SIDS causes

I heard from another mom (who has done research, but I have not yet done research myself) that SIDS was a big deal a decade or so ago because parents were told to have their infant sleep on it's belly. When babies started dying from SIDS, parents were told to actually lay their kid on it's back because when Baby sleeps on his belly, he sleeps too hard and can suffocate (what?). Parents started laying babies on their backs for sleep, and the number of SIDS deaths dramatically decreased.
But they're finding the SIDS was not caused by babies sleeping too hard on their bellies. In fact (again, according to this well informed mom), it was caused by the flame retardants in the mattresses. See, the flame retardants were chemicals in the mattresses, baby- while on his belly- would inhale them directly, couple that with a compromised immune system from a recent cold, being overly tired or even vaccine, and it would kill him. But when placed on his back, he didn't inhale them as much so SIDS dropped.
I'm wondering, have you ever heard of this? And if this is true, what can we be doing to prevent this? How do we reduce the amount of chemicals in our mattresses, blankets, pillows, furniture, etc?