Here's the answer I received from Avery:
Thank you for contacting Avery. These labels (the clear ones) are not acid free or
archival safe. Currently, Avery manufactures the following SKU numbers
which are acid free/archival safe:
All of these packages are Dual Technology Laser/Ink Jet, White Permanent
ID labels containing 15 sheets per package at suggested retail of $9.99.
6570 - 1.25" x 1.75" 32up
6571 - .625" x 3" 32up
6572 - 2 x 2.625 10up
6573 - 5" x 8.125" 2up
Please contact your preferred office supplier regarding these items.
Again, thank you for your interest in Avery.