Assuming you are travelling at a speed above zero, then the smell you are smelling couldn't be from the grips.
Reasoning is that they are lower than your helmet and the wind flow would mean their smell wouldn't be obvious to you.
As airborne particles are usually wetted and then carried to the ground during precipitation I would assume there would be less odour from the prevailing atmosphere during that occurence.
Are you smelling the smell when at a standstill after a ride, or when actually travelling??
Mick.