Critical Choices in Predicting Stone Wool Biodurability: Lysosomal Fluid Compositions and Binder Effects.

The hazard potential, including carcinogenicity, of inhaled man-made vitreous fibers (MMVFs) is correlated with their biodurability in the lung, as prerequisite for biopersistence. Abiotic dissolution testing serves to predict biodurability. We re-analyzed the International Agency for Research on Cancer Monograph on MMVFs and found that the correlation between in vivo biopersistence and abiotic dissolution presented therein confounded different simulant fluids and further confounded evaluation of leaching vs structural elements. These are critical choices for abiotic dissolution testing, as are binder removal and the rate of the flow that removes ions during testing. Therefore, we experimentally demonstrated how fluid composition and binder affect abiotic dissolution of a representative stone wool MMVF. We compared six simulant fluids (all pH 4.5, reflecting the environment of alveolar macrophage lysosomes) that differed in organic acids, which have a critical role in their ability to modulate the formation of Si-rich gels on the fiber surfaces. Removing the binder accelerates the average dissolution rate by +104% (max. + 273%) across the fluids by suppression of gel formation. Apart from the high-citrate fluid that predicted a 10-fold faster dissolution than is observed in vivo, none of the five other fluids resulted in dissolution rates above 400 ng/cm2/h, the limit associated with the exoneration from classification for carcinogenicity in the literature. These findings were confirmed with and without binder. For corroboration, five more stone wool MMVFs were assessed with and without binder in one specific fluid. Again, the presence of the binder caused gel formation and reduced dissolution rates. To enhance the reliability and robustness of abiotic predictions of biodurability, we recommend replacing the critically influential citric acid in pH 4.5 fluids with other organic acids. Also, future studies should consider structural transformations of the fibers, including changes in fiber length, fiber composition, and reprecipitation of gel layers.

6-Phenylhexyl silane derivatized, sputtered silicon solid phase microextraction fiber for the parts-per-trillion detection of polyaromatic hydrocarbons in water and baby formula.

We report the fabrication of 6-phenylhexylsilane derivatized, sputtered silicon, solid phase microextraction fibers that show parts per trillion detection limits for polyaromatic hydrocarbons, and negligible carry over and phase bleed. Their fabrication involves sputtering silicon on silica fibers under various conditions. Six different fibers were evaluated by generating three different thicknesses of sputtered silicon at two different throw distances, which altered the morphologies of the silicon surfaces. All of the fibers were coated with similar thicknesses of 6-phenylhexylsilane (ca. 2 nm). These fibers were characterized with multiple analytical techniques. The optimum fiber configuration was then used to analyze polyaromatic hydrocarbons via direct immersion, gas chromatography mass spectrometry. Our best fiber for the extraction of low molecular weight polyaromatic hydrocarbons in water had similar performance to that of a commercial fiber. However, our fiber demonstrated ca. 3 times the extraction efficiency for higher molecular weight polyaromatic hydrocarbons. In addition, it outperformed the commercial fiber by showing better linearity, repeatability, and detection limits. A method for analyzing polyaromatic hydrocarbons in baby formula was developed, which showed very good linearity (0.5-125 ppb), repeatability (2-26%), detection limits (0.12-0.81 ppb), and recoveries (103-135%). In addition, our fiber showed much less (negligible) carry over and phase bleed than the commercially available fibers.

Effects of Water and Chemical Solutions Ageing on the Physical, Mechanical, Thermal and Flammability Properties of Natural Fibre-Reinforced Thermoplastic Composites.

Biocomposites comprising a combination of natural fibres and bio-based polymers are good alternatives to those produced from synthetic components in terms of sustainability and environmental issues. However, it is well known that water or aqueous chemical solutions affect natural polymers/fibres more than the respective synthetic components. In this study the effects of water, salt water, acidic and alkali solutions ageing on water uptake, mechanical properties and flammability of natural fibre-reinforced polypropylene (PP) and poly(lactic acid) (PLA) composites were compared. Jute, sisal and wool fibre- reinforced PP and PLA composites were prepared using a novel, patented nonwoven technology followed by the hot press method. The prepared composites were aged in water and chemical solutions for up to 3 week periods. Water absorption, flexural properties and the thermal and flammability performances of the composites were investigated before and after ageing each process. The effect of post-ageing drying on the retention of mechanical and flammability properties has also been studied. A linear relationship between irreversible flexural modulus reduction and water adsorption/desorption was observed. The aqueous chemical solutions caused further but minor effects in terms of moisture sorption and flexural modulus changes. PLA composites were affected more than the respective PP composites, because of their hydrolytic sensitivity. From thermal analytical results, these changes in PP composites could be attributed to ageing effects on fibres, whereas in PLA composite changes related to both those of fibres present and of the polymer. Ageing however, had no adverse effect on the flammability of the composites.

