Measurement and analysis of chemically changed mineral fibers after experiments in vitro and in vivo.

Asbestos, as well as other natural and man-made mineral fibers used for in vitro and in vivo experiments, must be described and defined physically and chemically as exactly as possible before any application. The interactions of fibers with the physical, chemical (air, water, etc.) and biological (cells, tissues, etc.) environments cause important changes in fiber chemistry and crystalline structure. Also, these should be detected as precisely as possible after each experiment. Our recent investigations dealt with the development of a complex analytical system for such measurements and with some applications of these analytical procedures for fibrous material sampled in the environment and from biological materials. Chemical and physical microanalyses of asbestos and glass fibers obtained by environmental sampling (air, water) and from human and animal tissue have shown chemical and crystalline changes in these particles. Scanning electron microscopy, electron microprobe analysis and mass spectrometry analysis were used in these investigations. A partial or total leakage of elements could be observed. The leakage of elements in fibers is of a statistical nature. Some fibers remained chemically unchanged; in some fibers some elements were partially leached; and in some fibers the majority of metallic elements were leached. The potential meaning of this effect is also discussed.

Chemical mixtures in atmospheric aerosols and their correlation to lung diseases and lung cancer occurence in the general population.

Several chemical and epidemiological investigations have been done during the last decade showing that correlations do exist between ambient air concentrations of aerodisperse (particulate) pollutants and the health risk for the general population. Based on these recently published results, there are on-going discussions and considerations proposing changes in air particulate pollution definitions, measurement, analysis and air quality standards. In this review, we summarize the "chemical standpoint" of this problem and its impact on the measurement strategy and air quality standard assessment.

On the physics, chemistry and toxicology of ultrafine anthropogenic, atmospheric aerosols (UAAA): new advances.

The existing data about the epidemiology, toxicology, physics and chemistry of atmospheric particulate pollutants were recently essentially completed and extended. They do support the hypothesis that the fine and very fine dispersed fraction of the atmospheric anthropogenic aerosols (UAAA) are responsible for the aggravation of the health risk potential of the polluted atmosphere during the last decade. The recently published data dealing primarily with the physics, chemistry, sampling and analysis of these highly dispersed particulate air pollutants are reviewed, summarized and critically evaluated.

Natural fibrous zeolites and their carcinogenicity-a review.

More than 50 cases of pleural mesothelioma have been reported during the period 1974-1978 in a relatively small area of Turkey, centered in and around the villages of Karain and Tuzköy, in the province of Cappadocia. The area of Karain and Tuzköy is covered with volcanic tuffs, in which asbestos, glass and zeolite fibers were detected. The inhaled dusts of these fibrous materials might be the cause of the high mesothelioma rate. The most important publications on this problem are reviewed and the results of our own examinations are discussed.

On the release of asbestos fibers from weathered and corroded asbestos cement products.

The controversy on whether weathered and corroded asbestos cement products are emitting biologically significant asbestos fiber concentrations in ambient air has not been resolved. Nor is it known if the weathered and corroded asbestos cement products release asbestos fibers which have the same carcinogenic potency as "standard" chrysotile. The purpose of this research project was to develop a method for sampling and measuring asbestos fiber emissions from solid planar surfaces (i.e., roofs and facades) consisting of asbestos cement products and to develop methods for studying the physical and chemical changes and the carcinogenic potency of the emitted fibers. Using this method asbestos fiber emissions in ambient air have been measured in the FRG during 1984/1986. The emissions of asbestos fibers longer than 5 microns were in the range 10(6) to 10(8) fibers/m2.hr. The ambient air concentrations of these asbestos fibers were for the most part less than 10(3) fibers/m3. It was shown that the emitted asbestos fibers were chemically changed and it was shown with animal experiments that their carcinogenic potency did not differ from the carcinogenicity of "standard" chrysotile fibers.

Asbestos fibre release by corroded and weathered asbestos-cement products.

A description is given of portable equipment and a method of sampling and measuring asbestos fibre emissions from solid plane surfaces of asbestos-cement products (roofs and facades). Asbestos-cement products, e.g., roof tiles, contain as much as 11-12% of chrysotile asbestos. As a result of continuing exposure to the weather and to acid rain, the surface of asbestos-cement products becomes corroded and weathered. Cement particles, asbestos fibres and agglomerates of particles and fibres are therefore released from the surface and dispersed in air and water. The method described has been used to measure asbestos fibre emissions and ambient air concentrations in the Federal Republic of Germany over the period 1984-1986.

[Emission measurements of fibrous dust in the Federal Republic of Germany. Fibrous emissions from brake linings of motor vehicles]. / Immissionsmessungen von faserigen Stäuben in der Bundesrepublik Deutschland. Faserige Immissionen aus Bremsbelägen der Kraftfahrzeuge.

