Recently by Mark Sisson: Caveman Breath
Who doesn’t like a lovely day at the pool? Unless you can’t swim, there’s no reason not to love the cool water, the bright sun, the ping pong (every swimming club worth a dime has a ping pong table, or several of them), the face dunking, the high dive, and the chicken fights. But what if something sinister churned within the depths of the chlorinated water? What if by entering that pool you were risking life, limb, and the pristine alabaster of your eyeball? In today’s edition of Dear Mark, I’ve gone back to the roundup format. I begin with the question of swimming pool chemical safety, follow with a query about washing vegetables, and I finish the post with a short section on carb blocking agents. Sound good?
I was wondering about possible negative effects of pool water. I enjoy a good sprint workout in the pool, especially when traveling and staying in a hotel. Could the chlorine or other chemicals be harmful since they do sometimes make me itch a little afterwards and burns my eyes (especially if I open them underwater)?
Thanks and Grok on,
I hate to be the bearer of potentially bad news, but there’s probably something to this. Most pools use chlorine as a disinfectant, to keep the water clear of bacteria and other microbes, and it’s darn good at that. Reason? Chlorine, in its pure form, is toxic. The chlorine in the pool is obviously diluted, so it’s not going to burn or kill you outright, nor are you a microbe, but toxicity concerns remain. Your first clues that it might be doing something untoward, of course, are the burning eyes and itching skin. That’s pretty normal, albeit disconcerting. As a kid, I used to get red, burning eyes when I’d spend the day at the pool. Nowadays, I think back to that and wonder…
Anyway, red eyes clear up and itchiness subsides, but could other problems be lurking beneath the surface? Maybe. Chlorine reacts with other substances, including bodily fluids and various organic matter, to form disinfection byproducts (DBPs), which may have novel — and unwanted — health effects. Let’s take a look at some evidence:
- When chlorinated pool water meets dimethylamine (found in urine and sweat), nitrosamine carcinogens (the same type of compound that forms when we overcook bacon) form, and appear in pools at concentrations up to 500-fold higher than drinking water. Though it’s unclear whether or not these particular nitrosamines are absorbed by pool users, some nitrosamines are absorbed through (rat) skin. Why should you care? Well, nitrosamines are used to induce bladder cancer in rodents, and chlorinated pool and bathing water usage have been linked to bladder cancer in humans (though it’s just observational).
- Chloramine, another DBP, has been linked to asthma in pool workers and elite swimmers.
- A recent study found over 100 chemical byproducts in swimming pools, many of them toxic. Before and after 40 minutes of swimming laps in such a pool, healthy subjects’ biomarkers were tracked and recorded. One marker suggested increased lung permeability and inflammation, while another marker indicated a kind of DNA damage that, if unchecked, might lead to cancer. Subjects had also accumulated elevated levels of four of the most common DBPs after 40 minutes in the pool.
The good news is that you’re probably okay. Problems may arise when we absorb and uptake these DBPs (like chloroform) via inhalation, dermal absorption, and the ingestion of affected water on a regular basis. The populations that seem to suffer most from pool-related maladies are the ones who spend significant amounts of time at, in and around the pool — competitive swimmers (with their infamously long daily workouts), lifeguards, and other pool workers — and it doesn’t sound like you’re living in the water. If you stick to short, intense sprints, performed only when you have access to a pool on business or vacation, I wouldn’t worry.