The toxic smog season in India's capital has just begun, but those unable to escape cancer-causing poisonous fumes say the hazardous impact on health is already taking its toll.

On Tuesday, the level of PM2.5 particles—the smallest and most harmful, which can enter the bloodstream—topped 278 micrograms per cubic metre, according to monitoring firm IQAir.

That is 18 times the daily maximum recommended by the World Health Organization.

On the worst days, levels can shoot up as high as 30 times the daily maximum.

Piecemeal government efforts to mitigate the smog, such as a public campaign encouraging drivers to turn off their engines at traffic lights, have failed to make an impact.

A study in The Lancet medical journal attributed 1.67 million premature deaths to air pollution in the world’s most populous country in 2019.