Chrysotile fibers in tissue adjacent to laryngeal squamous cell carcinoma in cases with a history of occupational asbestos exposure.

Asbestos describes a group of naturally occurring fibrous silicate mineral compounds that have been associated with a number of respiratory maladies, including mesothelioma and lung cancer. In addition, based primarily on epidemiologic studies, asbestos has been implicated as a risk factor for laryngeal and pharyngeal squamous cell carcinoma (SCC). The main objective of this work was to strengthen existing evidence via empirical demonstration of persistent asbestos fibers embedded in the tissue surrounding laryngeal and pharyngeal SCC, thus providing a more definitive biological link between exposure and disease. Six human papillomavirus (HPV)-negative laryngeal (n = 4) and pharyngeal (n = 2) SCC cases with a history working in an asbestos-exposed occupation were selected from a large population-based case-control study of head and neck cancer. A laryngeal SCC case with no history of occupational asbestos exposure was included as a control. Tissue cores were obtained from adjacent nonneoplastic tissue in tumor blocks from the initial primary tumor resection, and mineral fiber analysis was performed using a scanning electron microscope equipped with an energy dispersive X-ray analyzer (EDXA). Chrysotile asbestos fiber bundles were identified in 3/6 of evaluated cases with a history of occupational asbestos exposure. All three cases had tumors originating in the larynx. In addition, a wollastonite fiber of unclear significance was identified one of the HPV-negative pharyngeal SCC cases. No mineral fibers were identified in adjacent tissue of the case without occupational exposure. The presence of asbestos fibers in the epithelial tissue surrounding laryngeal SCC in cases with a history of occupational asbestos exposure adds a key line of physical evidence implicating asbestos as an etiologic factor.

Talc and mesothelioma: mineral fiber analysis of 65 cases with clinicopathological correlation.

Malignant mesothelioma is strongly associated with prior asbestos exposure. Recently there has been interest in the role of talc exposure in the pathogenesis of mesothelioma. We have analyzed lung tissue samples from a large series of malignant mesothelioma patients. Asbestos bodies were counted by light microscopy and mineral fiber concentrations for fibers 5 µm or greater in length were determined by scanning electron microscopy equipped with an energy dispersive spectrometer. The values were compared with 20 previously published controls. Among 609 patients with mesothelioma, talc fibers were detected in 375 (62%) and exceeded our control values in 65 (11%). Elevated talc levels were found in 48/524 men (9.2%) and 17/85 women (20%). Parietal pleural plaques were identified in 30/51 informative cases (59%) and asbestosis in 5/62 informative cases (8%). Commercial amphiboles (amosite and/or crocidolite) were elevated in 52/65 (80%) and noncommercial amphiboles (tremolite, actinolite or anthophyllite) in 41/65 (63%). Both were elevated in 34/65 (52%). Asbestos body counts by light microscopy were elevated in 53/64 informative cases (83%). A history of working in industries associated with asbestos exposure and increased mesothelioma risk was identified in 36/48 cases in men, and a history of exposure as household contacts of an occupationally exposed individual was identified in 12/17 cases in women. We conclude that among patients with mesothelioma, the vast majority have talc levels indistinguishable from background. Of the remaining 11% with elevated talc levels, the vast majority (80%) have elevated levels of commercial amphibole fibers.

[Asbestos exposure and related diseases among friction products workers (1971-2016)]. / Esposizione ad amianto e patologie correlate in addetti alla produzione di materiali di attrito (1971-2016).

