Does anybody know if water purification tablets are safe for children - haven't been able to find this advice anywhere, thanks...

I read recently that the water purification tablets using Iodine should not be used by children under 10 or pregnant women, as are the ones that use Chlorine (Aquatabs,-used to be called Puritab I think). Some kind of filtering system may be better for you....or perhaps a standard travel kettle? Any one else got any ideas?