Nitrogen dioxide NO2 is a reddish-brown, highly reactive gas that is a significant air pollutant, primarily produced from combustion processes such as vehicle emissions and industrial activities. It can have detrimental effects on the respiratory system, particularly with prolonged exposure.Mechanism of action of nitrogen dioxide on the respiratory system:1. Inhalation: When inhaled, nitrogen dioxide enters the respiratory system and comes into contact with the moist surfaces of the airways and lung tissues.2. Oxidative stress: NO2 is a strong oxidizing agent, and its interaction with lung tissues can lead to the production of reactive oxygen species ROS and oxidative stress. This can cause damage to cellular structures, including proteins, lipids, and DNA.3. Inflammation: The oxidative stress induced by NO2 can trigger an inflammatory response in the respiratory system. This involves the activation of immune cells, such as macrophages and neutrophils, and the release of pro-inflammatory cytokines and chemokines. This inflammation can lead to tissue damage and remodeling in the airways and lungs.4. Impaired lung function: The combined effects of oxidative stress and inflammation can impair lung function by causing bronchoconstriction, increased mucus production, and reduced ciliary function. This can lead to a decrease in lung capacity and an increase in airway resistance.Specific health effects of prolonged exposure to nitrogen dioxide:1. Respiratory infections: Prolonged exposure to NO2 can increase the risk of respiratory infections, as the pollutant can impair the respiratory system's natural defense mechanisms, making it more susceptible to pathogens.2. Asthma exacerbation: Individuals with asthma may experience worsening of their symptoms due to prolonged exposure to NO2. This can lead to increased frequency and severity of asthma attacks, as well as a reduced response to asthma medications.3. Chronic obstructive pulmonary disease COPD : Long-term exposure to NO2 can contribute to the development or worsening of COPD, a group of lung diseases characterized by airflow obstruction and breathing difficulties.4. Reduced lung function: Prolonged exposure to NO2 can lead to a decline in lung function, particularly in children and individuals with pre-existing respiratory conditions.5. Increased risk of cardiovascular diseases: Although the primary effects of NO2 are on the respiratory system, there is evidence to suggest that long-term exposure to this pollutant can also increase the risk of cardiovascular diseases, such as heart attacks and strokes.In summary, the mechanism of action of nitrogen dioxide on the respiratory system involves oxidative stress, inflammation, and impaired lung function. Prolonged exposure to this air pollutant can lead to various health effects, including respiratory infections, asthma exacerbation, COPD, reduced lung function, and an increased risk of cardiovascular diseases.