My grandfather died of cancer when I was a small child. I had assumed it might have to do with all the chemicals used in farming. At Christmas I was looking at old photos. There was a picture of my dad and his sister on a hilltop by a lake. Dad said that was taken while they were in Colorado. He said his mom would take them sight-seeing while his dad visited a radon health mine for arthritis.
*2026 update: This Christmas, dad described symptoms that plagued his father for years that made it sound like grandpa had H. pylori. Huh.