The article by Ceppi and colleagues, Genotoxic Effects of Occupational Exposure to, Glass Fibres - A Human Biomonitoring Study, published in Mutation Research -Genetic Toxicology and Environmental Mutagenesis in 2023 was reviewed with great interest. The authors undertook a novel approach to conducting a biomonitoring study of genotoxicity markers among a population of glass fibre manufacturing workers in Slovakia. On the surface, the Ceppi et al. (2023) study provides an interesting application of genotoxicity markers among a human population of workers to explore potential markers of effect (DNA strand breaks) and potential risk of susceptibility (e.g., genetic damage, disease, death). However, limited data for exposure reconstruction, uncertain influences from smoking history, and lack of consideration of decades of human epidemiology research showing no increased risk of malignant or non-malignant respiratory disease and mortality among glass fibre manufacturing workers, reveals that the conclusions of the authors are overreaching and inconsistent with the existing science. The limitations of this study preclude the ability to draw causal inferences or conclusions about DNA strand breaks as a marker of exposure, effect, or susceptibility within this population of Slovakian glass fibre workers. Further longitudinal research is required (e.g., more robust temporal assessment of occupational exposures - fibres and other compounds - and smoking history) to support the study conclusions.

Man-made vitreous fibres (MMVF) are produced on a large scale for thermal insulation purposes. After extensive studies of fibre effects in the 1980ies and 1990ies, the composition of MMVF was modified to reduce the fibrotic and cancerogenic potential via reduced biopersistence. However, occupational risks by handling, applying, disposing modern MMVF may be underestimated as the conventional regulatory classification -combining composition, in-vivo clearance and effects- seems to be based entirely on MMVF after removal of the binder.
Here we report the oxide composition of 23 modern MMVF from Germany, Finland, UK, Denmark, Russia, China (five different producers) and one pre-1995 MMVF. We find that most of the investigated modern MMVF can be classified as \"High-alumina, low-silica wool\", but several were on or beyond the borderline to \"pre-1995 Rock (Stone) wool\". We then used well-established flow-through dissolution testing at pH 4.5 and pH 7.4, with and without binder, at various flow rates, to screen the biosolubility of 14 MMVF over 32 days. At the flow rate and acidic pH of reports that found 47 ng/cm2/h dissolution rate for reference biopersistent MMVF21 (without binder), we find rates from 17 to 90 ng/cm2/h for modern MMVF as customary in trade (with binder). Removing the binder accelerates the dissolution significantly, but not to the level of reference biosoluble MMVF34. We finally simulated handling or disposing of MMVF and measured size fractions in the aerosol. The respirable fraction of modern MMVF is low, but not less than pre-1995 MMVF.
The average composition of modern stone wool MMVF is different from historic biopersistent MMVF, but to a lesser extent than expected. The dissolution rates measured by abiotic methods indicate that the binder has a significant influence on dissolution via gel formation. Considering the content of respirable fibres, these findings imply that the risk assessment of modern stone wool may need to be revisited based on in-vivo studies of MMFV as marketed (with binder).

BACKGROUND: Man-made vitreous fibres (MMVFs) are used in products for insulation and as reinforcement in materials. Contamination of the skin may arise through direct or indirect contact, and from the deposition of airborne fibres. The scientific basis regarding the effects on skin of MMVFs dates from 1970-1980.
OBJECTIVE: To investigate whether currently used insulation MMVF products still cause skin discomfort.
METHODS: Focus group interviews and structured interviews were performed among workers engaged in insulation tasks and among do-it-yourself consumers with a recent experience of MMVF products.
RESULTS: A majority of interviewees experienced skin discomfort when handling MMVF products. Complaints caused by traditional (yellow) glass fibre products were more severe than those caused by products of rock or slag wool fibres. The wrists, forearms, neck and face were the locations where the skin was most affected. The situations causing problems varied between occupational tasks, but working with the hands over the head or in narrow spaces were described as the worst situations. Building construction apprentices performed insulation tasks more often than senior workers.
CONCLUSIONS: MMVF insulation products do still cause skin discomfort. Updated knowledge about people\'s experiences of work with such products should influence legislation.

Refractory ceramic fibres (RCF) and alkaline earth silicate (AES) wools are types of man-made vitreous fibre (MMVF) that are used in demanding high-temperature industrial applications, generally above 900 °C and up to 1400 °C. When exposed to prolonged high temperatures, MMVF can devitrify with the formation of cristobalite and other crystalline silica species, which is of potential concern because crystalline silica (CS) is classified as carcinogenic. This article reviews the chemico-physical processes and morphological consequences of fibre devitrification, the forms and micro-location of CS produced, and the toxicity of devitrified fibres and the CS species formed in this way. It also examines scenarios for worker exposure to the products of fibre devitrification in industries using RCF and/or AES wools. We identify gaps in knowledge and make recommendations for future research.