It's not enough to be harmful. Tooth x-rays expose you to far more... lol
These pieces would've been made between 1936 to 1959, some with longer ranges than others. Certain pieces can be dated in more detail by limited color production years, subtle changes that were made to the shapes over the years, etc. I recommend this book for researching the various vintage pieces. You may find the book cheaper than this listing. It's a wealth of information and its the only book that I know of that HLC allowed the authors access to their files, historical records, notes on prototypes, etc for the book. So it's as detailed as you'll get-- but it's also easy to use to just look up a random piece. Reading end to end is not necessary. One word of caution though--the price estimates are waaaay off. The book was done pre-EBay, etc so values are significantly lower. Half of their estimates is a decent ballpark. Common pieces like plates-- their value dropped more than rarer pieces like a 1950s juice pitcher. Also..older doesn't always mean more valuable. Few years of produc will trump age in value.
Hopefully this is helpful. This collection would be envied by any Fiesta collector..congrats and enjoy!