This from FelderOwner group
I think worrying about MDF is misguided. Its sawdust bound with a urea-formaldehyde resin. In a garden, the resin won't be absorbed by plants or mammals. It's too big to cross a cell membrane. Decomposition of the resin gives urea and formaldehyde. Urea is a fertilizer. Formaldehyde certainly has its issues if you are breathing it as it outgasses from Chinese plywood. But it is volatile, and a lot of it will just dissipate in the air outside. Some might get ingested, but most of that is metabolized before it circulates in the body. Normal blood levels are about 2 ug/ml, because it is a common metabolic degradant. Many of the drugs we take have formaldehyde as a byproduct. I'm way more worried about inhaling fine dust, including MDF and wood. That's bad, and I'm allergic. But my blueberries are happy to get whatever they get from my dust collection bags.