Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 41-42.

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: Hot surface ignition temperature; self-heating; combustible liquid additives. Includes bibliographical references (leaves 134-135).

The durability in the lung of inorganic fibrous materials, such as asbestos and man-made mineral fibres, appears to be a major determinant of their pathogenic potential. However, studies have been inadequate in explaining differences in the physiological durability of such inorganic fibres. This study used an iterative approach to determine key factors affecting physiological durability of a soda-lime silicate bulk glass, A-glass, E-glass, Lead-glass, Cemfil and alumino-silicate ceramic fibres. The aims were to develop a) the current theoretical understanding of durability and b) a suitable in-vitro screening test for durability. Materials were exposed to simulations of the lung environment, which included a) exposure to Gamble's fluid, water, serum and other simulated fluids, b) long-term exposure to the intra-macrophage environment and c) exposure to rat lung. Durability was characterised by scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray microanalysis (EDXA). The use of secondary ion mass spectrometry (SIMS) was also explored, though further development was required in this area. Fibre behaviour depended on fibre composition and thenature of the exposure environment. The ceramic was durable in all environments, whilst A-glass, Lead-glass and the soda-lime silicate were prone to nucleophilic attack and leaching. The effects of in-vivo exposure were consistent with the response in-vitro. However, exposure to the intramacrophage environment in-vitro did not affect fibre durability and this surprising result should be investigated. Physiological durability was related to the ability of the fibre to resist nucleophilic attack and a hybridization bonding model was examined in order to explain the behaviour of some silicate glasses. It was recommended that models based on the molecular bonding were developed to encompass a wider range of materials. Occupational exposure and inhalation of asbestos fibre can cause lung disease and although the mechanisms of asbestos pathogenicity remain uncertain, attention has also focussed on the potential effects of other inorganic fibres. Comparative studies on behaviour of these materials in the lung have strongly implicated the durability and hence lifetime of the fibre to be a major determinant of the pathogenic potential. However, durability studies have generally been inadequate in explaining differences in physiological durability of inorganic fibres and hence provision of theoretical models. This study used a novel iterative approach to determine key factors affecting physiological durability of a range of glass and ceramic materials. The objective was to develop the theoretical understanding of the durability of inorganic fibrous materials in the lung and appraise in-vitro methods for determination of fibre durability to validate a suitable screening test. The durability of a range of glass and ceramic materials has been characterised using in-vitro and in-vivo simulations of the human lung environment; novel exposure systems have been developed and durability behaviour has been characterised by application of traditional analytical methods and by development and application of secondary ion mass spectrometry (SIMS) techniques. Appraisal of in-vitro simulations revealed that fibre behaviour depended upon fibre composition and exposure conditions' durability of the fibres in-vitro was related to model fluid pH. Fibre response in-vivo was rationalised by assuming localised pH variation. This work supports the use of a range of in-vitro exposure conditions to identify key determinants of fibre durability and to characterise chemical behaviour, and is critical of the use of single in-vitro screening tests which will reflect fibre behaviour under specific conditions. Resistance of the inorganic fibre network to hydrolytic attack was suggested as a key determinant of durability and a theoretical model was developed to predict this.

The act of dust sampling to characterise potential hazards in the respiratory tract is a process that requires initial removal of non-inspirable particles followed by separation into regional fractions. Particles that are not inhaled cannot deposit anywhere in the respiratory system. Furthermore, there is an important category of aerosol for which the conditions for potential injury is inhalation and deposition anywhere in the respiratory tract. Thus inspirable dust sampling is fundamental to all aerosol sampling for health risk evaluation. A proper estimation of inhalation exposure will need to examine the relationship between the inspiration efficiency of a sampler and particle size distribution of a dust cloud; and methods to collect a representative sample in the workplace.

In recent years there have been many reports of dust explosions associated with industries handling particulate materials. A study has been undertaken to investigate the influence of various transporting parameters of a pneumatic conveying system on the tribo-electrification of powders. These parameters include powder transportation velocity, powder flow rate, space charge field of the powder passing through the pipes, particle size, resistivity and relative humidity. The specific charge is a linear function of the transport air velocity. The specific charge reaches a saturation level as the powder flow rate increases and falls at high powder flow rates. The saturation specific charge of powder particles is determined by a self generated space charge field during normal pneumatic conveying. The tribo-charging can hence be controlled by controlling the space charge field. Hazardous conditions may arise when the charged powder enters a storage silo as explosible dust concentrations can result and, with the presence of an ignition source, a risk of fire and explosion exists. It is generally accepted that dispersed flammable dust clouds may be ignited by discharges from electrostatically charged conducting objects. These discharges can however be excluded if grounded conductive equipment is used. The question 'Can a flammable powder be ignited by the charge accumulated on the powder itself, even if the powder is handled in earthed conductive installation?' is investigated. The magnitude and incendivity of discharges from the surface of bulked powder and the dust cloud to probes is studied It is possible to obtain incendive discharges which are capable of igniting a propane/air mixture with a minimum ignition energy of 0.25 mJ. The experimental results from a laboratory scale rig show that the largest probability of ignition of propane/air/nitrogen are defined for moderate streaming currents and specific charge densities.

