people swimming in the pool

when you take a swim in the local pool,how much of someone else's pee will you be swallowing, if you take amouth full of water? it's an important question. even olympianmichael phelps admits to occasionally spending a penny while swimming, and despite warning notices at mostpools against public urination, you can be sure that, when you next takea dip, someone will have ignored them. so when you doinadvertently take a gulp of water while swimming, how much of that will be someone else'sliquid waste?

for quick back in the envelopecalculation, assume we're talking about an olympic-sized pool here, containingaround two and a half million liters of water.now let's assume one of your fellow swimmers takes a long and satisfying, but surreptitious, pee, releasing about ahalf a liter of liquid into the pool. and finally, assume that you accidentallygulp up to a tenth of a liter of the resultingcocktail. in that mouthful, you imbibe a whopping 20 nanoliters of your fellow swimmers pee. if this was adroplet of pure pee,

it will be smaller than a grain of salt.of course, that's assuming that the pee mixes through the pool evenly, which it probably won't, at leastnot straight away. even so, you've not got much to worryabout beyond feeling icky, especially as there's not muchin pee that's harmful. there is a complication though. the uric acid in pee reacts with chlorineused to disinfect pools to produce a much more toxic substance. this is cyanogen chloride, and its nasty stuff.

so nasty, that all production must bereported to the organization for the prohibition of chemical weapons. on exposure, symptoms can vary from skin and eye irritation to nausea, vomiting, and, at high concentrations, death. but youneed quite a lot of it cause an effect. adults can be exposed to up to three and ahalf milligrams of the stuff a day before it's considered a problem.so how does that compare to what might be in your pee-infused mouthful ofswimming pool water? in that one mouthful, you'd be drinkingless

than two and a half picograms of cyanogen chloride. this is one thousand million times smaller the safe level. in fact, the folks over at ars technicacalculated that you'd need 3 million people in the pool, all peeingat the same time, and so much chlorine that it would beburning the skin of your bones before cyanogen chloride became close tobeing a problem. so despite the yuck factor of swallowingsomeone else's pee, and the fear factor that comes from

anything associated with cyanide, because of the low doses, the risks in this case are, if you'll forgive the pun, piddlinglysmall. for more information on pee, pools andcyanogen chloride, check out the links below. and as always,please do join the conversation in the comments.