Exposure to air pollutants can have significant adverse effects on the human respiratory system. The primary air pollutants that affect the respiratory system include particulate matter PM , nitrogen oxides NOx , sulfur oxides SOx , ozone O3 , and volatile organic compounds VOCs . These pollutants can cause inflammation, respiratory illnesses, and exacerbate pre-existing conditions such as asthma and chronic obstructive pulmonary disease COPD .1. Particulate Matter PM : PM consists of tiny solid or liquid particles suspended in the air, such as dust, smoke, and soot. When inhaled, these particles can penetrate deep into the lungs and cause inflammation, irritation, and damage to lung tissue. PM can also carry toxic chemicals, such as heavy metals and polycyclic aromatic hydrocarbons PAHs , which can be absorbed into the bloodstream and cause systemic health effects.2. Nitrogen Oxides NOx : NOx, primarily consisting of nitrogen dioxide NO2 and nitric oxide NO , are formed during combustion processes. NOx can react with other pollutants in the atmosphere to form secondary pollutants, such as ozone and particulate matter. In the respiratory system, NOx can cause inflammation, reduce lung function, and increase susceptibility to respiratory infections.3. Sulfur Oxides SOx : The primary sulfur oxide pollutant is sulfur dioxide SO2 , which is produced during the combustion of fossil fuels containing sulfur. SO2 can react with water vapor in the air to form sulfuric acid H2SO4 , which can cause respiratory irritation and exacerbate asthma symptoms. The reaction is as follows:SO2 + H2O H2SO3H2SO3 + 1/2 O2 H2SO44. Ozone O3 : Ozone is a secondary pollutant formed by the reaction of nitrogen oxides NOx and volatile organic compounds VOCs in the presence of sunlight. Ozone can cause respiratory irritation, inflammation, and reduced lung function. The formation of ozone can be represented by the following reactions:NO + O3 NO2 + O2NO2 + sunlight NO + OO + O2 O35. Volatile Organic Compounds VOCs : VOCs are a large group of organic chemicals that can evaporate easily into the air. Some VOCs, such as benzene and formaldehyde, are toxic and can cause respiratory irritation and other health effects. VOCs can also react with NOx to form ozone, as mentioned earlier.In summary, exposure to air pollutants can cause various chemical reactions in the respiratory system, leading to inflammation, irritation, and damage to lung tissue. These reactions can exacerbate pre-existing respiratory conditions and increase the risk of developing respiratory illnesses. Reducing exposure to air pollutants is essential for maintaining good respiratory health.