There are off gassing issues with most boards – plywood, OSB board, sheet rock, homasote etc. The fumes are nasty and in many case give people cancer over time. The best way to judge how bad the materials are is to go to the store and push the top couple boards aside then quickly take a deep whiff of the boards you just uncovered.

Most probably a noxious smell will greet your nose, make you light headed and maybe give you a headache. But with a lot of these boards if you leave them air out for a couple weeks or even better let them in the sun you get rid of a lot of the VOC’s. I’m not saying they are healthy but at least you reduce headaches etc.