Hi LGD,
Oeko-Tex is a certification for the materials in a mattress … not the mattress itself.
It’s more commonly seen with latex (polyfoam and memory foam more commonly has a CertiPur certification although there are a few polyfoam and memory foam manufacturers … mostly in Europe … that are Oeko-Tex certified). Almost all the latex you are likely to encounter in North America (Talalay or Dunlop and synthetic, blended, or 100% natural) will likely be Oeko-Tex certified.
Organic latex is a little more difficult to find but this is not a safety certification and is more about the way the latex is grown or processed. It’s more common to find organic fabrics or natural fibers in a mattress. There is more about organic certifications in post #2 here).
When you have lower back pain it would be even more important to make sure you have good spinal alignment on a mattress in all your sleeping positions and that your mattress isn’t too firm or too soft but each person is unique. Your own careful and objective testing and experience is the best way to know which mattress is the best match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences).
In case you haven’t read it yet … the tutorial post here has all the basic information, steps, and guidelines that can help you make the best possible mattress choices … and know how to avoid the worst ones.
Phoenix