BBC are reporting that there is a cloud of smog hovering over Marina Bay, which is caused by farmers burning down forests in order create new land.
The smog has been graded Mid to Low Health Quality and it has already been the cause of other sporting events to be cancelled due to a health risk. Authorities will keep an eye on the situation and will make a collective decision in the next few days.
F1 has been quite fortunate, only the Indian Practice Session was delayed by 20 minutes back 2013 due to bad air pollution. Obviously China is always plagued with bad press about poor visibility.
Bahrain International Circuit - Winter testing