TomorishKole, medical director of the race, acknowledged the fact. “It would be unhealthy to race this weekend (Sunday) due to the air pollution. It’s advisable for those having weak lungs or with a history of cardiac problems to cheer others,” he said.

The medical expert though said the weather conditions seemed better than a fortnight ago. Still, pollution was a concern. “People with breathing aliments shouldn’t think of the starting line,” he added.

Of the 34,000 competitors registered for Sunday’s race, only 13,000 will compete in the 21km event. Others will take part in the fun run (6km) or senior citizens’ race (3km).

As a precaution, there would be adequate medical assistance at the start and on the route to tackle unforeseen incidents, said Kole.

More than outstation participants, local runners have been the worst hit. Tanvir Kazmi, a distance runner from Greater Noida, has been participating in the half marathon since 2006, is planning to switch his training sessions indoors on the treadmill. “To stay healthy for the race is important,” he said on his plans.

In early November, Kazmi’s training was disrupted due to illness. “I have recovered and should be able to do well tomorrow,” he added.

Distance runners from the Army, however, were guarded on the eve of the race. The three-member elite team, including G Lakshmanan, one of India’s leading international runners in the field, arrived here on Friday from the higher altitudes of Ooty. “I hope we are able to cope up with the local weather conditions,” said Lakshmanan.