SUMMARY: Worldwide studies have been published on the mortality of workers employed in asbestos-based materials for the production of clutches and brakes. However no one of these studies is related to Italian cases. Furthermore, not even surveys have been conducted in Italy to characterize the correlation between asbestos exposures and the possible occurring of asbestos-related disease. Our objectives are the following: i) to assess and quantify the asbestos exposure cases, ii) to describe the nature and the frequency of asbestos-related diseases among blue collar employees of an important factory producing brakes and clutches with chrysotile asbestos content from 1971 to 1993 and iii) to provide preliminary data on cumulative asbestos exposure estimated using lung fibre burden analysis. Critical appraisal of airborne asbestos fibre measurements and identification of cases of asbestos-related diseases between the blue collar employees, either notified to the local health authority or recovered from the Italian national Mesothelioma registry was investigated. Lung fibre burden analysis using the lung tissue samples from two deceased blue collar employees was also performed. Airborne asbestos fibre measurements (carried out in 1982) suggested asbestos fibres average concentrations of about 0.3 f/ml, while all 1992 measurements showed results below 0.1 f/ml. Furthermore, since 1988, we identified four cases of pleural plaques, three cases of asbestosis and seven cases of lung cancer. No case of malignant mesothelioma was found. In both lung cancer cases, analysed to measure the lung fibre burden, commercial amphiboles were absent or in limited concentration but chrysotile and, especially, tremolite asbestos were present in noticeable amount. In conclusion, since 1971 and up to early 1980s, exposure to chrysotile asbestos and talc, likely contaminated by tremolite, had been significant and comparable to levels causing asbestosis long-term risk. No case of malignant mesothelioma was found, that is consistent with the absence of amphiboles and with the lower risk of mesothelioma associated with the chrysotile asbestos. However a subset of the blue collar employees, the ones employed later on, could still have not reached the full risk condition, and so being still at risk of developing malignant mesothelioma. In the two lung cancer cases studied, the lung fibre burden was essentially made of chrysotile and tremolite. Lastly, lung cancer occurrence in the population of blue collar employees has been likely underestimated and the correct determination of lung cancer risk should be done through the mortality analysis of this population.

[Detection and comparison of fiber count concentration in processing environment of asbestos and man-made mineral fiber].

Objective: To connect with the measurement data of asbestos dust fiber concentration in foreign countries, improve the accuracy of asbestos fiber detection in China, and understand the dust exposure in the working environment of asbestos and man-made mineral fiber production and processing sites in Zhejiang Province. The fiber count concentrations of working environment in glass fiber, ceramic fiber and asbestos processing plants were measured and compared. Methods: The dust concentration in the working environment of two glass fiber factories, one ceramic fiber factory and eight asbestos products processing factories was measured. The total dust mass concentration was measured according to GBZ/T 192.1-2007, and the fiber count concentration was measured by phase contrast microscope. Kruskal Wallis was used to test and compare the dust concentration in the working environment of each post. The correlation between asbestos mass concentration and fiber count concentration was analyzed by Spearman correlation. Results: Under the phase contrast microscope, there were many short and fine asbestos fibers in the field of vision, and there were many impurities around. The average dust concentration of asbestos processing plant was 3.2 f/ml, and the dust concentration of cotton ginning was the highest (6.68 f/ml) . There was a significantly positive correlation between asbestos fiber count concentration and mass concentration (r=0.535, P=0.033) . The average fiber count concentration of glass fiber factory was 0.001 f/ml, and the highest was 0.005 f/ml. The average fiber count concentration of ceramic fiber factory was 0.001 f/ml, and the highest was 0.006 f/ml. Conclusion: The fiber count concentration in the working environment of asbestos factory in Zhejiang Province is obviously over the standard, which is one of the important reasons for the high incidence of mesothelioma in this area. Short and small asbestos fibers are easy to be ignored when counting. It is necessary to improve the actual operation process of fiber counting to form a laboratory standard in China.

Effect of Long-Term Brushing on Deflection, Maximum Load, and Wear of Stainless Steel Wires and Conventional and Spot Bonded Fiber-Reinforced Composites.

