I would do a bit of research to find out if these contain any chemicals that could create harmful fumes when mixed with pigeon droppings.
An example of this is a pal of mine pigeons eyes kept watering, thought he had a respiratory problem. It transpired it was the sawdust that he collected from a saw mill which he put in and around the nestbowls, the wood being cut there was pressure treated with oil, the pigeons droppings on the sawdust created fumes that irritated the pigeons eyes.