The way to bio-soluble mineral wool: Regulatory aspects

In recent decades, many new types of mineral wool have been developed by the mineral fibre industry in the European Union. During this period, the authorities' assessment of mineral wool has also changed. Below is a brief overview of the state of play.

What does the "carcinogenicity index" KI mean?

The KI was introduced in Germany in 1994 as an aid to differentiate fibre dusts from mineral wool for an occupational health assessment. This value should give an indication of the solubility of glassy silicate fibres in lung tissue. The AI is calculated from the difference between the sum of the mass contents (in %) of the oxides of sodium, potassium, boron, calcium, magnesium, barium and twice the mass content (in %) of aluminium oxide.

KI = Σ Na, K, B, Ca, Mg, Ba oxides - 2 x Al oxide

What has changed since 1994?

In 1997 the EU Directive 97/69 EC on the classification of artificial mineral fibres including mineral wool was adopted. It lays down binding criteria for the classification or non-classification of man-made mineral fibres as carcinogenic throughout Europe (legal classification). The criteria are listed in Appendix 1.

The KI is not a criterion under EU law.

Parallel to and in addition to the legal classification, three equal criteria have been defined in Germany which evaluate fibre dusts with regard to a carcinogenic effect for the interests of occupational health and safety. Accordingly, mineral wool (during production, processing and placing on the market) must fulfil one of the following three criteria. They are laid down in the Ordinance on Hazardous Substances and the Ordinance on the Prohibition of Chemicals:

  1. a suitable intraperitoneal test has not shown any signs of excessive carcinogenicity,
  2. the half-life after intratracheal instillation of 2 mg of a fibre suspension for fibres with a length greater than 5 micrometres, a diameter smaller than 3 micrometres and a length to diameter ratio greater than 3 to 1 (WHO fibres) is not more than 40 days,
  3. the carcinogenicity index KI, which results from the difference between the sum of the mass contents (in %) of the oxides of sodium, potassium, boron, calcium, magnesium, barium and twice the mass content (in %) of aluminium oxide, is at least 40 for artificial mineral fibres.

What is the current status of the classification and evaluation of mineral wool?

Since the carcinogenicity index KI has never been a criterion for exemption with regard to the carcinogenicity of mineral wool under EU law (legal classification), it has been removed as an exemption criterion in the current versions of the Hazardous Substances Ordinance of 2 December 2024 in Annex II under number 5 and in the Chemicals Prohibition Ordinance of January 2017 in Annex I under entry 4.

Appendix 2 contains the information specified in Appendix II No. 5 of the Hazardous Substances Ordinance.

According to the documents of the Gütegemeinschaft Mineralwolle, all mineral wool used in Germany for heat or sound insulation has been tested on the basis of a biopersistence test.

The assessment of installed mineral wool based on the KI value therefore often led to false negative evaluations.

Appendix 1 

EU criteria, Note Q:

The classification as a carcinogen need not apply if it can be shown that the substance fulfils one of the following conditions:

  • a short term biopersistence test by inhalation has shown that fibres longer than 20 µm have a weighted half-life less than 10 days; or
  • a short-term biopersistence test by intratracheal has shown that the fibres longer than 20 µm have a weighted half-life less than 40 days; or
  • an appropriate intra-peritoneal test has shown no evidence of excess carcinogenicity; or
  • absence of a relevant pathogenicity or neoplastic changes in a suitable long term inhalation test.

Appendix 2

Appendix II No. 5 of the Hazardous Substances Ordinance

This is a translation of the original text. Only the original German text is legally valid.

(1) For the purposes of thermal and sound insulation, fire protection and technical insulation in building construction, the following may not be manufactured or used:

1. synthetic mineral fibres consisting of non-oriented vitreous (silicate) fibres with a mass content of more than 18 per cent of oxides of sodium, potassium, calcium, magnesium and barium,
and
2. mixtures and articles containing substances listed in point 1 in a total concentration of more than 0.1% by weight.

(2) Paragraph 1 does not apply

1.  to man-made mineral fibres if
a) a suitable intraperitoneal test has shown no evidence of excessive carcinogenicity,
or
b) the half-life after intratracheal instillation of 2 milligrams of a fibre suspension for fibres with a length of more than 5 µm, a diameter of less than 3 µm and a length-to-diameter ratio of greater than 3 to 1 (WHO fibres) is no more than 40 days, and

2. vitreous fibres intended for high-temperature applications, which
a) require a classification temperature of 1000 degrees Celsius to 1200 degrees Celsius and have a half-life of no more than 65 days after intratracheal instillation,
or
b) require a classification temperature of over 1200 degrees Celsius and have a half-life of no more than 100 days after intratracheal instillation.

(3) Spraying procedures that use carcinogenic mineral fibres are prohibited.

(4) Paragraph 1 to 3 apply to private households.