[Amitaabh]

Let me preface this by saying I know very little about chemistry.

I am trying to determine if BPA is possibly present in biodegradable polythene bags.

Wikipedia says that the types of biodegradable polythene films are starch based/bio based, and additive based. The types of additive based polythene films are oxodegradable, and enhancing hydrophilicity.

The Oxodegradable method does not utilize BPA it uses metal salts. (I doubt bpa could be used in this process but I could be wrong)

I dont think the starch based method will use BPA since it seems that it is just used to describe a polythene substance made with corn, potatoes, or wheat, and the process of producing polythene doesn't utilize BPA.

I cannot find information on the process of enhancing hydrophilicity of polythene films. Can BPA possibly be used in this process?

[Corribus]

BPA usually isn't an additive to plastic.  It's typically a remnant of the polymer manufacturing process - specifically in polycarbonates and some epoxy resins. 

When they speak of "additive" on the Wikipedia page, I believe they are referring to "copolymer" - something that becomes part of the polymer backbone during chemical polymerization.  This is different from something you mix into the polymer blend before extrusion into shapes - not a great choice of words by the Wikipedia authors. The "additives" listed on the Wikipedia page are common.  PLA and PVA are both common modified polyethylenes (EVOH, ethylene vinyl alcohol, is the copolymer of PVA and polyethylene... this is most likely what they are referring to as the ethylene with PVA additive).  They are more polar and hence biodegrade more easily.  This usually isn't a good thing for most applications - increased hydrophilicity leads to water absorption and a ruination of the polymer properties... which is why they degrade more easily.

So no, the additive here is likely not BPA and none of the likely copolymers remotely resemble BPA.