It could be any number of things.... most of which are nothing to do with pollution!
It's basically a 'you have a
problem' light that comes on with some simple problems, but also comes on when you have a more serious issue. It could be nothing - just a dodgy sensor throwing up odd readings. But it could be something more serious that needs to be checked out straight away. So get it checked ASAP and be careful when driving, just in case it's a bigger
problem.