Heating cherry pits can be dangerous?

Patient: HiMy grandmother bought one of those new bags to heat cherry pits on the microwaves.I think she has been heating it too much because in the first days it almost didn’t had any smell and now it has a realy bad and strong smell when heated…As i’ve read these pits have poison i wanted to know if there’s any danger because i thought that when the microwaves is used to heat food it could pass something dangerous to the food.I obviously know that small quantities can’t harm but as the cherry pits are heated every day i’m afraid it could accumulate or something….thanks.