Fiber-reinforced composite (FRC) retainers are an aesthetic alternative to conventional Stainless Steel splints. They are generally used with a full bonded technique, but some studies demonstrated that they could be managed with a spot bonding technique to significantly decrease their rigidity. In order to propose this FRC spot bonding technique for clinical use, the aim of this study was to evaluate mechanical properties and surface wear of fibers left uncovered. Tests were made by simulating tooth brushing, comparing FRC spot bonding technique splints with stainless steel and FRC traditional technique splints. Specimens were tested both at 0.1 mm of deflection and at maximum load, showing higher values of rigidity for the FRC full bonded technique. After tooth brushing, no significant reduction in values at 0.1 mm deflection was reported, while we found a similar reduction in these values for the Stainless Steel and FRC spot bonding technique at maximum load, and no significant variation for the FRC full bonded technique. SEM images after tooth brushing showed wear for FRC fibers left uncovered, while no relevant wear signs in metal and conventional FRC fibers were noticed. Results showed that FRC spot bonding technique has advantages in mechanical properties when compared to the FRC traditional full bonding technique, also after tooth brushing. However, the surface wear after tooth brushing in the FRC spot bonding technique is considerable and other tests must be performed before promoting this technique for routine clinical use.

Standardized methods for preparation and bi-variate length & diameter counting/sizing of aerosol and tissue digestion fiber samples.

Most fiber length distributions fit a log-normal distribution with their being many more shorter fibers present as compared to the longer fibers. As the longer fibers have been suggested to be more important for possible pathogenesis giving equal weight to all fiber lengths when sizing fibers will under sample the longer fibers. The methods described here, are based upon the optimization of fiber counting/sizing rules over a number years of experience and have been developed to provide a stable estimate of the mean number of particles and fibers present in the size ranges: particles, fibers < 5 µm; 5-20 µm; and >20 µm. These methods were first applied using TEM, however, with the development of high resolution SEM, it was found that higher reproducibility could be obtained with SEM.

Measuring EMPs in the lung what can be measured in the lung: Asbestiform minerals and cleavage fragments.

Asbestos mineral fibers have been associated with the development of a variety of diseases in humans and experimental animals, including asbestosis, lung cancer, and mesothelioma. Asbestos includes several mineral types divided into two mineral groups, serpentine and amphibole forms. Chrysotile is the serpentine mineral classified as asbestos, whereas the amphiboles include amosite, crocidolite, tremolite, actinolite and anthophyllite. There are a number of mineral fibers that occur with asbestiform morphology and that have been associated with various asbestos-induced diseases. These include the Libby amphiboles (associated with a vermiculite mine northwest of Libby, MT), erionite (in Turkey and North America), fluoro-edenite (in Sicily), and perhaps balangeroite (in Italy). In addition, each of the asbestos minerals occurs in a non-fibrous form, and these may occur as cleavage fragments that satisfy the definition for a fiber, i.e., particles with an aspect ratio of at least 3:1 and roughly parallel sides. Cleavage fragments of non-asbestiform minerals have not been associated with asbestos-induced diseases nor are these minerals regulated by the Occupational Safety and Health Administration. Finally, there are a number of other mineral species which can occur in human lung samples that satisfy the definition for a fiber as given above. These similarly have not been associated with asbestos-induced diseases. All of these various minerals satisfying the definition for a fiber can be referred to as elongated mineral particles (EMP). It is the purpose of this presentation to discuss the role of scanning electron microscopy (SEM) equipped with an energy dispersive x-ray analyzer (EDXA) in the detection and classification of EMP in human lung samples.

Measurement of elongate mineral particles: What we should measure and how do we do it?

The length distributions of single fibrils of Coalinga, UICC-B and wet dispersed chrysotile were measured by transmission electron microscopy (TEM). It was found that the distributions significantly diverged above approximately 10 µm (µm) in length, corresponding to differences in published results of animal experiments. This result is in contrast to published data in which counting of an insufficient number of fibers resulted in an erroneous conclusion that the length distribution of Coalinga chrysotile fibrils was indistinguishable from those of other sources of chrysotile. The size distributions of the respirable particle size fractions from acknowledged tremolite asbestos samples were found to be dominated by elongate particles longer than 5 µm that are within the dimensional range of non-asbestiform amphiboles. Prior studies have shown that these elongate particles obscure a correlation between a specific size range of particles and results of animal implantation studies that used tremolite of various morphologies. In the prior studies, a reference protocol was developed from four crushed non-asbestiform amphiboles to differentiate the size range of amphibole particles that correlates with the mesothelioma frequencies observed in the animal studies. In the work reported here, this correlation was tested with TEM analyses of amphiboles from Libby, MT, Sparta, NJ and Homestake mine, Lead, SD, which represent known environmental/occupational situations. Further TEM analyses of the tremolite samples used in the original animal implantation studies have also shown that the numbers of elongate tremolite particles with lengths ≤5 µm implanted into the animals are not correlated with the observed mesothelioma frequencies.

