Continuing its drive to clean Delhi's air, the Supreme Court of India passed a stern ruling early this month ordering the closure of 513 hazardous industrial units by January 31 next year if they failed to shift outside the city before the deadline. The court had passed a similar order in July this year calling for the closure of 168 hazardous, noxious, heavy and large industrial units exposing residential areas to pollution threats. Among the industries facing closure are brick kilns, metal forging units, chemical and dye units, many of them located in residential areas.