ah summer when the days are filled with
Sun more Sun and sunburns two years ago
we made a compilation of Sun themed
episodes but since then we've produced
so many more summery videos so slather
on the sunscreen and kick back in your
favorite deck chair because it's time
for our second summer compilation this
time though we're diving into the
science related to one of our favorite
summer activities swimming speaking of
diving into things if you're a water
lover you've probably had the
unfortunate experience of jumping into a
pool or lake and getting water up your
nose which of course hurts a lot that's
weird because our nasal passages are wet
all the time and some people even clean
them out with water using a neti pot so
why does getting water up your nose hurt
so much I'll pass it over to Hank to
explain
so you ever done cannonball into a
swimming pool or a pond and accidentally
like shot like water all up in your
brain through your nose yeah not a fan
and yet neti pots those teapot looking
things that people used to squirt water
into their noses when they're feeling
stuffy they're like soothing and
relatively painless
turns out the difference has to do with
the conditions inside your nasal
cavities see the inside of your nose as
you may have noticed is full of nerve
endings and not to get too up close and
personal here but it's also pretty warm
up there and kind of salty with a salt
concentration of about 0.9% when you
start up fresh cold swimming pool water
it's a shock to your system because it's
just so different from the natural
environment inside your nose salt
temperature could even make you feel
like you're having a brain freeze
probably because it's making the blood
vessels inside of your nose constrict
and since the freshwater doesn't match
up with your internal salt concentration
there's an uncomfortable feeling as they
try to equalize and the water flows into
your cells meanwhile your nasal
membranes respond to the irritation by
secreting a bunch of mucus which is why
your nose immediately starts running
neti pots which flush out your sinuses
to remove allergens and thin out mucus
get around this by using warm salty
water that matches your internal
environment but even though neti pots
and accidental cannonball snorts feel
totally different they can both put you
at risk for deadly infections so it's
very rare a snoot full of pond water or
an improperly cleaned neti pot just
might expose you to brain-eating amoebas
called Naegleria fowleri again this is
really rare there are only three or four
cases in the u.s. each year but it's a
water dwelling parasite that if snorted
up your nose can get into your brain and
start destroying tissue I'm not saying
you gotta give up cannonballs but maybe
just hold your nose do the thing that
everybody does you'll get around the
pain and the risk of a brain eating
infection at the same time
if you can avoid getting water up your
nose spending hours upon hours in a cool
swimming pool is pretty much the best
thing on a sweltering summer day if you
do that though you'll probably notice
yourself getting a bit pruney after a
while why does our skin do that well let
me explain
whether you're swimming or washing the
dishes or just taking a nice long
well-deserved bath if you're immersed in
water for longer than 10 minutes chances
are your fingers and toes will emerge
looking like raisins so what's up with
the wrinkled digits for years scientists
thought the phenomenon was the result of
some type of osmosis caused by water
passing into the dry outer layer of skin
the influx of water the thinking went
would expand the skin's surface area but
not the tissue below it so the skin
would bunch up and wrinkle but in 1935 a
pair of doctors noticed that this
effects didn't happen in their patients
with nerve damage one patient for
example was a boy who had lost feeling
in three of his fingers the researchers
found that when his hand got wet the
fingers that could feel wrinkled is
normal but the ones that were numb
remained smooth it turned out that the
pretty digits weren't caused by just the
passive flow of water through the skin
it was an active response of the nervous
system to prolonged moisture the nervous
system causes the wrinkling by
constricting the blood vessels below the
skin which causes the upper layers of
skin to pucker since the phenomenon is
caused by an involuntary nerve response
some biologists have thought that it
must have some evolutionary function but
what possible purpose could it serve one
recent theory suggests that wrinkly skin
may have given our ancestors a better
grip while working in wet conditions
like gathering food from a stream or
damp vegetation may have also given us
better footing while walking across
slippery landscapes in the rain in a
2013 study evolutionary biologists
tested this theory by asking subjects
with either wrinkly or non wrinkly
fingers to pick up a variety of wet and
dry objects like marbles they found that
the subjects with wrinkly digits picked
up the wet objects 12% faster than their
counterparts but there was no difference
when it came to picking up dry objects
the wrinkles apparently helped channel
the water away much like the treads on
your car's tires but then this raises
