Laboratory Analytics for AMF
Artificial mineral fibers (AMF) are considered the small relatives of asbestos
In certain dimensions, these fibers are also respirable and can cause cancer depending on their retention time in the body. For this reason, the production of hazardous fibers has been banned in Germany since June 2000. During demolition, renovation, and maintenance work, workers inevitably encounter AMF, and property owners also face this contaminant when acquiring older properties. The German Hazardous Substances Ordinance provides the legal framework for handling these fibers in paragraphs 10 and 11, while the Technical Rules for Hazardous Substances (TRGS) 521 list the state of technology, occupational medicine, and hygiene practices. In the private sector, legal threshold values are still lacking.
Classification of “Old” and “New” Mineral Wool
TRGS 521 distinguishes between mineral wool based on the time of the usage ban. Products sold after the year 2000 are considered harmless to health. Materials installed before 1996 are assumed to be “old” mineral wool. The fiber dust in these materials contains artificial inorganic mineral fibers longer than five micrometers (µm) and with a diameter smaller than three micrometers. Fiber dust with these dimensions is classified as respirable. The second important criterion is the retention time (biopersistence) in the body. For “new” mineral wool, the biopersistence is estimated to be less than 40 days. For products from before 1996, the fibers can remain in the respiratory system for 40 to 200 days, potentially causing cancer. The combination of fiber structure and solubility forms the basis for the Carcinogenicity Index (CI). TRGS 905 defines three risk levels: substances with a CI value equal to or less than 30 are classified as carcinogenic to humans and are in Group K1B. TRGS 905 places substances with a CI index between 30 and 40 in Group K2: they raise concerns about potential carcinogenic effects. Products with a CI index greater than 40 are considered non-carcinogenic.
Cancer Research Findings Related to Fiber Dust
The Committee for Hazardous Substances of the German Federal Institute for Occupational Safety and Health (BAuA) commissioned a study in 2010 on exposure-risk relationships for aluminum silicate fibers. The statements in this report describe the current findings of cancer research concerning fiber dust. The safest findings relate to asbestos fibers. The risk of fiber splitting lengthwise and the practically indefinite retention time in the body have led to the undeniable proof of asbestos’ cancer risk. Laboratory research is supported by findings in occupational medicine.
In 2017, the German Social Accident Insurance (DGUV) reported about 1,000 annual deaths among asbestos workers. The latency period in most cases exceeds thirty years. For artificial mineral fibers, epidemiological assessment is significantly more challenging. Due to the high prevalence of lung cancer among cancer types, identifying additional occupational cases is difficult. However, a clear link exists when occupational exposure results in mesothelioma. Mesothelioma is a rare form of cancer that mainly affects the lung and abdominal lining. This type of disease is very rare in the general population, making it possible to infer an occupational cause. Clear indications of the carcinogenic effects of AMF are evident in animal experiments.
In laboratory tests, rats, hamsters, and mice were directly injected with fiber material into the abdominal cavity, a method known as intraperitoneal administration. Numerous experiments tested dust with varying structures (length and cross-section) and different retention times in the body. Researchers also demonstrated the influence of solubility on specific fiber structures. The asbestos fiber crocidolite is consistently used as a reference value. Crocidolite most closely resembles artificial mineral fibers in structure, although its solubility is approximately one hundred years.
Suitable Laboratory Analytics for AMF
A material analysis should be conducted if construction documents do not clearly indicate when the insulation wool was installed. For “old” wool, TRGS 521 generally assumes a cancer risk. In the first stage of laboratory analysis, the fiber quality is determined, i.e., the length and cross-section of the fibers (see photo, top left). If the fibers contain a mass fraction of over 18% of the oxides of sodium, potassium, calcium, magnesium, and barium combined, the material is classified as a “biopersistent fiber” according to the Hazardous Substances Ordinance, Appendix II No. 5. The combination of both values determines the Carcinogenicity Index.
From the perspective of the sample collector, air sampling is more time-consuming. Using a gold-coated polycarbonate filter, 3,500 liters of air are drawn at a flow rate of 7.6 liters per minute. This process takes approximately eight hours. In the laboratory, the fibers are “counted” and converted to one cubic meter of air. A concentration of 500 to 1,000 fibers per cubic meter (F/m³) in the air is considered a significant increase. A fiber concentration exceeding 1,000 F/m³ indicates a highly elevated burden.