The air we inhale is not a simple, uniform substance but rather a complex mixture of various gases, tiny particles, and other airborne elements. Understanding the diverse composition of this inhaled air is important for comprehending its effects on living systems and overall environmental health.
The Gaseous Makeup of the Air
The atmosphere surrounding Earth is primarily composed of several gases, each present in distinct proportions. Nitrogen, a largely unreactive gas, makes up approximately 78.08% of dry air. Oxygen, essential for respiration in most living organisms, is the second most abundant gas, present at about 20.95%. Argon, an inert gas, constitutes roughly 0.93% of the atmosphere.
Beyond these major components, air also contains a variety of trace gases, collectively making up less than 1% of the total. Carbon dioxide, a greenhouse gas involved in plant photosynthesis and a product of respiration and combustion, is typically found at around 0.04%. Other trace gases include neon, helium, methane, krypton, hydrogen, nitrous oxide, and xenon.
Water vapor is another significant gaseous component of the atmosphere, though its concentration varies greatly depending on location and environmental conditions. It can range from nearly imperceptible amounts in dry regions to as much as 4% in humid, tropical areas. While not included in standard dry air percentages, water vapor plays a role in weather patterns.
Beyond Gases: Particles and Other Airborne Elements
Beyond the gaseous constituents, the air we breathe also contains a wide array of non-gaseous components, including solid particles and liquid droplets. These tiny elements, often referred to as particulate matter or aerosols, originate from natural processes and human activities. They vary significantly in size, shape, and chemical makeup, influencing air quality and health.
Natural airborne particles include dust, lifted by wind from soils and deserts, and pollen, released by plants, especially during specific seasons. Fungal spores are also present, along with sea salt particles carried into the air by ocean spray. Volcanic eruptions and wildfires contribute large amounts of ash and smoke particles to the atmosphere.
Human-made, or anthropogenic, particles are a substantial part of airborne matter, particularly in urban and industrial areas. These include soot from the combustion of fossil fuels and wood, as well as fine particulate matter (PM2.5 and PM10) generated by vehicle exhaust, industrial emissions, and power plants. PM10 refers to particles with a diameter of 10 micrometers or less, while PM2.5 are even finer, at 2.5 micrometers or less, allowing them to penetrate deeper into the lungs and even enter the bloodstream.
The air also contains aerosols, suspensions of fine solid particles or liquid droplets. This term encompasses natural forms like fog and mist, and human-caused pollutants.
Volatile Organic Compounds (VOCs) are gases emitted from various products and processes, containing carbon. Sources range from industrial emissions, gasoline, and diesel exhaust to building materials, cleaning supplies, and natural plant emissions.