Don't Put The "P" In "Pool"!
Surveys say that one in five people admit to urinating in the swimming pool.
That's how many admit to it, so imagine how many people really do!
"It's harmless", they say, "there's chlorine in pool water."
Yes, but that actually makes it worse.
There is chlorine, but it's there to kill microorganisms.
The danger is that it reacts with uric acid to create hazardous chemicals.
A recent study by a chemical engineer at Purdue University
along with three chemists from China Agricultural University
reports that they found harmful urine-caused chemicals
in every pool they sampled over the past 10 years.
That's a lot of pee.
The paper observes that urination
"is a voluntary action for most swimmers"
and therefore there are
"important benefits to pool water and air chemistry
that could result from improved hygiene habits
on the part of swimmers."
In other words:
Don't pee in the pool.
How Clean Is Municipal Water?
A typical swimming pool will be filled with city tap water, which has
already been filtered and treated with chemicals.
The filtering removes suspended material.
Chemicals can eliminate some dissolved contamination
by flocculation, binding the contaminants into flakes
that fall to the bottom in settling pools.
Added chemicals can then kill microbial pathogens.
My first job was as a lifeguard at a municipal swimming pool.
Then I went to Purdue and took several chemistry courses while
studying electrical engineering.
Because, as it turns out:
The whole world is made of chemicals.
So bear with me.
When we would fill the pool at the start of summer, it was definitely murky.
Yes, the town water was filtered,
and it looked just fine in a glass or pitcher only a few inches in size.
But in a swimming pool the shallowest part is maybe 3 feet deep.
When you're looking through at least 3 feet of municipal water,
much more than that when you're looking anything but straight down,
you notice that it isn't perfectly clear.
Throw a coin into the shallow end, and you might not see it on the bottom.
After we pumped the water in a loop through diatomaceous earth filters
for a few days, it cleared up.
You could easily see a coin in the bottom of the 14-foot diving well.
Or a hairpin.
Diatomaceous earth is a wonderful filter.
As far as I know, the water had been just fine for drinking.
I assume it passed regular tests.
This was in southern Indiana, so who knows.
But drinking water doesn't have to be a reagent-grade chemical.
Dissolved and suspended mineral material will be just fine
at the levels remaining after typical water treatment with
filters and settling pools.
The big concerns are pathogens and dissolved toxic chemicals.
Sewage is an obvious source of pathogens (make sure to put the water
treatment plant upstream of the sewage treatment plant!),
as is runoff from livestock.
Good luck when the local hillbillies throw their dead animals into
the creek to bloat and float downstream to the municipal water intake.
Yellow Rain: Soviet Nerve Agent or Bee Poop?
Industry and agriculture can be huge sources of toxins.
Agricultural chemicals are a nightmare — most pesticides are
nerve agents, and Agent Orange was just another herbicide.
There's ordinary incidental agricultural runoff, and then there are the
hillbillies dumping their leftover chemicals directly into the local streams.
Industrial waste can include carcinogens, neurotoxins, cytotoxins and more.
For the Latin-averse, those are cancer-makers, brain-killers, and cell-killers.
So, state and local laws regulate the treatment and testing of municipal water
for good reason.
Chlorine or Chloramine?
Chlorine (or Cl2) has traditionally been
the most commonly used method for controlling microorganisms
in drinking water and recreational water systems.
But more and more municipal drinking water systems these days use
chloramine or NH2Cl instead of chlorine.
NH2Cl, a hazardous chemical.
Chloramine is nasty stuff.
It's why you should never mix ammonia (NH3)
and bleach (a solution of 3-6% sodium hypochlorite or NaClO),
as that's a deadly way to make chloramine at home.
Of course, chlorine gas is about as deadly.
But it's not as trivial to produce in the typical home.
Chloriminated municipal tap water in a white polyethylene bucket.
Water treated with chloramine has a green tint.
This tint is so strong that you can easily observe it
by filling a 5-gallon (about 20 liter) white polyethylene bucket
with chloraminated tap water.
Chlorination, in which you dissolve chlorine gas in water,
does a good job of killing microorganisms and disinfecting the water.
However, dissolved chlorine can easily form hazardous byproducts
including potentially carcinogenic trihalomethanes and haloacetic acids.
This is why pool pee is dangerous.
