Bangalore's Air: Major Pollutants And Their Sources

Bangalore, India, is known as the country's Silicon Valley and is one of its fastest-growing cities. As the city rapidly expands, its air quality is deteriorating. Bangalore is the 361st most polluted city in the world and the 82nd most polluted city in India. The city's major air pollutants include nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs), carbon dioxide (CO2), and particulate matter (PM). The primary source of these pollutants is the transportation sector, with the city's growing population increasingly relying on private vehicles.

Nitrogen dioxide (NO2) and sulfur dioxide (SO2)

The impact of these pollutants on human health is significant. High-intensity exposure to NO2 in confined spaces has led to catastrophic consequences for humans, including fatalities. Even ambient NO2 exposure may increase the risk of respiratory tract infections by interacting with the immune system. SO2 also negatively affects respiratory health, contributing to respiratory symptoms in both healthy individuals and those with pre-existing pulmonary conditions. Studies have shown that exposure to SO2 causes changes in airway physiology, including increased airway resistance.

Bangalore, as the third most populous city in India, has a vast number of vehicles on its roads, resulting in substantial emissions. Many of these vehicles fall below the quality control standards seen in countries like the United States or Australia. The continued use of diesel as a fuel and the prevalence of older, low-quality cars and buses contribute to the city's air pollution. Additionally, the lack of stringent charges for parking or road rule violations, which have proven effective in reducing vehicle usage elsewhere, further compounds the issue.

To address this problem, Bangalore needs to take more effective measures to phase out poor-quality vehicles and encourage the use of public transportation. The city is known for having one of the more efficient public transport systems in India, but more needs to be done to reduce the reliance on personal vehicles. Implementing initiatives to incentivize public transportation use and properly enforcing penalties for traffic violations can help reduce vehicle emissions and improve Bangalore's air quality.

Particulate matter (PM2.5 and PM10)

Particulate matter, or PM, is a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen, while others are so small they require an electron microscope for detection. PM2.5 and PM10 are categories of particulate matter defined by particle diameter.

PM2.5 refers to fine inhalable particles with diameters of 2.5 micrometers or less. To put this in perspective, the average human hair is about 70 micrometers in diameter, making it 30 times larger than the largest fine particle. These particles can be made up of hundreds of different chemicals and come in many sizes and shapes. They are emitted directly from sources such as construction sites, unpaved roads, fields, smokestacks, and fires. Most PM2.5 particles form in the atmosphere as a result of complex reactions between chemicals such as sulfur dioxide and nitrogen oxides, which are themselves pollutants emitted from vehicles and factories.

PM2.5 is of particular concern due to its health risks. As fine particles can reach deep into the lungs and even the bloodstream, long-term exposure to PM2.5 has been linked to premature death, especially in people with chronic heart or lung diseases. It also reduces lung function growth in children and contributes to thousands of hospitalizations for cardiovascular and respiratory diseases each year. In California, for example, PM2.5 exposure contributes to about 2,800 hospitalizations annually. Additionally, PM2.5 affects visibility by altering how light is absorbed and scattered in the atmosphere, creating a hazy effect.

PM10 refers to particles with diameters of 10 micrometers or less, which are inhalable into the lungs. While PM2.5 comprises a portion of PM10, they often derive from different emission sources and have distinct chemical compositions. The health effects of long-term exposure to PM10 are less clear than those of PM2.5, although studies suggest a link between PM10 exposure and respiratory mortality. The International Agency for Research on Cancer (IARC) concluded in a 2015 review that particulate matter in outdoor air pollution causes lung cancer. Similar to PM2.5, certain groups, including older adults with chronic heart or lung disease, children, and asthmatics, are most at risk of adverse health effects from PM10 exposure.

In Bangalore, India, the overall air quality index was reported as 125, with a PM2.5 AQI of 98 and a PM10 AQI of 125 on May 14, 2025. Bangalore is ranked 82nd among the most polluted cities in India. The main sources of pollution in the city are roads, including vehicles and road dust, as well as the construction industry. While Bangalore's air quality is not as hazardous as some other Indian cities, there is room for improvement to ensure the well-being of its citizens, especially those sensitive to air pollution.

Construction dust and road dust

Bangalore, the capital city of the Indian state of Karnataka, is ranked 82nd among the most polluted cities in India. The city's air quality is primarily affected by pollutants from vehicles and road dust, as well as construction dust.