the question if wrinkly skin gives us a
better grip then why isn't our skin
wrinkly all of the time well maybe
because shriveled fingers and toes are
less sensitive which is no advantage at
all
raise any fingers isn't the only thing
pool water can do to your body if you're
swimming around for a long time in a
pool you might find that your eyes get
all red and kind of burn you might think
that's just a reaction to the chlorine
but it's not here's Hank with more
maybe you've had this experience after a
long day at the pool your eyes start
stinging a little they might even turn
all red a burning itchy bloodshot mess I
a might think that's the price you pay
for swimming without goggles and that
your eyes are just sensitive to the
chlorine in the water
the real answer is a lot more disgusting
apologies in advance the stinging
redness actually means the water you've
been in for the past hour includes a
fair amount of urine sweat or even poop
yep your eyes are actually doing you a
sort of favor and screaming out in their
bloodshot pain that you've been in water
that's less than sanitary to be fair
chlorine is still involved the real
offenders here are a class of chemicals
called chloramines which form when
chlorine reacts with the nitrogen rich
ammonia or similar compounds in those
bodily fluids see and sweat for example
both contain urea
a molecule with two ammonia like parts
when urea comes in contact with chlorine
it swaps out its hydrogen's for chlorine
and voila chloramine is born that
chloramine is what actually irritates
your eyes not the cleaning stuff that
was put in the pool originally so how do
you know whether you should risk jumping
into the water go with your nose it
turns out that the chlorine odor you
associate with pools isn't actually
chlorine that's also chloramine and not
only is the smell a sign that there's a
lot of bodily fluid in the pool but
because all that chlorine is bound to
nitrogen it means that there's probably
not that much free chlorine left to do
what it's meant to do disinfect but
because chlorine only works well ripping
apart bacteria and destroying viruses
when it's dissolved in water as
hypochlorous acid once it's part of a
chloramine molecule that killing power
goes way down so if there is a strong
smell to the pool you might want to
reconsider your swim and if you want to
help rather than hinder the red-eye
problem take a quick shower before you
swim in about a minute you can wash away
any sweat or dirt that you might
otherwise bring into the pool that would
make more chloramines and I shouldn't
have to say it but pretty please don't
pee in the pool
well I bet you're not gonna be able to
forget that lovely bit of information
about pools anytime soon
and it gets worse because all that pee
in the pool that's making your eyes red
it could be downright dangerous for you
here's Stefan with why
if you've ever been a competitive
swimmer or just spent a lot of time the
pool you might have peed in the water
once or twice or maybe a lot according
to interviews Olympic swimmers pee in
the pool all the time even though it
sounds disgusting a lot of people say
you're in is sterile plus chlorine is a
disinfectant so what's a little pee
between friends right you might actually
want to take your business to the
bathroom for one it turns out that P is
and all that sterile but there's another
problem to mixing urine with the
chlorine in your pool can make chemicals
that might cause respiratory and nervous
system problems a urine is mostly water
but it contains a lot of junk that your
body doesn't want anymore including uric
acid and urea both nitrogen containing
molecules uric acid is produced when
your body breaks down molecules called
purines like the ones in some of your
DNA bases and urea is made from the
breakdown of protein and when these
waste molecules mix with chlorine in the
pool that's meant to destroy bacteria
and viruses they react to form
disinfection by-products or DB PS for
short specifically urea reacts to create
a type of chemical called chloramines
swapping out its hydrogen atoms for
chlorine atoms try chloramine especially
is pretty reactive and can corrode the
metal in and around pools and you might
know it by its smell that classic
chemical pool smell is caused by
chloramine gases not chlorine a lot of
people like lifeguards have reported
that they get red eyes a runny nose or a
scratchy voice after being around the
pool too much which could potentially
have something to do with irritation
from lots of try chloramine some
researchers think chloramines could
cause respiratory problems in swimmers
too since they probably breathe in a
bunch more than your average pool goer
but we'll need to do more research to
really understand the health effects
we've known about the connection between
urea and try chloramine for a while now
but we've pretty recently found a link
between uric acid and a molecule called
cyanogen chloride cyanogen chloride gas
doesn't have a familiar smell but it's
real bad news and can cause respiratory
cardiovascular and central nervous
system problems it's part of a group of
chemicals called cyanides which all have
a carbon atom bonded to a nitrogen atom
their toxins and nasty ones at that
