"Mike Dennis" writes:

Does anyone know why NASA changed the ET foam to the current formula? I
read somewhere that it was changed for environmental reasons.

The foam was changed for environmental reasons, but the foam that flew
on Columbia's ET was the old stuff.

[...]

Just imagine: if the foam was changed due to environmental concerns, the
blame may ultimately rest on Greenpeace! ;-)

Just imagine: if the foam had been changed earlier, it may not have
shed and Columbia could have landed safely. If only NASA had listened
to Greenpeace earlier!

(My conclusion is as logical as yours, i.e. not very, but it has the
benefit of being based on a fact rather than a false rumor.)