Human respiratory system

Much of the concern about particulate matter in the atmosphere arises because particles of certain size ranges can be inhaled and retained by the human respiratory system. There is also concern because particulate matter in the atmosphere absorbs and scatters incoming solar radiation. For a detailed discussion of the human respiratory system and the defenses it provides against exposure of the lungs to particulate matter, see Chapter 7. 

Because a filter sample includes particles both larger and smaller than those retained in the human respiratory system (see Chapter 7, Section III), other types of samplers are used which allow measurement of the size ranges of particles retained in the respiratory system. Some of these are called dichotomous samplers because they allow separate measurement of the respirable and nonrespirable fractions of the total. Size-selective samplers rely on impactors, miniature cyclones, and other means. The United States has selected the size fraction below an aerodynamic diameter of 10 /xm (PMiq) for compliance with the air quality standard for airborne particulate matter. 

PM io - Particulate material less than 10 xm diameter is formed as a byproduct of combustion processes through incomplete combustion and through the reaction between gaseous pollutants in the atmosphere. PM10 is a particular problem as it causes damage to the human respiratory system. 

Tu, K.W. and E.O. Knutson, Total Deposition of Ultrafine Hydrophobic and Hygroscopic Aerosols in the Human Respiratory System, Aerosol Sci. and Technology. 453-465 (1984). 

Fig. 3.1 Schematic diagram of the human respiratory system. The gross anatomy of the lung, the covering membranes (pleura), airways and air sacs (alveoli) are shown. The average diameter of portions of the air flow system are indicated trachea, 20 mm bronchus, 8 mm terminal and respiratory bronchioles, 0.5 mnn alveolar duct, 0.2 mm alveolar sacs, 0.3 mm.

Deposition doses in the human respiratory system were estimated based on the roadside PNCs in various locations. These showed the similar trend to the roadside PNCs since the dose estimates did not take into account the size distributions of particles at each site. Average deposition doses over all the considered locations were found to be 3.61 0.17 x 1010 h 1 for male subjects, with exceptionally high values (1.61 0.08 x 1011 h ) for site at Birmingham where the study was carried out along the roadside about 15 years ago (i.e. in 1996-1997). 

Anatomy and physiology. The human respiratory system is divided into upper and lower respiratory tracts. The upper respiratory system consists of the nose, nasal cavities, nasopharynx, and oropharynx. The lower respiratory tract consists of the larynx, trachea, bronchi, and alveoli, which are composed of respiratory tissues. 

Tu, K.W. Knutson, E.O. (1984) Total deposition of ultrafine hydrophobic and hygroscopic aerosols in the human respiratory system. Aerosol Science Technology, 3, 453-65. 

Public concern for the hazards of particle suspensions in the indoor and outdoor environment has produced regulations limiting particle concentrations and exposure levels. In the workplace, dust hazards are constrained by total mass concentration as well as concentration of specific toxic chemicals. In the ambient air, protection is stipulated in terms of total mass concentration of suspended particles andcertain chemical species, namely, lead and sulfate. Recently, measures of exposure have begun to distinguish between fine particles less than 2.5 fxm and coarse particles between 2.5 and 10 fxm. This separation relates to the ability of particles to penetrate the human respiratory system, and to different sources of fine and coarse particles. 

I. Salma, I. Balashazy, R. Winkler-Heil, W. Hofmann, Gy. Zaray, Effect of particle mass size distribution on the deposition of aerosols in the human respiratory system,... 

Figure 27.1. Anatomy of the human respiratory system. (Adapted from Life ART illustration series, Lippincott Williams Wilkins, Hagerstown, MD, 1994. This figure was completely redrawn by the author from materials cited.)...

The hydrocarbons (all of the above except 2-butoxyethanol) are all neurotoxicJ2°l 2-Butoxyethanol targets the respiratory system, liver, kidneys, lymphoid system, and bloodJ13 Some studies have reported that new carpet VOC emissions are sufficiently low to not adversely affect indoor air quality nor impact the human respiratory system or CNSJ20,24 Other studies, however, have reported that human exposures to new carpet emissions at very low concentrations of both the individual chemicals and total VOCs do induce serious respiratory and CNS effectsJ25,2 The diametrically opposite conclusions reached by the two sets of studies can be attributed to... 

Sulfur dioxide Irritates the human respiratory system and promotes respiratory diseases. 

Dennis WL (1971). The effect of breathing rate on the deposition of particles in the human respiratory system. In Inhaled Particles, III (WH Walton, ed.), pp. 91-102. Old Woking Unwin. 

Landahl HD (1950). On the removal of air-borne droplets by the human respiratory system. The lung. 

Grodins and associates (28) in 1954 recognized that during inhalation of C02-enriched gas mixtures the human respiratory system shows characteristics of a negative feedback controller (see Figure 2). In particular, when the C02 content of the inspired air is altered, pul-... 

Fig. 2,2 Collection efficiency (fraction deposited) of various parts of the human respiratory system and a normalized volume-size distribution of the rural aerosol. The ordinate is given as a linear scale. (From Jaenicke 1986.)...

Many studies have explored the effects of inhaled NO in humans. A fundamental basis for these studies is the demonstration of an active L-arginine-NO pathway in humans. Kobzik et al. (1993) demonstrated that a variety of cells in the human respiratory system, including endothelial cells, contain NO synthase. Blockade of this pathway by an arginine analog (N°-monomethyl-L-arginine) causes an increased PVR, as demonstrated in healthy adults by Stamler et al. (1994) and in children studied during heart catheterization by Celermajer et al. (1994). Human HPV can be reversed by the addition of NO to inspired gas (Frostell et al 1993). 

When some elastomers are burned they evolve what is known as acid gas or halogen gas . These gases are typically composed of hydrochloric or hydrofluoric acid. They are toxic even in relatively small volumes and can cause serious damage to the human respiratory system. Fatal results can occur from bad Are situations. 

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