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Greim H.,TU Munich | Utell M.J.,University of Rochester | Maxim L.D.,Everest Consulting Associates | Niebo R.,Everest Consulting Associates
Inhalation Toxicology | Year: 2014

In 2011, SCOEL classified RCF as a secondary genotoxic carcinogen and supported a practical threshold. Inflammation was considered the predominant manifestation of RCF toxicity. Intrapleural and intraperitoneal implantation induced mesotheliomas and sarcomas in laboratory animals. Chronic nose-only inhalation bioassays indicated that RCF exposure in rats increased the incidence of lung cancer and similar exposures resulted in mesothelioma in hamsters, but these studies may have been compromised by overload. Epidemiological studies in the US and Europe showed an association between exposure and prevalence of respiratory symptoms and pleural plaques, but no interstitial fibrosis, mesotheliomas, or increased numbers of lung tumors were observed. As the latency of asbestos induced mesotheliomas can be up to 50 years, the relationship between RCF exposure and respiratory malignances has not been fully determined. Nonetheless, it is possible to offer useful perspectives. RCF and rock wool have similar airborne fiber dimensions and biopersistence. Therefore, it is likely that these fibers have similar toxicology. Traditional rock wool has been the subject of numerous cohort and case control studies. For rock wool, IARC (2002) concluded that the epidemiological studies did not provide evidence of carcinogenicity. Based on analogies with rock wool (read across), it is reasonable to believe that increases in lung cancer or any mesotheliomas are unlikely to be found in the RCF-exposed cohort. RCF producers have developed a product stewardship program to measure and control fiber concentrations and to further understand the health status of their workers. © 2014 Informa Healthcare USA, Inc. Source

Maxim L.D.,Everest Consulting Associates | Niebo R.,Everest Consulting Associates | Utell M.J.,University of Rochester
Inhalation Toxicology | Year: 2014

Screening tests are widely used in medicine to assess the likelihood that members of a defined population have a particular disease. This article presents an overview of such tests including the definitions of key technical (sensitivity and specificity) and population characteristics necessary to assess the benefits and limitations of such tests. Several examples are used to illustrate calculations, including the characteristics of low dose computed tomography as a lung cancer screen, choice of an optimal PSA cutoff and selection of the population to undergo mammography. The importance of careful consideration of the consequences of both false positives and negatives is highlighted. Receiver operating characteristic curves are explained as is the need to carefully select the population group to be tested. © 2014 Informa Healthcare USA, Inc. Source

Walker A.M.,World Health Information Science Consultants | Maxim L.D.,Everest Consulting Associates | Utell M.J.,University of Rochester
Inhalation Toxicology | Year: 2012

Background: Animal studies on refractory ceramic fiber (RCF) have led to the suggestion that RCF might resemble asbestos in carcinogenicity. Human data are available to test this hypothesis. Methods: We compared the occurrence of lung cancer and mesothelioma in 605 men engaged in the manufacture of RCF and followed since 1987 to cancer rates that would have been anticipated if airborne RCF were carcinogenic to the same degree as are crocidolite, amosite or chrysotile asbestos. We integrated the results of workplace exposure monitoring with mortality follow-up using formulas presented by Hodgson and Darnton (2000) to estimate hypothesized risks under different asbestos scenarios. Results: During 15,281 person-years of observation, there were 12 deaths from lung cancer. General population rates predicted 11.8 cases expected for an observed/expected (O/E) ratio of 1.0. Anticipated numbers of deaths from lung cancer under hypotheses of carcinogenicity similar to that of amphiboles and chrysotile were 62 and 17, allowing for rejection of amphibole-like effects (p < 10-5) but not chrysotile-like carcinogenicity (p = 0.15). There were no cases of mesothelioma, as compared to 4.9 anticipated under a crocidolite-like hypothesis (p = 0.007 to reject), 1.0 for amosite (p = 0.38) and 0.05 for chrysotile (p = 0.95). Conclusion: There was no increase in lung cancer or mesothelioma in these workers exposed to RCF. If the cohort had the same exposure to crocidolite asbestos the number of lung cancer and mesothelioma cases would have been significantly greater than observed. The data do not yet permit a similar conclusion with respect to chrysotile asbestos. © 2012 Informa Healthcare USA, Inc. Source

Utell M.J.,University of Rochester | Maxim L.D.,Everest Consulting Associates
Inhalation Toxicology | Year: 2010

This paper provides a review of the relevant literature on refractory ceramic fibers (RCFs), summarizing relevant data and information on the manufacture, processing, applications, potential occupational exposure, toxicology, epidemiology, risk analysis, and risk management. RCFs are amorphous fibers used for high-temperature insulation applications. RCFs are less durable/biopersistent than amphibole asbestos, but more durable/biopersistent than many other synthetic vitreous fibers (SVFs). Moreover, as produced/used, some RCFs are respirable. Toxicology studies with rodents using various exposure methods have shown that RCFs can cause fibrosis, lung cancer, and mesothelioma. Interpretation of these animal studies is difficult for various reasons (e.g., overload in chronic inhalation bioassays). Epidemiological studies of occupationally exposed cohorts in Europe and the United States have demonstrated measurable effects (e.g., mild respiratory symptoms and pleural plaques) but no disease (i.e., no interstitial fibrosis, no excess lung cancer, and no mesothelioma) to date. The RCF industry, working cooperatively with various government agencies in the United States, has developed a comprehensive product stewardship program (PSP) to identify and control risks associated with occupational exposure. One provision of the PSP is the adoption of a voluntary recommended exposure guideline (REG) of 0.5 fibers/milliliter (f/ml). Selected on the basis of prudence and demonstrated feasibility, compliance with the REG should reduce risks to levels between 0.073/1000 and 1.2/1000, based on extrapolations from chronic animal inhalation studies. © 2010 Informa UK Ltd. Source

Trumbore D.,Owens Corning Asphalt Technology Laboratory | Osborn L.,Heritage Research Group | Blackburn G.,PetroLabs Inc | Niebo R.,Everest Consulting Associates | And 2 more authors.
Inhalation Toxicology | Year: 2011

Recent studies have reported divergent results in rodent cancer assays using fume condensates from a variety of asphalt products. This paper presents results of a study investigating the role of oxidation, or extent of oxidation, on these findings. Five straight run asphalts, made from widely used crude oils, were used as inputs to both production scale and laboratory oxidation units and processed to a range of softening points used in common roofing products. For each of the five asphalts studied, the oxidation reaction significantly decreased measures of polycyclic aromatic compounds (PACs) that have been linked, previously and in analyses included in this study, to tumor induction in rodent bioassays. Mutagenicity index determined by the modified Ames assay was reduced between 41% and 50% from the input asphalt to the final oxidized product. A fluorescence method tuned to a subset of PAC compounds that have been associated with carcinogenic behavior in mouse bioassays was reduced between 39% and 71%. The decrease was largest in the first quarter of the oxidation reaction. These findings indicate that oxidation, by itself, was not a likely factor in the tumor induction seen in the previous studies. Rather, other factors such as the conditions of fume generation and crude source (coupled with possible differences in distillation endpoints) were more likely to have determined the outcomes. Analyses of previously published data, presented in this paper, suggest that the modified Ames and fluorescence assays are valuable screening tools for use in future health-related asphalt research. © 2011 Informa Healthcare USA, Inc. Source

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