Kathmandu choked on polluted air for 75 of the last 90 days

Simulated plumes of PM2.5 surge across the Indo-Gangetic Plain and Himalayan Foothills as seen in this timelapse animation between 1st January to 13th March 2025. Visualization by Arshini Saikia/ ICIMOD and Manohar Dahal/ ICIMOD

Kathmandu– As air quality in Kathmandu hit the hazardous or extremely hazardous category this week, new ICIMOD analysis shows that high pollution has been the norm in 2025: with inhabitants suffering 75/90 days of unhealthy air in the past three months.

Experts at the centre attribute the spike to pre-monsoon forest fires across Nepal, especially in the west where many districts are in moderate to extreme drought.  

On April 3, the Government of Nepal’s Air Quality Monitoring dashboard recorded a 24-hourly AQI of 365 (Bhaktapur), 273 (Shankapark), 248(Ratnapark), 235 (Bhaisipati) and 235(Khumaltar). 

Sagar Adhikari, Air Pollution Analyst, ICIMOD, says “The prevailing dry conditions have led to more instances of forest fires across the country. In addition to the existing pollution being emitted from different sectors i.e. residential, transport and dust, forest fires have worsened these conditions. Existing meteorological conditions are also leading to pollution stagnating over the valley.” 

Notable emissions coming from forest fires include carbon monoxide, fine particulate matter in the form of PM2.5 and black carbon. When breathed in, these finer particles of this pollution can enter the bloodstream and lead to respiratory conditions, and even death.  

Naryan Babu Dhital, Assistant Professor at Patan Multiple Campus, Tribhuvan University says, “While estimates of mortality and morbidity rates from forest fires do not yet exist, this does show the urgency for investing in primary baseline data. Our research shows that ambient PM2.5 air pollution has contributed to 48,000 deaths in 2019. We used secondary data including the Global Burden of Diseases data source to carry out our analysis.” 

Black carbon or soot which is emitted from these forest fires, is part of a number of harmful pollutants that are also seen as powerful ‘climate forcers’. These climate forcers have the ability to greatly impact climate systems, including those in the Hindu Kush Himalaya. A recent policy brief released by the Clean Air Fund makes the case for reducing black carbon emissions, as these are known to quicken glacial melt and alter the monsoon. 

“We know that black carbon has contributed significantly to glacial melt across the Hindu Kush Himalaya, with some regions seeing up to 39% of melt attributed to this super pollutant. Tackling black carbon requires a coordinated, cross-sectoral approach that not only protects glaciers but also ensures cleaner air for millions of people in the region”, says Khushboo Sharma, Air Pollution Analyst, ICIMOD 

Meanwhile, a nationwide air quality monitoring network, led by Nepal’s Department of Environment, provides critical data to track pollution hotspots and inform public health measures. Crop burning is also known to significantly add to harmful emissions, and coincides with peak forest-fire season. 

Experts press for faster emissions reductions at the global level to limit temperature rise as well long-term strategies at the national level to curb forest fires – including better fire monitoring systems and sustainable land management – are critical to preventing future crises.

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