Alternatives to plywood subflooring

I am looking for an alternative to plywood as a subflooring material since plywood contains formaldyhyde. Could you please give me suggestions? The easiest way to reduce formaldehyde emissions from subflooring is to use exterior-grade plywood instead of interior-grade. The waterproof glues used in exterior materials contain phenol-formaldehyde rather than urea-formaldehyde. While this is still formaldehyde, these products emit (according to one source) 10-20 times less formaldehyde than those used in interior grade plywood or particleboard. This may cost a bit more, however. There are several other options as well including:

• Cork made with polyurethane-based or non-phenolic binder
• Strawboard (made from pressed straw) using non-formaldehyde resins
• Cementboard (concrete core with fiberglass facing). This is more expensive than other options and is used primarily when floor height or moisture are concerns.