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Particulates respiratory tract

The likelihood that materials will produce local effects in the respiratory tract depends on their physical and chemical properties, solubiHty, reactivity with fluid-lining layers of the respiratory tract, reactivity with local tissue components, and (in the case of particulates) the site of deposition. Depending on the nature of the material, and the conditions of the exposure, the types of local response produced include acute inflammation and damage, chronic... [Pg.229]

Cilia Fine hairlike structures found in the membranes that line the respiratory tract that assist in particulate removal. [Pg.1421]

Implications to Humans. Acidic precipitation has not been observed with concentrations that pose a concern to human exposure. The acidic airborne pollutants in the particulate or gaseous forms such as the oxides of sulphur and of nitrogen, and the associated photochemical oxidant ozone, are inhaled. This may lead to the irritation of the respiratory tract, and subsequently to impaired lung function, aggravated asthma and bronchitis. [Pg.56]

Studies on the particulate distributions from compressed natural gas (CNG) or diesel-fuelled engines with diesel oxidation catalyst (DOC) or partial diesel particle filter (pDPF) have also been performed. The results obtained are used as data for the model, to study the particle penetration into the human respiratory tracts. As a result, the number distribution of particles in different parts of lungs can be modeled [99-101]. Understanding the particle formation and their effects and finding the methods to ehminate the formed particulates from exhaust gas contribute to a cleaner urban environment and thus to a better quality of life. [Pg.155]

The ICRP (1994b, 1995) developed a Human Respiratory Tract Model for Radiological Protection, which contains respiratory tract deposition and clearance compartmental models for inhalation exposure that may be applied to particulate aerosols of americium compounds. The ICRP (1986, 1989) has a biokinetic model for human oral exposure that applies to americium. The National Council on Radiation Protection and Measurement (NCRP) has also developed a respiratory tract model for inhaled radionuclides (NCRP 1997). At this time, the NCRP recommends the use of the ICRP model for calculating exposures for radiation workers and the general public. Readers interested in this topic are referred to NCRP Report No. 125 Deposition, Retention and Dosimetry of Inhaled Radioactive Substances (NCRP 1997). In the appendix to the report, NCRP provides the animal testing clearance data and equations fitting the data that supported the development of the human mode for americium. [Pg.76]

Table 24—Retention of particulate matter in the respiratory tract of standard man... Table 24—Retention of particulate matter in the respiratory tract of standard man...
During occupational exposure, respiratory absorption of soluble and insoluble nickel compounds is the major route of entry, with gastrointestinal absorption secondary (WHO 1991). Inhalation exposure studies of nickel in humans and test animals show that nickel localizes in the lungs, with much lower levels in liver and kidneys (USPHS 1993). About half the inhaled nickel is deposited on bronchial mucosa and swept upward in mucous to be swallowed about 25% of the inhaled nickel is deposited in the pulmonary parenchyma (NAS 1975). The relative amount of inhaled nickel absorbed from the pulmonary tract is dependent on the chemical and physical properties of the nickel compound (USEPA 1986). Pulmonary absorption into the blood is greatest for nickel carbonyl vapor about half the inhaled amount is absorbed (USEPA 1980). Nickel in particulate matter is absorbed from the pulmonary tract to a lesser degree than nickel carbonyl however, smaller particles are absorbed more readily than larger ones (USEPA 1980). Large nickel particles (>2 pm in diameter) are deposited in the upper respiratory tract smaller particles tend to enter the lower respiratory tract. In humans, 35% of the inhaled nickel is absorbed into the blood from the respiratory tract the remainder is either swallowed or expectorated. Soluble nickel compounds... [Pg.450]

Exposure to hexachloroethane vapors can cause irritation to the respiratory system. Acute exposure to 260 ppm hexachloroethane had no apparent effect on the lungs and air passages in rats, but acute exposure to a concentration where particulate hexachloroethane was present in the atmosphere caused lung irritation (Weeks et al. 1979). On the other hand, intermediate-duration exposure to 260 ppm hexachloroethane appeared to cause some irritation of the respiratory epithelium, which may have increased susceptibility to respiratory infection. When exposure ceased, the animals recovered, so there were no histopathological indications of tissue damage after a 12-week recovery period. Lesions of the nasal passages, trachea, and bronchi increased mycoplasma infections mucus in the nasal cavities and decreased oxygen consumption were indicators of respiratory tract irritation from repeated episodes of hexachloroethane exposure. [Pg.38]

The respiratory system may be damaged directly by particulate matter that enters the blood systems or lymph system through the lungs. In addition, the particulate material or soluble components of it, heavy metals, for instance, may be transported to organs. Particles cleared from the respiratory tract are to a large extent swallowed into the gastrointestinal tract. [Pg.107]

