Air PollutionAir Quality

What is PM2.5 Particulate Matter?

If we talk about air quality, India has reached an alarming state. Increased PM2.5 impacts air quality, the environment, and human health. The World Health Organization’s recent report showed that 8.0 million deaths per year are seen due to bad air quality. This represents 6.7% of the global disease burden that might be related to particulate matter. Exposure to ozone recorded 1.52 million premature deaths.

Factors for Increased PM2.5 Concentration

The combination of suspended solid particles and liquid droplets in the air forms particulate matter. It also contains dust and soot. PM2.5 is an ultra-fine inhalable particle having a diameter of 2.5 micrometers, and it can penetrate deep into the lungs, causing respiratory diseases and ailments. It also comprises metals and heavy metal ions (Cadmium, Nickel, Potassium, Copper), organic and inorganic compounds, allergens, many microbial compounds, and Polycyclic Aromatic Hydrocarbons (PAHs). 

Increased air temperature during the winter season and atmospheric inversions in the Northern hemisphere increase PM2.5 concentration in the air. During the summer season, stationary air mass, forest fires, and secondary aerosol formation increase PM2.5 concentration. 

In northern India, several factors contribute to increasing particulate matter concentration. Physical, chemical, and meteorological factors affect the concentration of pm in the environment. Physical and chemical factors, inclusive of particle size, number, density, and concentration in the atmosphere, affect the mobility (movement) of particles. Other than this, meteorological factors like wind speed, wind direction, and weather conditions such as rainfall affect the processes of transport and the fate of PM in the environment. 

size of pm2.5

In summers, residential energy contributes 62% to PM2.5 concentration and 70% to winters. Research experiments have shown that concentration rises at night. India has reported 60 ug/m3 and 40 ug/m3 as 24-hour and annual PM2.5 concentrations, respectively.


The presence and emergence of PM2.5 in the environment are still debatable. Sources are the origin from where this pollutant enters the environment.

1. Natural Sources

Several natural events, such as rain and runoff, affect the mobility of PM 2.5. Rainwater washes away the pollutant and changes its fate in the environment. Forest fires, volcanic eruptions, and natural calamities such as earthquakes lead to an increase in Particulate Matter concentration. It has a reduced rate of atmospheric descent, which increases its persistent time in the environment.

2. Industries and treatment plants

Processes of product production in the Paper pulp industry, oil refineries, brick kilns, power plants, and municipal waste treatment plants release PM 2.5 into the environment.

sources of pm2.5

3. Emissions

Emissions from vehicles, coal combustion, burning of leaves and woods, agricultural activities, stubble burning, biomass burning, and biofuel burning lead to increased particulate concentration. Gaseous emissions from power plants react in the atmosphere and form particulate matter.

4. Household activities and personal habits

PM 2.5 is also released from tobacco smoking, candle burning, cooking activities like sautéing, frying, irregular maintenance of kitchen chimneys, kerosene heaters, gas stoves, fireplace operation, etc. Other than this, construction activities increase the concentration of PM2.5.


A. Impacts of PM2.5 on the environment

Particulate matter not only impacts human health but also the environment. The environmental impact of PM2.5 is seen as visibility reduction, acid rain, increased air pollution, material damage, ecosystem damage, reduced functioning of plants & trees, contaminated streams & oceans, and decreased crop productivity and yield. Its dispersal is easy due to size and causes it to change its environmental fate. 

1. Haze production

The haze reduces the visibility and increases the chances of road accidents. Particulate Matter leaves a stain affecting the materialistic environment such as buildings, statues, monuments, etc.

2. Soil fertility

Different chemical composition of particulate matter shows different effects. It also affects soil fertility leading to a reduction in crop yield and agricultural productivity.

3. Nutrient cycle

Particulate Matter interferes with nutrient cycling affecting the rhizosphere.

impact of PM2.5 on environment

4. Plant Photosynthesis

Fine particles, when settled over leaves, block the penetration of sunlight into leaves and disrupt the process of plant photosynthesis. The generation of abrasions and radiative heat affects the photosynthesis of plants due to the layering of PM2.5 over leaves. This reduces photon flux reach towards photosynthetic tissues.

5. Deposition in water bodies

The settling of toxic PM2.5-containing heavy metals into water bodies, including streams and oceans, affects the marine and aquatic ecosystems. Several aquatic life forms die due to their reduced acidic tolerance. This also impacts humans when they include contaminated aquatic food in their diet.

6. Disturbing ecosystems

Particulate matter also disrupts the food chain and food web in the ecosystem because of their shared dependencies, different toxicity tolerances, and associated effects. Its concentration affecting the ecosystem has direct links to climate change. 


B. Impacts of PM2.5 on human health

In epidemiological studies, severe health effects are linked with particulate matter having a diameter of 2.5 microns. The effects of particulate matter in the human body depend on its exposure duration and concentration.

The health effects of PM2.5 differ by age group, gender, and race. Studies and research show white people, children, and women are highly susceptible to being affected when exposed to it.

health impacts of pm2.5

1. Penetration to the respiratory system

Particulate matters have a tendency to carry toxic materials with themselves due to their reduced diameter and increased surface area. The small-sized PM easily escapes from nostrils and penetrates deep down towards the bronchi and alveoli, corroding the alveolar wall in the lungs.

According to WHO, in 2016, 4.2 million premature deaths were recorded because of PM2.5 exposure.

2. Increased Hospitalizations & absenteeism

Exposure to PM2.5 increases hospitalizations, visits to the emergency room, and absenteeism from schools and offices, especially in cases with pre-existing disorders, old people, and children. Particulate matter causes pneumonia and bronchitis.

3. Malignant effects

Exposure to Particulate Matter 2.5 shows malign effects in early life, including respiratory, cardiovascular, and prenatal disorders. This elevates infant mortality chances.

4. Human cornea and conjunctiva

Exposure to the high concentration of PM2.5 leads to burning, itching, and redness of the eyes, allergic conjunctivitis. Laboratory studies show it reduces the survival of Human Corneal Epithelial Cells (HCEC) by triggering cell autophagy. It is also responsible for cell shrinkage.

5. Reduced antioxidants

Particulate Matter reduces antioxidants in the human body. Hydroxyl ion-induced oxidative stress damages the DNA. Teratogenesis, mutagenesis, and carcinogenesis are induced by damaged DNA when it is not repaired in time.<