The Indo-Gangetic Plain, home to nearly a billion people, is witnessing an alarming surge in dense and prolonged fog episodes, a phenomenon increasingly linked to rising pollution and unchecked human activity, according to the World Meteorological Organization (WMO).
The UN weather and climate agency, in its latest air quality and climate bulletin issued on Friday, warned that the frequency and intensity of fog events across the fertile belt are being exacerbated by fine particle emissions from vehicles, industries and burning of crop residue.
Fog typically forms when the air near the ground cools to the dew point, allowing moisture to condense on particles known as ‘fog condensation nuclei’ (FCN). The WMO noted that elevated concentrations of PM2.5, spewed from tailpipes, industrial flue gases, coal-fired brick kilns and domestic biomass use, provide abundant nuclei for persistent fog formation.
The situation worsens in winter when temperature inversions trap pollutants beneath a layer of warmer air, prolonging fog events and choking the plains in a toxic blanket.
“Urban sprawl in the Indo-Gangetic Plain has intensified emissions and created urban heat islands, disrupting local weather dynamics,” the bulletin stated. The report also highlighted emissions from construction, ammonia from livestock and poor sanitation as critical contributors, with ammonia interacting with other chemicals to form stable FCNs.
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Post-monsoon stubble burning in Punjab and Haryana continues to be a dominant seasonal driver. Satellite observations confirm steep increases in aerosol optical depth during these months, mirroring sharp spikes in fog density across the region.
The WMO further cautioned that the interaction between fog droplets and aerosols alters aerosol chemistry, with damaging consequences for both the climate system and air quality. Elevated levels of toxic metals and organic compounds in fog water pose serious health risks.
Beyond health, the fallout is visible in transport disruptions, with flights, trains and road traffic routinely paralysed. “Poor visibility during fog episodes impacts transportation, causing delays and accidents. Fog also causes severe health conditions such as asthma, bronchitis and other respiratory ailments,” the WMO said.
With over 900 million residents exposed to worsening fog conditions, the agency underscored the urgency of curbing emissions from agriculture, industry, transport and domestic use to avert an escalating public health and environmental crisis.
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