Size Distribution and Rate of Production of Airborne Particulate Matter Generated during the Cutting of Metals

Abstract

During deactivation and decontamination activities, thermal cutting tools, such as plasma torch, laser and gasoline torch, are used to cut metals. These activities generate fume particles and other particulates that are of respirable size range (size < 10 μm) and inhaled by workers. Inhaling these metal fumes reportedly causes ill health effects such as acute respiratory syndrome and chromosome damage in lymphocytes when adequate respiratory protection is not used. In the nuclear industry, metals may be contaminated with radioactive materials. When they are cut, as in glove box size reduction, high concentrations of airborne transuranic particles are produced. The dose delivered to the respiratory tract depends on the size distribution of the airborne particulates (aerosols) and their concentration and radioactivity/toxicity. The concentration of airborne particulate matter in an environment is dependent upon the rate of their production. Thus, measuring aerosol size distribution generation rate is important for (1) the assessment of inhalation exposures of workers, (2) the selection of respiratory protection equipment, and (3) the design of appropriate filtration systems. Measurements of the particles generated during cutting of metal plates with a plasma arc torch revealed the presence of particles with bimodal size distribution. The mass median aerodynamic diameters of particles was close to 0.2 μm and 7 μm. This study presents data regarding the metal cutting rate, particle size distribution, and their generation rate, while using different cutting tools and metals. INTRODUCTION In industry, different thermal cutting tools (e.g., laser cutting, plasma torch, gasoline torch) are used to cut metals. These cutting methods generate particles of different sizes, which become airborne and are inhaled by workers. Inhalation of mixed metal fumes from various materials, such as aluminum, antimony, beryllium, cadmium, copper, iron, zinc, lead, magnesium, manganese, platinum, selenium, silver, tin, and vanadiun, reportedly cause ill health effects such as acute respiratory syndrome (Ellenhorn, 1997; Taylor, 1997). Jelmert et al. (1994) has reported chromosome damage in lymphocytes of stainless steel welders. Department of Energy's (DOE’s) deactivation and decontamination (D&D) activities involving cutting of radioactive materials pose additional problems associated with inhalation of radioactive aerosols. In DOE's D&D activities, workers' exposures are minimized by enforcing respirator use. The type of respirator that will be used for a particular operation depends on a number of factors that include the concentration of airborne radionuclides in the working environment, and particle size distribution. The concentration of airborne particulate matter in an environment is dependent upon the rate of production and removal, the latter depending on ventilation (air changes per unit time). The rate of generation of the respirable particulate matter is determined by the rate at which different metals are cut by a cutting tool, and the fraction of the metal that become respirable (aerodynamic diameter < 10 μm) when released in the kerf. Particle size distribution determines what fraction of the inhaled particles will deposit in which compartment of the respiratory tract. Thus, for assessment of inhalation exposures due to metal cutting, it is important to determine rate of cutting of metals by different tools, rate of generation of particulates, the fraction of the particulate matter that becomes respirable as well as the size distribution of the respirable fraction. A number of studies have been conducted by various researchers (Newton et al., 1981-82; 1987; Hoover et al., 1982; 1986; Windelberg et al., 1987; Steiner, 1988; Lillienberg and

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Cite this paper

@inproceedings{Dua2000SizeDA, title={Size Distribution and Rate of Production of Airborne Particulate Matter Generated during the Cutting of Metals}, author={Surendra K. Dua and Carmen A. Aponte and Anil K. Srinivasamurthy and Kunal Rupani and Ali Ebadian}, year={2000} }