The 2013 Shape Run, originally scheduled for July 7, has been postponed to Oct 27 on account of the haze.
"The health and welfare of our runners are our top priority," said Diana Lee, general manager, fashion & beauty, of organiser SPH Magazines.
"So after much deliberation, we have decided to postpone the race to a date where the conditions are safer and allow them to fully enjoy the race. We seek the understanding of our runners, sponsors and partners for this postponement and sincerely apologise for all inconveniences caused."
Approximately 10,000 participants have signed up for this year's edition of the women-only run.
Runners will be notified about the postponement via SMS and e-mail.
They can check the details of the new race date, and get the latest updates through Shape's Facebook page (www.facebook.com/shapesingapore) and the official Shape Run 2013 website (www.shape.com.sg/shaperun2013/).
Runners with enquiries can also call 6684-0834 from Mondays to Fridays between 10am and 5pm for assistance.