When we swallow a little pool water while swimming, we usually brush it off without a second thought. Chlorine kills all germs immediately, right? Unfortunately, that's not the case, and the Center For Disease Control and Prevention reports that germ-filled pools are causing a large increase in recreational water illnesses (RWIs) "caused by germs spread by swallowing, breathing in mists or aerosols of, or having contact with contaminated water in swimming pools, hot tubs, water parks, water play areas, interactive fountains, lakes, rivers, or oceans."
Yes, chlorine does kill harmful germs that make us sick, but what many people don't know is that it takes a longer amount of time to eliminate certain bacteria growth. For instance, the CDC says the most common RWI is diarrhea, which is caused by a common parasite in pools called cryptosporidium ("crypto" for short). Even in properly disinfected pools, crypto can last for days! This water-related illness became so common that from "2004 to 2008, reported crypto cases increased over 200 percent." So, if you find yourself with an upset stomach this Summer, it might not actually be from an undercooked hamburger.
As if we weren't grossed out enough by the news that chlorine is not what makes our eyes red in the pool (it's urine!), now we're going to be extracautious in public areas like water parks and pools — especially in mysteriously warm areas.