Plants in raised beds can suffer more quickly and more severely from drought due to improved drainage, so keep an eye on watering needs.
Modern wood treatments do not contain potentially harmful heavy metals, so are safe to use. If in doubt, line the inside of the bed with polythene.
New railway sleepers may contain creosote that should not be used where skin contact is a possibility. Creosote is thought to have dissipated from older sleepers, and these may be used without concern about skin contact.