Anthophyllite asbestos from Staten Island, New York: Longitudinal fiber splitting.

Asbestos ore was sampled from a historical anthophyllite mine in Staten Island, New York. High-resolution transmission electron microscopy (HRTEM) was used to image the structure of nineteen fibers of the anthophyllite asbestos. The anthophyllite was characterized by a high level of chain width disorder, involving wide chain multiplicity faults (CMFs) that were frequent in fibers, randomly spaced, and ranged from one to eight chains in width. This chain width disorder was manifest by streaking of electron diffraction rows of chain width. The anthophyllite asbestos fibers were found to be produced by longitudinal splitting rather than crystal growth. Such splitting is a function of cleavage along CMFs rather than crystal boundaries. The morphology of the fibers is consistent with anthophyllite asbestos mined in Finland associated with lung cancer and mesothelioma. These findings may have regulatory implications.

Widespread elevated iridium in Upper Triassic-Lower Jurassic strata of the Newark Supergroup: implications for use as an extinction marker.

Anomalous levels of iridium in sedimentary strata are associated with mass extinction events caused by impact events. In the case of the end-Triassic extinction event, the anomalies as well as the extinctions are linked to the eruption of the Central Atlantic Magmatic Province (CAMP) flood basalts. We report new data on concentrations of iridium in continental strata of the Fundy, Deerfield, Hartford and Newark basins, both above and below the oldest CAMP flows in these basins, that demonstrate that these anomalies are more common than previously known. We conclude that the enrichments were at least in some instances likely derived locally by concentration due to leaching directly from the lavas into sediments proximal to the CAMP flows due to post-eruptive hydrothermal activity. In other instances, the enrichments likely record the global fallout of aerosols and/or ash particles during the eruptions of the CAMP basalts. The common association of the highest levels of enrichment with organic matter suggests either redox control or stabilization by formation of organometallic complexes following post-eruptive redistribution. These findings demonstrate the importance of considering the distribution and magnitude of iridium anomalies in considering the source of the iridium and possible extinction mechanisms.

Tremolite-actinolite fiber coatings of sub-nanometer silica-rich particles in lungs from deceased Quebec miners.

Tremolite-actinolite (TA) fibers from the lungs of deceased former Quebec mine workers were found to be coated with sub-nanometer particles. Qualitative chemical analyses were performed on the particles indicating that they were composed of silicon and oxygen. The crystal lattice structure of all amphibole minerals, including the TA series, is arranged as pairs of linear chains of SiO4 tetrahedra that are linked together to form double chains. Our observations of the TA fibers from miner's lungs, made using a high-resolution transmission electron microscope, indicated that the tetrahedral silica chains were progressively split, forming dispersed sub-nanometer particles. The non-tetrahedral sites were removed at the surface of the TA fibers, presumably by the oxidation process involved in attempted phagocytosis, which also resulted in fragmentation of the tetrahedral chains. It was found that the silicon-rich particles (SRPs) were variable in diameter, consistent with fragments formed from the splitting of the tetrahedral chains. The TA fibers from lungs displayed coatings and linear interior zones of SRP parallel to the planes of longitudinal fiber splitting. The literature on very small nanoparticles is consistent with deep penetration of SRP into cell DNA interiors, oxidative stress, and carcinogenesis.

Analytical transmission electron microscopy of amosite asbestos from South Africa.

Using the recognized amosite standard, we have performed transmission electron microscopy (TEM), scanning electron microscopy (SEM), and chemical analyses. We use high-resolution transmission electron microscopy (HRTEM) and zone-axis selected area electron diffraction (SAED) to describe the molecular structure of the fibers. We find that both microscopic observational evidence and statistical dimensional characteristics indicate that the amosite fibers are formed by longitudinal splitting, with surfaces produced by fine twinning and lateral boundaries formed by parting parallel to the planes of double and triple sheets of amphibole chain structures. Our findings indicate that amosite would not be regulated under current asbestos regulations, which define amphibole asbestos as whole crystals that are not split and that form fibril bundles, not found in our standard. However, it is fully documented that amosite causes mesothelioma, lung cancer, and asbestosis.

Laryngeal Lavage: A Potential Method of Evaluation of Amphibole Fiber Exposure.

OBJECTIVE: Our objective is to propose a simple procedure for evaluating potential recent heavy exposure to tremolite. METHODS: One day after an accidental exposure to tremolite in rock dust, sputum was sampled; 3 months later a laryngeal lavage was taken. The sputum was examined with scanning electron microscopy (SEM); the lavage was examined with transmission electron microscopy (TEM). RESULTS: The sputum was found to contain abundant tremolite while the lavage contained very thin, high aspect-ratio fibers, many in the "Stanton Fiber" range. The abundance of tremolite from the larynx suggests accumulation. The thin fibers exhibit splitting from thicker fibers that were in the lungs. CONCLUSIONS: Laryngeal lavage may be an important index of asbestos exposure and is a less complex and more diagnostic alternative to bronchoalveolar lavage or sputum sampling.

Analytical Transmission Electron Microscopy of Amphibole Fibers From the Lungs of Quebec Miners.

The objective of this study is to describe the morphology, molecular structure, and chemistry of amphibole fibers from lung samples from workers in the chrysotile mines at Asbestos and Thetford Mines, Quebec. A fibrous tremolite-actinolite contaminant in an asbestos ore sample from the deposit at Asbestos was used for comparison. Lattice imaging was performed using high-resolution transmission electron microscopy (HRTEM). Silica-rich amorphous coatings (SIRA) that may be related to carcinogenesis are noted on all of the HRTEM photographs of fibers retained in lung, but not on fiber surfaces of the bulk comparison sample. Fibers found in lung samples and in a bulk comparison sample are produced primarily by splitting of thicker crystals and, as such, might not be considered asbestos fibers on the basis of certain mineralogical criteria. Implications of SIRA coatings with respect to carcinogenesis are worthy of further study.

Zircon U-Pb geochronology links the end-Triassic extinction with the Central Atlantic Magmatic Province.

The end-Triassic extinction is characterized by major losses in both terrestrial and marine diversity, setting the stage for dinosaurs to dominate Earth for the next 136 million years. Despite the approximate coincidence between this extinction and flood basalt volcanism, existing geochronologic dates have insufficient resolution to confirm eruptive rates required to induce major climate perturbations. Here, we present new zircon uranium-lead (U-Pb) geochronologic constraints on the age and duration of flood basalt volcanism within the Central Atlantic Magmatic Province. This chronology demonstrates synchroneity between the earliest volcanism and extinction, tests and corroborates the existing astrochronologic time scale, and shows that the release of magma and associated atmospheric flux occurred in four pulses over about 600,000 years, indicating expansive volcanism even as the biologic recovery was under way.