Air pollution

Prelims and Mains

Summer air pollution in India is driven by coarse PM10 and ozone, where winter pollution is dominated by fine PM2.5 trapped by cold, still air.

• Ground level ozone is not emitted directly: it forms when nitrogen oxides and volatile organic compounds react in strong sunlight.
• Heat speeds the reaction that makes it, so a heatwave does not only heat the air: it cooks its pollutants into ozone, which outlasts the heat itself.
• Heat lows produce hot winds that carry West Asian and Thar dust, and thunderstorm downdrafts raise local dust storms (andhi).
• Delhi's Air Quality Early Warning System, set up after the 2018 dust storms, gives multi pollutant forecasts.

Prelims and Mains

The clean mobility scheme for Delhi NCR replaces BS IV and older trucks and buses with BS VI or electric vehicles, through the National Capital Region Planning Board.

• Bharat Stage (BS) norms regulate tailpipe nitrogen oxides, carbon monoxide and particulate matter; BS VI tightened limits and added cleaner fuel and onboard diagnostics.
• Older vehicles emit more because worn engines burn fuel incompletely and lack diesel particulate filters and selective catalytic reduction.
• The 2018 source apportionment study by the Automotive Research Association of India (ARAI) and The Energy and Resources Institute (TERI) found transport contributes 14 per cent of PM2.5 in Delhi NCR.
• Trucks and buses are 3 per cent of the fleet but 36 per cent of transport PM2.5.

Prelims and Mains

PM2.5 and PM10 can cross the placental barrier and cause oxidative stress and inflammation.

• The inflammation suppresses a protein that keeps the placenta in balance and governs embryo growth, so the placenta invades the uterine wall poorly and forms a weaker nutrient exchange layer.
• Pollution also alters epigenetic switches, so the harm persists after birth.