"WMO Warns Wildfires and Heatwaves Worsening Global Air Quality and Health"
PM2.5
Particulate matter under 2.5 micrometres; penetrates lungs and bloodstream, causing cardiovascular and respiratory disease.
Ground-level ozone
A respiratory irritant formed when pollutants react in sunlight; peaks during hot, sunny, stagnant conditions.
Air pollution is one of the leading environmental health risks globally. The World Meteorological Organization (WMO), the United Nations' weather and climate agency, publishes an annual Air Quality and Climate Bulletin that tracks the intersection of atmospheric pollution and climate change. A central concern in this bulletin is PM2.5, particulate matter with a diameter of less than 2.5 micrometres. Because of its tiny size, PM2.5 can bypass the body's natural defences, penetrate deep into the lungs, and enter the bloodstream, causing cardiovascular and respiratory disease. By contrast, the coarser PM10 particles (less than 10 micrometres) are largely filtered in the upper respiratory tract and do not penetrate the bloodstream, a distinction that matters for both health assessment and policy. The WHO's revised Global Air Quality Guidelines (AQGs), updated in 2021, set the annual mean PM2.5 limit at 5 micrograms per cubic metre and the 24-hour mean at 15 micrograms per cubic metre, significantly stricter than the 2005 standards. India's National Clean Air Programme (NCAP), launched in 2019, targets a 20–30% reduction in PM2.5 and PM10 concentrations by 2024 compared to 2017 baseline levels, but critics note that even achieving this target would leave Indian cities far above the WHO's 2021 thresholds.
Wildfires and biomass burning are major sources of air pollution. When vegetation burns, it releases a broad suite of pollutants: carbon monoxide, methane, ozone precursors, and sulphur dioxide, alongside fine particulate matter. This is the same set of gases that burning crop residue releases into the atmosphere. Ground-level ozone, distinct from the protective stratospheric ozone layer, forms when pollutants react under intense solar radiation and high temperatures. It does not peak during inclement or rainy weather; it accumulates precisely during hot, sunny, and stagnant atmospheric conditions, which is why heatwaves dramatically worsen ozone pollution. Black carbon (soot), another product of incomplete combustion, is a short-lived climate pollutant with a dual impact: it harms human health and, when deposited on snow and ice, reduces surface reflectivity (albedo), accelerating glacial and ice-sheet melt.
The WMO's latest bulletin identifies a dangerous feedback loop between climate change and air quality. Climate change increases the frequency and intensity of heatwaves and wildfires. Wildfires generate large quantities of PM2.5 and other toxic pollutants. These pollutants in turn worsen climate change, black carbon, for instance, is a potent short-lived climate forcer. The result is a self-reinforcing cycle that undermines both air quality targets and climate commitments simultaneously.
A key finding of the bulletin is that conventional risk models may underestimate wildfire-attributable mortality by up to 93%. This is because microparticles generated by burning vegetation are significantly more toxic than those from industrial or vehicular sources, even car exhaust. Yet most air quality assessments treat all PM2.5 as equivalent, regardless of source. This methodological gap means the true health burden of wildfires is systematically undercounted in national and global mortality statistics. …
In the context of WHO Air Quality Guidelines, consider the following statements:
1.The 24-hour mean of PM2.5 should not exceed 15 micrograms per cubic metre and annual mean of PM2.5 should not exceed 5 micrograms per cubic metre.
2.In a year, the highest levels of ozone pollution occur during the periods of inclement weather.
3.PM10 can penetrate the lung barrier and enter the bloodstream.
4.Excessive ozone in the air can trigger asthma.
Which of the statements given above are correct?
Consider the following:
1.Carbon monoxide
2.Methane
3.Ozone
4.Sulphur dioxide
Which of the above are released into atmosphere due to the burning of crop/biomass residue?
In the cities of our country, which among the following atmospheric gases are normally considered in calculating the value of Air Quality Index?
1.Carbon dioxide
2.Carbon monoxide
3.Nitrogen dioxide
4.Sulfur dioxide
5.Methane
Select the correct answer using the code given below.
Consider the following statements regarding ground-level ozone:
1.Ground-level ozone is formed when pollutants react under intense solar radiation and high temperatures.
2.Ground-level ozone levels are highest during periods of inclement and rainy weather.
3.Ground-level ozone is a respiratory irritant and can trigger asthma.
4.Ground-level ozone is the same as the stratospheric ozone that protects life from ultraviolet radiation.
Which of the statements given above are correct?
Consider the following statements regarding PM2.5 and PM10 as air pollutants:
1.PM2.5 particles can penetrate the lung barrier and enter the bloodstream.
2.PM10 particles can also penetrate the lung barrier and enter the bloodstream.
3.Wildfire-generated PM2.5 is more toxic than PM2.5 from vehicular exhaust.
4.Conventional risk models may underestimate wildfire-attributable mortality.
How many of the above statements are correct?
Which of the following pollutants are released into the atmosphere due to the burning of crop or biomass residue?
1.Carbon monoxide
2.Methane
3.Ozone precursors
4.Sulphur dioxide
Select the correct answer using the code given below.
With reference to India's National Clean Air Programme (NCAP), consider the following statements:
1.NCAP was launched in 2019 with a target of 20–30% reduction in PM2.5 and PM10 concentrations.
2.The baseline year for NCAP's reduction targets is 2017.
3.NCAP's targets, even if achieved, would meet the WHO's 2021 revised annual PM2.5 standard of 5 µg/m³.
Which of the statements given above is/are correct?
Match the following aerosol pollutants with their primary environmental impact:
List I (Pollutant) — List II (Impact)
A.Black carbon — 1. Reduces surface albedo of snow and ice, accelerating melt
B.Ground-level ozone — 2. Causes respiratory disease; peaks during hot, sunny conditions
C.PM2.5 from wildfires — 3. More toxic than industrial PM2.5; mortality underestimated by risk models
D.Microplastics — 4. Found in air, soil, and oceans; transported to remote environments
Want the full note, Prelims Facts & MCQ answers?
Create a free account — takes less than a minute.
Create free account