The Centers for Disease Control and Prevention (CDC) explain that these symptoms in a swimmer using an indoor swimming pool might be due to water quality, air quality, and pool disinfecting chemical issues resulting in higher levels of chloramines. The chloramines are what cause your eyes to sting after you swim.
What Are Chloramines?Chloramines are a by-product of the pool disinfectant chlorine. Without some form of pool disinfection, you would get very sick when you swim. Many swimming pools use chemical disinfectants to treat pool water, and in the USA, a commonly used chemical is chlorine (chlorine is also the chemical in bleach that you might use when you wash clothing).
According to HealthyPools.org, used properly, chlorine does not pose any known health risks to swimmers. Chlorine makes the water safer for swimmers.
When chlorine interacts with sweat and other things brought into the pool (by a swimmer, a pool toy, etc.), chloramines are formed. As the level of chloramines (the "bad" stuff) goes up, the level of chlorine (the "good" stuff) goes down. If the level of chlorine gets too low and the level of chloramines gets too high, then that swimming pool smell, along with the other uncomfortable results, can occur.
How Swimming Pools Get Rid of ChloraminesChloramines are going to be present if a swimming pool uses chlorine as a disinfectant and if the pool is used by swimmers! The key is getting rid of excess amounts of chloramines in the pool water and air.
Keeping the proper level of chlorine in the swimming pool is the first step. The proper level of chlorine to keep the pool water clean helps to "balance" the water so the chloramines are destroyed, but just keeping the pool chemicals at the correct levels will not work if the air quality is not good.
The second key to low chloramines in and indoor pool is proper ventilation to maintain good air quality. Moving fresh air into the pool (and venting old air out of the pool environment) will reduce the level of chloramines in the air. The air flow needs to be set up to draw air across the pool so that all of the air in the indoor pool environment is moving and being replaced with fresh air.
If both of these steps are being used, an indoor pool should not have a buildup of chloramines. If it does, then the chances are the air flow is not adequate. The air might be moving, but it might be set-up to re-circulate through an air heater, cooler, or dehumidifier rather than being set to vent or exhaust so it does not return to the pool enclosure. If the old pool air is not being replaced with new air, then chloramine build up will not be fixed by keeping pool chemical levels under control. It takes both good air and good chemicals.
One further step that can be used when there is a big problem is called super chlorination. The level of chlorine in the swimming pool can be raised to a very high level - so high that swimmers are not allowed into the swimming pool to swim - this is called super chlorination. The result of super chlorination is sort of like super-cleaning the pool. Chloramines are removed and, once the high level of chlorine goes back to normal levels (it takes time, but the levels will go down as the chlorine does its cleaning job), the pool is ready to use and, more or less, chloramine free. Note that this only works if the air quality is good; proper ventilation methods must be used in an indoor swimming pool.
What Else Could Keep Chloramine Levels Low?There are a few other things that could be done with an indoor pool that uses chlorine to keep chloramine levels lower. Other disinfectant methods (UV or ozone are two examples) could be used to allow lower levels of chlorine to be used, resulting in lower chloramines in the pool water. Making sure all swimmers take good showers before entering the pool helps as it reduces the perspiration (or other things) that a swimmer is bringing into the pool, which reduces the amount of chloramines formed. Swimmers should also use the toilet facilities at the pool, not the pool as a toilet - unhygienic swimming pool behavior may be one of the big causes of high chloramines in lap and swim lesson pools. Mixing bleach and ammonia (mixing chlorine and urine) is bad!
Advice for Swimmers That Feel the Effects Chloramines?Talk with the pool operator to see if they are aware of the appropriate air circulation and chemical recommendations from the CDC and encourage them to require all swimmers to take showers - and cooperate with them by taking a shower yourself.