**Policy Summary: Airborne Pathogenic Bacteria in Densely Populated Areas of Delhi**
A recent study by scientists at the Bose Institute, an autonomous institute of the Department of Science and Technology (DST), has revealed a significant correlation between population density, air pollution, and the abundance of airborne pathogenic bacteria in Delhi. The research, published in *Atmospheric Environment: X*, found that airborne pathogenic bacteria, primarily responsible for respiratory, gastrointestinal tract (GIT), oral, and skin infections, are twice as abundant in densely populated areas of Delhi compared to less crowded regions.
The study highlights the role of particulate matter (PM2.5) as a carrier for these bacteria, facilitating their spread deep into the lungs and other parts of the body. The Indo-Gangetic Plain (IGP), known for its high population density and air pollution, experiences stagnant wind and low boundary layer height during winter due to western disturbances and increased relative humidity, leading to the accumulation of pollutants.
The research, led by Dr. Sanat Kumar Das, identified the transition periods between winter and summer, particularly during hazy days or winter rains, as high-risk windows for the spread of airborne diseases. The combination of pollution and weather patterns allows microbes to persist in the air for extended periods.
This study underscores the need for urban health planning to address the risks posed by airborne pathogens in megacities like Delhi. Understanding the interplay between weather, pollution, environmental factors, and population density is crucial for predicting outbreaks, improving urban design, and safeguarding public health. The study serves as a "wake-up call" for governments and health experts to proactively address the issue.
(NKRPSM Release ID: 2163068)
(DOI: https:doi.org10.1016j.aeaoa.2025.100351)
Key Entities Referenced
Ministry of Science Technology: The Indian government ministry responsible for science and technology policy and administration.
Delhi: A densely populated urban metropolitan city and one of the most polluted cities of the world, located in India. Also refers to the National Capital Territory of Delhi.
IndoGangetic Plain: A large and densely populated plain in India with high air pollution, where Delhi is located.
Bose Institute: An autonomous research institute under the Department of Science and Technology (DST) that conducted the study on airborne pathogens in Delhi.
Department of Science and Technology: A department under the Ministry of Science and Technology, which funds and oversees scientific research in India.
PM2.5: Particulate matter with a diameter of 2.5 micrometers or less, a major air pollutant that acts as a carrier for pathogenic bacteria.
Respiratory, Gastro Intestinal Tract, Oral and Skin infections: Infections that are caused by airborne pathogenic bacteria.
Atmospheric Environment: X: An international journal where the study on airborne pathogens in Delhi was published.
Ministry of Science & Technology
Invisible bacteria get free ride in the city air,
threatening human health
Posted On: 02 SEP 2025 4:30PM by PIB Delhi
Airborne pathogens, bacteria capable of causing infections in the lungs, gut, mouth and skin, are twice as
abundant in densely populated parts of Delhi compared to less crowded regions.
Indo-Gangetic Plain (IGP) in India is one of the most densely populated regions in the world with highest air
pollution. During winter, entrance of western disturbance causes sudden drop in atmospheric temperature,
thereby subsequently increasing relative humidity (RH), which is responsible for stagnant wind and low
boundary layer height, favouring accumulation of lower atmospheric pollutants over IGP. Delhi, an urban
region within IGP, is most populous and rapidly growing city in the country and one of the most polluted
cities of the world.
A significant increase in airborne microbial population has earlier been reported in winter over IGP. However,
there is limited information regarding the effect of meteorology, air pollution and population on airborne
bacterial communities that can help understand their impact on human health.
A study of health risks posed by airborne pathogens over urban metropolitan city like Delhi in India by
scientists from Bose Institute, an autonomous institute of Department of Science and Technology (DST) has
revealed for the first-time that airborne pathogenic bacteria mainly responsible for Respiratory, Gastro-
Intestinal Tract (GIT), Oral and Skin infections are two times higher over densely populated urban regions
due to higher concentrations of tiny particles PM .
2.5
PM2.5—the microscopic dust specks help bacteria to hitch ride through the city air. Since the particles are
small enough to sneak deep into the lungs they act as carriers of the pathogenic bacteria, thus spreading the
infection to different parts of the body.
Fig: Population dependent alteration in urban airborne pathogenic bacterial community over Delhi: A
comparative investigation between airborne bacterial communities over high populated region (HPR) and
low populated region (LPR) within Delhi city, as shown in the above figure.
The research led by Dr. Sanat Kumar Das found that the transition from winter to summer, especially during
hazy days or winter rains, creates high-risk windows when airborne diseases are more likely to spread. During
these periods, the cocktail of pollution and weather patterns creates the perfect storm for microbes to linger in
the air longer than usual. Link to the published paper: (https://doi.org/10.1016/j.aeaoa.2025.100351The study published in an international journal, named ‘Atmospheric Environment: X’ could be a wake-up
call for urban health planning. Megacities like Delhi, where millions breathe in polluted air daily, may also be
exposing residents to invisible bacterial communities enriched with pathogens. Understanding how weather,
pollution, environmental factors and population density affect these airborne bacteria and resultant disease
transmission, could help governments and health experts better predict outbreaks, improve urban design and
protect citizens.
***
NKR/PSM
(Release ID: 2163068)