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Survey: 1 in 4 Adults Would Swim with Diarrhea

Diarrheal outbreaks linked to swimming are a persistent challenge for aquatic venues


swimming-with-diarrheaAmericans will soon head to the pool as Memorial Day weekend marks the unofficial start of the swimming season, but a new survey reveals that there may be more in the pool than just water.

The survey, conducted on behalf of the Water Quality and Health Council, found that 1 in 4 adults (25 percent) would swim within one hour of having diarrhea, half of adults (52 percent) seldom or never shower before swimming in a pool, and that 3 in 5 adults (60 percent) admit to swallowing pool water while swimming.

These results are concerning to experts from the U.S. Centers for Disease Control and Prevention (CDC), the Water Quality and Health Council, and the National Swimming Pool Foundation® (NSPF®), given that waterborne outbreaks of diarrheal disease caused by the germ Cryptosporidium (or “Crypto”) remain a challenging health concern.

Crypto is a parasite that can spread when someone swallows water that has been contaminated with the fecal matter (poop) of an infected swimmer. Crypto is the most common cause of diarrheal illness and outbreaks linked to swimming pools or water playgrounds. In addition to diarrhea, some people experience lack of appetite, nausea, vomiting, weight loss, stomach cramps or pain, and fever.

The CDC advises those infected with Crypto to avoid swimming until two weeks after recovering from diarrhea. Parasites can remain in the small intestine for weeks and cause symptoms to reappear days after the infected person recovers.

“Normal chlorine disinfection of swimming pool water does a great job in destroying most germs, but Crypto presents a special challenge,” said Dr. Chris Wiant, chair of the Water Quality and Health Council. “An awareness of Crypto helps us remember that a healthy pool depends on swimmers being considerate of one another. Showering before swimming, refraining from peeing in the pool, and not swimming for two weeks after experiencing diarrhea can help keep swimming fun and healthy for everyone from ‘water babies’ to seniors.”

Other key findings of the national Healthy Pools survey include:

  • 72 percent of adults are unaware that Crypto is a parasite often spread in water.
  • 84 percent of adults are unaware that the use of chlorine at CDC-recommended levels will NOT kill Crypto instantly in swimming pools.

Crypto is not easily killed by chlorine and can live up to 10 days in well-treated pools,” said Michele Hlavsa, RN, MPH, epidemiologist and chief of the CDC’s Healthy Swimming program. “Just a small number of Crypto germs can make someone sick. That’s why it is important to keep Crypto out of the water in the first place.”

Swimmers and parents of young swimmers can take a few easy steps to prevent Crypto outbreaks:

  • Stay out of recreational water (e.g., pools, lakes, rivers, oceans) if sick with diarrhea and until diarrhea-free for two weeks. Patients typically continue to shed Crypto for up to two weeks after diarrhea stops.
  • Shower before you get in the water. Rinsing off in the shower for just one minute removes most of the dirt or anything else on your body.
  • Don’t swallow the water.
  • Report diarrhea incidents that occur in the water to aquatics staff immediately.

Drowning prevention is also key to maintaining a healthy and safe swimming experience. According to the survey, 60 percent of parents reported engaging in some type of distracted activity while their children swam in a pool, such as using a phone or tablet, reading a book, drinking alcohol, sleeping or leaving the pool altogether.

“Parents should designate a ‘Water Watcher,’ because supervision can save a life,” said Thomas Lachocki, Ph.D., CEO of NSPF®. “Water Watchers are important even if a lifeguard is present. Water Watchers should be at least 16 years old and able to recognize and execute a rescue, provide a floating or reaching object, alert someone nearby to help or call 9-1-1, and be able to administer CPR.”

The Water Quality and Health Council is once again making free pool test kits available this summer through its award-winning Healthy Pools awareness initiative. Swimmers can test their backyard pools or community pools to ensure a proper pH and chlorine level. Visit healthypools.org to order a free pool test kit.

The 2017 Healthy Pools survey was conducted online by Sachs Media Group, an independent research firm based in Tallahassee, Fla. Sachs Media Group interviewed 3,114 adults (18+ years old), April 28-30, 2017. The survey measured perceptions and misconceptions related to swimming pools and public health, with a margin of error of +/- 2.0 percent.

To learn more about the Water Quality and Health Council and its efforts to raise awareness of the importance of disinfection for public health, please visit waterandhealth.org.


