PM2.5 levels 20x higher than WHO norms: Expert

India is the second most polluted country globally, with an average PM2.5 concentration of 58.7 µg/m³ far exceeding the WHO guideline of 5 µg/m³.

Thirteen of the world’s top 20 most polluted cities are in India, including Delhi (the most polluted capital) and industrial hubs like Byrnihat (PM2.5 lev els-25x WHO limits).

Around 99% of Indians breathe air. worse than WHO standards, with rural areas also heavily affected by biomass burning and industrial emissions. Guwahati, the largest city in India’s northeastern region, has emerged as one of the most polluted cities in the world, ranking second in the 2023 World Air Quality Report with an average annual PM2.5 concentration of 105.4 µg/m³ more than 20 times the WHO’s recommended lev el of 5 ug/m³. Once known for its lush greenery and proximity to the Brahmaputra river, the city is now facing deteriorating air quality, posing risks to public health and the environment. Understanding the reasons behind this pollution and exploring practical reduction methods is crucial for restoring the city’s air to healthier levels.

As of April 1, 2025, Guwahati’s Air Quality Index (AQI) stands at 162, classified as “Unhealthy with PM2.5 levels at 72 µg/m³ and PM10 at 133 µg/m³ The city has shown a worrying 9% rise in AQI from 2020 to 2025, with a dramatic 50% increase between 2024 and 2025 alone. Breathing Guwahati’s air in currently equivalent to smoking 3.1 cigarettes per day posing severe health risks to residents.

Major Causes of Air Pollution in Guwahati: The city’s streets are clogged with a growing number of vehicles – cars, scooters, buses, and trucks -emitting carbon monoxide (CO), nitrogen oxides (NOx), and fine particulates. Traffic congestion, especially during peak hours, exacerbates the problem, with pollutants lingering in the atmosphere due to poor dispersion in Guwahati’s river valley setting.

The transport sector contributes significantly to Guwahati’s pollution, emit ting 5,250 tons of PM2.5 annually. The city’s vehicle population has exploded alongside its growing population (estimated to reach 3 million by 2025), with road dust from vehicles being a major contributor. The phenomenon of “induced demand” from flyover construction has ironically led to more private vehicles on roads.

Improper waste management leads to frequent fires at dumping grounds. particularly near the ecologically sensitive Deepor Beel wetland. These fires emit continuous toxic gases, with one site reportedly burning for a month straight. Waste burning accounts for 850 tons of PM2.5 emissions annually. Development of controlled landfill sites to reduce methane emissions and fire risks could be considered very important.

The PM2.5, a key pollutant, penetrates deep into the lungs and bloodstream, raising risks of asthma, heart disease, and lung cancer. Reports indicate that expo-sure to such levels could reduce life expectancy by about two years, a more severe impact than many communicable diseases. Environmentally, black carbon from Guwahati contributes to glacier melting in the Himalayas by absorbing sunlight and trapping bent, disrupting regional climate patterns. Guwahati’s rapid infrastructural development generates substantial dust pollution (4,700 tons of PM2.5 yearly).

Road expansion projects have involved cutting thousands of trees, removing natural air filters. Ongoing infrastructure projects and roadworks kick up significant amounts of dust, a major contributor to PM10 levels. The Brahmaputra’s sandy banks and hill-cutting activities further add to airborne particles, particularly during the dry season (November to April).

Small and medium-scale industrial units add to the pollution burden.

Guwahati’s population has surged, with its metropolitan area estimated at 1.1 million in 2020 and projected to reach 1.5 million by 2005. This growth has fuelled unplanned urban expansion, increasing demand for housing, transportation, and infrastructure. The resulting construction activities release dust and particulate matter (PM2.5 and PM10) into the air, while the rising population strains natural resources.

Guwahati’s valley-like topography surrounded by hills traps pollutants, especially during winter when temperature inversions occur. Low rainfall during winter and pre-monsoon periods exacerbates the problem. During winter and pre-monsoon periods, low rainfall, temperature inversions, and reduced wind speeds trap pollutants close to the ground. Events like Diwali, with firecracker use, spike PM2.5 levels dramatically, often pushing ait quality into the “unhealthy range.

Recommendations: Public trans port use must be encouraged by expanding and modernizing Guwahati’s bus network, as well as by incentivizing electric vehicles (EVs) through subsidies and charging infrastructure. Promoting cy cling could also be considered utmost important and for this cycling lanes must be built along the city roads. Implementation of stricter emission norms for vehicles and enforcement of regular checking are also important.

Though not heavily industrialized, Guwahati hosts small-scale industries and the Guwahati Refinery, which emit pollutants like sulphur dioxide (SO,) and volatile organic compounds (VOC). Poor waste management, including methane emissions from dumping grounds like those near Deepor Beel, worsens air quality when spontaneous fires occur. The Guwahati Refinery and other industrial facilities contribute 2,150 tons of PM2.5 emissions annually,

There must be an improved implementation for door-to-door waste col lection system with proper segregation of degradable and non-degradable items like plastic etc., establishment of com-posting facilities for wet waste and cycling systems for dry waste and modernization of waste disposal methods to prevent spontaneous fires.

Enforcement of dust control measures at construction sites, implementation of stricter emission standards for industries and promotion of cleaner technologies in brick kilns (650 tons PM2.5 annually) are the need of the hour

Unnecessary tree cutting must be avoided and afforestation programmes must be implemented, green buffers should be developed around industrial areas, there should be massive plantation in the city including microforest development in all schools, colleges, office campus etc., across the city.

There should be rigorous implementation of the city’s “Clean Air Action Plan’ under “New Car Assessment Pro-gram without any further delay. Also necessary installation of more real-time air quality monitoring stations high pollution periods must be ensured.

Introduction of indoor air purifiers, especially for vulnerable groups must also be ensured.

Guwahati’s air pollution crisis stems from rapid urbanization, inadequate planning, and geographical challenges. While the city is implementing its National Clean Air Program action plan, accelerated efforts across all sectors are need-ed. The solutions require coordinated action between government agencies, industries, and citizens. With proper waste management, cleaner transportation, regulated construction, and green urban planning. Guwahati can work to-ward cleaner air and better health for its residents. The time to act is now, before the situation worsens further.

(The author is the founder Head i/c (2009-2014), Department of Bioengineering and Technology, GUIST and represently the Vice Chancellor of Krishnaguru Adhyatmik Visvavidylaya, Barpeta)

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