pk muttered:

Uk sleepers agr generally treated softwood. some sleepers imported fro the
ffar east are untreated hardwood and avoid ALL the problems of tar/chemical
leaching. Plus, cross cut into slices they make a great paving feature.

But create a lot of problems for endangered species like Urangutans, tigers
and the like when their forest is cut down... make sure it's from managed
plantations only.