Even then dave, particulates and emissions have come crashing down - it used to be that you could only have one at low levels with the expense of the ters but it was Lubrizol who found a solution to that.
There is space to still improve though, despite our Sulphur levels being usually lower than most States and our centistoke at 70+ (much higher), the Americans outstrip us on NOx and particulates and we will still be twice their level when we (the EU) come down next year - something introduced in that "so-called polluter" G-Shrub's time.....they also have far more active NOx and SOx trading in their markets now.