Respiratory protection is protection against gases, fumes, mists, vapors, and particulates that can enter the respiratory tract through the mouth and nose and either settle in the air passages and lung or be taken into the blood stream and transmitted through the body. [Pg.139]

The importance of tobacco includes both those constituents in smoke that may interact with nicotine directly, as well as those that indirectly influence a smoker s perception and behaviors. For example, some tobacco smoke constituents may alter the site of absorption of nicotine, such as bronchodilators (e.g., cocoa, licorice), which allow deeper inhalation and subsequent deposition of constituents in more highly permeable areas of the respiratory tract. Likewise, product changes to alter or control particle size, or to provide particulate carriers for vapor-phase smoke constituents, also could facilitate changes at the site of absorption (Ingebrethsen 1993). This would also include the use of acids or bases to alter the form of nicotine and basicity of smoke. Again, a wide range of relevant findings is indicated by internal documents (Ferris Wayne et al. 2006 Keithly et al. 2005 Pankow 2001). [Pg.462]

Particle deposition in the respiratory tract can initiate inflammatory responses. With repeated deposition, inflammation becomes chronic, and the site or sites of deposition beeome laden, not only with the particulates, but with several types of cells—fibroblasts, macrophages, leukocytes, and lymphocytes. These cells are normal constituents of the lung, an organ composed predominantly of connective tissue. Lung connective tissue forms the thin membrane that defines the functional alveolar-capillary unit. Inside this air sac and on the membrane are specialized eells required for gas exchange, maintenance, and repair (Fig. 3.6). [Pg.121]

The chief factor that determines the site of deposition of particulate matter in the respiratory tract is its size. Particles having an aerodynamic diameter of 5-30 pm are primarily... [Pg.6]

Despite apparent widespread use, the toxicological data on these compounds are insufficient (5J. Because of the strong oxidation properties, low concentrations of NaDCC and TCCA particulates are extremely irritating to the respiratory tract and mucous membranes of the eyes (6J They can also cause irritation... [Pg.123]

The need to determine accurately the phase-specific concentrations of these pollutants reflects several concerns Compared to gaseous materials, particle-phase materials may penetrate more deeply into the human respiratory tract particle-phase pollutants scatter light much more effectively than gaseous materials, and they thus have a greater contribution to visibility reduction gaseous nitric acid has a much higher deposition velocity than particulate nitrates and can be a substantial contributor to the acidification of lakes, streams, forests, and vegetation. [Pg.13]

Most of the information on the effects of air pollution on humans comes from acute pollution episodes such as the ones in Donora and London. Illnesses may result from chemical irritation of the respiratory tract, with certain sensitive subpopulations being more affected (1) very young children, whose respiratory and circulatory systems are poorly developed, (2) the elderly, whose cardiorespiratory systems function poorly, and (3) people with cardiorespiratory diseases such as asthma, emphysema, and heart disease. Heavy smokers are also affected more adversely by air pollutants. In most cases the health problems are attributed to the combined action of particulates and sulfur dioxides (SO2) no one pollutant appears to be responsible. Table 4.2 summarizes some of the major air pollutants and their sources and effects. [Pg.36]

While gases are more likely to travel freely through the entire respiratory tract to the alveoli, passage of aerosols and particles will be affected by the upper respiratory tract, which can act as an effective filter to prevent particulate matter from reaching the alveoli. Mucous traps particles to prevent entry to alveoli, and the mucociliary apparatus in the trachea traps and pushes particles up the trachea to the esophagus where they are swallowed and possibly absorbed in the GI tract. [Pg.96]

If the test material is particulate, consideration must be given to the particle size and its inhalation potential. Particles of 4 microns in size are considered to be inhal-able larger particles will be cleared from the respiratory tract by ciliary action and subsequently swallowed (oral exposure) or expelled by sneezing or expectoration. [Pg.370]

Pritchard, J.N. Black, A. (1984) An estimate of the tar particulate matter depositing in the respiratory tracts of healthy male middle- and low-tar cigarette smokers. In Aerosols, ed. B.Y.H. Liu D.Y.H. Piu. Amsterdam Elsevier. [Pg.251]

Due to the extremely high boiling point of chromium, gaseous chromium is rarely encountered. Rather, chromium in the environment occurs as particle-bound chromium or chromium dissolved in droplets. As discussed in this section, chromium(VI) trioxide (chromic acid) and soluble chromium(VI) salt aerosols may produce different health effects than insoluble particulate compounds. For example, exposure to chromium(VI) trioxide results in marked damage to the nasal mucosa and perforation of the nasal septum, whereas exposure to insoluble(VI) compounds results in damage to the lower respiratory tract. [Pg.38]


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See also in sourсe #XX -- [ Pg.235 ]




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