The Air We Breathe
Our atmosphere is vital to all living things on our planet. How much do you know about the air we breathe?
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Air pollution includes smoke, soot, carbon monoxide, sulfur dioxide, dust and anything that is unhealthy for life on Earth. Most of these pollutants result from burning biomass (biological material usually from plants) or fossil fuels (coal and gasoline).
Ozone is a gas made up of three atoms of oxygen and occurs in both Earth’s upper atmosphere and at ground level. It can be good or bad for us depending on where it is found. When in or above the stratosphere (the higher atmosphere that ranges from 5 to 11 miles up), ozone forms a crucial sunscreen – the ozone layer – that protects us from the harmful ultraviolet rays of the Sun. But ozone can also act as a pollutant at ground level, formed when pollution (say from cars) reacts with sunlight. A main ingredient of smog is ozone, which burns the lungs when breathed in and can trigger asthma attacks. NASA monitors the ozone layer and lower-level ozone using satellites and instruments on planes and on the ground.
On average, this is how long it takes for dust, soot and water-soluble chemicals to be washed out of the atmosphere by falling rain.
In the US, air quality is driven by six main pollutants: lead, carbon monoxide, ozone, sulfur dioxide, nitrogen oxides and particulates smaller than 2.5 microns. The good news is that concentrations of these pollutants have fallen over the past two decades, largely thanks to the 1990 Clean Air Act Amendments that reduced allowed industry emissions. Pollution reductions from mobile sources (for example, cars) have also been substantial.
From space, we can see pollution moving across the oceans from one continent to another. For example, vast quantities of industrial aerosols (microscopic particles suspended in the atmosphere) and smoke from events such as wood or vegetation burning can travel from one side of the globe to another.
Ground-level ozone (as opposed to ozone in the ozone layer high up in the atmosphere) is a pollutant that burns the lungs when inhaled. Ozone at the Earth’s surface is a main ingredient in smog but is not emitted directly from car exhausts. It is formed when pollution from vehicles, factories and other sources reacts in sunlight. Sunny California has the perfect conditions for unhealthy levels of ozone to form.
While nitrogen dioxide is produced naturally by lightning and bacterial processes involved in plant growth and decay, the strongest sources are man-made, from the burning of fossil fuels like coal and gas. From space we can see that nitrogen dioxide collects mainly around large cities and industrialized areas.
NASA satellites have been measuring the amount of ozone in our atmosphere for over 30 years. However, since most of the ozone exists high in the stratosphere, it is difficult to measure ozone levels in the troposphere precisely, the layer of the atmosphere closest to the surface where we live and breathe. Pollutants in the troposphere measured by the Aura satellite include sulfur dioxide, nitrogen dioxide and some volatile organic compounds (such as formaldehyde).
From 1751-2012, humans added 590 ± 75 billion tons of carbon to the atmosphere in the form of carbon dioxide. In 2012, 92% of all human-produced carbon dioxide originated from burning coal, natural gas, oil and gasoline.
NASA's Aura mission was built to understand the chemistry of our atmosphere. The satellite's measurements enable scientists to monitor some of the pollutants that are found in the air that we breathe. Aura’s instruments also monitor gases high in the atmosphere and have helped provide a continuous record of ozone measurements essential for tracking changes in the ozone layer.