The particles can exist in any shape, size, and can be solid particles or liquid droplets. They are divided into two main groups and these groups differ in several ways. One of the differences is the size; the largest are called PM10 and the smallest are PM2.5.


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  • 1 Emission Sources
  • 2 Elements that constitute them
  • 3 Classification
    • 1 Effects on human health
    • 2 Product derived from a natural or anthropogenic process
      • 2.1 Types of aerosols
    • 4 Impact on the environment
      • 1 Visibility
      • 2 Climate
      • 3 Materials
      • 4 Ecosystem
    • 5 Protective measures for health
    • 6 See also
    • 7 Source

Emission Sources

Particulate emission sources can be natural or anthropogenic. Natural sources include: soil erosion , fractionated biological material, volcanic eruptions, forest fires, etc. Anthropogenic sources include: combustion of petroleum products , burning in agricultural fields and various industrial processes.

Elements that constitute them

The particles can have a homogeneous physicochemical composition or consist of various organic and inorganic compounds. Among the organic components are: phenols , acids , alcohols and biological material, pollen , protozoa , bacteria , viruses , fungi , spores and algae . Among the inorganic compounds are nitrates , sulfates , polymers , silicates , heavy metals such as iron ,lead , manganese , zinc or vanadium]], as well as elements derived from pesticides and pesticides.


The particles are classified according to their effect on human health, as a product derived from a natural or anthropogenic process and by their physical characteristics.

Effects on human health

  • Settling particles (> 10 µm): These are particles that tend to precipitate easily due to their weight, which is why they remain suspended in the airfor short periods of time. They generally do not pose significant risks to human health.
  • Particles smaller than 10 micrometers – PM10 (<= 10 µm): They are particles with an aerodynamic diameter equivalent to or less than 10 µm. They are considered harmful to health because they are not retained by the natural cleaning system of the respiratory tract.
  • Particles smaller than 2.5 micrometers – PM2.5 (<= 2.5 µm): They are particles with an aerodynamicdiameter equivalent to or less than 2.5 µm. They represent a higher risk for human health, it can be a factor of premature death in the population .

Product derived from a natural or anthropogenic process

  • Powders: They are small solid particles (from 1 to 1,000 µm), they are formed by fragmentation in milling, screening, explosions and soil erosion processes . They are kept in suspension and move by means of air currents.
  • Smoke: They are fine solid particles that result from the incomplete combustion of organic materials such as coal , wood and tobacco . Its diameter ranges from 0.5 to 1 µm.
  • Fumes: They are fine solid particles. They are formed by the condensation of the vapors originated in sublimation, distillation , calcination and smelting processes . They measure between 0.03 and 0.3 µm.
  • Fly ash: They are fine non-combustible particles that come from the combustion of coal. Its size ranges from 1 to 1,000 µm. Among its components are inorganic metal substances , silicon oxides , aluminum , iron and calcium . When deposited on surfaces, they act as abrasives.
  • Fog: They are small drops that are formed by condensation of a vapor, dispersion of a liquid or as a product of a chemical reaction . They measure between 0.0002 and 10 µm.
  • Aerosols: An environmental aerosol is a suspension in the air of solid or liquid fine particles. They are divided into primary and secondary aerosols. Primary are relatively stable particles that are emitted directly into the atmosphere , while secondary are particles that form in gas-to-particle conversion processes. They measure between 0.01 and 100 µm in diameter.

Types of aerosols

  • Aerosols with a diameter of 0.01 to 0.1 µm are known as “ultrafine particles”. These are products of the homogeneous nucleation of supersaturated vapors SO2NH3 , NOx and products of combustion.
  • Aerosols with a diameter between 0.1 and 2.5 µm are known as “fine particles”. They are formed in the coagulation of ultra fine particles, through conversion processes – gas to particle – known as heterogeneous nucleation and by condensation of gases. Most of the elements that make up these particles in industrialized countries are: SO4 sulfates , NO3 nitrates , NH3 ammonia , elemental carbon and organic carbon . They also contain a variety of metallic elements that come from combustion processes . Aerosols containing sulfates and nitrates, react with H2O water molecules dispersed in the environment, in the form of rain , fog , snow or dew , to form acids. This phenomenon is recognized as acid rain , which severely affects ecosystems .

Impact on the environment


Visibility is the distance at which an object can be perceived against the sky as a horizon without an exact distinction of its details. In regions where the particle concentration fluctuates around 20 µg / m 3 , the average visibility is 50 to 60 km. In contrast to urban areas where the particle concentration exceeds 100 µg / m 3 , the average visibility is reduced at 8 or 10 km. When photochemical smog occurs, the particles double their concentration and visibility is reduced to 5 or 7 km. The reduction in visibility is one of the most evident proofs of the increase in particle contamination. In Mexico City the average visibility in January 1937It was 10 to 15 km and at the beginning of the 1970s it decreased between 2 and 4 km.


The particles reflect and absorb part of the solar energy , which causes a decrease in temperature in some regions of the planet.


The particles act as catalysts on metal surfaces, favoring their oxidation . They can also absorb gases such as sulfur oxides and nitrogen oxides , which react with the humidity of the environment and form particles of sulfuric or nitric acid . These acids corrode the construction materials of buildings and monuments, which constitute the historical heritage of humanity acid rain .


Particles and other air pollutants cause the alteration of typical soil elements and physicochemical properties of water . They intervene significantly in the formation of the acid rain phenomenon , its impact on the biosphere is determined by the degree of toxicity and organic content of the same.

Protective measures for health

Among the measures that can be taken to protect health are considered:

  • Avoiding exposure to airfree condition when the quality of the air is not satisfactory
  • Exercise and other outdooractivities during the period of hours that this contaminant has low concentrations.
  • Eat plenty of antioxidant-containing foods like fruits and vegetables and water .
  • Do not exercise and activities that require considerable physical effort in eroded soils suchas sports fields without vegetation cover or pavement, as it affects and does not benefit health.
  • Protect the airways with mouth covers or damp cloths in case of chutes.
  • Promote the reforestation and recovery of eroded soils.


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