BREAKING DOWN 'Unintentional Tort'. In certain cases, a person causing an accident may be held legally responsible for their negligence and may have to pay a plaintiff for physical injuries, property damage and/or financial loss.
Straw is normally used for a bedding material, while hay is used as a feed supplement. Straw is dried out and works well for building nests and providing cushioning for animals to sleep in. It is not moist like hay and is unlikely to mold.
I don't think any research has been done on bean straw specifically. However, like most other straw, it is a good bedding source and as long as horses have plenty of good quality hay to eat they should not be consuming the straw.