Road dust
Also called: Fugitive dust · Topic: Geographical Issues: Pollution, Urban Waste, Slums and Land Degradation · NCERT: Beyond NCERT
Meaning
Road dust is fine soil, sand and worn-down material from roads that passing vehicles and wind lift into the air. It is a kind of fugitive dust, meaning dust that rises from open surfaces rather than coming out of a chimney or exhaust pipe. Fugitive dust also includes dust from construction sites and bare land. Most road-dust particles are coarse PM10, meaning particles 10 micrometres across or smaller. They are much less often PM2.5, the finer particles that reach deep into the lungs. Road dust matters because India's National Clean Air Programme (NCAP, launched January 2019) sets its targets as cuts in PM10. Sweeping and spraying water on roads can lower PM10 quickly and cheaply. But they do little about PM2.5, which comes mostly from burning fuel and waste.
Example
Delhi, in the Indo-Gangetic plain, has spent its clean-air money mainly on road-dust control: sweeping machines, water sprinklers and paved road edges. Its PM10 readings can improve this way. Its winter smog stays severe, because the PM2.5 from vehicles, industry and burnt waste is barely touched.
Don't confuse with
- Combustion-source PM2.5: these are fine particles from burning coal, diesel, wood or crop stubble. Road dust is mostly coarse PM10 that is stirred up, not burnt.
- Smog: this is smoky fog, a mix of smoke and fog over a city. Road dust is only one of the things that feed it.