Yes, OSB or Oriented Strand Board does have a low, but existing toxicity, due to the resin in it. The resin puts out a low level of formaldehyde gas, which is not more than 10 percent of national standards. This makes the chance of toxicity low, but it does exist, if a person is more susceptible to it, such as if they have an impaired immune system, are elderly or a baby. It also has methylene-disocyanate (MDI), which is also toxic. These chemicals come from it being made by pieces of wood being glued together. It is also sometimes coated with a boric acid product that is toxic to termites, but this is not dangerous to people.