Pollution in New Delhi on Tuesday hit a dangerous level and doctors called for the city’s half marathon this month to be canceled, Reuters reported. The Indian Medical Association urged the city’s biggest running race, due on November 19, to be called off. It said the air quality is particularly poor early in the day, when the race is to be run. The air quality index hit the “severe” level of 451 on a scale where the maximum reading is 500 and where anything above 100 is considered unhealthy by the Central Pollution Control Board.