Mechanisms and shapes of causal exposure-response functions for asbestos in mesotheliomas and lung cancers

Naturally occurring asbestos in Southern Italy: Geological and mineralogical investigation of fibrous antigorite from Calabrian serpentinites in view of its hazard assessment

In the last few decades, non-occupational asbestos-related diseases have been documented in populations living near naturally occurring asbestos (NOA) sites, including regions in Greece, Cyprus, China, New Caledonia, Turkey, and Italy. This highlights the critical need to assess geological and environmental hazards associated with NOA. Fibrous antigorite, among the >400 naturally occurring fibrous minerals, has emerged as a potential health and environmental hazard. This work examines the morphometrical, mineralogical and surface properties of a fibrous antigorite vein from a serpentinite body at San Mango D'Aquino (Calabria, Italy), relevant to assessing its potential toxicity. The geological site, described through field and petrographic analyses, was selected as representative of serpentinites outcropping over a large area in central Calabria. Results on the morphometric variation induced by a standardized mechanical stress, mineral solubility, and surface chemical reactivity indicated that: i) the fibrous morphology, expressed as % of WHO (World Health Organization) fibres, was largely preserved and consistent with asbestos standards; ii) antigorite fibres have a durability higher than chrysotile and close to a previously characterized fibrous antigorite from Val Varenna, Italy; iii) fibres showed a remarkable redox reactivity, even higher than chrysotile, suggesting that they may promote particle-derived radical imbalance in vitro and in vivo. Our findings revealed that the antigorite fibres from San Mango possess several critical properties commonly associated with asbestos toxicity. On this basis, we identify the NOA site of San Mango as a potential emission source of hazardous antigorite fibres, with significant environmental and public health implications for the surrounding communities.

A risk assessment of mechanics who changed chrysotile asbestos containing brakes and other vehicle components in the 1950s-early 2000s era: an update on the 2004 evaluation

For the past 50 years, there has been an ongoing interest in understanding the potential health hazards, if any, to vehicle mechanics who worked with asbestos-containing brakes in the 1950s-early 2000s era. Two reviews have been published on this topic, one by Langer (2003) ("Reduction of the biological potential of chrysotile asbestos arising from conditions of service on brake pads") and another by Paustenbach, et al. (2004) ("Environmental and occupational health hazards associated with the presence of asbestos in brake linings and pads (1900 to present): a 'state-of-the-art' review"). This analysis is an update on those papers since a considerable amount of research has been published over the past 20 years on this topic. The following important aspects are addressed in this review: new information on the toxicology of chrysotile, toxicology studies of brake dust associated with grinding, additional epidemiology studies and meta-analyses published on auto mechanics of the era, previously unfound data on how brakes (during the era when chrysotile was used) were manufactured, and new work describing the transformation of chrysotile to various degradation products during vehicle braking. This update also addresses questions about the health hazards associated with asbestos in vehicle clutches, transmissions, and gaskets. The exposure data indicate that the airborne concentrations of chrysotile fibers associated with vehicle mechanic work when asbestos was in auto brakes were, on average, less than 0.04 f/cm3 (8-h TWA) and the average lifetime cumulative dose was in the vicinity of 0.5-3 f/cm3-year for mechanics of that era. Although many of these fibers may have no toxicity due to thermal degradation and the conversion to degradation products, 31 epidemiology studies have evaluated the risks of mesothelioma for vehicle mechanics of this era and all but one indicate that there was no increased incidence of this disease in these workers. The weight of evidence continues to indicate that the asbestos-related health risks to vehicle mechanics from asbestos-containing components were de minimis. The risks associated with take-home and bystander exposure of a mechanic were also addressed and they were found to pose a de minimis or zero health risk to those potentially exposed. Based on our evaluation, there is no indication that asbestos from asbestiform tremolite was present at detectable concentrations in bulk samples of brakes or in the air during brake work. The recent U.S. Environmental Protection Agency (EPA) risk assessment of 2024 on chrysotile and their views of the hazards of asbestos-containing brakes were discussed. Their analyses did not alter our views that exposures to mechanics posed no increased risk of asbestos related disease. The latest knowledge about the role of genetic susceptibility on the development of mesothelioma is also addressed.

