A memory foam mattress is one of the most toxic mattresses you can choose because they could potentially interfere with your endocrine system, hormones and other bodily functions.
Memory foam, made from a substance called viscoelastic, was designed in the mid-1960s for NASA airplane seats and is popular because it is both highly energy absorbent and soft. Memory foam molds to the body in response to heat and pressure, evenly distributing body weight, then returns to its original shape once you remove the pressure.
In addition to protecting against impact, these properties make memory foam very comfortable.
After its initial NASA success memory foam showed up as cushioning in helmets and shoes, it was used in prosthetics and products to prevent pressure ulcers in products like seating pads for the severely disabled. Now it's used in pillows, mattress pads and mattresses. Sleep specialist claim studies showing that memory foam actually helps you sleep better are lacking.
Most mattresses are made with either memory foam or inner springs and both usually contain polyurethane foam, a highly flammable product. Due to this and government laws, fire-retardant chemicals are usually applied which means most mattress stink when you first open them and manufacturers advise you to let the mattress air-out for a couple days before sleeping on it.
The smell goes away, but the chemicals are still there and you are literally inhaling and absorbing these chemicals.
The "off-gassing" from synthetic materials and flame retardants can be particularly harmful to the elderly, infants, children and pregnant women.
Research shows that exposure to toxins during pregnancy can be harmful to both the woman and fetus and toxins found in mattresses that make their way into the bloodstream of a pregnant woman pass through the placenta and to the fetus. Evidence also suggests that synthetic foams may contribute to a range problems including autism, asthma, ADHD and even cancer. Full report at Sleep Junkie.