PM 2.5
PM 2.5 stands for particulate matter of 2.5 micrometers in diameter. Unlike the major air pollutants of ground-level ozone, sulfur dioxide, carbon dioxide, and nitrogen dioxide, particulate air pollution is defined by its size rather than about the chemical it contains. Particulate matter, or PM for short, is the term used for particles that are found in the air, including that of dust, dirt, soot, smoke, and liquid droplets. These particles can be suspended in the air for long periods of time, in which some particles are even large and dark enough to be seen as soot or smoke while others are so small that individually, they can only be detected with an electron microscope. Many man-made and natural sources emit PM directly into the atmosphere or emit other pollutants that react in the atmosphere to form PM, in which these solid and liquid particles may come in a broad range of sizes. Particles less than ten micrometers in diameter, which is PM 10, pose a health concern because they can be inhaled into and build up within the respiratory system. For the sake of a comparison, most bacteria cells are at least five micrometers across with the diameter of a red blood cell being six micrometers and a strand of hair as 70 micrometers. However, PM 2.5 is a measurement for particles less than 2.5 micrometers in diameter and are referred to as “fine” particles that are believed to pose the greatest health risks. This is because of their small size as approximately 0.33 of the average width of a human hair, causing these fine particles to lodge deeply within the lungs. Therefore, it is typical to say that in micrograms per cubic meter, the smaller these particulates are, the more damage they can cause on the human body. Sources of these fine particles include all types of combustion activities such as motor vehicles, power plants, and wood burning, and certain industrial processes. In between particles with diameters of 2.5 and ten micrometers are “coarse” particles, in which sources of these include the crushing or grinding of operations and the dust from paved or unpaved roads. Other sources of coarse particles include the chemical change of gases formed in the air and indirectly when gases from burning fossil fuels react with sunlight and water vapor in the air. Approximately one out of every three people in the United States is at a higher risk of experiencing PM 2.5-related health effects. However, the group at the highest risk of such is active children because of the fact that they often spend a lot of time playing outdoors with still developing bodies. Often times the elderly population is also at risk because of the weakness of their bodies’ defense. People of all ages who are very active outdoors are also at an increased risk because especially during physical activity, PM 2.5 penetrates deeper into the parts of the lungs that are more vulnerable to injury. A human body is not good at blocking PM 2.5, no matter how strong the immune system is, as these particles are small enough to bypass the respiratory system’s defenses and get into the lungs, where they can even penetrate the bloodstream and cause a manner of mayhem and trouble. It is proven that people who live in high PM 2.5 cities have more heart attacks, depressed lung functions, worse asthma, and overall, die younger than the people who breathe clean air. Therefore, more weight is typically given to PM 2.5 rather than PM 10 levels when it comes to prioritizing the strength of air pollution. PM 2.5 is also a criteria pollutant, which are one of the six common air pollutants that are found all over the world identified by the Clean Air Act as potential pollutants that can injure health, harm the environment, and harm property. As one can see, PM 2.5 is a criteria pollutant of particulate matter from human activities that is less than 2.5 micrometers in diameter and causes health problems like heart attacks.