Toxicity Dust”

Health and Safety Factors. Terephthahc acid has a low order of toxicity. Inhalation by rats for 6 h/d, 5 d/wk for 4 wk produced no fatahties at a dust exposure level of 25 mg/m. The mean acute oral toxicity for rats is over 18 g/kg (86), and for mice over 6 g/kg (87). When terephthahc acid was fed as 3% of the diet to rats, urinary calcuh formed in 90 d, some of which led to cancer. High doses of terephthahc acid lead to formation of calcium terephthalate at levels exceeding its solubihty in urine. This insoluble material leads to the calcuh and provides a threshold below which cancer is not observed (88). Normal precautions used in handling industrial chemicals should be observed with terephthahc acid. If ventilation is inadequate, a toxic-dust respirator should be used to avoid prolonged exposure. 

Fabric filters can be more costly to operate and maintain than electrostatic precipitators, cyclones, and scrubbers however, fabric filters are more practicable for filtration of specific dusts. For example fabric systems are the typical control method for toxic dusts from insecticide manufacturing processes, salt fumes from heat treating, metallic fumes from metallurgical processes, and other applications. Any other control method may not be as efficient, nor economically feasible for such applications. 

Health Hazards Information - Recommended Personal Protective Equipment U.S. Bu. Mines approved toxic dust mask chemical goggles rubber gloves neoprene-coated shoes Symptoms Following Erqrosure Inhalation produces slight toxic effects. Contact with eyes irritates eyes and causes skin rash General Treatment for Exposure INHALATION remove to fresh air. EYES wash with water for 20 min. call a physician. SKIN wash with water Toxicity by Inhalation (ThresholdLimit Value) Data not available Short-Term Exposure Limits Data not available Toxicity by Ingestion Grade 2 oral rat LDjq 820 mg/kg Late Toxicity Data not available Vapor (Gas) Irritant Characteristics Data not available Liquid or Solid Irritant Characteristics Data not available Odor Threshold Data not available. 

Air cleaning (dust collection) can be cost effective for LVHV systems handling valuable dusts. Care must be taken when handling potentially toxic dusts from air cleaners. Regular, routine reconditioning of fabric filters (e.g., by automatic shaking or pneumatic pulsing) is impottant. This can be accomplished on a set maintenance schedule or as a function of pressure drop across the fabric filter. It is not recommended to recirculate airflow back to the workplace because of the low air volume and potential hazards in the event of filter failures. 

COSHH (Control of Substances Hazardous to Health) UK legislation regulating toxic dusts, vapors, and gases. 

Partial enclosure An enclosure used for work with toxic dusts, gases, or vapors in which one or more of the sides may be open to the remainder of the work area. 

A dust cloud comprising a distribution of particle sizes soon fractionates, e.g. visible matter settles to the ground in a few minutes. Hence the size distribution of airborne particles may differ significantly from that of the source material. (This is particularly relevant to occupational hygiene measurements involving toxic dust emissions.)... 

Heterogeneous catalysts are often located at the top of a reactor and manipulated with temporary handling equipment. To avoid exposure to toxic dust, local ventilation should be installed if this is impracticable, scrupulous use of personal protective equipment and rigid compliance with systems-of-work are essential. Respiratory equipment may include self-contained or line-fed breathing apparatus. 

Three classes of dust can exist in the workplace, namely, toxic dusts, inert dusts, and proliferative dusts. We have already seen the effects of some of the toxic dusts, such as lead. The other two groups are considered below. 

More serious than dermatoses caused by skin contact with Tetryl, TNT, DNT, Hg-Fulminate, solvents etc, during explosives and ammunition production, are exposures to toxic dusts, fumes and vapors. Among these are TNT, DNT, oxides of N, Pb-dusts and vapors, and solvent vapors. Special skin cleansing agents and solns for detecting these harmful materials on the skin are discussed in Ref 1... 

Incompatible Waste (1) A hazardous waste unsuitable for placement within a specific portion of a landfill because it may cause containment material to corrode or decay or, when combined with other wastes, might produce heat, pressure, fire, explosion, violent reaction, toxic dusts, mists, fumes, or gases. (2) Hazardous wastes which, if mixed, would become more hazardous than either waste individually. 

Environmental Considerations. The principal environmental problem is the prevention of particulate dust emission, which can be handled by cloth filtration equipment. Filtration of taphole fumes consisting of submicrometer particles, which rapidly dog the filtration media, is both difficult and expensive. Dust collectors operating at low air to cloth ratios are required. Dust created in material handling equipment is of relatively large particle size and easily handled by doth filtration. Treatment of the furnace CO gas stream is complicated by the high temperature of the gas, its explosiveness, toxicity, dust concentration, and partide size. 

Glazes should be prepared where adequate ventilation is available. If glazes are routinely prepared from powders, a face mask should be used. Another option, if available, is to use a plain-opening exhaust hood or wear a toxic-dust respirator approved by the National Institute for Occupational Safety and Health. Also, gloves should be worn during the preparation and application because glaze substances can be irritating to the skin. 

Selecting a flame retardant for an adhesive system has many ramifications, depending on the formulation being modified, the end use, how it will be processed, and the cost/performance ratio. When one is choosing a flame retardant, characteristics such as water extraction, particle size, viscosity, toxicity, dusting, uniformity, as well as economics must be considered. The materials chosen to perform the function of flame retardation must not interfere with the final product s performance. The major problem with incorporating flame retardants in adhesives is that very often a significant amount is required, and they interfere with the other properties of the adhesive and contribute to the cost. This is why bromo bisphenol epoxy resins are often employed in flame-retardant epoxy adhesives. 

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