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Asthma and Air Pollution in Los Angeles
Published in John R. Goldsmith, Environmental Epidemiology: Epidemiological Investigation of Community Environmental Health Problems, 2019
Roger M. Katz, Ron G. Frezieres
There has been some interest in trying to establish an air quality standard for sulfate aerosols based on the presumption that it was the sulfate aerosol which was the main villain in the complex of pollutants of which sulfur dioxide and black suspended matter are the principal inputs. This interest was supported by laboratory tests in guinea pigs which showed that acid sulfates such as sulfuric acid and ammonium bisulfate (sulfuric acid in which one of the hydrogen atoms has been replaced by the ammonium ion — since it still contains a hydrogen atom it is still acid) were the most active of a large series of compounds in causing the guinea pigs to have an increase in airway resistance. Increase in airway resistance is one of the characteristic physiological features of an asthma attack.
Air pollution impacts
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
We have seen in Section 2.2.3 that NO and NO2 are present in variable proportions in the outdoor atmosphere. While the initial emissions, principally from motor vehicles and other combustion sources, are usually dominated by NO, the latter is oxidised to NO2 during photochemical reactions in the atmosphere, and ambient NO2 concentrations may be higher than those of NO. There are also significant indoor emissions and exposures due to sources such as gas hobs. Of the two gases, NO2 has much the higher toxicity to people; the occupational exposure limit for NO is 25 ppm, whereas that for NO2 is 3 ppm. NO2 has lower solubility than SO2, so that a much higher proportion penetrates into the deep lung, and the main sites of action are the terminal bronchioles. As with other soluble gases, nasal breathing will protect better against NO2 than oral breathing. NO2 is a powerful oxidant, and it is thought that its main damage mechanism is destruction of cell membranes by lipid peroxidation. The body does have natural defences against this process due to antioxidant chemicals in the alveolar epithelium. High NO2 concentrations can overwhelm the antioxidative defence capacity and allow penetration of the NO2 through to the cell walls. There are also direct effects on the respiratory system, including increased airway resistance (due to inflammation), increased incidence of respiratory illness and damage to lung tissue.
Placebo and somatization
Published in Herman Staudenmayer, Environmental Illness, 2018
This point was clearly demonstrated by Luparello and colleagues in a series of double-blind, placebo-controlled studies on the effects of suggestion on airway resistance in asthmatics (Luparello et al., 1968; McFadden et al., 1969). Bronchoconstriction in response to saline occurred in about 50% of subjects who were told they were inhaling the nebulized allergen to which they attributed their asthma attacks. Bronchoconstriction was measured with changes in airway resistance, a measure obtained in a whole-body Plethysmograph. Airway resistance is less effort dependent and therefore less likely to be affected by the subject than some other pulmonary function measures. These investigators also identified a mechanism — activation of efferent cholinergic pathways — through which the phenomenon was mediated by demonstrating that they could prevent the bronchoconstriction response to suggestion by intravenous atropine sulfate.
Investigation of airflow at different activity conditions in a realistic model of human upper respiratory tract
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Reza Tabe, Roohollah Rafee, Mohammad Sadegh Valipour, Goodarz Ahmadi
The airflows through the respiratory passages are quite complex. Investigation of the characteristics of airflow helps researchers to better understand both the respiratory physiology and diagnostics of diseases. One of the important quantities in describing the respiratory tract airflow is the airway resistance, which is defined as the ratio between pressure drop and flow rate (Paxman et al. 2019). Also, understanding the nature of fluid motion in the respiratory tract is an essential step to clarifying the fate of inhaled pharmaceutical or pollutant aerosols in the airway passages. Adult humans breathe over 10,000 L of air per day while the aerosol counts are somewhere between 100 billion and 10 trillion solid particles or liquid droplets (Tsuda et al. 2013).