What type of shotgun pellets are allowed for waterfowl hunting in the u. s.? lead steel ceramic asbestos?

In the United States all shot pellets used to hunt waterfowls must be non-toxic so they must definitely not be made of lead or asbestos. The approved alternative to use as shot pellets for waterfowls in the US is steel, which is much harder than lead.

Question: What type of shotgun pellets are allowed to hunt waterfowl in the US?

Answer: steel.