Particulate matter (PM): Introduction, definition, and classification


In the first phase of creation, the earth cools from the gaseous state and becomes hard. Although the earth’s interior is fluid and viscous, its outer surface is hard. Some gaseous substances, not being liquid or hard, surround the earth and stick to the earth by gravity. This is how the Earth’s atmosphere originates. The atmosphere is made up of various gaseous elements, aqueous elements, dust particles, salts, particulate matter, etc.  These dust particles float to the lower layers of the atmosphere. Its amount is not always the same in all spaces of the world. The amount of these particles varies depending on space and time. These are floating solid particles that are separated from the atmospheric gas and water vapor.

A portion of these particles cannot be seen with the naked eye. These particles are particulate matter. Human economic activity, natural phenomena, etc. are responsible for the mixing of particulates in the air. Sea salt particles, plant pollen, and numerous germs are risen by air. Also, a large number of particulates are mixed into the air by volcanic eruption and smoke. The amount of these particulates is highest in arid lands and desert atmospheres. All these particulate matter greatly affect the weather and climate (1) & (3).

Definition of particulate matter

Particulate matter is the sum of small hard and liquid particles, that float in the lower layers of the atmosphere, which cannot be seen with the naked eye, which is formed by various human activities and natural activities. This complex mixture includes both organic and inorganic particles, such as dust, pollen, fumes, and liquid droplets (3).

Characteristics of particulate matter (PM)

Particulate matter has some characteristics. It is discussed below.

  • It can be both hard and liquid.
  • These are small in size and are not visible to the naked eye. It can be seen with the help of a microscope.
  • Particulate matter contains both organic and inorganic particles.
  • The amount of these particles in the atmosphere varies depending on space and time.
  • These particles float in the lower layer of the atmosphere.
  • They greatly affect climate and weather, which adversely affect human health (2) & (3).

Source of particulate matter

Particulate matter components included finely divided solids or liquids such as dust, fly ash, fumes, aerosols, fog, and condensed vapors. These are suspended in the air for extended periods of time. Particulate matter (PM) particles are emitted from both natural and man-made sources. Its components can be directly emitted (primary emission) or secondary emissions.

Primary sources

The primary sources of particulate matter are derived from both human activity and natural activity. A significant portion of the sources of particulate matter are generated by human activity and are released into the air. Such activities include agricultural activities, industrial processes, combustion of wood and fossil fuels, construction and destruction activities, and the dusting of roads into the air.

Another element among the primary sources of particulate matter is directly mixed into the air through natural emissions. This direct natural emission comes from wildfires, sea sprays, and the recovery of organic matter in the leaves. The first of these products is mainly PM2.5 and the second is produced mainly PM10. Mineral dust has both natural and human sources. It can be tempted from arid and semi-arid regions and conducted by agricultural or construction activities. The burning of fossil fuels is the primary source of particulate matter caused by human activities.

Secondary sources

Secondary sources release atmospheric pollutants directly into the atmosphere which helps in the formation of particulate matter. Thus these pollutants are the secondary sources of the formation of particulate matter. These secondary pollutants are Sox, NOx, VOCs, and ammonia.

These primary and secondary sources of particulate matter greatly affect climate and weather, which has adverse effects on human health, plants, and ecosystems (1) & (2).

Classification of particulate matter

There are three types of particulate matter based on size. These are inhalable coarse particles, fine particles, and ultrafine particles (2).

Particulate matter



1. Inhalable coarse particles

These particles are larger than 2.5 micrometers and smaller than 10 micrometers in diameter.


Inhalable coarse particles are found near dusty industries and roadways. These particles are originated by agricultural activities, construction and mining activities, wildfires, windblown dust from open lands, volcanic eruptions, sea sprays, etc.

2. Fine particles

These particles are smaller than coarse particles. Fine particles are 2.5 micrometers or less than 2.5 micrometers in diameter. The size can range up to 2.5 micrometers. Fine particles are usually found in haze and smoke. Fine particles primarily come from car, truck, and bus exhausts, Burning of fossil fuels, forest and grass fires, burning candles or oil lamps,

3. Ultrafine particles

Ultrafine particulate matter is less than 0.1 microns or 100 nm in diameter. These particles originated from burning biofuels, Sea plant pollen, and numerous germ, metal processing activities.

Effects of particulate matter

Particulate matter is very dangerous for human health, plants, ecosystems, and climate. It causes various diseases in the body of people and also greatly affects the weather and climate. The effects of particulate matter are discussed below.

1. Effects of particulate matter on human health

Fine particles are very dangerous for human health. Fine particles are small in size. So these particulates can easily enter into the human respiratory system and then attack the bronchi. These particles affect the lungs. As a result lung cancer is seen in the human body. It also causes various diseases in the human body. Such as irritated eyes, nose and throat, asthma, and lung diseases, heart attacks and arrhythmias, Reduced lung function, cardiovascular and respiratory disease, etc (1).

2. Effects of particulate matter on climate

Climates are greatly affected by this.  As it affects the weather at the regional level and this is the reason for the failure of the Indian monsoon. Particulate matter is responsible for drought in tropical regions. It plays a role in the greenhouse effect and global warming as they are lightly absorbed. And they contribute to the rise in global temperature.

They also reflect the sunlight. So they play a role in increasing the temperature. In the atmosphere, the ozone warms the climate. But particulate matter can have either warming or cooling effects on the climate. Its burning contributes to the warming of the atmosphere. These are one of the leading causes of air pollution and also increase the earth’s temperature. These particles have an adverse effect on the climate. As a result, the earth’s climate is being severely damaged (1) & (2).

3. Effects of particulate matter on vegetation

The effect of particulate matter on plants may be associated with a decrease in the light required for photosynthesis and an increase in leaf temperature due to altered surface optical properties. It can cause leaf injury, and stomatal damage, and therefore has a negative impact on plant growth (1) & (2).

4. Effects of particulate matter on the ecosystem

The ecosystem is affected by particulate matter. A regional impact of this is on the ecosystem linked to climate change. Particulates can carry long distances through the air and then settle on land or water. Particulate matter may make the rivers and lakes acidic. As a result, various fish and marine animals present in rivers and lakes died. River and lake ecosystems are damaged.  Thus the balance of the environment is disturbed (1).

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