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Out of the Jungle: Yellow Fever on the Rise

Brown Howler Monkey According to a recent Science Daily report, thousands of brown howler monkeys in a forest in southeastern Brazil have died of yellow fever.

Brown Howler Monkey

According to a recent Science Daily report, thousands of brown howler monkeys in a forest in southeastern Brazil have died of yellow fever.

Yellow fever, a deadly scourge transmitted by mosquitoes that has impacted the course of human history time and time again, is on the rise in Latin America. The first yellow fever death in Brazil in 17 years occurred in January 2017, when a young person who worked in the jungle succumbed to the disease. A recent Pan American Health Organization (PAHO) “Situation summary in the Americas” reported that since the current outbreak began in Brazil in December 2016, there have been over 1,400 confirmed or suspected cases and at least 234 deaths in six states of that country. Suspected and confirmed yellow fever cases have also been reported in Colombia, Ecuador, Peru, Bolivia and Suriname.

Yellow fever is indigenous to some tropical regions of Central and South America and Africa, and is caused by the yellow fever virus, one of a family of Flaviviruses, which includes West Nile virus, dengue virus and Zika virus. “Flavus” is Latin for “yellow.” Because it is borne by an arthropod (mosquitoes are arthropods), it is also known as an “arbovirus.” Yellow fever is the most severe arbovirus ever to circulate in the Americas, according to a recent commentary in The New England Journal of Medicine (NEJM).

Out of the Jungle

The yellow fever virus is transmitted through both a sylvatic (jungle) cycle and an urban cycle. According to the PAHO “Control of Yellow Fever Field Guide,” in the sylvatic cycle, the virus circulates among primates, primarily monkeys, through the bites of several species of mosquitos, and may result in death (see photo above). In the Americas, in the urban cycle, the virus is circulated among humans through the bite of the Aedes aegypti mosquito, the same mosquito that transmits Zika virus, chikungunya and dengue fever.

The urban cycle is initiated when a person who was infected with the disease in the jungle enters an urban center in which there is a high density of A. aegypti mosquitoes. If that individual is bitten by the A. aegypti mosquito while the virus is circulating in his or her blood, the disease can be spread to others subsequently bitten by the same mosquito, setting off a chain of transmission. Large outbreaks can result in urban areas where there are high mosquito densities and a high percentage of unvaccinated or otherwise unimmunized people. So far there is no evidence of urban transmission in Brazil.

Yellow Fever Symptoms

Following infection, the virus incubates in the human body for three to six days. Although many people develop no symptoms at all, fever, headache, jaundice, muscle pain, nausea, vomiting and fatigue may develop. Yellow fever is named for the jaundice exhibited by some patients. According to the World Health Organization, a small fraction of people infected with yellow fever develop severe symptoms and of those, approximately half die within seven to ten days.

A Vaccine and Vector Control

Fortunately, a very effective vaccine for yellow fever was developed in 1937 that is in wide use where the disease is endemic. According to the NEJM commentary, the current outbreak in Brazil is precariously centered in areas close to urban centers. Because urban Brazilians are not typically vaccinated against yellow fever, there is a concern that widespread urban transmission could begin, which could lead to “travel” cases in the US, such as we have seen with dengue, chikungunya and Zika viruses. Local US transmission can become a potential issue in regions such as the Gulf Coast states where A. aegypti mosquitoes thrive. In the age of world travel, we are a connected community, and with increasing tourism into jungle areas, the risk of importing yellow fever grows more likely.

As we know from recent experience with Zika virus, controlling the mosquito vector is a significant strategy for avoiding arboviruses. This includes removing outdoor standing water, properly chlorinating backyard swimming pools, maintaining window and door screens, and applying mosquito repellent appropriately (see tips). These are solid precautionary measures we can all take to help avoid any of the potential arboviruses circulating in our midst. Travelers to yellow fever endemic areas should ensure that they are immunized for yellow fever. Recently CDC announced a shortage of yellow fever vaccine, but noted there is a plan for providing safe vaccine at a limited number of clinics until the supply is replenished. For updates on the vaccine’s availability, please consult the CDC Travelers’ Health website. Travelers to areas in which yellow fever is endemic can also consider using bed netting, wearing protective clothing and applying mosquito repellent.

The more things change, the more they stay the same. Yellow fever is back (it never really went away), but unlike the devastating outbreaks documented throughout history, we now have proven effective measures to preclude them … if they are utilized.

Fred M. Reiff, P.E., is a retired official from both the U.S. Public Health Service and the Pan American Health Organization, and lives in the Reno, Nevada area.


