From the prologue excerpt we discover that metal, at least in part of Andor, is melting.

That got me to wondering if a'dam would melt too? I think not. My reasoning is that Aviendha's visions in Rhuidean imply that the Seanchan will defeat the Aiel eventually. The Seanchan cannot do that if their a'dam melt off their damane. Damane are the real power behind the Seanchan.

Although if I am wrong, and the Seanchan do start losing lots of a'dam, then it would be extremely interesting to see what the heck that does to the Seanchan. Captured channelers (e.g. AS, Sea Folk, Aiel Wise Ones, etc.) who had not become like Shaiine (former AS captured and trained by Tuon) would undoubtedly escape. How would the Seanchan play any role in TG if the a'dam start melting away?

Conclusion: The melting a'dam is a relatively local event, perhaps a bubble of evil. If I am wrong and it is widespread then the a'dam better be melting away too otherwise that is just stupid to have all metal melt except a'dam.