Thermal Failure Analysis of Fiber-Reinforced Silica Aerogels under Liquid Nitrogen Thermal Shock.

Aerogel materials are recognized as promising candidates for the thermal insulator and have achieved great successes for the aerospace applications. However, the harsh environment on the exoplanet, especially for the tremendous temperature difference, tends to affect the tenuous skeleton and performances of the aerogels. In this paper, an evaluation method was proposed to simulate the environment of exoplanet and study the influence on the fiber-reinforced silica aerogels with different supercritical point drying (SPD) technology. Thermal conductivity, mechanical property and the microstructure were characterized for understanding the thermal failure mechanism. It was found that structure and thermal property were significantly influenced by the adsorbed water in the aerogels under the thermal shocks. The thermal conductivity of CO2-SPD aerogel increased 35.5% after the first shock and kept in a high value, while that of the ethanol-SPD aerogel increased only 19.5% and kept in a relatively low value. Pore size distribution results showed that after the first shock the peak pore size of the CO2-SPD aerogel increased from 18 nm to 25 nm due to the shrinkage of the skeleton, while the peak pore size of the ethanol-SPD aerogel kept at ~9 nm probably induced by the spring-back effect. An 80 °C treatment under vacuum was demonstrated to be an effective way for retaining the good performance of ethanol-SPD aerogels under the thermal shock. The thermal conductivity increases of the ethanol-SPD aerogels after 5 shocks decreased from ~30 to ~0% via vacuum drying, while the increase of the CO2-SPD aerogels via the same treatments remains ~28%. The high-strain hardening and low-strain soften behaviors further demonstrated the skeleton shrinkage of the CO2-SPD aerogel.

Asbestiform minerals in ophiolitic rocks of Calabria (southern Italy).

Ophiolitic rocks cropping on Calabria territory, southern Italy, can hold asbestiform minerals potentially harmful for human health. The aim of this work was to detect the fibrous phases of ophiolites along the Coastal Chain of northern Calabria and southern part of the Sila massif. Above 220 massive samples were collected in the study areas and analyzed using optical and electron microscopy, X-ray diffractometry, and Fourier transform infra-red spectrometry. The main fibrous constituent belonged to tremolite-actinolite series followed by fibrous antigorite that becomes more abundant in the samples collected in Reventino Mount surroundings. Results highlighted that serpentinites samples mainly consisted of antigorite and minor chrysotile. Samples collected along the coastal chain of northern Calabria did not hold fibrous materials. The results will be useful for Italian natural occurrences of asbestos (NOA) mapping in order to avoid an unintentional exposition by human activity or weathering processes.

Releasability of asbestos fibers from weathered roof cement.

Chrysotile asbestos fibers were added to roofing products, including roof cement, for several decades. The fibers were described as "encapsulated" and therefore incapable of being released, an assertion that is disproved by the study reported herein. Three test panels of roof cement from the original container were exposed to ambient weathering in 2015 and 2016. Two panels were then sampled using the ASTM D5755 microvacuum method. Sampling revealed a light brown sub-layer under the dark brown surface layer, both of which crumbled and became friable during sampling. Analysis of the microvacuum samples with transmission electron microscopy showed that the material on the 2 panels contained 4,432,000 and 3,320,000 asbestos structures per cm² with nearly all of the structures consisting of fibers less than 5 µm long. Energy dispersive spectrometry determined that none of the fibers reported were coated with asphalt. The presence of free fibers was confirmed by direct examination of the surfaces of the panels and of dust released from handling the panels via scanning electron microscopy. This study confirmed the releasability of uncoated asbestos fibers from dried roof cement that was indicated in 2 previous studies published in 2007 and 2010. These results suggest that the finding of the Fifth Circuit Court in 1997 that uncoated airborne asbestos fibers cannot be released from roof cement, and therefore do not present a potential exposure by inhalation, was erroneous in retrospect. The exemption of roof cement from regulation under the Occupational Safety and Health Administration Construction Industry Standard for asbestos by the Court should not be relied on by employers of workers who remove weathered asbestos-containing roof cement, and precautions should be taken against exposure to airborne asbestos fibers during this work.

