What's in those factory farm eggshells, anyway?

I've been crushing eggshells from conventionally grown chickens, crushing them, then spreading them on top of my sheet mulch bed.

Wondering:
-if antibiotics and hormones (and whatever else) that factory farm chickens ingest eventually concentrate in eggshells
-if these things don't decompose / break down
-how much if any of these things are taken up by plants
-if the plants take them up, then are they harmful to adult human health, or environmental quality

I realize I have a lot of questions here, and, with these things going through so many stages, it almost seems that there's unlikely to be any problem as a result of me using them on the sheet mulch bed. Also, it seems likely some of these things may concentrate in eggshells, some may be stable, some may be taken up by some plants, under some conditions, and that some of these things may be harmful to some people! But, I'd like to know if anyone is aware of research or has ideas where I can go for more info. Just writing this question out, I've nearly come to delete the question entirely!! But since I've come this far with the question, and many other people I know use eggshells in their garden too, I am going through with the question

I am a uni student in Thailand, and am a member of a local urban gardening group. Few of us grow chickens, and I myself do not. I sometimes get eggshells from the food vendors at my uni's dormitory.

I have no knowledge, but have no concerns at all about it.

A factory chicken has 28 days to accumulate the bad stuff before it's killed and eaten. An egg has ruffly one day to accumulate the bad stuff before it's layed.

I'd say the egg is safer than the chicken, but have no evidence either way

I've stopped adding eggshells to my gardens after listening to Dr Elaine Ingham's talks. But if you're looking for scientific info, have you tried running a few search terms through google scholar? https://scholar.google.com
I'll do some looking around myself, when I get some more time.