You know those roles of black plastic you can get a home depot? What does the plastic have to be made of to be safe for lining a garden bed?
What if the plastic is exposed to sunlight - what plastic is still safe to grow edible vegetables from?
Landscape fabrics are made of woven polypropylene which is considered to be stable, or safe, for organic gardens. As it is woven it will allow water through it. Cheap landscape fabric is not UV stable and tears like tissue paper after a while. I can't find anything about decay products even though manufacturers of commercial grade products describe them as "resistant" not impervious.
The commercial grade products I have used in retaining walls look good even after ten + years in close contact with the soil.
Given the short life cycle of vegetables any commercial grade fabric will do the job.Replace the fabric every ten years and you should be guaranteed not to have any contaminants.