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Biomedical subjects

A M Langer

Publications and source records attributed to A M Langer.

At least 55 records · Page 3Linked to original sources
PubMed1979

The contamination of Lake Superior with amphibole gangue minerals.

Iron ore called taconite is mined in the Biwabik Iron Formation in the Eastern Mesabi region of the Mesabi Range, in eastern Minnesota. After mining, ore is shipped to Silver Bay, Minnnesota for processing and wet magnetic extraction. Tailings from the process are dumped, as a slurry, into a man-made containment delta constructed in Lake Superior. Submicroscopic amphibole fibers and/or cleavage fragments, a component of the gangue, apparently escape from the delta at Silver Bay, and enter Lake Superior. These particles contaiminate the potable water supplies of municipalities drawing directly from the lake. One of the gangue minerals is the amphibole grunerite, whose asbestiform variety is called amosite. Major emphasis of this study was directed at identification of submicroscopic particle pollutants, based on morphology, structure and chemical composition. Quantitative determination of fibrous amphibole phases, present in a range of water samples, was undertaken. Transmission electron microscopy, selected area electron diffraction, and an electron microprobe technique was used for identification and enumeration and this information was compared with data sets determined from standards. Grunerite fiber and/or acicular cleavage fragments, in some instances indistinguishable from asbestiform grunerite, are present in the tailings, lake water and drinking water of a number of municipalities, a result of contamination of the lake at the Silver Bay milling operation. This amphibole is found in drinking water in concentrations which range from 0.6 to 2.8 X 10(6) fiber/liter. The risk to health, associated with direct ingestion of grunerite fiber is unknown and is extrapolated from the asbestiform grunerite (amosite) data base. The biological activity of other fibrous amphiboles observed, unrelated to any asbestiform silicate variety, is presently unknown and warrants investigation.

Asbestos↗
PubMed1978

Variation of properties of chrysotile asbestos subjected to milling.

Mechanical milling is commonly used to produce short chrysotile asbestos for experimental purposes. Such manipulation also decreases fiber crystallinity, alters Si-O and Mg-O interlayer bonding, induces coordination changes in the brucite layer, diminishes the ability of fiber to reduce specific free radicals and physisorb organic molecules, and decreases hemolytic potency and antagonist sorption capabilities. The degree of alteration is related to the time of milling. Results of biological experimentation with these materials must be interpreted with caution. Interaction mechanisms in the biological setting are suggested for chrysotile fiber.

Animals↗
PubMed1977

Environmental asbestos pollution related to use of quarried serpentine rock.

Crushed serpentinite quarried in Montgomery County, Maryland, has been extensively used for paving roads and other surfaces. The mineral assemblage includes antigorite or lizardite as well as chrysotile and tremolite. Air samples taken in the vicinity of serpentine-paved roads show that chrysotile concentrations are about 10(3) times greater than those typically found in urban ambient air in the United States.

Air Pollutants↗
PubMed1976

Consumer talcums and powders: mineral and chemical characterization.

Representative consumer talcums and powders, including 20 body powders, baby powders, facial talcums, and also one pharmaceutical talc, were analyzed to determine their mineralogical and chemical composition. Where known, all were formulated prior to 1973. Of the 20 products 10 contained detectable amounts of tremolite and anthophyllite, principally asbestiform, while some also contained fragmented forms of these minerals. The amounts ranged from tenths of a percent to over 14% by weight; two contained detectable amounts of chrysotile asbestos fiber. Eight contained quartz, seven ranging from 2 to 5%, with one as high as 35%. The analyses showed that the consumer products examined were rarely the pure mineral talc, but rather were mixtures of various minerals; some samples consisted of three to five minerals, only one of which was talc. Other common mineral phases included chlorite, platy serpentine, pyrophyllitem mica, and carbonate minerals. Kaolin additive was identified in two products. The single pharmaceutical talc examined contained only a trace amount of quartz. The chemical composition of these products, including both major oxide and trace element content, correlated with their mineral components. Four samples contained substantial concentrations of nickel, cobalt, and chromium, suggesting latice substitution or the presence of trace mineral phases. Geological provenance of the talcs may be ascertained on the basis of chemistry. Possible adverse health effects from intermittent use of these products, especially those that contain asbestiform and fragmented anthophyllite and tremolite, chrysotile, quartz, and trace metals, are presently unknown and warrnat evaluation.

Asbestos↗
PubMed1975

Exposure to asbestos in the use of consumer spackling, patching, and taping compounds.

Analysis of representative samples of spackling, patching, and jointing compounds, purchased at retail stores in the New York City area, has shown that some contain asbestos minerals as well as other biologically active substances. Measurements suggest that home repair work involving the use of such materials may result in exposure to dust at concentrations sufficient to produce disease.

Asbestos↗
PubMed1974

Approaches and constraints to identification and quantitation of asbestos fibers.

Asbestos fibers, members of complex crystal-chemical systems, possess some range in characteristic properties. Identification of fibers requires morphological, structural, and chemical data. Most current work centers on identification of single, sublight-microscopic fibers present as contaminants in a range of media. Constraints encountered in the analysis of such materials are: sample preparation of the differing media; level of fiber exposure (contamination); presence (kind and amount) of other particles; tissue types and their different preparation techniques; homogeneity of samples and their preparations; use of proper instrumental technique; time required for analysis, and quantitation.

