…you’re giving me cancer. Seriously.
Summer is coming up and I’m sure some of you are looking forward to taking a dip in the pool. Swimming is America’s second favorite exercise after all. So, in order to ensure the health of swimmers, disinfectants are added to the water to prevent the outbreak of infectious diseases. Especially for public pools, just think about the amount of disinfectants that have to be added to keep the water sterile.
I’m studying the toxicological effects of disinfectants in the environment for my thesis, so when I came across a paper about disinfectants and human health, I thought it was worth the read. While most people are interested in whether there are health effects from disinfecting our tap water (as opposed to not??), studying these chemicals in swimming pools and water parks are actually the perfect place to start, because they are disinfected to the extreme. It’s not so much the disinfectants themselves (chlorine, bromine etc.) we are worried about, it’s after they interact with organic matter, they form disinfectant byproducts (DBPs) which can be toxic.
Back to the pool…ok, so you’re wading around, think of the organic soup you are sitting in. Its probably a lovely mix of dirt, skin, hair, and sweat. Mmmm. But it gets better, don’t forget about all those pool pissers and bathers wearing sunscreen and lotions. The urine and personal care products are especially important because they are rich in nitrogen. And nitrogenous disinfectant byproducts (N-DBPs) are known to be mutagenic and specifically, cause bladder cancer, the sixth most common cancer in the US.
In order to quantify the toxic potential of recreational swimming pools, researchers collected water from different facilities that all use a common tap water source. The goal being to see which method of disinfection utilized lead to the least genotoxic water, rather than characterizing the individual DBPs present in the samples. This was done by exposing Chinese Hamster Ovary cells (CHO) to whole water samples and measuring DNA damage of individual cells through a comet assay.
The results below show that compared the tap water, all other water samples collected elicited a higher genotoxic response in CHO cells. The most genotoxic sample by far was S4, the only water site that was disinfected with bromochlorodimethylhydantoin (BCDMH). As BCDMH reacts with water, it slowly releases chlorine and bromine, which disinfect the water. However these halogens can react with organic matter and form cytotoxic and genotoxic N-DBPs. The reason for such high genotoxic response from S4 is also to due to the total organic carbon (a measure of organic matter) being incredibly high, 125mg/L, yuck! More organic matter the disinfectants can interact with, greater the chance toxic DBPs will form.
The best disinfectants to have in place are UV+chlorine which had significantly lower genotoxicity compared to pools disinfected with chlorine alone. UV treatment may be important in breaking down the N-DBPs and thus lower genotoxicity. Measuring the N-DBP, nitrosamine, outdoor pool concentrations were 5 times lower than in indoor pools, probably do to UV and solar radiation.Some other recommendations may be to shower not just after you take a swim, but before as well. Washing away lotions or any other personal care products on your skin will reduce the chance they will form mutagens once in contact with treated water. Also, stay away from that uncomfortably warm spot next to the 6 year old in swimmies…