I don't know-- but I have heard that they are bleached in a couple of chemical solutions -- sulfur dioxide and some kind of chlorine, before being soaked in high fructose corn syrup and strong red dye. I think they should be avoided, as pretty as they are.
I heard formaldehyde! Someone once chided me for eating the cherry out of my drink. I was stunned--we're drinking alcoholic beverages--certainly no better for you! I like the cherries; a few now & then won't hurt!
The cherries in Oregon became mushy. There was a man named Ernest Wiegand who started working on this. He ordered cherries from Italy, they were soaked in calcium salts and then soaked, or dipped, in maraschino liquor. It started in about 1925, I believe.