There's a massive PR engine at work for both the wooden and plastic side, but the things brought up most are fire and chemical composition. You would think that nothing could worse for a fire than wooden pallets (It's a constant concern for us, not so much pallets but just wood products in general) but there's a serious hazard with the manufacture of some plastic pallets. (Think oil fire.) I'm sure some of this has been overcome or can be, but it was an issue just a few years ago for sure.

In order to combat the fire front manufacturers starting using chemical composition to make their pallets flame retardant. One of the those chemicals is called deca bromine and is considered to be extremely hazardous. This creates a problem specifically in scenarios where food contact is common.

This is a dated article, but it references some of the concerns.

http://www.palletenterprise.com/articledatabase/view.asp?art...