The air we breathe contains a mixture of tiny solid and liquid droplets known as particle pollution. These atmospheric particles come in various sizes, and scientists categorize them to understand their effects. One category is coarse particles, a group of pollutants distinguished by their size and composition from their smaller counterparts.
Understanding Coarse Particles
Coarse particles are defined by their aerodynamic diameter, which is between 2.5 and 10 micrometers (μm), a classification referred to as PM10-2.5. To visualize this scale, the average human hair is about 70 micrometers in diameter, making it significantly larger than the biggest coarse particle.
These particles are distinct from fine particles (PM2.5), which are 2.5 micrometers or smaller. Their composition reflects their origins, consisting of dust, soil minerals, and biological materials like pollen or mold spores. Because of their larger mass, coarse particles settle out of the air more quickly than fine particles, which can remain suspended for longer periods.
Where Do Coarse Particles Come From?
Natural sources contribute significantly to coarse particles in the atmosphere. Wind lifts desert dust and soil into the air, while ocean spray aerosolizes sea salt. Other natural contributors include plant pollen, mold spores, and volcanic ash.
Human activities, primarily mechanical processes, are also major producers. These include crushing and grinding at construction sites and mining operations. Agriculture contributes through tilling fields, and a substantial portion comes from roadways due to tire and brake wear and the resuspension of road dust.
Coarse Particles and Your Health
Because they are relatively large, most inhaled coarse particles are trapped in the upper respiratory tract, including the nose, throat, and larynx. The body’s natural defenses, like mucus, capture these particles before they travel deeper into the lungs. They are then removed by coughing, sneezing, or swallowing.
Exposure to high concentrations of coarse particles can still cause health issues, such as irritation of the eyes, nose, and throat. For individuals with existing respiratory conditions like asthma or COPD, exposure can aggravate symptoms and lead to hospital admissions. Children and the elderly are also more susceptible to the effects of this pollution.
Environmental Footprint of Coarse Particles
Coarse particles also affect the environment, with one of the most noticeable effects being reduced visibility. The particles scatter and absorb light, creating haze that can obscure views and pose safety risks by limiting visibility for drivers. This affects both urban areas and scenic national parks.
When these particles settle, they can soil buildings and statues, leading to physical damage. Their deposition also impacts ecosystems by coating plant leaves, which can interfere with photosynthesis. Depending on their chemical makeup, they can alter the nutrient balance in soil and the acidity of water, affecting plant and animal life.