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Color-coded Tips for Treating Algae in the Swimming Pool

Algae Swimming PoolAlgae in the swimming pool is an unwelcome sight, but one that usually can be dealt with effectively. The following “color-coded” tips can help you or your pool service professional identify and eliminate, or at least control, the most common types of algae. It is important to follow manufacturers’ directions for using and storing all pool chemicals.

Green Algae

Green algae usually appears when pool sanitizer levels are low or water circulation is poor; green algae turns pool water cloudy and murky. It is the easiest type of algae to remediate, but left unaddressed, green algae can worsen to the point of obscuring the floor and steps of the pool and potentially even a struggling bather, raising the drowning risk. Eradicate green algae by raising the chlorine level or adding an algaecide. Following treatment, it is important to run the filtration system continuously to clear the water by trapping the dead algae in the filter.

Avoid green algae by maintaining proper pool chemical levels. Additionally, avoid cross-contaminating your pool with green algae spores by thoroughly washing swimsuits and water toys before re-using them in the pool following a visit to a natural water body.

Black Algae

Black algae appears as black dots on pool plaster, especially where the plaster is pitted, etched, or where calcium deposits have developed. Poor water circulation in those areas helps protect black algae. In fact, the more deteriorated the plaster, the worse the potential problem.

Tackle black algae as soon as it appears by scrubbing the affected area with a stainless steel brush. The scrubbing action removes a protective coating that develops over black algae. Daily brushing is required until the algae spots disappear. In severe cases, it may only be possible to control black algae, and not to eliminate it completely. It is essential to keep scrubbing black algae spots as soon as they appear.

An additional recommended step is to treat affected surfaces with “trichlor” on horizontal pool surfaces and a copper-based broad spectrum algaecide on vertical pool surfaces. Broad spectrum chelated copper algaecide can also be used as a preventative measure. A word to the wise: Have your pool water analyzed for metal levels prior to adding any metallic algaecide, such as copper-based products. If metals are present in the pool water, adding a metallic algaecide could cause the pool water to become oversaturated with metals, which could lead to staining or water discoloration. It is also advisable to keep copper to a minimum from a human toxicity standpoint. Most drinking water municipalities keep copper levels below 1.3 ppm. The manufacturers of copper algaecides should be able to provide the “ppm added” from use of their product. Excess copper in swimming pools can cause blue-green coloration of the hair, nails and skin.1

Yellow/Mustard Algae

Yellow or mustard-colored algae is probably the most challenging type of algae to eradicate. First, the diagnosis may be difficult. Yellow algae in a blue pool may look green, but the pool is not likely to contain green algae unless the water is cloudy and murky. Yellow algae may also be mistaken for dirt or pollen. The diagnostic test is to see whether or not the yellow substance returns to the side walls of the pool after it is scrubbed. Dirt or pollen will drop to the floor of the pool, but yellow algae will reappear on the walls.

To further complicate matters, yellow algae can thrive in a well-balanced chemically treated pool. It can be introduced into your pool from lakes, ponds, on the wind or in the rain. It can also be transmitted through previously contaminated pool equipment, such as skimmers, leaf rakes or vacuum hoses and heads. Treat yellow algae with an algaecide or chlorine enhancer that specifically targets yellow algae.

Anti-algae Basics

To help avoid algae of all types, keep in mind the basics of chemical and physical pool maintenance.

CHEMICAL MAINTENANCE: Proper pool chemistry means free chlorine and pH are within target ranges. According to the US Centers for Disease Control and Prevention’s Model Aquatic Health Code, pool water free chlorine levels should be in the range of 1-4 ppm and the pH should be between 7.2 (minimum) and 7.8 (maximum). The ideal pH in a pool is 7.4 to 7.6.

PHYSICAL MAINTENANCE: Physical maintenance of the pool means keeping up with brushing and vacuuming the pool and cleaning skimmer and pump baskets. Algae love rough and deteriorating pool surfaces, so sanding and crack repair are helpful. Clean pool filters as the first step in battling algae. Operating pumps and filters for at least 8 to 10 hours per day throughout the summer keeps water moving, a deterrent to algal growth.

This article is based on “Tips and tricks for identifying and treating tough algae,” by Terry Arko in the March 2017 edition of The IPPSAN, a publication of the Independent Pool & Spa Service Association, Inc.

