Air pollution in Delhi is much bigger problem than in Beijing

"In some places in Delhi, the levels of fine particles that cause the most lung damage, called PM2.5, routinely exceed 1,000 in winter in part because small trash and other fires are so common, according to scientists. In Beijing, PM2.5 levels that exceed 500 make international headlines; here, levels twice that high are largely ignored."

See this recent NYTimes article for information and the experience of an American correspondent and his family who lived in Delhi for three years.