A Physician’s View on Minimizing Swimming Pool Health Risks

How to winterize an In Ground Pool
by Peggy Geimer, M.D, September 29, 2010


A Matter of Hygiene:  A Physician’s View on Minimizing Swimming Pool Health Risks

New preliminary research on swimming in indoor chlorinated pools in Spain draws an uncertain line between exposure to certain pool water contaminants and health effects.  After reading these studies, I asked myself:  What do these tentative findings mean to me and my family of swimmers? I agree with the researchers that it’s not time to get out of the pool, but it is time to focus on better swimmer hygiene.  

Swimming is a healthy form of exercise for people of all ages.  As a physician who is trained to consider swimming pools from a public health standpoint, here’s what I see:  The contaminant chemicals in question, called disinfectant byproducts, are generated from chemical reactions between (a) one absolutely necessary addition to pool water (disinfectant) and (b) various unnecessary additions to pool water (organic substances, including swimmer waste products, sweat, oils, lotions, etc.). 

Disinfectant:  Necessary Addition

Used correctly, chlorine disinfectants are a good and necessary addition to swimming pools.  Swimming pool disinfectants destroy the germs that would otherwise make swimmers sick, with everything from diarrhea to swimmers’ ear and athlete’s foot.  Chlorine disinfectants have a unique advantage over alternatives in that they provide a residual level of disinfection, meaning disinfectant remains in pool water long after its initial application, helping to protect swimmers against harmful microbes.   But we cannot stop chlorinated disinfectants –or any chemical disinfectants for that matter—from also reacting with organic substances that may be present in pool water.  What we can do, and what CDC urges us to do, is refrain from inadvertently adding organic substances into the pool.

Organic Matter:  Unnecessary Addition

When swimmers enter pools without first showering, they introduce perspiration, urine, fecal matteri, lotions and body oils into the water.  As these substances make contact with the disinfectant in the water, chemical reactions produce an array of disinfection byproducts of variable health concern.   For that reason, ridding the pool of unnecessary organic substances is a high priority of the Centers for Disease Control and Prevention.

A 2009 Water Quality & Health Council survey of 1,000 U.S. adults found that almost half (47%) of those surveyed admit to one or more behaviors that contribute to an unhealthy pool.  Roughly one third (35%) pass the shower without stopping and three quarters (73%) say their fellow swimmers fail to shower before swimming.  The survey also revealed that 20% of those asked admit to “peeing in the pool.”  Such unhygienic behaviors are directly responsible for degrading the quality of pool water.  I have also heard of swim team practice rules that no bathroom breaks are allowed.  What would your child do under those circumstances? 

Here’s my logic:  A + B C.  We want to minimize C.  We must have A.  Therefore, we must minimize B.  We can do this by following and promoting the CDC rules for Healthy Swimming:  showering before swimming, taking frequent bathroom breaks, washing our hands after using the bathroom, and never swimming when we have diarrhea.  Considering the “yuck” factor alone, no one wants to swim in water that contains the organic substances that give rise to disinfection byproducts.  Given the new preliminary research, we may have further reason to pay attention to swimmer hygiene.


Peggy Geimer, M.D.
Corporate Medical Director, Arch Chemicals, Inc.

On behalf of the Chlorine Chemistry Division of American Chemistry Council

How Much POOP is in your POOL?

CDC staff estimates that each swimmer brings in about 0.14 g of fecal matter into the pool-largely because we fail to shower or wash our 'private parts' with soap and water prior to jumping in the pool.

Multiply 0.14 g by the estimated number of swimmers in the pool and then multiply by 0.0022 to get pounds of poop in your pool. yuck!