Potassium aluminium silicate amorphous glass fibres

Additional toxicological data

Administrative data

Endpoint:

additional toxicological information

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: in house methodology developed in conjunction with other fibre manufacturers, in house testing facility is not a GLP accredited laboratory

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Type of study / information:

simulated bio-solubility testing to assess how easily fibres will be broken down in the fluids of the lung and macrophages

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

a flow test where fibres are continuously exposed to a simulated body fluid at 37°C for 3 weeks. Soluble species in the fibres dissolve out into the fluid and these can be measured in the solution. Knowing the surface area, mass and flow rate used, the dissolution rate of the fibre can be calculated.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

silicon(4+) dialuminium(3+) dipotassium hexaoxidandiide

EC Number:

931-219-8

Molecular formula:

SinO(3n-1)2(n-1) polymeric anions ionically bonded to Al3+ and K2+ cations

IUPAC Name:

silicon(4+) dialuminium(3+) dipotassium hexaoxidandiide

Test material form:

solid: fibres

Details on test material:

- Name of test material (as cited in study report): Superwool XT
- Substance type: Inorganic

Results and discussion

Any other information on results incl. tables

The following fibre chemistries have been tested many times in Morgan. These reflect both past, existing and future commercial fibres. The first 4 compositions belong to the AES family (REACH registration 01-2119457644-32-0000) and Superwool XT is the new Potassium Alumino Silicate fibre

The average dissolution rates measured are shown in the table below;

 

Fibre	Dissolution rate (ng/cm^2hr)	Standard deviation	Number of tests
Superwool 607 (Plus)	290	115	35
Superwool 607Max	285	90	23
Superwool 612	100	40	32
Superwool 607 HT	110	30	30
Superwool XT	485	110	6
Rockwool HT	270	60	7

 

Superwool 607, 607 Max, 612 and 607 HT were all tested using pH 7.4 solution, as the AES chemistry is most sensitive to this pH. All of these fibres have been submitted to testing under Note Q conditions and have passed according to the EU protocol requirement⁽³⁾.

 

Superwool XT is more sensitive to the pH 4.7 solution and so it was tested in this pH. Rockwool HT is another vitreous fibre which is sensitive to pH 4.7 and which has passed the Note Q bio-persistence testing. The solubility for this fibre has therefore also been included as a control to illustrate that solubility at either pH is a valid assessment of bio-persistence.

 

Generally fibres with dissolution rates >100ng/cm²hr are expected to pass the IT clearance test⁽³⁾. This appears to be valid regardless of the solution used. It is also seen that fibres with higher dissolution rates also have lower bio-persistence. However this is not always the case as weaker fibres will need lower dissolution rates and stronger fibres will need higher dissolution rates.

 

Fibres that have not passed the Note Q testing generally have dissolution rates that are <25ng/cm²hr.

 

It is also clear that the chemical species in the fibres can change dramatically but do not change the underlying premise that high dissolution rate generally results in an IT half-life that is <40 days as required by the Note Q protocol.

Applicant's summary and conclusion

Conclusions:

These solubility tests demonstrate that high dissolution rates (>100ng/cm2hr) result in fibres that pass the Note Q IT clearance test. The fibre chemistry basis can be highly different from fibre to fibre provided the species dissolve at either pH 7.4 or 4.5.

Reference 1 reports that vitreous fibres are characterised in the lung by their bio-persistence and not by any direct chemical toxicity. Bio-persistence is strongly related to Bio-solubility as described in this report. The AES family of fibres, Potassium Alumino Silicates and Rockwool HT all display similar levels of bio-solubility when measured in the same laboratory test.