New study highlights link between swimming pool urination and cancer-causing toxin

With swimming pool season rapidly approaching, a recent study published by researchers at the University of South Carolina may give pool goers some cause for concern. According to the study, which was published in the Journal of Environmental Science & Technology, a cancer-causing toxin known as cyanogen chloride can be caused by swimmers urinating in the water.

While urine is effectively sterile once it leaves the human body, the researchers found that uric acid present in urine reacts with the chlorine in pool water to create cyanogen chloride and trichloramine.

While the latter is fairly harmless in low quantities, even small amounts of cyanogen chloride have been linked to serious health conditions – including higher rates of cancer.

As part of the study, researchers measured the amount of cyanogen chloride that swimmers were exposed to after just 40 minutes in an indoor pool.

The findings revealed some alarming results:

1) Increased micronuclei in blood lymphocytes – associated with cancer risk.
2) Urine mutagenicity, a biomarker of exposure to cancer-causing agents.
3) An increase in serum CC16, which suggests an increase in the risk of lung cancer.

The pool used in the study had a cyanogen chloride concentration of 30 parts per billion – a level that researchers believe represents an average amount for a moderately-used indoor pool.

At much higher concentrations – around 2,000 parts per billion – cyanogen chloride is a highly toxic blood agent capable of causing convulsions – and even death. A swimming pool would be unlikely to reach anywhere near that level, but increased rates of urination were linked to higher concentrations of cyanogen chloride in the study.

“Uric acid chlorination may account for a large fraction of cyanogen chloride formation in swimming pools. Given that uric acid introduction to pools is attributable to urination, these findings indicate pool chemistry is at serious risk of causing negative health impacts if swimmers continue to urinate into the water. At higher concentrations, the health benefits of swimming are negated by the harmful impact of cyanogen chloride”

Previous studies have already found a link between higher rates of bladder cancer in regular swimmers compared to non-swimmers, while the same also applies to melanoma cancer. People who don’t actually enter the water are still at risk: in an indoor pool environment, cyanogen chloride has been found to mix with the ambient air.

An earlier study by a Dutch team went as far as concluding that “swimming in a chlorinated pool presents an unacceptable cancer risk”. The authors of the recent study do not go to this extreme, but the implication is still clear: swimming in a pool where high concentrations of urine are present does increase the risk of cancer and other health issues.

Beyond cancer, the study found that cyanogen chloride can affect the immune system, disrupt the central nervous system, damage the cardiovascular & renal systems and cause serious respiratory issues.

The authors of the report did note that their research was one of only a handful of in-depth studies conducted in the US into cyanogen chloride in an indoor pool setting, and that further studies are required to validate the data.

“There is a lot more to do, including analyses of a variety of other pools and hot tubs and a more quantitative assessment of the impact of human usage on the potential health effects of pool and hot tub waters”

That being said, the authors of the report hope that it may encourage swimmers and pool users to think twice being urinating into the water. “We strongly recommend all swimmers to visit the bathroom first, and to shower before entering the pool. These simple steps can drastically lower the risk of cyanogen chloride being produced.”