Registration Dossier

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

Constituent 1
Reference substance name:
Potassium aluminium silicate amorphous glass fibres
EC Number:
931-219-8
Molecular formula:
SinO(3n-1)2(n-1) polymeric anions ionically bonded to Al3+ and K2+ cations
IUPAC Name:
Potassium aluminium silicate amorphous glass fibres
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/cm2hr)

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.