Moisture and rust are the only enemies of cast iron. Rust can ruin the finish and will ultimately ruin the skillets if proper care is not taken. However, the problem of rusting is very easy to prevent in a few simple steps.
Stop buying expensive nonstick cookware that will most certainly end up in the trash, After washing cast iron skillets Do not attempt to prevent rusting by drying the pans with a towel. Even the most absorbent dish towels will not completely get rid of the moisture. Turn on the stovetop, and allow the heat to help prevent rusting... The cast iron skillets will be thoroughly dry after all of the water has evaporated. Allow the skillets to remain on the hot stove for about one minute after all signs of water have disappeared. This will ensure the handles are also completely free from moisture that would inevitably cause rusting. You should select cookware that will last a long time. you should stop using Teflon-coated pots and pans. There already is a big debate about whether or not non-stick surfaces are unhealthy. The other thing to be aware of is that Teflon just does not last very long. i recommend that you choose a skillet made of steel or cast iron. It is true that a cast iron skillet is more expensive, but it lasts a long time...
When copper starts to discolor, use a copper cleaner, such as Radiance, to polish the exterior of the pan. Cookware manufacturer Calphalon also suggests making a homemade paste from 1/4 cup of white vinegar and 2 tablespoons of coarse salt, which you can rub onto the copper with a sponge, and then rinse off................................---Enamel Cast Iron Cookware--

Allow the cookware to cool before exposing it to cold water, which can damage the enamel. Then hand-wash it with hot, soapy water and a sponge or a soft abrasive pad or a brush. For stubborn residue, soak the pan in warm soapy water for awhile before scrubbing it with a soft, abrasive pad. Some companies, including Le Creuset, claim that their enamel cast iron cookware is dishwasher safe, but they warn that dishwashing can dull the finish of the enamel.

I'd scrub with soap & hot water, rinse, and then pour some bleach in & fill with water & let it stand for awhile. It's worth a try anyway.

On the other hand, if they're really AWFUL & old & inexpensive and you'd rather chuck 'em in the trash, go for it.
In my experience the mold is growing on the food, not the pots and pans itself. On plastic I've had problems with mold discoloring it. For example mold growing in the refrigerator on leftovers stored in a plastic cereal bowl. For pots and pans, scrape the moldy food into the garbage and you could try soaking the pan with hot soapy water. If the pans are aluminum be careful using bleach it can corrode the metal. Lots of soap and water and a good boil should clean them just fine anyway. hope this helps...