![]() The predominant physiological effect of short-term ozone exposure is being unable to inhale to total lung capacity. What are ozone's acute physiological and symptom effects? Antioxidants present in cells and lining fluid may protect the epithelial barrier against damage by ozone or its reaction products. Epithelial cells also release a variety of inflammatory mediators that can attract polymorphonuclear leukocytes (PMNs) into the lung, activate alveolar macrophages, and initiate a train of events leading to lung inflammation. These cells become injured and leak intracellular enzymes such as lactate dehydrogenase into the airway lumen, as well as plasma components. Epithelial cells lining the respiratory tract are the main target of ozone and its products. ![]() When breathed into the airways, ozone interacts with proteins and lipids on the surface of cells or present in the lung lining fluid, which decreases in depth from 10 µm in the large airways to 0.2 µm in the alveolar region. Several effects with distinct mechanisms occur simultaneously following a short-term ozone exposure and will be described below.įigure 3: Ozone is highly reactive in the respiratory tract In some cases, ozone itself may react directly with these structures. These reactions and their products are poorly characterized, but it is thought that the ultimate effects of ozone exposure are mediated by free radicals and other oxidant species in the ELF that then react with underlying epithelial cells, with immune cells, and with neural receptors in the airway wall. In the lungs, ozone reacts rapidly with a number of biomolecules, particularly those containing thiol or amine groups or unsaturated carbon-carbon bonds. Consequently, the majority of inhaled ozone reaches the lower respiratory tract and dissolves in the thin layer of epithelial lining fluid (ELF) throughout the conducting airways of the lung. How does ozone react in the respiratory tract?īecause ozone has limited solubility in water, the upper respiratory tract is not as effective in scrubbing ozone from inhaled air as it is for more water soluble pollutants such as sulfur dioxide (SO 2) or chlorine gas (Cl 2). Further research is needed to test the importance of these exposures on health effects. This provides a potential pathway for people indoors to experience respiratory effects mediated by ozone reaction products. Ozone levels may also affect indoor levels of some aldehydes formed as reaction products of ozone with indoor substances (Apte et al 2008). People with the lowest cumulative exposure are those resting for most of the day in an air-conditioned building with little air turnover. In addition, during exercise people breathe more deeply, and ozone uptake may shift from the upper airways to deeper areas of the respiratory tract, increasing the possibility of adverse health effects. People with the greatest cumulative exposure are those heavily exercising outdoors for long periods of time when ozone concentrations are high. Ozone concentrations indoors typically vary between 20% and 80% of outdoor levels depending upon whether windows are open or closed, air conditioning is used, or other factors such as indoor sources. ![]() The cumulative amount of exposure is a function of both the rate and duration of exposure.Īlthough ozone concentrations in the outside (ambient) air are generally similar across many locations in a particular airshed, a number of factors can affect ozone concentration in "microenvironments" within the larger airshed (e.g., inside a residence, inside a vehicle, along a roadway). The rate of exposure for a given individual is related to the concentration of ozone in the surrounding air and the amount of air the individual is breathing per minute (minute ventilation). Primary exposure occurs when people breathe ambient air containing ozone. Fewer individuals experience the more severe effects such as hospitalization or death. Many individuals experience the least serious, most common effects shown at the bottom of the pyramid. The relationship between the severity of the effect and the proportion of the population experiencing the effect can be presented as a pyramid. Figure 2: Pyramid of effects caused by ozone ![]()
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