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1 Peterson, J. et al. (2006). Cupric keratosis: green seborrheic keratoses secondary to external copper exposure. Europe PMC 77(1): 39-41. Abstract online, available: http://europepmc.org/abstract/med/16475494.

Sweet Evidence for an Unsavory Practice: Peeing in the Pool

PeeInPoolPeople urinate in swimming pools. It’s been a widely discussed topic since we published the results of our 2009 survey concluding that one in five American adults admit to having “peed in the pool.” Now there is physical evidence for this unsavory act, and it appears in the form of an artificial sweetener, of all things. A Canadian research team has identified a chemical compound in pool water that indicates the presence of urine. The “chemical marker” is acesulfame-K, or “ACE,” a synthetic sweetener found in prepackaged foods. ACE passes through the body essentially unaltered, and is excreted exclusively in the urine. The researchers posit that ACE could be a useful indicator of pool water quality.

The Problem with Peeing in the Pool

Besides being a rather discourteous thing to do, peeing in the pool contributes to poor pool water quality. Urine contains nitrogen-containing compounds that combine chemically with chlorine disinfectant to produce eye, skin and respiratory irritants. That strong chemical smell around some pools is not “the smell of chlorine,” but chemical products of chlorine’s reaction with urine, perspiration, cosmetics and body oils from swimmers. Chlorine, added to destroy waterborne pathogens that could make swimmers sick, is depleted by its reaction with these impurities. That’s why the Centers for Disease Control and Prevention encourages swimmers to shower before swimming and refrain from sneakily relieving themselves underwater.

Strategies to Avoid Using the Pool as a Toilet

We believe the key to ending peeing in the pool is multi-pronged and includes effective swimmer education and scheduled pool breaks, especially for young swimmers. We recommend swimmer hygiene messaging be a part of all swimming lessons and that clear signage around the pool encourage sanitary practices. Certain pool regimens also can be helpful. As the National Swimming Pool Foundation (NSPF) notes in a recent press release, being submerged in water stimulates the body to create more urine. NSPF offers the following commonsense recommendations to help prevent peeing in the pool:

  • Swim coaches should require bathroom breaks 30-60 minutes into practice.
  • Parents of young children should enforce a snack, sunscreen or bathroom “out of pool” time every 30 minutes.
  • Facility managers should schedule short breaks, such as 10 minute “adult swims” or out of pool activities every hour.

Swimming is fun and the health benefits of aquatic recreation are enormous. As evidence mounts that swimmers are fouling the very waters they enter to enjoy, the time is right to confront the problem.

Chris Wiant, M.P.H, Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council and a member of the National Drinking Water Advisory Council.

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Smells Like Chlorine?

Smells Like Chlorine

The nose is an extremely sensitive “detector” that sends information to the brain where it is interpreted.

They say “the nose knows,” but I say the nose can be confused. Chlorine odors are a good example. Several different chlorine odors can arise from various chlorine-based substances and in different circumstances. They are not all simply due to “chlorine.” A prime example is the irritating smell commonly attributed to chlorine around some poorly managed swimming pools. That smell is from a couple of chemical compounds in the chloramine family. Some chloramines form when chlorine disinfectants react chemically with nitrogen-based substances from the bodies of swimmers, including urine. The poolside pronouncement of “too much chlorine in the pool” may be more aptly described as “too much peeing in the pool.” Ironically, the odor could signal that more chlorine is needed in the pool.

Not One Chloramine

Chloramines start out as ammonia— NH3— which looks like a three-legged stool with the nitrogen atom as the “seat” and a hydrogen atom at the end of each “leg.” Ammonia is common in the environment, and Ammoniaalthough household ammonia has a very sharp odor, ammonia has no odor at the very dilute levels typically found in water. When chlorine is added to water in sufficient amounts, it breaks ammonia down into nitrogen (N2) gas and hydrogen (as water or H2O). But if the amount of nitrogen increases (from peeing in the pool, for example), the balance between chorine and nitrogen is disturbed and the ammonia is only partially deconstructed.

TrichloramineWhen three chlorine atoms replace the hydrogen atoms on the ammonia molecule, the resulting compound is trichloramine, a pungent, irritating compound that is often mistaken for “too much chlorine” in the pool, even at very low concentrations. Trichloramine and its sister chemical dichloramine (with two chlorine atoms and one hydrogen forming the “legs”) are responsible for the odor you might smell when you enter an enclosed pool area in which there is poor airflow through the building. Besides just smelling bad, these same two chemicals can also turn swimmers’ eyes red.

