The pollutant concentrations for Middle Newton were:
NO2 = 1.27 AQI
VOC = 9.43 AQI
PM 2.5 = 12.17 AQI
PM 10 = 27.61 AQI
You'll see the NO2 levels are 3-times that of Orchard but still incredibly low. 0-20 AQI poses no threat to human health. I can think of 2 reasons behind the readings:
1. Singapore's legislation means all cars are very new. From walking the streets, I see very few cars that are older than 3 years! As such, they'll be much more fuel-efficient and cleaner-burning. NO2 is just linked to traffic, so that could be the reason for the low readings.
2. The data is inaccurate. If you watch my GoPro footage of the walk, you'll notice significant amounts of traffic at points, and I'm standing 1-2 feet away.