This article was first published in The Skeptical Inquirer.
If you’ve ever forgotten your goggles and decided to make like a fish and open your eyes underwater, you may have been putting yourself at greater risk than you realize. Indeed, opening your eyes underwater increases the risk of a few types of eye irritation and damage.
In studies examining the eye effects of public swimming pools with chlorine or bromine treated water, red eyes, irritation, and itchiness are commonly reported. One study done in Italy found that even exposure to pool air was enough to cause ocular issues, as it does for the respiratory health of lifeguards. In a study involving fifty non-goggle-wearing subjects who had their eyes examined immediately before and after swimming, 68 percent showed symptoms of corneal edema, and 94 percent showed some degradation in the covering of their cornea.
Chlorine-based compounds seem to be the main issue, with concentrations of just 0.5 mg/L posing a risk to the integrity of the corneal covering. Other methods of pool treatment, in particular salt treatment, may pose less of a threat, but more research is needed. One of the prime culprits of eye irritation in a chlorine pool are monochloramines. They form when chlorine in the water reacts with organic substances like sweat or urine and are primarily responsible for the “pool smell.” One way to reduce their presence in pool water is by taking a pre-swim shower. Unfortunately, a 2017 study found that only roughly 35 percent of bathers took a shower when no sign was posted, even when showers were obviously available.
We might know to worry about potential infectious agents in lakes or ponds, but even indoor pools can harbor microbes, as evidenced by a case report of 147 people infected with Pseudomonas aeruginosa after swimming in an indoor pool. Conjunctivitis, or pink eye, is also a common problem in swimming pools. In one 2017 study of 107 subjects, 21 percent had previously had swimming pool conjunctivitis. When asked what the cause was, 56 percent chose chlorine; in reality, most cases are due to adenovirus.
If you’re spending a significant amount of time in bodies of water of any sort, consider wearing swimming goggles. The safety they’ll afford your eyes is well worth looking a little bit dorky.