Bayesian analysis of the rate of spontaneous malignant mesothelioma among BAP1 mutant mice in the absence of asbestos exposure

Cancers of the mesothelium, such as malignant mesothelioma (MM), historically have been attributed solely to exposure to asbestos. Recent large scale genetic and genomic functional studies now show that approximately 20% of all human mesotheliomas are causally linked to highly penetrant inherited (germline) pathogenic mutations in numerous cancer related genes. The rarity of these mutations in humans makes it difficult to perform statistically conclusive genetic studies to understand their biological effects. This has created a disconnect between functional and epidemiological studies. However, since the molecular pathogenesis of MM in mice accurately recapitulates that of human disease, this disconnect between functional and epidemiological studies can be overcome by using inbred mouse strains that harbor mutation(s) in genes involved in the disease. Most mouse studies have focused on the effect of asbestos exposure, leaving the effects of genetic mutations in the absence of exposure understudied. Here, using existing peer-reviewed studies, we investigate the rate of spontaneous MM among mice with and without germline genetic mutations, in the absence of asbestos exposure. We leveraged these published data to generate a historical control dataset (HCD) to allow us to improve statistical power and account for genetic heterogeneity between studies. Our Bayesian analyses indicate that the odds of spontaneous MM among germline BAP1 mutant mice is substantially larger than that of wildtype mice. These results support the existing biological study findings that mesotheliomas can arise in the presence of pathogenic germline mutations, independently of asbestos exposure.

Mapping roof coverings of asbestos-cement, the first step to control the technical condition/threat and establish priorities for replacement in developing countries

This paper presents a systematic and data-driven approach to prioritize interventions in urban areas with asbestos cement (AC) roofs, addressing the urgent need to mitigate asbestos-related risks. The objective is to propose a comprehensive methodology that considers multiple criteria at the neighborhood level, allowing for a nuanced assessment of intervention priorities. The methodology involves the normalization of various parameters, including population density, facility density, and the area covered by asbestos-cement roofs. In addition, an innovative aspect is introduced by incorporating weathering status identification data, represented as an index, validated in previous research, further enriching the evaluation process. The integration of these diverse factors allows for a holistic understanding of the risk landscape associated with AC roofs in urban settings. The cornerstone of the proposed approach is the development of a Priority Intervention Index (PII) at the neighborhood level. This index serves to standardize the assessment of intervention priorities, enabling a fair and transparent comparison across different regions. To enhance practical application, the PII is discretized into three categories, low, mid and high intervention priority. The results obtained are robust, replicable in other scenarios, and practical for decision-makers. The new methodology provides a structured and quantifiable approach to identify and prioritize areas for asbestos-related interventions based on well-defined criteria at the neighborhood level. The resulting prioritization strategy offers urban planners and local officials a clear and evidence-based tool to allocate resources efficiently and effectively manage the inherent risks associated with AC roofs in urban environments. The paper will describe how the prioritization can be applied "at the neighborhood level" by urban planners and local officials.

An updated evaluation of reported no-observed adverse effect levels for chrysotile, amosite, and crocidolite asbestos for lung cancer and mesothelioma

This analysis updates two previous analyses that evaluated the exposure-response relationships for lung cancer and mesothelioma in chrysotile-exposed cohorts. We reviewed recently published studies, as well as updated information from previous studies. Based on the 16 studies considered for chrysotile (<10% amphibole), we identified the "no-observed adverse effect level" (NOAEL) for lung cancer and/or mesothelioma; it should be noted that smoking or previous or concurrent occupational exposure to amphiboles (if it existed) was not controlled for. NOAEL values ranged from 2.3-<11.5 f/cc-years to 1600-3200 f/cc-years for lung cancer and from 100-<400 f/cc-years to 800-1599 f/cc-years for mesothelioma. The range of best-estimate NOAELs was estimated to be 97-175 f/cc-years for lung cancer and 250-379 f/cc-years for mesothelioma. None of the six cohorts of cement or friction product manufacturing workers exhibited an increased risk at any exposure level, while all but one of the six studies of textile workers reported an increased risk at one or more exposure levels. This is likely because friction and cement workers were exposed to much shorter chrysotile fibers. Only eight cases of peritoneal mesothelioma were reported in all studies on predominantly chrysotile-exposed cohorts combined. This analysis also proposed best-estimate amosite and crocidolite NOAELs for mesothelioma derived by the application of relative potency estimates to the best-estimate chrysotile NOAELs for mesothelioma and validated by epidemiology studies with exposure-response information. The best-estimate amosite and crocidolite NOAELs for mesothelioma were 2-5 f/cc-years and 0.6-1 f/cc-years, respectively. The rate of peritoneal mesothelioma in amosite- and crocidolite-exposed cohorts was between approximately 70- to 100-fold and several-hundred-fold higher than in chrysotile-exposed cohorts, respectively. These findings will help characterize potential worker and consumer health risks associated with historical and current chrysotile, amosite, and crocidolite exposures.