Science Diet has recently acquired a patent to use polyethylene in their products. The purpose is to extend the shelf life of their products. Polyethylene is a common plastic that is widely used to create plastic bottles, plastic bags, plastic films, and many more products. Using this plastic in food could be dangerous for you and your pets. Many people are not aware of the potential side effects. It is possible that polyethylene products can cause cancer. PetsitUSA will keep you updated with news on these products, but you may want to consider avoiding these products, especially reusing plastic bottles.
Update: You can find more information on the low-density polyethylene at http://www.medicinenet.com/plastic/page4.htm.
Update #2: You can find information about the patent at the following link: http://patft.uspto.gov.