Bernie, I have to ask, how much contamination are we talking about here? I am asking to learn, not argue, so please dont take offense.
I would think that most pallets that have been "contaminated", would show signs of spills. I know many things could be invisible, but to what extent could a hazardous chemical have been spilled, soaked in, dryed and still be so bad that i wouldnt want to build a small structure with it? Im not saying there would potetially still be bad stuff...and a "little cancer" is still as bad as it gets...but i question if this is a bit over blown.
As an example, you will NEVER hear me say cig's are good for someone, or that they dont harm a persons health...But I think its silly for people to ban cig's when they all drive to work in a gas car. Would you rather suck on the tail pipe of a car for 4 seconds or a cig for 5 minutes? Im guessing you all realize the car is worse...yet no-one asks to outlaw the use of the car, bus, semi, truck... In the same sense, I think that the wood COULD contain some left over spill and that could potentially contain some chemical...but unless you have already stops driving/going outside where cars are/spraying raid in your home/using scented candles/Buying carpeting that was held together with glue (main source of formaldy...in your home) etc...then i think its a little over kill to worry about some latent chemical soaked into a piece of dried wood.
If a pretty picture of an eagle or a skydiver and a witty quote is all it takes to motivate you, you probably have an easy job....the kind robots will be doing soon.