Air Pollutants↗
PubMed1974

Inorganic particles in human tissues and their association with neoplastic disease.

An increased gastrointestinal cancer risk is associated with occupational exposure to asbestos fiber. Examination of tissues obtained from extrapulmonary organs of exposed workmen demonstrates the presence of asbestos fibers and bodies. The amount of fiber present in these tissues is many magnitudes less than encountered in the lung tissues from the same individuals. Ingestion of asbestos fiber in some environmental instances may approach in magnitude the amount resulting from occupational exposure. Disease factors are discussed.

Asbestos↗
PubMed1974

Research perspectives concerning asbestos minerals and their effects on biological systems.

The interaction of asbestos minerals with biological materials is under intensive investigation throughout the world today. Physical scientists should be responsible for the selection of fibers, and their varietal types, for biological studies; they should characterize these experimental materials physically and chemically to the level of sophistication which currently exists in their fields; they should develop definitive assay methods to monitor changes in such characteristics after biological residence; they should actively participate in the formulation of theories or mechanisms of particle interaction in biological systems.Physical scientists should begin the characterization of minerals in the environment and the determination of ambient fiber levels in air and potable water supplies. Such characterization of the environment requires standardized instrumentation and preparation techniques. Acquisition of data in numbers large enough to achieve statistical significance requires the development of automated counting strategies. Instrumentation and software have yet to be developed. The training of physical scientists in environmental areas is lagging behind current national needs and must be accelerated.

Asbestos↗
PubMed1974

The subject of continuous vigilance.

Asbestos disease in the occupational setting has been documented since the beginning of this century. Modern usage of asbestos fiber has brought with it concomitant and widespread contamination of the environment. The need to control asbestos is required in the forms of legislation and surveillance, to prevent the spread of asbestos disease into the general population.

Air Pollutants↗
PubMed1974

Electron microscopical investigation of asbestos fibers.

Examination of asbestos fibers by electron microscopical techniques enables the observer to distinguish among the fiber types by morphological and structural characteristics. Chrysotile asbestos fibers are composed of bundles of fibrils. Fibers are often curvilinear with splayed ends. Individual fibrils consist of a central capillary defined by an electron dense crystalline wall. With increasing time of electron bombardment, the capillary wall decreases in thickness, deforms, and is encapsulated in an electron translucent material. The change in electron opacity is considered to be a product of structural disruption brought about by dehydroxylation due to electron radiation. A well recognized sequential deformation pattern may be used for identification purposes.Amphibole fibers tend to be straight, splintery, and electron-opaque, although curved fibers are occasionally observed. Diffraction contrast figures are visible as dark bands moving parallel and at right angles to the fiber axis. Crocidolite forms the shortest and thinnest fibers, followed in size by amosite and anthophyllite. Size distribution characteristics of the amphibole fiber types are different. The selected area electron diffraction pattern for chrysotile is unique. Reflections range in forms from streaked to arcuate. Reflection intensity and shape are related to the degree of openness of the fiber bundle and the extent of physical degradation of the fiber. The amphibole asbestos fibers possess diffraction patterns having similar characteristics prohibiting individual identification. Microchemical analysis is required for identification in such cases.A discussion of the industrial hygiene threshold limit values for ampliphibole asbestos fibers is presented. The discussion is based on their differing size distribution characteristics.

Air Pollutants, Occupational↗
PubMed1974

Identification and quantitation of asbestos in talc.

The currently used analytical methods for identification, characterization and quantitation of asbestos fiber in consumer talcum products include polarized light microscopy, x-ray diffraction analysis, transmission electron microscopy with selected area electron diffraction and electron microprobe techniques. Light microscope methods have severe limitations imposed by the ultimate size resolution of the light-optical system. Small particles go unresolved; those marginally resolved may possess optical properties different from those properties cited in the literature; most optical properties, e.g., indices of refraction, are difficult to measure on small particles. In addition to these difficulties, talc fibers often possess optical properties different from those of talc plates, which further confound analysis. Light microscopy is recommended for use only as a preliminary tool on limited, large-sized, samples. Transmission electron microscopy is a good standard technique for visualization of contaminant asbestos fibers. Together with selected area electron diffraction, talc fibers may be easily differentiated from amphibole asbestos fibers on the basis of both morphological and structural characterization. Chrysotile fibers are easily distinguished on this basis as well. The amphibole asbestos minerals require chemical characterization to differentiate among the different fiber types. Probe analysis is mandatory for such fibers. The major drawbacks to electron beam instrumentation for the mineralogical characterization of talcum products are the time and effort required for data acquisition. These techniques do not lend themselves to routine study.X-ray diffraction analysis, utilizing the step-scan method, offers a relatively rapid, quantitative technique for gross fiber analysis. Based on comparison with standard specimens the fiber content of talcs may be quantitatively determined. It is essential to employ a specimen preparation technique which yields homogeneously dispersed particles. Tremolite may be determined at levels as low as 0.10% by weight, chrysotile 0.25%, and anthophyllite at 2.0% by weight occurrence in talc. The variance of these values depends upon many factors, including the mass absorption coefficient of the fiber types as compared to talc and selected diagnostic reflections and their relative intensities. Each of the above techniques is described in detail. A method for routine analysis of consumer talcum products is suggested.

Asbestos↗