Chromated copper arsenate, which is highly toxic, used to be used to make pressure treated wood. Throwing a piece on the fire would have released a good bit of

Chromated copper arsenate, which is highly toxic, used to be used to make pressure treated wood. Throwing a piece on the fire would have released a good bit of arsenic. Since 2003 pressure treated wood is made with alkaline copper quanternary, copper azole or micronized copper azole. They are all very much all less toxic since they are believed not be be able to be absorbed by the body, but I still wouldn't throw any on a fire.