From their site:
A 100% natural cotton surface with an allergy barrier that is a soft knit fabric backed with ultra-thin breathable, waterproof polyurethane membrane.
so its organic cotton with a layer of what I presume is "soft knit" polyester and polyurethane (probably in the form of foam for cushioning).
Polyurethane materials can make hard plastics, soft plastics, foams, adhesives and even paints and varnishes. Definitely NOT something organic you want your baby breathing in all night long.
From an article called "Five Problems with Crib Mattresses (Toxic Chemicals)"
Polyurethane foam (essentially solid petroleum) is extremely flammable. To combat this hazard, industrial toxic fire retardants are added. The most common chemical fire retardant used to treat polyurethane foam has been pentaBDE, a toxin associated with hyperactivity and neuro-behavioral alterations. PentaBDE is not bound to the foam, and leaches out into the surrounding air.
And the sad thing is so many moms buy these products from BRU because they are trying to do whats best for their baby (its a top registered-for product on their site). Its another shameless marketing ploy.
More to come on how to make your mattresses safe for baby.......