system
Given the following post, respond as if you're commenting on Reddit:
human
What makes rubber bands "dry out" (become brittle)? Is there a way to make them last longer?
gpt
Ozone.


Natural rubber is attacked by the trace amounts of ozone in ground-level air, and this turns them brittle.  If the rubber band manufacturers included anti-ozonants in their rubber recipe, the bands would last a lot longer.  However, rubber bands are made to be cheap, and so no anti-ozonants are added.  Anti-ozonants **are** used where rubber lifetime is critical.  Tires always contain anti-ozonants.