Delhi.Doctors say that the runners are taking a major health risk by competing in Sunday's New Delhi half-marathon.Women's marathon world record-holder Brigid Kosgei from Kenya and Ethiopia's two-time men's winner Andamlak Belihu are among the 49 elite athletes running the 21-kilometre (13.1 mile) race, while thousands of amateurs are taking part virtually, reports AFP.Organisers say the "highest level of safety-standards, with bio-secure zones" have been laid on for the race starting at the Jawaharlal Nehru Stadium.But with New Delhi recording more than 500,000 virus cases, and air quality in the world's most polluted capital hovering between 'unhealthy' and 'hazardous', health experts said the athletes should think twice."It will be.