Are paper bags or plastic bags more environmentally friendly?

The following task concerns the environmental impact of paper and plastic bags.
Listed below are a series of links to documents that illuminate the controversial debate. You may click on the links in whatever order you choose. Use the documents to answer the question: Are paper bags or plastic bags more environmentally friendly? 

ARTICLE

Sustainability expert discusses issue

SCIENTIFIC RESEARCH PAPER (ABSTRACTS)

Components of plastic: experimental studies in animals and relevance for human health

The treatment of pulp and paper mill effluent: A review
 

GRAPHIC
Paper or Plastic?

VIDEO
Nightly News with Brian Williams

MSNBC panel of experts (California ban of plastic bags)