Chlorine (and bromine, also sometimes used in pools) as well as some other common household chemicals, such as bleaches, deep cleaners, detergents, solvents, etc., can and will affect karat gold causing a condition called stress corrosion.
Non Technical- Actually, these chemicals don't effect gold, but rather the other metals mixed in with the gold, causingthe jewelry to crack and break. Over the years, we've had rings literally fall apart due to contamination. Unfortunately, they cannot be saved.
Technical- There is a chemical reation caused by the introduction of these harsh chemicals taking place at the microscopic grain boundries in the alloys that weakens the bonds between them thus allowing easy breakage of the metal. White gold is more readily damaged by these chemicals than is yellow golddue to the different alloys used in karating. Additionally, areas where the metal was stessed (prongs due to bending during setting) are affected more than unstressed areas.
Chlorine is found with increasing use in household 'non-abrasive' cleaners and of course in laundry detergents and bleach. It is also used in pool and hot tub water treatment and in high concentrations in tap water. In some communities the chlorine in tap water is at levels normal for swimming pools.
At maximum concentration such as pure household bleach, chlorine is so reactive that 14k gold jewelry left in pure bleach solution for 24 hours will be destroyed beyond repair; in extreme cases the gold will be dissolved! DON'T EVER SOAK JEWELRY IN BLEACH!
Solutions-
1. Don't expose your jewelry to chemicals. Don't wear while swimming, cleaning, in hot tubs, sauna's or anywhere there may be chemicals. Even salt (aka sodium chloride) should be avoided (For example, at the ocean). Follow this simple rule- Jewelry should be the first thing off and the last thing on.
2. Platinum heads (settings)- Though considerably more expensive, platinum, or even palladium, is impervious to these chemicals and seems to wear forever (saving money on prong work in the future). It reminds me of one of my favorite sayings- "When you pay for quality, you only cry once". :)