Respiratory assessment of refractory ceramic fibers in a heating technician population.

Refractory ceramic fibers (RCF) have been extensively used for insulation in condensing boilers. The aim of this study was to evaluate the respiratory exposure to these fibers among maintenance heating technicians. We first created a working group (Carsat Brittany and Finistère Occupational Health Services) and carried out a sampling strategy. Atmospheric measurements were done during work tasks, and filters were analyzed by phase contrast microscopy (PCM) and scanning electron microscopy (SEM) in French approved laboratories. Four companies were included for a total of 15 days of work. During those 15 workdays, 12 SEM and 21 PCM samples were taken and analyzed. The phase contrast microscopy and SEM average results were 0.04 and 0.004 fibers/cm3, respectively. In conclusion, the study confirms heating technician RCF respiratory exposure during maintenance work for both condensation gas boilers and atmospheric boilers. Collective and individual prevention measures should be implemented along with appropriate medical follow-up.

Composition, Respirable Fraction and Dissolution Rate of 24 Stone Wool MMVF with their Binder.

BACKGROUND: 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. RESULTS: 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. CONCLUSIONS: 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).

Assessment of Health Risk from Historical Use of Cosmetic Talcum Powder.

This study's objective is to assess the risk of asbestos-related disease being contracted by past users of cosmetic talcum powder.  To our knowledge, no risk assessment studies using exposure data from historical exposures or chamber simulations have been published. We conducted activity-based sampling with cosmetic talcum powder samples from five opened and previously used containers that are believed to have been first manufactured and sold in the 1960s and 1970s.  These samples had been subject to conflicting claims of asbestos content; samples with the highest claimed asbestos content were tested.  The tests were conducted in simulated-bathroom controlled chambers with volunteers who were talc users.  Air sampling filters were prepared by direct preparation techniques and analyzed by phase contrast microscopy (PCM), transmission electron microscopy (TEM) with energy-dispersive x-ray (EDX) spectra, and selective area diffraction (SAED).  TEM analysis for asbestos resulted in no confirmed asbestos fibers and only a single fiber classified as "ambiguous."  Hypothetical treatment of this fiber as if it were asbestos yields a risk of 9.6 × 10-7 (under one in one million) for a lifetime user of this cosmetic talcum powder.  The exposure levels associated with these results range from zero to levels far below those identified in the epidemiology literature as posing a risk for asbestos-related disease, and substantially below published historical environmental background levels.  The approaches used for this study have potential application to exposure evaluations of other talc or asbestos-containing materials and consumer products.

Pleural mesothelioma and lung cancer risks in relation to occupational history and asbestos lung burden.

BACKGROUND: We have conducted a population-based study of pleural mesothelioma patients with occupational histories and measured asbestos lung burdens in occupationally exposed workers and in the general population. The relationship between lung burden and risk, particularly at environmental exposure levels, will enable future mesothelioma rates in people born after 1965 who never installed asbestos to be predicted from their asbestos lung burdens. METHODS: Following personal interview asbestos fibres longer than 5 µm were counted by transmission electron microscopy in lung samples obtained from 133 patients with mesothelioma and 262 patients with lung cancer. ORs for mesothelioma were converted to lifetime risks. RESULTS: Lifetime mesothelioma risk is approximately 0.02% per 1000 amphibole fibres per gram of dry lung tissue over a more than 100-fold range, from 1 to 4 in the most heavily exposed building workers to less than 1 in 500 in most of the population. The asbestos fibres counted were amosite (75%), crocidolite (18%), other amphiboles (5%) and chrysotile (2%). CONCLUSIONS: The approximate linearity of the dose-response together with lung burden measurements in younger people will provide reasonably reliable predictions of future mesothelioma rates in those born since 1965 whose risks cannot yet be seen in national rates. Burdens in those born more recently will indicate the continuing occupational and environmental hazards under current asbestos control regulations. Our results confirm the major contribution of amosite to UK mesothelioma incidence and the substantial contribution of non-occupational exposure, particularly in women.

