My cousin works for a lumberyard, and was talking this summer how green treated wood has changed. It no longer has arsenic in it. However, he warned that you MUST use stainless steel screws or triple coated screws. He is seeing newer decks falling apart because the wrong kind of screws were used. He said it doesn't take very long at all for the incorrect screws to deteriorate in green treated wood. I highly doubt it's from the chlorine. If it were, there would be many people on this board having similar problems...