However there are more arguments in favour of

Unlimited upstream investigating supply chains never end, and may even lead to endless circles (e.g. iron ore mined with steel machines). The same may apply downstream, because materials may be recycled forever. Therefore both the beginning and end of the life PF-00562271 need to be defined. “Origin” may be defined as the location of extraction, being a mine, land (agriculture or nature) or sea. But this definition is insufficient where many resources are purchased for the process of extraction.