1	17	17	0
	4-2	21	20	-1
	4-3	18	18	0
	4-4	20	20	0

Interpretation of results:

not sensitising

Conclusions:

Kieselguhr soda ash flux calcined is not classified as a skin sensitiser in accordance with CLP Regulation (EC) no. 1272/2008

Reference 3

Endpoint:

skin sensitisation: in vitro

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

an in vitro skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study are available

Reason / purpose for cross-reference:

data waiving: supporting information

Reason / purpose for cross-reference:

data waiving: supporting information

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Read-Across Justification for skin sensitization

Synthetic wollastonite is a UVCB substance, the main constituents of which are amorphous in nature. It also contains crystalline silica. The percentage of crystalline silica may range up to 1.5% (<=0.21% respirable). The skin sensitivity information has been read-across from the analogue substance Kieselguhr, soda ash flux-calcined. The analogue has been chosen for its similarity in structure and properties to Synthetic wollastonite. The main difference in structure between Synthetic wollastonite and Kieselguhr, soda ash flux-calcined is the presence of a calcium ion in Synthetic wollastonite. It is clear from a number of studies carried out on amorphous and crystalline silica and the analogue substance Silicic acid, calcium salt that results were consistent between the two substances and that there was no effect from the presence of the calcium ion. Moreover, it is well documented that these substances have a low potential for hazard to health and the environment. 

The toxicological properties of both forms are well described and may be used to predict the sensitizing effects of exposure to Synthetic wollastonite, and to support the available data for this substance.

In the key study (Bradshaw 2010) performed on the analogue substance Kieselguhr soda ash flux calcined, skin sensitisation was assessed using the local lymph node assay. Following a preliminary screening test in which no clinical signs of toxicity were noted at a concentration of 10% w/w, this concentration was selected as the highest dose investigated in the main test of the Local Lymph Node Assay. Three groups, each of four animals, were treated with 50 µl (25 µl per ear) of the test material as a suspension in propylene glycol at concentrations of 10%,5% or2.5% w/w. A further group of four animals were treated with propylene glycol alone. The test material was considered to be a non-sensitiser under the conditions of the test.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the result of the study on the analogue substance Kieselguhr soda ash flux calcined, Synthethic Wollastonite was not considered to be a skin sensitiser in the LLNA and therefore does not warrant classification in accordance with CLP .