Chloramination, the addition of chloramine,
can also form these byproducts plus N-nitrosodimethylame,
but they're all formed at much lower concentrations.
Back to the Pool
In a swimming pool you're letting people,
who are potentially quite dirty, into the water.
How long has it been since they last bathed in warm water and soap?
Have they stepped in any residual animal waste in the adjacent park?
Might someone, ah, fecally contaminate the pool water?
So, in a swimming pool you add chlorine to kill any added microorganisms.
You notice the resulting chlorine odor, especially in an indoor pool.
People will complain, "There's too much chlorine, it hurts my eyes!"
If the water makes your eyes burn,
that almost certainly means that the pH is out of whack.
Human sweat, human urine, and rain are all acidic,
and they're all added to outdoor swimming pool water.
If people's eyes are burning, it's almost certainly because
the water is too acidic.
It should be a just little basic, but not too much.
Measure the pH, you may need to add some soda ash or otherwise
drive the pH back up toward 7.5.
Meanwhile, the chlorine level is probably just fine.
While chloramine is becoming much more common in drinking water systems,
as far as I know swimming pools are mostly staying with chlorine.
What's the Danger?
Disinfection Byproducts Resulting from Chlorination of Uric Acid:
Implications for Swimming Pools"
describes the chemical risks and what they found in analysis of water
from a large number of swimming pools.
The real danger comes from what they call
nitrogen-containing disinfection byproducts
The nitrogen-containing ones are the especially dangerous ones:
potentially carcinogenic, cytotoxic, and genotoxic.
They mostly come from the chlorination of human body fluids,
primarily urine and sweat.
Uric acid, C5H4N4O3
Sweating in the pool?
Studies have estimated that energetic swimmers (either in an organized
contest, or I'm sure in long sessions of pool tag) may introduce
from 0.2 to 1.76 liters of sweat per person.
Other studies have estimated urine
introduction at just 25 to 117 mL per person per session.
That sounds low!
That range must be averaged across all swimmers, peeing and non-peeing.
They estimate one person in five pees in the pool,
so 125 to 585 ml per peeing swimmer.
Yeah, that sounds reasonable.
The thing is, sweat is mostly water and salts.
There is a little uric acid in sweat,
but not much compared to urine.
People sweat and, much worse, pee,
and the uric acid reacts with dissolved chlorine.
The resulting dangerous N-DBPs include
trichloramine or NCl3
and cyanogen chloride or CNCl.
At this point I need to quote from the paper:
A common misconception within the swimming community is that urination
in pools is an acceptable practice, although signs and placard are posted
in many pools to encourage proper hygiene.
It is also well-known that many swimmers ignore these warnings,
particularly noteworthy among these are competitive swimmers.
USA Swimming recognizes urination in pools as an important problem
and has implemented an educational campaign to encourage coaches
and swimmers to adopt better hygiene habits.
You know how some people say
"I'm spiritual, but I'm just not into organized religion"?
That's how I am with the supposed glories of organized sports.
What a bunch of self-important semi-professional pool-peeing primadonnas.
The Specific Dangers
Here's what you can get when you react dissolved chlorine gas with
pee-introduced uric acid:
Trichloramine or NCl3
is associated with acute lung injury.
Cyanogen chloride or CNCl
can affect multiple organs via inhalation,
including the lungs, heart, and central nervous system.
Yes, both NCl3 and CNCl outgas from the water, so you can be
injured just by watching people swim in pee-defiled pools
in enclosed spaces.
The paper reports that cyanogen chloride
"is ubiquitous in chlorinated swimming pools",
observed at 1 to 21 μg/L.
Yes, because human urine is ubiquitous in swimming pools.
They also detected chloroform or CHCl3,
also caused by reactions of uric acid with dissolved chlorine gas.
So Let This Be A Lesson To You
Don't pee in the pool.
And I Haven't Even Mentioned the Transsexual Crocodiles and Fish
How your pee can change the sex of fish and reptiles
Human urine, especially when dosed with medical hormone treatments,
can contain enough sex hormones to cause fish and reptiles in the
sewage discharge area to change sex.
Prescription pharmaceuticals are mostly excreted through urine.
Typical wastewater treatment systems only remove
about half of these excreted pharmaceuticals.
The Cultural History of Train Toilets