these chemicals mess with how your cells
use oxygen so your cells struggle to
produce energy and if the concentration
is high enough all kinds of things can
go wrong in one study published in the
journal Environmental Science and
Technology in 2014 researchers created
synthetic urine and combined it with
various concentrations of chlorine and
within an hour the uric acid
some cyanogen chloride the amount varied
based on the chlorine concentration they
used but it was around 2 to 8 milligrams
per liter now there aren't many official
guidelines about what concentration of
liquid cyanogen chloride is dangerous
but some sources recommend avoiding
exposure to more than 0.6 milligrams per
cubic meter of the gas form so getting 2
to 8 milligrams per liter of cyanogen
chloride sounds like a huge deal but
it's pretty unlikely you'll ever find
that much in your swimming pool because
this experiment used higher
concentrations of chlorine than you'd
find outside of a lab so you probably
don't need to panic if you go to a pool
party every once in a while
DBP levels might be an issue at large
swim meets where hundreds of swimmers
are probably peeing in the water
especially if a lot of people are peeing
in the same spot say at the foot of the
diving board that area will have higher
concentrations of DB pees like tri
chloramine or cyanogen chloride and
researchers are trying to figure out if
long-term exposure to d bps are related
to the unusually high amounts of asthma
reported among competitive swimmers
which has been documented in multiple
surveys now it looks like d bps are
probably not a life or death issue in
the pool although they're not harmless
either so getting out of the pool drying
off and going inside to use the bathroom
is kind of a pain but your lungs and
probably your friends will thank
at this point you might be thinking that
maybe you should avoid pools altogether
you could always swim in a lake after
all but well olivia has some information
you might want to consider first
if your summer has ever included cooling
off with a nice swim in a lake you might
be acquainted with something called
swimmers itch these itchy red bumps
appear on the exposed parts of your skin
after you take a dip in a lake or pond
and they can last for a week or more
but swimmers itch is more than just an
annoying rash it's actually caused by
parasites that burrow into your skin and
then die there yeah you the culprits are
tiny worms called schistosomiasis oum
species specializes in a specific bird
or mammal host some schistosomiasis do
so myiasis but the ones that cause
swimmers itch aren't after you they're
part of a different group of species
whose hosts include ducks geese muskrats
and raccoons that itchy rash is what
happens when one of these
schistosomiasis take adult parasites
live in their hosts blood and when they
lay eggs the hosts eventually poops them
out with a little luck the eggs end up
in water where they hatch into larvae
that swim around in search of the
aquatic snails that they need to infect
to complete the next stage of their
lifecycle the baby schistosomiasis a
second type of larvae called Cir carry
into the water this is where swimmer
itch gets its technical name circ aerial
dermatitis these little guys each less
than a millimeter long head out to look
for a member of their original host
species to start the cycle all over
again you'd think it would be easy to
tell the difference between a human and
a muskrat or goose or whatever but
sometimes this are Kerry Eve mess up and
burrow into a human swimmers skin it's a
fatal mistake they can't develop there
and so they die and because dead baby
parasites are definitely not something
that's supposed to be in your body they
trigger an allergic reaction as they
break down that's what the itching and
redness is from because it's an allergic
reaction some people are more sensitive
than others it just depends on how
strongly your immune system responds and
if you're exposed to swimmers edge over
and over again you can actually become
more sensitive to it over time you're
most likely to get swimmers itch in
fresh water but it's possible to get it
in salt water too so even at the ocean
you're not completely safe if you keep
your risk small towel off or shower as
soon as you get out of the
water and don't do anything to attract
birds that might host schistosomiasis a
small price to pay to avoid parasites
dying a slow death under your skin
basically there are some downsides to
swimming pretty much anywhere but there
are upsides too
after all it is great exercise and it
does help you cool off when temperatures
spike and that's more than enough to
convince me to follow the sage advice of
Dory from Finding Nemo and just keep
swimming thanks for watching this swim
compilation and thank you especially to
our patrons on patreon the support of
our patrons is what allows us to make
all these videos and we really can't
thank them enough but we can try so
we're making our next compilation topic
a patrons pick we've chosen some fun
potential themes and we're leaving it up
to our scishow patrons to pick which one
we go with if you want to put your vote
in or just learn more about supporting
the show head over to
patreon.com/scishow
[Music]