Air Quality: What's Really In The Air We Breathe?

The air we breathe is a mixture of gases, with nitrogen making up about 78% of the Earth's atmosphere and oxygen making up about 21%. The remaining 1% includes trace amounts of argon, carbon dioxide, water vapour, and other gases such as ammonia, carbon monoxide, helium, hydrogen, and methane. The composition of the air changes as we inhale and exhale, with levels of oxygen decreasing and carbon dioxide increasing. The air we breathe is also affected by human activity, with an increasing number of harmful substances being picked up by the air we breathe.

Air is made of almost 100 different elements, including nitrogen, hydrogen, oxygen, and carbon dioxide

The air we breathe is made up of a variety of gases and particles, some of which are essential for life. The Earth's atmosphere is composed of almost 100 different elements, and air is a mixture of gases, most of which are naturally occurring. Nitrogen (N2) constitutes about 78% of the air we breathe and is the most abundant naturally occurring gas. It is crucial in the nitrogen cycle, which allows nitrogen to enter the soil and water, bind with other elements, and become accessible to living things.

Oxygen (O2) is the second most abundant gas, making up approximately 21% of the atmosphere. This is the perfect amount for our lungs to absorb, providing fuel for all our activities. Oxygen is also essential for cellular respiration in humans and animals and causes oxidation reactions that help break down matter and release nutrients into the soil.

Argon (Ar), an inert gas, is the third most abundant gas, comprising 0.93% of the atmosphere. While argon is used in lighting applications, it does not play a significant role in our daily lives. The atmosphere also contains trace amounts of other gases, including carbon dioxide (CO2), neon (Ne), helium (He), methane (CH4), krypton (Kr), and hydrogen (H2).

In addition to these primary constituents, the air contains a variety of particles, both natural and human-made. These particles can range from microscopic to visible in size and include bioaerosols, dust, sea salt, ash from volcanic eruptions or forest fires, and industrial pollutants such as chlorine, fluorine compounds, and mercury vapour. Water vapour is also present in the air, with concentrations varying from trace amounts at the poles to up to 4% water vapour in the lower troposphere near the tropics.

Air contains tiny microbial organisms called bioaerosols, which can travel long distances via wind, rain, or a sneeze

The air we breathe is a mixture of gases, with nitrogen making up about 78% of the Earth's atmosphere and oxygen about 21%. However, the air contains much more than just gases. It contains tiny microbial organisms called bioaerosols, which include live or dead fungi, bacteria, viruses, actinomycetes, and their secondary metabolites. These microbes cannot fly but can travel long distances through the air via wind, rain, or even a sneeze.

Bioaerosols are tiny particles that are released into the air from various sources, including human activities such as talking, coughing, and sneezing, which eject microbes from the upper respiratory tract. Sneezing is the most vigorous of these mechanisms, generating up to one million droplets less than 0.1 μm in diameter. These droplets can contain organic particulates that protect bacterial cells and enhance their survival in the air. Bioaerosols can also come from food stuffs, house plants, pets, and even dust released from carpets.

The study of airborne biological materials and the factors influencing microbial survival in the air is called aeromicrobiology. Bioaerosols can impact a variety of ecosystems, including atmospheric, terrestrial, and marine environments. They can remain viable in soil for years and travel thousands of kilometers before deposition, although their distance and direction are influenced by meteorological, physical, and chemical factors.

Bioaerosols pose serious health hazards to humans and animals, as their small size allows them to easily enter the lungs if inhaled, potentially causing respiratory and other infections. They can transmit microbial pathogens, endotoxins, and allergens, and have been linked to outbreaks of diseases such as meningococcal meningitis, Mycoplasma pneumonia, and tuberculosis. The presence of viruses in bioaerosols, such as SARS-CoV-1 and SARS-CoV-2, also highlights the importance of understanding and controlling these airborne particles.

Air pressure changes with altitude—it is high at sea level and low at the top of a mountain

Air pressure, or barometric pressure, is the pressure exerted by the Earth's atmosphere. It is caused by the gravitational pull of the planet on the atmospheric gases above its surface. The pressure is determined by the mass of the planet, the radius of the surface, and the amount and composition of the gases and their vertical distribution in the atmosphere. This pressure is felt by us because there is a large volume of air pushing down on Earth's surface.

At sea level, we experience high air pressure because the entire atmosphere is pushing down on us. The standard pressure at sea level is 1 atm or 101,325 pascals (Pa). The pressure is measured in milibars, and 1 atm is roughly equivalent to 1,013.25 millibars.

As we move up in altitude, the pressure exerted by the atmosphere decreases. This is because, as elevation increases, there is less atmospheric mass above us. The pressure exerted by the atmosphere is directly proportional to the amount of mass above the measurement point. So, at the top of a mountain, the air pressure is lower than at sea level. This difference in pressure can be felt by our bodies as we ascend or descend in altitude, causing our ears to pop.

Barometers are used to measure air pressure. This measurement of pressure has many applications, including in aviation, where it is used to adjust the altimeter setting. It is also used in survey work and map-making to determine the height of hills and mountains.

Air contains solid particles called aerosols, such as dust, sea salt, and ash from erupting volcanoes or forest fires

Air is a mixture of gases, most of which are naturally occurring. It contains nitrogen, oxygen, argon, carbon dioxide, and trace amounts of other gases, such as helium, neon, methane, krypton, and hydrogen. The air we breathe is vitalised by the inclusion of oxygen, which makes up about 21% of the atmosphere. This is a perfect amount for our lungs to absorb into our blood without damaging our tissues.

However, the air also contains a significant amount of human-made air pollutants, which can be harmful to human health and the environment. These include particulate carbon (soot) emitted by coal-burning power plants, and sulfur and nitrogen dioxides released by factories burning fossil fuels. These human-made chemicals can cause damage to the environment in the form of acid rain.

Airborne particles come in a variety of sizes, ranging from tiny nanoparticles to visible particles. These particles can be the result of industrial processes, combustion sources, or natural sources such as forest fires. Fine dust, for example, is a common airborne particle with a diameter of less than 2.5 or 10 micrometres. Smaller particles can penetrate deeper into our airways and lungs, potentially causing respiratory issues.

Air also contains solid particles called aerosols, which include dust, sea salt, and ash from erupting volcanoes or forest fires. These aerosols can be natural or human-made, with the latter being caused by manufacturing and the use of combustion engines. Aerosols affect the climate by influencing cloud formation and scattering or absorbing sunlight.

Additionally, living organisms called bioaerosols can be found in the air. These microbial organisms can travel long distances through wind, rain, or even a sneeze.

Air pollution is measured with the Air Quality Index (AQI)

The AQI is calculated using a complex formula that takes into account various factors, including the concentration of pollutants in the air, weather conditions, and the time of day. It provides a quantitative way to assess air quality and is designed to help people understand the potential health risks associated with different levels of air pollution.

The AQI is divided into six color-coded categories, each representing a range of index values. These categories are: Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous. An AQI value of 50 or below represents good air quality, while an AQI value over 300 indicates hazardous air quality. When the AQI value is above 100, the air quality is considered unhealthy first for sensitive groups and then for everyone as the value increases.

The AQI is an essential tool for monitoring air pollution and its potential impacts on human health. By providing accessible information about air quality, the AQI helps individuals make informed decisions to protect their health, such as choosing to stay indoors or wear a mask when pollution levels are high. Additionally, the AQI assists governments and organizations in developing policies and initiatives to improve air quality and reduce pollution.

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