Air Pollution-II. Particulate Matter

PM stands for particulate matter (also called particle pollution): It is the sum of all solid particles and liquid droplets found suspended in the air. These complex mixtures include both organic ( mainly natural hydrocarbons and synthetic organic compounds) and inorganic particles( usually heavy metal elements like lead and mercury and other toxic non-HC compounds), dust, soot, smoke and liquid droplets. Some particles, such as dust, dirt, soot (Carbon dust emitted in the air due to incomplete combustion of fuels), or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope. The source of the particles can either be natural or anthropogenic.

Particulate matter is of two types:

  • PM10 : inhalable particles, with diameters that are generally 10 micrometres and smaller; and
  • PM2.5: fine inhalable particles, with diameters that are generally 2.5 micrometres and smaller.
    • How small are 2.5 micrometres? Think about a single hair from your head. The average human hair is about 70 micrometres in diameter – making it 30 times larger than the largest fine particle.
      PM matter
      one can imagine the size of the particles floating in the air.

      Why the size of the particle matters?

    • Inhalation of particulates can have adverse health impacts, and there is understood to be no safe threshold below which no adverse effects would be anticipated. The size of the particles helps us to understand the severity of breathing them every day. Fine particles are absorbed deep inside the lungs and there is no way to remove them.
    • “Larger” particles (> 10 µm), which are visible to the naked eye, are not those of most concern in terms of health. They are trapped in the upper respiratory tract (nose and throat) and do not enter the lower respiratory tract. Particles 2.5 to 10 µ in diameter reach the upper regions of the bronchial tree and may be filtered out by its cilia and dislodged by coughing. The most dangerous are fine particles of less than 2.5 µ in diameter. These can penetrate deeply into the respiratory system as far as its terminal structures and are deposited by sedimentation or enter the bloodstream. They can carry toxic, allergenic, mutagenic or carcinogenic compounds, such as polycyclic aromatic hydrocarbons and heavy metals.
    • The biggest impact of particulate air pollution on public health is understood to be from long-term exposure to PM2.5, which increases the age-specific mortality risk, particularly from cardiovascular causes. Several plausible mechanisms for this effect on mortality have been proposed, although it is not yet clear which is the most important.  Exposure to high concentrations of PM (e.g. during short-term pollution episodes) can also exacerbate lung and heart conditions, significantly affecting the quality of life, and increase deaths and hospital admissions. Children, the elderly and those with predisposed respiratory and cardiovascular disease, are known to be more susceptible to the health impacts of air pollution.
      • lungs
        The fine particles reach up to the alveoli and alveolar duct from where they cannot be removed. Long exposure to fine particles causes inflammation in the lungs, various diseases leading to death.

Sources of PM:

These particles come in many sizes and shapes and can be made up of hundreds of different chemicals. Particulate matter emissions are generated from different sources:

  1. Mechanical: Coarse particles have an aerodynamic diameter ranging from 2.5 to 10µm (PM10-2.5), which distinguishes them from the smaller airborne particulate matter referred to as fine (PM2.5) and ultrafine particles (PM0.1). These are produced by the mechanical break-up of larger solid particles, powdering, crushing, cracking, transport of non-cohesive materials (sand and gravels), soil erosion (by the wind for example). The coarse particles also include dust from roads, agricultural processes, uncovered soil or mining operations, particles produced from incomplete combustion of fossil fuels. These particles are usually a few microns to a few hundred microns in diameter
  2. Chemical or thermal: These particles form when chemical reactions or high-temperature evaporation followed by condensation change the state of the material. Most particles form in the atmosphere as a result of complex reactions of chemicals such as sulfur dioxide and nitrogen oxides, which are pollutants emitted from power plants, industries and automobiles.
  3. Biological: Pollen grains, fungi, bacteria.

Emissions of particulate matter can, therefore, be from natural sources or from human activities:

    • Particulate matter emissions from human activities are closely dependent on dust removal equipment, processes and operating conditions. The main sources of emissions are:
      • ploughing.
      • construction sites, public works and civil engineering,
      • quarrying (Extracting stone or other materials): This process release dust and chemicals in the air causing massive air pollution. This is one of the reasons which is responsible for the deteriorating health conditions of the workers and nearby residents.
        Blasting the rocks is a part of mining and quarrying

        quarry gold mine
        Gold mine in Australia.
      • Combustion of solid mineral fuels, liquid fuels and biomass.
    • thermal
      Thermal power plants pollute the air by emitting particulate like fly ash and mercury.

      Particulate matter emissions from natural sources are closely related to climate and natural conditions – dust carried by the wind from the area of no green cover, smoke from the combustion of inflammable materials, wind erosion, forest fires, volcanic eruptions, pollen, etc.

      forest fire
       Forest fire is a huge concern for now.

What are the Harmful Effects of PM?

Particulate matter contains microscopic solids or liquid droplets that are so small that they can be inhaled and cause serious health problems. Some particles less than 10 micrometres in diameter can get deep into your lungs and some may even get into your bloodstream. Of these, particles less than 2.5 micrometres in diameter, also known as fine particles or PM2.5, pose the greatest risk to health. The size of particles is directly linked to their potential for causing health problems.

Exposure to small particles less than 10 micrometres in diameter poses the greatest problems, causing:

  • Nonfatal/fatal heart attacks
  • Irregular heartbeat
  • Aggravated asthma
  • Decreased lung function
  • Increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing
  • Premature death in people with heart or lung disease
  • Long term exposure to particulate matter reduces life expectancy. Increase in the allergies, cardiovascular diseases and lung cancer are the main reason in the reduction in life expectancy. Reduce lung function in children and adults lead to bronchial asthma which is the cause of low-quality life.
  • Cardiovascular Problems: Fine particles can easily enter the body without facing resistance from the body. Therefore fine particles have a drastic impact on the heart and the functions of the heart. Therefore, the particulate matter is responsible for many cardiovascular diseases. Frequent exposure to PM can lead to a large amount of inhalation of particles. Therefore, accumulation of PM will cause the buildup of plaque in the arteries and vascular inflammation.
  • Atherosclerosis: Air pollutant inhalation can cause plaque buildup in the walls of the blood vessels which will lead to hardening of arteries and in turn cause hypertension and left ventricular failure.
  • Birth Defects and Failed Pregnancy: Particles ability to enter into the body makes it easy to enter any pregnant mothers body and then into the child during long exposure to particulate air pollutants. Thus, harmful chemical pollutants can cause any type of birth defects. It is also the reason failed pregnancies specifically in town and cities facing extreme levels of pollution.
  • Death: High levels of aerosols and other pollutants can cause premature death. Air pollution due to coal industries is the cause of many premature deaths every year in India and globally.


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