Air pollution is the presence of harmful substances in the atmosphere that can damage human health, animals, plants, and the environment. Clean air normally contains 78% nitrogen, 21% oxygen, and 1% other gases. When pollutants like carbon monoxide, sulfur dioxide, and particulate matter enter the atmosphere, they contaminate this natural composition and create health risks for all living organisms.
Air pollutants are classified into two main categories. Primary pollutants are directly emitted into the atmosphere from sources like vehicles and factories. These include carbon monoxide, sulfur dioxide, and particulate matter. Secondary pollutants form through chemical reactions in the atmosphere. For example, nitrogen oxides and volatile organic compounds react with sunlight to create ground-level ozone, a major component of smog.
Air pollution comes from various sources, both human-made and natural. Transportation sources like cars, trucks, and aircraft emit carbon monoxide, nitrogen oxides, and particulate matter. Industrial activities including power plants and factories release sulfur dioxide, nitrogen oxides, and volatile organic compounds. Residential sources contribute through heating and cooking activities. Natural sources include wildfires and volcanic eruptions, which can release large amounts of particulate matter and gases into the atmosphere.
Air pollution has serious impacts on both human health and the environment. Health effects include respiratory diseases like asthma, cardiovascular problems, lung cancer, and premature death. Pollutant particles enter the lungs and cause inflammation, leading to various health complications. Environmental effects include acid rain formation, ecosystem damage, climate change, and reduced crop yields. Globally, air pollution causes 7 million premature deaths per year, with 90% of people breathing polluted air, resulting in a $2.9 trillion economic cost.
Air quality is measured using the Air Quality Index or AQI system to inform public health decisions. The AQI scale ranges from 0 to 500, with different color codes: green for good air quality, yellow for moderate, orange for unhealthy for sensitive groups, red for unhealthy, purple for very unhealthy, and maroon for hazardous conditions. Air quality is monitored through ground-based stations, satellite measurements, and mobile sensors that collect real-time data on pollutants like PM2.5, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide.