Swimming pools are a shared environment, constantly exposed to substances introduced by swimmers, the surrounding air, and the landscape. Pool contamination is not just visible debris; it involves a complex mixture of microscopic biological materials and chemical byproducts. The safety and cleanliness of the water depend entirely on how effectively these contaminants are managed and neutralized.
Biological and Chemical Contaminants
The primary source of pool contamination is the human body, introducing a host of biological materials. Every swimmer carries microscopic traces of fecal matter, along with sweat, urine, saliva, skin cells, hair, and residues from products like sunscreen and makeup. Studies suggest the average person has about 0.14 grams of fecal material that washes off immediately upon entering the water. These organic substances, particularly the nitrogen compounds in urine and sweat, become the raw material for chemical contamination.
The most significant chemical issue is the formation of chloramines, which are disinfection byproducts. Chloramines are created when chlorine reacts with nitrogen and ammonia compounds from bodily fluids. This reaction consumes the active, germ-killing form of chlorine and creates compounds less effective at sanitizing the water. The strong, unpleasant odor often associated with a heavily chlorinated pool is actually the smell of these chloramines off-gassing. High levels of chloramines indicate the pool is struggling to manage the organic waste introduced by swimmers.
Health Risks of Contaminated Water
Exposure to these biological and chemical contaminants can lead to Recreational Water Illnesses (RWIs), which are most commonly spread by swallowing contaminated water. The most frequent RWI is diarrhea, often caused by highly chlorine-tolerant parasites like Cryptosporidium (Crypto) and Giardia. The outer shell of the Cryptosporidium parasite protects it, allowing it to survive for days even in properly chlorinated water.
Ingestion of these parasites can cause cryptosporidiosis or giardiasis, both resulting in gastrointestinal symptoms like watery diarrhea, cramps, and nausea. Cryptosporidiosis typically lasts one to two weeks, while giardiasis can persist for two to six weeks or longer. Beyond parasites, chloramines are irritants that cause the stinging, red eyes and itchy skin common after swimming. Exposure to airborne chloramines in indoor facilities can also trigger respiratory issues and asthma in regular swimmers.
Maintaining Water Quality
The defense against pool contamination relies on a multi-faceted approach centered on disinfection, circulation, and swimmer responsibility. Disinfectants like chlorine and bromine are added to the water to actively destroy harmful microorganisms and oxidize organic waste. However, the effectiveness of the chlorine is heavily dependent on the water’s pH level, which ideally should be maintained in the range of 7.2 to 7.8.
If the pH rises above this target, the chlorine’s sanitizing power is drastically reduced. For instance, at a pH of 8.0, chlorine is only 20 to 25 percent as effective as it is in the optimal range. Regular testing of the water is necessary to monitor both disinfectant levels and pH balance.
The pool’s mechanical systems, including the pump and filter, must run continuously to ensure proper circulation. This process distributes the disinfectant evenly and pushes water through the filter to remove particles. Swimmers also play a direct role in minimizing contamination by taking a cleansing shower before entering the pool and by refraining from swimming if they are ill with diarrhea.