Have you ever been walking down a busy high-street and been overcome by the smell of exhaust fumes from cars passing by? The air in front of you seems to be clear, but the smell is overwhelming. This is because once the initial white smoke comes out of a car exhaust and dissipates, harmful chemicals remain in the air but appear invisible to the human eye.

Research by The Independent used an infra-red camera to look at a bus stopped at some traffic lights surrounded by cyclists and shoppers. The camera showed that harmful particles such as nitrogen oxides were swirling around the cyclists and being blown to the other side of the street, where they would balloon up into the shoppers’ faces without them knowing.

It makes you wonder how differently we would feel if the chemicals emitted from car exhausts were visible in the air around us.