The two rooms in the home that are at greatest risk for problems of mold and mildew are the kitchen and bathroom. Both rooms are prone to problems because of the high level of moisture. While the kitchen is one room, the bathroom tends to be at greatest risk. Between moisture coming from hot shower and baths, water splashes from the sink, shower, and tub onto the floor and if not cleaned up, mold and mildew can develop. What makes this a serious problem is that when baseboards, shower curtains, and even bathroom window curtains become wet, mold develops, which contains spores that become airborne, causing big issues with health.
The best step is to prevent problems of mold and mildew in the bathroom, which can be accomplished in a number of ways. First, make sure the room has a good exhaust fan that is used after taking a shower or bath to help eliminate moisture from the air. In addition, any water that gets on the floor should be cleaned up immediately. Then, if you have a fabric shower curtain, be sure to have a quality plastic or vinyl liner to serve as a barrier but also wash the shower curtain often. Then as far as the bathroom window curtains, make sure you choose short curtains rather than those that go all the way to the floor and if they will be hung in a bathroom used often, choose curtains that can be machine washed.
Another thing that would help is during warm months, once you get out of the shower or bath, open the window to allow fresh air inside, which again would help the humidity and moisture dissipate. Remember, mold and mildew can grow quickly so at the first sign of trouble, you need to take action. This means no matter the bathroom surface, you will need a good disinfectant. Bleach mixed with hot water is one of the best options but in the case of black mold, which is very dangerous, it will only lighten the color, not eliminate the mold. For this reason, if you find black mold on the bathroom window curtains or any other items in the bathroom, they would need to be tossed out.
Now, if mold on the curtains is not black or you have an issue with mildew, you may be able to salvage your bathroom window curtains. In this case, if the fabric can be washed in bleached, then you could fill the bathtub with a mixture of one three cups of bleach to one gallon of hot water. Soak the curtains for at least 24 hours, rinse, and then launder normally. If the bathroom curtains cannot be washed in bleach, you could choose a non-bleach product and follow the same instructions, or choose to simply replace them. Obviously, the goal from that point would be to prevent the problem in the first place, which is possible.
By keeping the floor, shower curtain, and bathroom curtains clean and void of mold and mildew, the room would not only look better but more importantly, be safer to everyone in the home, even pets. Mold, especially black mold is not something to play around with so if you ultimately needed to purchase new curtains, that would be the best route. That coupled with prevention would ensure you have a beautiful but also healthy bathroom to enjoy.