Respirators sizing

Partieles in the respirable size range, i.e. about 0.5-7 pm, will, onee dispersed, remain airborne for extended periods. Indeed sinee tliey are sensitive to slight air euiTents tliey may be permanently suspended. 

Paraffin wax fume Paraquat, respirable sizes Parathion... 

The LC50 values of methyl parathion have been established in rats. A 1-hour LC50 of 200 mg/m and a 4-hour LC50 of 120 mg/m for males were determined by Kimmerle and Lorke (1968). One-hour LC50 values of 257 mg/m for male rats and 287 mg/m for female rats were determined for 70-80% pure methyl parathion by EPA (1978e) the rats were exposed to aerosols of respirable size. Survivors of toxic doses recovered clinically by 10-14 days postexposure. Sex-related differences in acute mortality of rodents have also been observed after exposure to methyl parathion by other routes (Murphy and Dubois 1958). 

Before discussing the three categories of delivery device, the nature of the emitted aerosol will be considered. Droplet formation may be characterized in terms of the nature of the propulsive force and the liquid being dispersed, and this topic is dealt with for specific situations in the following sections. However, dry particles, which are delivered from suspension in pMDIs or from DPIs alone or from a blend, must be prepared in respirable sizes. The production of respirable aerosol particles has traditionally been achieved by micronization of the drug [25]. This... 

Knowing the results of epidemiology studies on the association between diesel exhaust exposure and lung cancer, and animal studies on the toxicity of two types of soot, what can we conclude concerning the toxicity to humans of soot associated with fires Combustion processes produce small, respirable size soot particles. The composition of the soot from fires can vary widely with the condi-... 

Dust Airborne solid particles (an aerosol) that range in size from 0.1 to 50pm and larger in diameter. A person with normal eyesight can see dust particles as small as 50 pm in diameter. Smaller airborne particles cannot be seen unless strong light is reflected from the particles. Dust of respirable size (below 10 pm) cannot be seen without the aid of a microscope. 

It has recently been noted that if copper-induced MEE does occur, it is a very rare event. Despite extensive use of copper in many industries, only a handful of MEE cases are reported in the literature. Further limitations of these reports include possible contamination of the fume by other substances more likely to have caused MFF, atypical symptoms and complaints, and lack of consistency among types of work associated with symptoms. One reason that MFF may have rarely been described after copper exposure is that aerosolized copper particulates formed during welding, thermal cutting, and other hot work are mostly greater than respirable or submicron size. Studies of air in a brass foundry found that only 5% of the total copper exposure was respirable (aerosol less than or equal to 1 )im), whereas 40% of the zinc oxide exposures were to an aerosolized particulate of respirable size. ... 

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for particulate matter containing no asbestos and <1% crystalline silica is 3mg/m for respirable size fraction and lOmg/m for inhalable mass fraction. Exposure to any substance in the particulate mass that has a designated TLV should be controlled to that value. 

In guinea pigs, aerosols of larger, but still respirable, size were more lethal than those of... 

It should be noted that the sampler used in the study, (a stacked filter unit), collected only particles less than 15pm aerodynamic diameter, i.e. particles of respirable size. State standards for TSP are based on High Volume samplers which have no inlet cutoff. Hence, particles as large as 100 microns can be captured by these instruments. Therefore, measurements made in this study may not indicate whether particulate standards have been violated, since a significant portion of the total suspended particulate mass is not measured by the stacked filter unit (SFU). 

On the other hand, particles from fossil fuel combustion and gas-to-particle conversion are generally much smaller (< 2.5-/Am diameter) and fall in the respirable size range. These particles can reach the alveolar region where gas exchange occurs. This region is not coated with a protective mucus layer, and here the clearance time for deposited particles is much greater than in the upper respiratory tract hence the potential for health effects is much greater (Phalen, 1984). 

Talcott, R and W. Harger, Airborne Mutagens Extracted from Particles of Respirable Size, Mutat. Res., 79, 177-180 (1980). 

Diesel emission particulates, mostly of respirable size, are assuming increased importance as a source of atmospheric particulate pollutants. They may also present significant hazard in certain working environments such as bus garages and mines. 

The preparation of synthetic atmospheres for nonreactive gases and vapors is relatively straightforward, but the preparation of fumes, aerosols, and particulates is considerably more difficult. For purposes of industrial hygiene sampling, a polydisperse aerosol containing respirable-size particles is required. 

The delivery of pharmaceutical aerosols as a dry powder is no longer perceived as the second best method to deliver drugs to the lung. This is because of the mounting technologies, which are capable of making stable powders of respirable size and devices competent to deliver accurate doses and versatile payload. 

However, even with this limited data set it was possible to state that emissions from high-temperature sources are contained in particles which are in the (respirable) size range that can be trapped in the respiratory region. If the data contained in Table III and Table IV are compared for the elements that both techniques could detect (Fe and Zn), then the total atmospheric loading for Fe is 0.108 g/m by NAA and 0.098 g/m by AAS and for Zn is 0.037 g/m by NAA and 0.028 g/m by AAS. These samples were obtained on different days and yet the total loadings were comparable. However, the distribution of metals in the various particle... 

This study has confirmed that metals from high temperature combustion sources are emitted in the form of respirable-sized particles and the air burden shows a definite time dependence. These results presented in this study are representative of a series of samples taken during the period May 1976-November 1977. Because of limitations in sampling equipment. 

There has been sustained interest in the development of analytical methods for realtime monitoring of environmental pollutants in recent years. Semi-volatile organic compounds tend to be adsorbed onto the surface of aerosol particles of respirable sizes and pose potential health hazards. Conventional methods used for the analysis of organic compounds that are present on the surface of aerosol particles are based on particle collection followed by extraction and chromatographic analysis of extracted species [90,91]. These methods require large amounts of sample and long analysis times. 

Cormleyu I, Addison J. The in vitro cytotoxicity of some standard clay mineral dusts of respirable size. Clay Miner 1983 18(2) 153-163. 

Bergman and M. S. Paterson, Silica powders of respirable size. I. Preliminary studies of dissolution rates in dilute sodium hydroxide, /. Appl. Chem. 369, 1961. 

Volcanoes Volcanoes are natural events that result in the release of huge quantities of particulates into the atmosphere. I35 On May 18, 1980, Mount Saint Helens, in Washington state, erupted violently. Volcanic ash expelled during the eruption was of respirable size and resulted in a large number of respiratory injuries to those exposed J36 ... 

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