CDC – Urine, not chlorine, is what causes red, irritated eyes after swimming in a pool. The Center for Disease Control and Prevention has cleared up this swimming pool myth in its annual healthy swimming report.

The CDC’s report says that the nitrogen in urine binds with the chlorine in the pool to form an ammonia derivative called chloramine, causing the irritation our eyes often experience in pools. Michele Hlavsa of the CDC’s healthy swimming program explains, “It’s chlorine mixed with poop and sweat and a lot of other things we bring into the water with us.”

pee in pools

Since the urine binds with the chlorine, when people pee in the pool, it actually depletes the amount of chlorine in the pool. Perhaps more importantly, the lower levels of chlorine make it more difficult to kill harmful germs in bacteria that the chlorine is there to deal with in the first place.

In addition to the red eyes that many of us are familiar with, swimmers may also cough or experience a runny nose as a result of high levels of chloramine. The lack of chlorine can also leave swimmers vulnerable to waterborne diseases, something Hlavsa says people don’t pay attention to enough.

Indoor pools may be more susceptible to chloramine due to the recycled air. Swimmers who open their eyes underwater also put themselves at risk, so those who don’t wear goggles should be extra cautious.

The report also debunks the myth about chlorine causing the pungent smell that often accompanies pools. The CDC insists that a healthy pool won’t have a strong chemical smell. Instead, a strong smell emanating from a pool indicates a larger amount of urine, feces, sweat, dirt, and other substances.

With its healthy swimming report, the CDC is not trying to dissuade people from swimming this summer, but rather to take proper precautions. Pools should have good water quality and adequate airflow. People should avoid pools with a strong odor and always shower before going for a swim.

Source: CDC.