Pressure treated wood is treated to a lesser amount now than in years past. The chemicals used to treat the wood have been found to be carcinogenic. Some schools have removed treated wood play ground equipment because of this. I am not one to discount medical studies or medical research but all my brood pens are made of treated wood. I have had dogs in and out of them for years. Is it possible one died from exposure? Possible, but I doubt it. I have no qualms using treated wood. EWO