Effect of oxidant air pollutants on the respiratory system: insights from experimental animal research

Abstract

In the present paper, we have reviewed experimental animal studies on the effects of the two most important oxidant airborne pollutants, nitrogen dioxide and ozone, on the respiratory system.The toxic effects depend on concentration and length of exposure, and are generally similar for both oxidants, with ozone operative at lower concentrations. High doses of both oxidants cause death due to lung oedema Exposure to sublethal levels causes functional alterations such as airflow limitation and airway hyperresponsiveness to bronchoconstrictor stimuli. These effects, which are generally reversible, are associated with epithelial injury, oedema and airway and parenchymal infiltration by inflammatory cells. Loss of cilia of airway epithelium and necrosis of type I alveolar epithelial cells are the most prominent consequences at the epithelial level. Inmation is characterized by early neutrophilic infiltration, followed by an increased number of mononuclear cells, predominantly alveolar macrophages.After long-term exposure, whilst nitrogen dioxide causes predominantly emphysema, ozone produces mainly pulmonary fibrosis. Biochemical effects include lipid peroxidation, increased antioxidant metabolism, and alteration of enzyme activity. Nitrogen dioxide and ozone may also alter the immunological response and reduce the defence against infections, increasing the susceptibility of exposed animals to infections.

Epidemiological studies of the respiratory effects of air pollution

“…Highly reactive-hydroscopic gases (e.g. SO 2 ) are absorbed almost entirely in the nose during normal nasal breathing; on the other hand, ozone (O 3 ) readily can reach the alveoli. Exercise during exposure increases the pollutant effect on ventilatory function.…”

“…There has been a study in Los Angeles that showed significant associations both of O 3 and nitrogen dioxide (NO 2 ) with total and cause-specific mortality [42]; PM was not significant. No lowest observed effect levels (LOELs) have been defined for acute mortality associated with O 3 or NO 2 .…”

“…Eur Respir J 1996; 9: 571-584. This review of epidemiological studies of the respiratory effects of exposures to air pollutants follows excellent reviews of experimental studies in animals and humans that have recently appeared in the Journal [1][2][3]. It has relied both on prior reviews of the topic and on the extensive literature of the major research reports.…”

Effects of ambient air pollution on allergic rhinitis among preschool children in Changsha, China

“…These studies mainly focused on the background air pollution. However, the impact of air pollutants on health is closely related to the extent of individual exposure, which includes not only exposure concentration but also exposure time [14]. Although numerous studies indicated that the airway health could be caused by short-term exposure to air pollutants at high concentration, long-term exposure to air pollutants at low concentrations may also induce an equivalent effect, which suggests an accumulative effect of air pollution exposure on health [15][16][17][18][19].…”

Passive Sampling of Ambient Nitrogen Dioxide at Toll Plazas in Malaysia

“…Mücke and Wagner [13] reported that even NO 2 at low concentrations can affect respiratory tract by increasing respiratory resistance, changing pulmonary functions, decreasing defence against disease and causing morphological damage to lungs. Short-term exposures to about 100 parts per billion (ppb) were found to be harmful to rats in an experimental study [14], while long-term effects have been perceived to reduce immunity, leading to respiratory infection [15]. Using NO 2 as an indicator pollutant in this study would help us determine whether the levels of air pollution concentration present in a particular region may cause adverse health impacts, and make recommendations for pollution control, considering that NO 2 emanated from combustion is accompanied by other pollutants.…”