You do realize that you need to grind/pulverize the 13x absorbent and inhale the fibers right? And even that relationship is dubious since as mentioned, only the Zeolites native to Turkey have been liked to lung cancer. High quality 13x is not coming from Turkey, so you are mixing up different minerals. 13x molecular sieve is synthetically made, not mined.
Hey...slow down a bit. The original concern was raised by a supplier of zeolite (Airdive - Australia)..I'm just prompting discussion. The study from Turkey is but one of several linking Zeolite to Mesotheleomia. And yes, the fibres would need to be exposed through the structure of the material being broken down....which could potentially happen given the vibration an pounding typical of small boats. There is also the possibility that a filter tower that has not been drained frequently enough, could result in dampening of the zeolite, and as the fibres are contained within a kaolin clay there is a concern that the 3-4mm ball structure could break down. I hadn't realised high quality 13X MS was synthetic - I would need to check on the origins of the material supplied here in Australia. No panic here, but for SSBA applications, I'd prefer activated alumina if there is any doubt.
And Iain - you're right. 20 years back what got me started in Hookah diving, was a mate with a Clisby compressor. It was a great unit.