Diagnosis of Asbestos-Related Diseases: The Mineralogist and Pathologist's Role in Medicolegal Field.

Because asbestos diseases represent a complex pattern of legal, social, and political issue, the involvement of the mineralogist and pathologist for a multidisciplinary assessment of its diagnosis helps investigate the relationship between mesothelioma or lung cancer and occupational or environmental asbestos exposure.In the present study, we consider the concentrations of asbestos bodies (ABs) detected by optical microscopy (OM) and scanning electron microscopy (SEM) and the burden of different kinds of mineral fibers (among which is asbestos) identified by SEM combined with an energy dispersive spectrometer (EDS), in 10 lung tissue samples of subjects with occupational and nonoccupational exposure to asbestos.In all subjects with occupational exposure to asbestos, more than 1000 ABs per gram of dry weight were detected both with OM and SEM; this concentration is internationally accepted as suggesting high probability of past occupational exposure to asbestos.In 9 lung samples of the 10 investigated by SEM-EDS different inorganic fibers were found. Asbestos fibers have been identified too, and more than 100,000 fibers per gram of dry weight were detected in subjects with occupational exposure; this concentration is internationally accepted as suggesting high probability of past occupational exposure to asbestos.Instead, when the ABs burden is low or moderate (such as in subjects with absent or probable asbestos exposure), the correlation between ABs concentration determined by OM and those determined by SEM is lost. Therefore, when the ABs value in OM is borderline, the SEM investigation became essential. Furthermore, the mineralogical analysis by SEM-EDS (identification and quantification of inorganic fibers in general and asbestos in particular) of the fibers detected in the lung tissues is very useful, if not necessary, to complete the pathological diagnosis of asbestos-related malignancies in medicolegal field.

Evaluation of the dark-medium objective lens in counting asbestos fibers by phase-contrast microscopy.

A Japanese round-robin study revealed that analysts who used a dark-medium (DM) objective lens reported higher fiber counts from American Industrial Hygiene Association (AIHA) Proficiency Analytical Testing (PAT) chrysotile samples than those using a standard objective lens, but the cause of this difference was not investigated at that time. The purpose of this study is to determine any major source of this difference by performing two sets of round-robin studies. For the first round-robin study, 15 AIHA PAT samples (five each of chrysotile and amosite generated by water-suspended method, and five chrysotile generated by aerosolization method) were prepared with relocatable cover slips and examined by nine laboratories. A second round-robin study was then performed with six chrysotile field sample slides by six out of nine laboratories who participated in the first round-robin study. In addition, two phase-shift test slides to check analysts' visibility and an eight-form diatom test plate to compare resolution between the two objectives were examined. For the AIHA PAT chrysotile reference slides, use of the DM objective resulted in consistently higher fiber counts (1.45 times for all data) than the standard objective (P-value < 0.05), regardless of the filter generation (water-suspension or aerosol) method. For the AIHA PAT amosite reference and chrysotile field sample slides, the fiber counts between the two objectives were not significantly different. No statistically significant differences were observed in the visibility of blocks of the test slides between the two objectives. Also, the DM and standard objectives showed no pattern of differences in viewing the fine lines and/or dots of each species images on the eight-form diatom test plate. Among various potential factors that might affect the analysts' performance of fiber counts, this study supports the greater contrast caused by the different phase plate absorptions as the main cause of high counts for the AIHA PAT chrysotile slides using the DM objective. The comparison of fiber count ratios (DM/standard) between the AIHA PAT chrysotile samples and chrysotile field samples indicates that there is a fraction of fibers in the PAT samples approaching the theoretical limit of visibility of the phase-contrast microscope with 3-degree phase-shift. These fibers become more clearly visible through the greater contrast from the phase plate absorption of the DM objective. However, as such fibers are not present in field samples, no difference in counts between the two objectives was observed in this study. The DM objective, therefore, could be allowed for routine fiber counting as it will maintain continuity with risk assessments based on earlier phase-contrast microscopy fiber counts from field samples. Published standard methods would need to be modified to allow a higher aperture specification for the objective.