Oxo-biodegradables: These consist of transition metals (some of which are regulated) that theoretically foster oxidation and chain scission in plastics when exposed to heat, air and/or light. Based over 20 analyses over the past 4 years by the BPI, these metals include but are not limited to cobalt, manganese, magnesium, iron and zinc. The theory behind chain scission is that it is supposed to shorten the polymer chains to the point where they can be consumed by microorganisms found in the disposal environment and used as a food source.