The construction industry in Bangalore contributes significantly to air pollution. Various infrastructure projects and the development of large residential and commercial complexes result in high levels of construction dust in the city. This dust consists of fine particles of metals, plastics, concrete, and other similar materials. The Karnataka State Pollution Control Board (KSPCB) has issued directives to mitigate construction dust, including instructing construction sites to handle waste within their sites and send it to designated spots, advising against dumping construction sand in the open without mitigation measures, and directing the Bruhat Bengaluru Mahanagara Palike (BBMP) to use road sweepers to clear dust from roads.

In addition to construction dust, road dust is a significant contributor to Bangalore's air pollution. The city's busy roads, including the 59-km Outer Ring Road, often have large amounts of fine dust due to construction, unpaved service roads, and the transportation of sand. Motorists and residents are affected by the dust that is stirred up by vehicles, especially on unpaved or potholed roads. The Energy Research Institute's (TERI) study found that road dust contributed more than 50% of PM10 (10 mm particulate matter) pollution in the city.

The Karnataka government has issued directives to address road dust pollution, including instructing road development agencies to ensure regular watering at construction sites, use covered trucks to transport materials, and implement measures such as fixing sprinklers and creating green air barriers. Despite these efforts, the implementation of dust control measures remains a challenge, and the condition of roads in Bangalore is often described as poor, with dust and pollution affecting the daily lives of residents and motorists.

Fossil fuel consumption and vehicle emissions

Bangalore, the capital city of the Indian state of Karnataka, is ranked 82nd among the most polluted cities in India. The city's air quality is primarily affected by road traffic, including cars and buses, as well as road dust, which consists of accumulated soot and other fine particulate matter.

Vehicular emissions are a significant contributor to air pollution in Bangalore. Motor vehicles are estimated to contribute nearly 24% of the world's direct CO2 emissions, and carbon monoxide (CO) emissions, which arise from the incomplete combustion of fossil fuels, are highly detrimental to health as they affect the body's ability to absorb oxygen. Studies have found that in highly polluted cities like New Delhi, vehicular emissions are the primary source of CO. While Bangalore is known for having a relatively efficient public transportation system compared to other Indian cities, the lack of initiatives to reduce private vehicle usage and enforce strict rules regarding parking and road regulations has contributed to the high number of vehicles on the roads, exacerbating air pollution.

In addition to CO emissions, vehicular emissions in Bangalore produce other pollutants such as nitrogen dioxide (NO2) and sulfur dioxide (SO2), which can combine with other chemicals to form a variety of harmful compounds. Nitrous oxide (NOx), which arises from the high-temperature combustion of fossil fuels, is also a significant contributor to air pollution in Bangalore and other Indian cities. These emissions have detrimental effects on human health and contribute to the formation of ground-level ozone (O3), which is a major component of smog.

To address the issue of vehicular emissions and improve air quality, policymakers in India are promoting the adoption of electric vehicles (EVs). This shift towards electrification is a crucial step towards reducing fossil fuel consumption and mitigating the environmental and health impacts of vehicle emissions in Bangalore and across India.

Furthermore, the construction industry in Bangalore also contributes to air pollution by releasing high amounts of particulate matter, such as fine particles of metals, plastics, and dust from concrete, into the atmosphere. These emissions, along with those from vehicular sources, have led to moderate to unhealthy air quality levels in Bangalore, particularly during certain months, posing risks to sensitive groups such as the young, elderly, and those with pre-existing medical conditions.

Carbon monoxide (CO) and carbon dioxide (CO2)

Carbon monoxide (CO) is a colorless, odorless, and tasteless gas that is produced by the incomplete combustion of carbon-containing fuels. Common sources of CO include vehicle exhaust, malfunctioning home heating systems, and fires. It is highly toxic to humans, as it binds to hemoglobin in the blood when inhaled, reducing the blood's ability to carry oxygen, which can lead to carbon monoxide poisoning. Symptoms of CO poisoning include headaches, dizziness, weakness, nausea, and confusion, and high concentrations can be fatal.

On the other hand, carbon dioxide (CO2) is also a colorless, odorless, and tasteless gas, but it is naturally occurring and required for plant and animal life. It is produced by the decomposition of organic matter, animal and human respiration, and some industrial processes. While CO2 is generally not toxic to humans in typical atmospheric concentrations, in enclosed or poorly ventilated spaces, high levels of CO2 can displace oxygen, leading to suffocation, asphyxiation, and even death.

Both carbon monoxide and carbon dioxide can be harmful to human health, especially in confined spaces. The effects of these gases on the body differ, with CO poisoning being a more common occurrence worldwide compared to CO2 fatalities.

In Bangalore, carbon monoxide levels are monitored as part of the city's Air Quality Index (AQI). As of May 14, 2025, the AQI for carbon monoxide in Bangalore was reported as 3, indicating moderate levels.

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