A study on urban air quality by the World Health Organization has said India appears among the group of countries with highest particulate matter levels. Of the 1,600 surveyed cities, Delhi was said to have the dirtiest air.
Although the Indian government has rejected the WHO findings, medical experts say the situation is serious enough notwithstanding whether or not Delhi is the world's worst city for air pollution.
A.K. Singh, a doctor at Fortis Hospital, said that exposure to excessive particulate matter affects breathing and the respiratory systems, damages lung tissue, and can cause cancer or even premature death.
The elderly, children and people with chronic lung disease or asthma are especially sensitive to particulate matter.
"The ill effects of air pollution on human health are diverse," Singh told IANS. "It (pollution) increases the chances of developing stroke, heart disease, lung cancer and both chronic and acute respiratory diseases including asthma.
"It principally affects the body's respiratory system (lungs and airways) and the cardiovascular system (heart function and blood circulation)," the doctor said.
June 5 is marked as World Environment Day to generate awareness about the environment and enhance political and public attention vis-a-vis pollution.
Following the WHO report, Delhi's Lt Governor Najeeb Jung set up a high-powered committee headed by Chief Secretary S.K. Srivastava to study the pollution in the river Yamuna and vehicular pollution in the city.
Sumit Sharma at The Energy and Resources Institute told IANS: "It is an important step taken by the Lt. Governor... However, it would require continual scientific assessments and pro-active planning to first abate and later prevent the rise of air pollution in the city."
Sharma said the committee should be expanded to involve key scientific institutions to prepare an action plan for immediate and long-term control of air pollution in the capital and surrounding areas like Ghaziabad in Uttar Pradesh and Faridabad and Gurgaon in Haryana.
Although the non-polluting compressed natural gas (CNG) is compulsory for public vehicles in Delhi, the quality of air in the capital is poor due to polluting vehicles that come to or pass through the capital from elsewhere in the country.
According to official data, Delhi has some 7.2 million vehicles -- more than the combined vehicle population of Mumbai, Chennai and Kolkata. Delhi has at least 2.1 million cars -- the highest for any one Indian city.
Sharma said air pollution caused by vehicles can be controlled by early introduction of BS-V fuel and BS-VI standard vehicles in the city.
According to him, this measure should apply all across the country since trucks are the biggest air polluters.
Dr Singh recommends limiting exercise or strenuous activities outdoors -- to escape pollution.
"Always avoid exercise near high traffic areas. Areas within half a kilometre of a busy highway is likely to have much more pollution even when the rest of the community has a green air quality forecast."
He warns that children were at particular risk even if they don't have asthma. "They tend to be more active, breathe faster and expose their lungs to more pollutants."