Air pollution contributes to the development of respiratory diseases in humans through the presence of various pollutants in the atmosphere. These pollutants can be classified into primary and secondary pollutants. Primary pollutants are emitted directly from sources, such as vehicles, industries, and power plants, while secondary pollutants are formed through chemical reactions in the atmosphere.Some of the main air pollutants that contribute to respiratory diseases include particulate matter PM , ground-level ozone O3 , nitrogen oxides NOx , sulfur dioxide SO2 , and volatile organic compounds VOCs . The chemical mechanisms involved in the formation of these pollutants and their effects on human lung tissue are as follows:1. Particulate Matter PM : PM is a mixture of solid and liquid particles suspended in the air, which can be inhaled into the respiratory system. PM can be emitted directly from sources primary PM or formed through chemical reactions in the atmosphere secondary PM . PM can penetrate deep into the lungs, causing inflammation and oxidative stress, which can lead to respiratory diseases such as asthma, bronchitis, and chronic obstructive pulmonary disease COPD .2. Ground-level Ozone O3 : Ozone is a secondary pollutant formed through a series of chemical reactions involving nitrogen oxides NOx and volatile organic compounds VOCs in the presence of sunlight. When inhaled, ozone can cause oxidative stress and inflammation in the lungs, leading to respiratory diseases such as asthma and COPD.3. Nitrogen Oxides NOx : NOx, mainly consisting of nitrogen dioxide NO2 and nitric oxide NO , are primary pollutants emitted from combustion processes, such as vehicle engines and power plants. NOx can react with other chemicals in the atmosphere to form secondary pollutants, such as ozone and particulate matter. NO2 can cause inflammation and damage to lung tissue, leading to respiratory diseases such as asthma and bronchitis.4. Sulfur Dioxide SO2 : SO2 is a primary pollutant emitted from the burning of fossil fuels containing sulfur, such as coal and oil. SO2 can react with other chemicals in the atmosphere to form secondary pollutants, such as sulfate particles a component of PM . Inhaled SO2 can cause irritation and inflammation of the respiratory system, leading to respiratory diseases such as asthma and bronchitis.5. Volatile Organic Compounds VOCs : VOCs are a group of organic chemicals that can evaporate easily into the air. They are emitted from various sources, such as vehicle exhaust, industrial processes, and consumer products. VOCs can react with NOx in the presence of sunlight to form ground-level ozone, which can cause respiratory diseases as mentioned earlier.In summary, air pollution contributes to the development of respiratory diseases in humans through the formation and presence of various pollutants, such as PM, O3, NOx, SO2, and VOCs. These pollutants can cause inflammation, oxidative stress, and damage to lung tissue, leading to respiratory diseases such as asthma, bronchitis, and COPD.