You have to be careful with flax seed oil as it can go rancid very quickly through exposure to air or heat. How the oil is extracted too is important in order to retain its properties. Furthermore, too much flax seed oil is toxic.
PCB is Polychlorinated Biphenyl, a chemical compound containing chlorine (C12) and Biphenyl (C12H10). It is usually found with a Benzene ring and from aromatic oils. I doubt very much if flax seed has this compound.
I do know of a botanical oil containing oils extracted from the seeds of flax (only 5%), rice bran (or rice skin) (40%), avocado (10%), olive (5%), corn (10%), green tea (10%) and sunflower (20%). The "cold pressed" method is used so that there is no exposure to heat to change the qualities of the oil. The blend is then encapsulated in a gell made of cellulose fibre (no gluten or animal content). Suitable for lactose intolerant individuals as there is no milk protein (caesin) and vegetarians.
They are a rich source of polyunsaturated fatty acids containing Omega 3, 6 n 9 and the unique Linoleic and Linolenic acids (arachidonic acid or ARA and decosahexanoic acid or DHA). The Linoleic and Linolenic acids are precursors of prostagladins which are essential substances as vital regulators for the body. Other important aspects are the phyto (plant) sterols and compounds found are campesterols, sistosterols, stigmasterols and oryzanol (mainly from rice bran oil). These are necessary for blood ("life force" of the body) circulation and health.
If you want more info, please go to www.phytosterol.ca on the sterols. The brand is Rice Bran plus veg. oils and is very good and potent in assisting in recovery from uric acid, arthritis, high cholesterol, thick blood, etc. Give me your email and I will contact you regarding this product.