When I was growing up, we just worried about cuts and scrapes. Now it seems my grandkids have friends with all sorts of conditions. Latest one is kidney cancer. I've never heard of that.?

Selection bias? Reason you have never heard of it is you may have grown in a healthier neighborhood in a genetically healthy family, called a selection bias. Also, now with advanced medicine we recognize many conditions early, called a recognition bias. However i cannot discount increasing environmental hazards, related to increase of industrialization & nuclear exposure, as cause for increase of cancers & other.