The brake and clutch linings of automobiles contain 10 to 70% of asbestos, mainly chrysotile. They are therefore considered to be a significant source of carcinogenic asbestos fibers in ambient air. This could be confirmed by measurements done in urban ambient air in different parts of West Germany. Asbestos fiber concentrations till 1000 fibers/m3 (for fibers longer than 5 microns) were found. It could be also shown, that materials used in the brake lining production as well as dust emitted during car braking contained asbestos fibers with high carcinogenic potency.

Some aspects of analysis of single fibers in environmental and biological samples.

Nuclepore filters were used for sampling and evaluation of fibrous particles in ambient air, in liquids and in biological materials. The fiber counting and fiber size measurements were done by means of SEM-methods. The number of fibers and the distributions of fiber lengths and diameters were plotted. The specific identifications of asbestos, glass and other mineral fibrous particles were made by electron microprobe analysis. Certain elements proved to be approximative identification factors for different fibrous minerals in ambient air, in liquids, on material surfaces, or in biological materials. For ambient air, asbestos, glass, and many other inorganic fibrous particles were found in the urban atmosphere as well as in the atmosphere of remote regions. Fibrous gypsum, fibrous ammonium sulfates, fibrous silicates, fibrous mica, and quartz were identified among these particles. Even in remote ambient air, relatively high concentrations of inorganic fibrous particles could be measured.

Aerosols and protective clothing.

A complex test method for evaluating protective apparel in aerosol hazard conditions has been developed and examined under laboratory conditions. The effectiveness of the barrier or "collection efficiency" of aerosol protective apparel (APA) depends upon its structural properties such as porosity, thickness, and permeability as well as on its hydrodynamic properties, i.e., pressure drop. Aerosol generating systems and methods of measuring penetration and evaluating data are described. A method of testing protective apparel materials using a standard asbestos aerosol then is described and discussed in detail.

Size-selective preparation of inorganic fibers for biological experiments.

Size-selective procedures were developed for the preparation of fiber fractions of uniform size of chrysotile, crocidolite, amosite and glass. The raw material was first ground to a suitable fineness, then prescreened in a vibrating bed aerosol generator and finally suspended in liquids by ultrasonic agitation. Size-separation was then achieved by slow sedimentation. In addition, fiber fractions of exceedingly long-fibers were prepared by utilizing a vibrating sieve in the gas phase or in liquids.

On the milling and ultrasonic treatment of fibres for biological and analytical applications.

The possible physical and chemical changes that could occur in fibre samples subjected to milling and ultrasonication during their preparation for biological applications are discussed. Milling changes not only size distribution but also the shape and crystal structure of fibres; ultrasonication had no influence on crystal structure. Changes in size and particle concentration were seen in samples of amphibole asbestos and glass fibres and to a much greater extent in chrysotile fibres.

On the problem of milling and ultrasonic treatment of asbestos and glass fibers in biological and analytical applications.

In preparing fiber suspensions for biological applications, as well as in many analytical procedures, the fibers--e.g. asbestos and glass--often have to be mechanically diminished and ultrasonically treated. Such treatments may sometimes produce changes in the physical and chemical properties of the original fiber samples. Measurements have been made to estimate the changes in fiber shape, size, and structure after milling and ultrasonic treatment. The results have shown that milling procedures not only change the size distribution, but also the particle shape and crystal structure of asbestos fibers. Ultrasonic energy (50 kHz) had practically no influence on the crystal structure, but in long-term applications it produces changes in fiber size and fiber concentration.

[A vibrating bed aerosol generator for fibrous and powder dust particles (author's transl)]. / Ein Schwingbett-Aerosolgenerator für faserige und pulverförmige Stäube

A fluidized bed with defined mechanical vibrations has been used for the pulverization of powders of fibrous and spherical particles. By means of this process, it was possible to prepare for practical purposes useful aerosols with constant concentrations. In certain size ranges the concentrations as well as the fiber and particle size distribution were adjustable and could be varied as a function of physical properties of the vibrating fluidized bed.

[Investigations on the carcinogenic burden by air pollution in man. XVI. Formation of combined carbon black and benzo(a)pyrene aerosol (author's transl)]. / Untersuchungen über die karzinogene Belastung des Menschen durch Luftverunreinigungen. XVI. Herstellung von Mischaerosolen aus Russ und 3,4-Benzpyren.

Two methods for the preparation of carbon black aerosols have been investigated: incomplete combustion of acetylene, acetylene + benzene and other hydrocarbons as well as a "resublimation" of amorphous carbon. The first method was developed for generating soot aerosols in animal experiments, but the latter method needs more basic investigation. Using radioactive acetylene and benzene the produced soot aerosol could be labelled by 14C. Benzo(a)pyrene aerosol was prepared by means of a vapour condensation and was also radioactive labelled. With a combination of both generators, a combined carbon black and benzo(a)pyrene aerosol was prepared. The benzo(a)pyrene amounts bound to the soot were in the range of from 1 ng to 50 microgram per 1 mg soot. Experiments dealing with adsorption and desorbtion of benzo(a)pyrene on soot in the gas phase have shown, that benzo(a)pyrene is relatively tightly adsorbed and cannot be easily or completely desorbed.