Particles are dangerous for our health. The toxicity of particles depends on their chemical composition and their size: the finer the particle is, the deeper it penetrates into our lungs. Scientists classify particles into two different size ranges which are known as PM10 and PM2.5.
“PM” stands for Particulate Matter which is another name for particles. PM10 refers to all particles which are less than 10 microns (μm) in size. PM2.5 refers to all particles less than 2.5 μm in size. The size of airborne particles is significant as this determines where in the respiratory tract the particles are deposited when we breathe them in. It also governs how the particles are cleared from our system and how quickly.
The Respiratory System: Look at the diagram [that follows] of our respiratory tract and the penetration of particles according to their size.
You can see that the coarsest particles (from 3 to 10 micrometers in diameter) tend to be deposited in the upper parts of the respiratory system. These particles can generally be expelled back into the throat.
PM2.5 are responsible for causing the greatest harm to human health because they are so small. These fine particles can be inhaled deep into the lungs, reaching the 600 million pulmonary alveoli. They can cause breathing and respiratory problems, irritation, inflammation and cancer.
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1: Pharynx 2: Larynx 3: Trachea
4: Bronchus 5: Bronchioles 6: Pulmonary Alveoli
The preceding material on Particulate Matter
Everybody Round the Earth, http://www.atmosphere.mpg.de/enid/2__Particles/- _Particles_and_respiratory_tract_297.html
PARTICULATE MATTER (PM) can be defined as very fine solid or liquid airborne particles such as gas, dust, soot, and ash.
• PM10 are invisible to the naked eye and small enough to be inhaled, which means they are respirable.
• PM2.5 are small enough to be breathed into the deepest parts of lungs, and can pass through the lungs and into the bloodstream. They may also cause heart problems.
• Some airborne particles can latch on to bacteria and other toxics already in the air creating a health risk from two sources at once when these are inhaled.
• Regulatory agencies (EPA, DNR) have set standards for PM10 that must be met by industry. • However, due to exemptions, the mining industry does not have to “count” all the PM
they produce. The dust they don’t have to count is called “fugitive” dust. • Mining will increase the amount of particulate matter in the air via blasting, crushing,
transporting and processing of the mined sand as well as from diesel truck emissions
and other combustion sources.
• Increasing the amount of PM10 in the air increases morbidity. Decreasing PM10 reduces morbidity. This is particularly true of PM2.5.i