DichloramineThe problem with trichloramine and dichloramine goes beyond that irritating smell. When trichloramine is present in the pool, the level of “free chlorine” available to disinfect the water and protect swimmers from microbial disease is greatly diminished. That’s why it’s important to check pool water regularly for the pH and the presence of free chlorine1. Pool managers are obliged to do just that, and pool patrons can do the same with easy-to-use pool test strips.

MonochloramineTrichloramine and dichloramine have a third sister – monochloramine. As the name suggests, in this compound, only one of the hydrogen atoms on the ammonia has been replaced with chlorine. This chemical, however, carries no odor and is an effective disinfectant that has been used successfully by many water treatment plants for many decades. What a difference a minor change in a chemical formula can make!

Monochloramine is typically formed in source water by first adding chlorine to break down any ammonia (into nitrogen and water) and then adding back trace amounts of ammonia in carefully monitored amounts to produce only monochloramine.

Bleach Smell

Unlike the chloramine family of compounds, chlorine bleach is a solution of water and sodium hypochlorite with the chemical formula NaOCl [bleach contains sodium (Na), oxygen (O) and chlorine (Cl)]. The odor of bleach (bleach that is not infused with a fragrance) is not nearly as pungent as that of di- and trichloramines. When the chlorine in bleach combines with nitrogen-based substances, however, smelly di- and trichloramines can form by chemical reaction. This could happen in the swimming pool environment, for example.

Chlorine Gas

Chlorine is a common, naturally occurring element, but due to its reactivity, it usually occurs in nature combined with other elements, such as sodium in common table salt, NaCl. It is also produced industrially as part of the “chlor-alkali” process in which both chlorine and sodium hydroxide (NaOH) are generated by applying electricity to salty water. In that process, chlorine is produced as a gas consisting of twin atoms chemically bound together, and is represented by chemists as “Cl2.” Both chlorine and sodium hydroxide are used to help produce hundreds of everyday products, including water treatment chemicals, PVC pipes, pharmaceuticals, paper, aluminum, silicon chips for computers and even the titanium metal used in joint replacements.

Chlorine gas is a respiratory irritant that the human nose can detect at very low levels (0.2-0.4 parts per million in air; just for reference, one part per million is equivalent to four drops of ink in a 55-gallon barrel of water). At these low concentrations, chlorine gas smells very much like household bleach. When levels rise to the range of 1-3 ppm, however, mild mucous membrane irritation is noted and higher level exposure becomes increasingly dangerous.2 That is why the chlor-alkali industry takes extensive measures to ensure the safe production, handling and transportation of chlorine gas and even the less reactive sodium hypochlorite and calcium hypochlorite.

Not Just One Chlorine Compound

Chlorine is a reactive element that is found in many different compounds exhibiting different but sometimes similar properties, including odor. It is credited to have dramatically improved public health over the past 100 years through its ability to disinfect water.  I hope this discussion helps to clarify “the smell of chlorine.” Now your nose knows! 

Stephan A. Hubbs retired from water treatment operations at the Louisville Water Company in 2004. He was involved in the development of the first chlorine by-products regulation in 1975-1979 and remains an active volunteer in the drinking water community today.

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1 Hypochlorous acid, or HOCl, for you chemists!

2 The Chlorine Institute, Inc., Pamphlet 63: First Aid, Medical Management/Surveillance and Occupational Hygiene Monitoring Practices for Chlorine, Edition 8, June, 2011.

Go Swimming This Winter!

Looking for a fun way to stay fit this winter? Consider swimming in an indoor pool. Swimming provides a great workout for the whole body—core (including abdomen), arms, legs, glutes and back, according to WebMD. It helps increase flexibility and strength without taxing the joints, a welcome advantage for people with arthritis. And feeling buoyant in the water can be both relaxing and soothing, reducing mental stress.

Indoor Pool Air Quality

One potential deterrent to indoor pool swimming is the strong chemical odor around some indoor pools. We have addressed the phenomenon popularly known as “too much chlorine in the pool” numerous times, but it bears repeating here: The irritating chemical odor around some pools is not due to chlorine, but to certain substances formed when chlorine disinfectant combines with nitrogen-containing contaminants brought into the pool by swimmers.

To compound matters, inadequate air exchange over the pool contributes to the build-up of irritants in the indoor pool space. If your indoor pool air is irritating, speak to the pool manager about air flow in the room, but consider your own personal “swimmer hygiene” as well.

