Nitrogen oxides (NOx) are key contributors to smog and poor air quality, especially in urban areas. They are formed during the hightemperature combustion of fossil fuels and set off chemical reactions that create harmful pollutants.
• Ground-level ozone: NOx reacts with volatile organic compounds (VOCs) in sunlight and heat to form ground-level ozone — a major component of smog and a harmful air pollutant, distinct from the protective ozone layer in the upper atmosphere.
• Particulate matter (PM2.5): NOx combines with chemicals like ammonia and moisture to form fine particles that penetrate deep into the lungs.
• Reduced visibility: Nitrogen dioxide (NO2), is a reddish-brown NOx gas. It is the same that causes the brown haze typical of urban smog.
• Acid rain: NOx reacts with water vapor to form nitric acid, which damages ecosystems, forests, and waterways.
• Health effects: NOx exposure irritates airways and is frequently seen as a contributing factor in worsening asthma and bronchitis, with children, seniors, and people with pre-existing conditions most at risk.
• Ecosystem damage: NOx contributes to nutrient pollution in lakes and rivers, fueling algal blooms that harm aquatic life.
