Every winter, this pall of death hangs around Delhi, making its way into people's lungs, causing asthma, bronchitis, drowsiness and nausea. Other damages include heart disorders, hypertension, intellectual impairment, even cancer. Back-of-the-envelope calculations suggest that Delhi probably has the highest number of child asthmatics in India. Smog can also stunt the growth of foetuses, reveal studies by American, Polish and Czech scientists. In a recent report in New Scientist, Frederica Perera of New York's Columbia University revealed that Polish babies exposed to high levels of PM10s (particles less than 10 micrometres in diameter) were born with small heads and bodies. She suspects their subsequent ability to learn may suffer and they may become more prone to cancer.