EU regulations meant that fumes produced from the enamelling process had to be trapped and filtered. Most manufacturers gave up because of the extra costs involved. Only some, like Meile and Le Creuset continued. Until fairly recently, baths had to be sent out of Europe to Russia for re-enamelling!! Fortunately, there's a UK company that does them now, though it'll probably cost a fortune to have it done. Have a look here.
Hi Ginger, it is possible to have a bath re-enamelled, but from what I remember it can be quite an expensive job, but if it is very old bath, it will be of a much better quality than the new ones, have a look at this link, they aren't the only company that does it, but might be worth a look, good luck, Ray