No description available.

MPH, Occupational Hygiene,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand / Introduction Coal mine workers are exposed to a mixture of dusts including coal dust and silica (as alpha quartz), in this respect the mixture of dusts is termed mixed coal dust. The illnesses commonly associated with the inhalation of mixed coal dust are (1) coal workers’ pneumoconiosis, (2) silicosis, and (3) chronic obstructive pulmonary disease. Objectives The main aim of this research report is to determine whether current dust levels in Mpumalanga coal mines were above generally recommended standards and to review information on the burden of coal associated diseases in the coal miners of Mpumalanga. The objectives of this research project are (1) to describe the coal dust and silica concentrations as measured by personal breathing zone sampling in Mpumalanga coal mines over the period 2003 to 2006 and (2) to describe the burden of coal-associated diseases reported by autopsy examinations received from NIOH Pathology Department and in the SAMODD data base in Mpumalanga coal mines over the period 2002 to 2006. Page 4 of 71 Methods Dust Personal breathing zone sampling data were obtained from gravimetric sampling programmes established according to the DMR – SAMOHP from fifty three coal mines in the Mpumalanga region. During the time of the study, the sampling programme strategies were co-ordinated by a central laboratory services: “Colliery Environmental Control Services”. The raw data were obtained from this laboratory for the periods 2003 to 2006 in Microsoft excel spread sheet format. Burden of disease NIOH - PATHAUT The annual reports of the NIOH on the autopsy data for the coal mining sector were obtained from the web site of NIOH. Sample data sheets were drawn up to extract only relevant information from the reports. DMR - SAMODD The DMR collects medical information from coal mines across South Africa, and this information was obtained from the local inspectorate. The data contained in the report were of all the mines in South Africa, a filter was applied in a Microsoft Excel spread sheet to extract the relevant information for Mpumalanga coal mines. Page 5 of 71 Results Dust There was a reduction in the recorded concentration of respirable dust levels in the collieries over the four year period 2003 to 2006. The average coal dust exposures fell from 1.9 mg/m³ in 2003 to 1.3 mg/m³ in 2006. The Department of Mineral Resources places emphasis on the 90th percentile and most of the sampling strategies are centred on this figure. Although the 90th percentile decreased from 4.82 mg/m³ to 3.02 mg/m³ (i.e. 1.8 mg/m³) over the four year period, this level is still unacceptable as it is above the required statutory limit of 2.0 mg/m³. Silica exposures also showed a reduction from an average of 0.047 mg/m³ in 2003 to 0.034 mg/m³ in 2006. Disease burden: PATHAUT Pulmonary tuberculosis - the number of employees at autopsy with pulmonary tuberculosis (PTB) decreased from 12 in 2002 to 8 in 2006, but there is not enough information to establish a trend over the five year period. Silicosis: - the number of employees at autopsy with silicosis was between 3 to 4 cases per year except in 2004 where there was an outlier of 11, but in general the cases stayed constant over the five year period. The rate of silicosis per 1000 Page 6 of 71 autopsies however indicates an increase over the five year period as the rate increased from 37 to 52. Emphysema: - the number of emphysema cases stayed fairly constant with 32 cases in 2002 and 30 cases in 2006, but with an increase in 2003 and 2004 to 42 and 43 respectively. The rate per 1000 autopsies increased from 294 in 2002 to 390 in 2006. Coal workers’ pneumoconiosis: - there was a decrease in coal workers’ pneumoconiosis from 2002 to 2006 from 10 to 2 cases, but there were 11 and 15 cases in 2003 and 2004. SAMODD Coal workers’ pneumoconiosis: - the total number of employees reported with Coal Workers Pneumoconiosis (CWP) decreased for the period 2003 to 2006, from 12 in 2003 to three in 2006. Chronic obstructive pulmonary disease: - No useful information was available for this illness. Silicosis: - One case was reported in 2002, and 2 cases in 2003 and 2004, no cases were reported for 2005. Tuberculosis: - with initially only three cases in 2002, cases increased during 2003 to 2005 to 53, 44 and 50 respectively. A reduction was observed in 2006 to 13 cases. Page 7 of 71 Conclusion There may be an overall reduction in the dustiness of the coal mining industry in Mpumalanga province as the arithmetic mean of the samples collected decreased from 1.9 to 1.3 mg/m³ over the four year period 2003 to 2006. The level of exposures to silica might be lower because the exposures reduced from a mean of 0.047 in 2003 to a mean of 0.034 mg/m³ in 2006. The recorded data suggest a decline in CWP; this is in line with international data from the United Kingdom, USA, Australia, Germany, France and Belgium. Pulmonary tuberculosis - was constant over the five year period based on limited autopsy data, but the SAMODD data base indicates a decline for the year 2006 but overall shows an increase in the number of tuberculosis cases in Mpumalanga coal mines. Silicosis cases were fairly constant, but the rate per 1000 autopsies increased by 15/1000 over the five year period. The number of recorded cases from the DMR SAMODD is too few to make any useful deductions. Emphysema numbers were constant, but the rate per 1000 autopsies increased by 96/1000 over the five year period. No useful interpretation can be made from the data received from the DMR on chronic obstructive pulmonary disease.

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