I've checked two newspapers, and they no longer seem to publish a daily 'Smog index', like they used to. Maybe they've just given up?
Mind you, I remember staying at the Park Royal (Beach Road)
Serviced Apartments back in the '94, and not being able to see the ECP, about c800 metres away. In fact I captured that on home-vid, that was pretty bad! [In due course I'll see if I can work work out how to capture a 'still image' from the video].
Funny, I've always associated smog with industry rather than agriculture. But I have to say SG is by far the most polluted city that I've lived in.
Doing some digging around I find:
URL CENSORED DUE TO COPYRIGHT ISSUES
PSI at 8am = 60/Moderate
http://www.weather.gov.sg/wip/web/ASMC/Haze_Information
Background on haze.