Why is chlorine added to pool water anyway? Chlorine-based disinfectants are needed to control waterborne germs, helping to keep pool water safe for swimmers. Chlorine’s presence is non-negotiable (it’s even present in “salt” pools), so to minimize irritants forming, swimmer hygiene must be addressed. Many swimmers do not realize how much influence their hygiene has on pool water quality. Swimmers should shower before entering the pool and refrain from “peeing in the pool.” Showering thoroughly with soap removes body oils, perspiration, makeup, lotions and traces of urine and fecal matter from the skin. When chlorine combines with these substances, there is less of it available to destroy the germs in the water that can make swimmers sick. Inadequate pool chlorine levels can lead to swimmer’s diarrhea and swimmer’s ear, for example. And peeing in the pool, no matter how stealthily it can be done, is not cool!

A Family Affair

Swimming can be a family affair. Parents, swimming is an “electronic gadget-free” activity! The pool is a unique environment in which to connect family members across the generations. The buoyancy of pool water is a great equalizer as older swimmers are able to avoid high impact to their aching joints. Older family members can help teach younger ones to swim and then race them across the pool.

Ensuring that each family member can swim is an investment that can pay dividends over a lifetime. In addition to being a life-saving skill, swimming can enhance the quality of life. A variety of outdoor recreational activities in and around the water, including boating, fishing, water-skiing and more, become available and enjoyable for confident swimmers.

So, as counter-intuitive as it may seem to locate your swim suit and goggles and head for the pool when the weather forecast includes ice and snow, consider the benefits and the fun of winter indoor swimming.

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Why Cryptosporidium is Responsible for over 80% of Swimming Pool Illness Outbreaks, and What Can be Done about It

Causes of recreational water illness outbreaks

Causes of recreational water illness outbreaks, 2005-2006 (CDC MMWR Report, Sept. 12 2008)

Cryptosporidium is a microscopic parasite that is responsible for the majority of swimming pool illness outbreaks in the US with symptoms ranging from diarrhea to death. An outbreak this summer in Ohio sickened hundreds of swimmers. With that level of notoriety, it should come as no surprise that “Crypto” was the subject of much discussion at the recent National Swimming Pool Foundation’s annual World Aquatic Health Conference in Nashville (October 19-21). The figure at right illustrates the dominant role of “Crypto” in 35 reported recreational water illness outbreaks between 2005 and 2006.

Crypto lives in the intestines of mammals and is what is known as an enteric pathogen, spread through the feces of infected people and animals. According to the Centers for Disease Control and Prevention (CDC), Crypto can cause diarrheal disease in people two to ten days after they become infected. Swimming pool Crypto outbreaks start when fecal matter from an infected swimmer or animal contaminates pool water. Given that a single fecal event can release over one billion organisms into the water and ingesting as few as 10 or fewer organisms can cause infection in a healthy person,1 the disease potential of Crypto is both extremely high and easily observed once an outbreak begins. Symptoms usually last from one to two weeks, but may last longer in people with weakened immune systems. Infectious oocysts can be excreted for up to 60 days after gastrointestinal symptoms have ended. Death can result when the immunocompromised (e.g., young children, the elderly and the chronically ill) are infected.

Chlorine Resistance

Unlike the other waterborne pathogens represented in the pie chart above, Crypto is chlorine-resistant. This unique characteristic explains why it is the most common cause of illness in pool swimmers. Most waterborne pathogens are destroyed by chlorine, and many pools are adequately chlorinated to achieve that level of protection. In its infectious form, however, Crypto sports a thick, protective, outer shell known as an “oocyst.”

Filtering Crypto

In this year’s World Aquatic Health Conference’s “Advanced Filtration Science” symposium, University of North Carolina at Charlotte researcher and professor Dr. James Amburgey provided helpful perspective around the Crypto issue by noting that analytical testing for Crypto is expensive, and that often the pool management is unaware of its Crypto problem until there is an outbreak. His experiments show Crypto oocysts escape swim diapers within five minutes of a diapered child being in the pool. Additionally, research shows 8.3% of noninstitutionalized adults are fecally incontinent.2 Just one fecal “event” in a pool can release over one billion oocysts into the water!

Optimizing Filtration

Because chlorine disinfection is ineffective against Crypto at normal swimming pool levels, oocysts must be removed through filtration (or exposed to advanced disinfection units employing ozone or UV light). Dr. Amburgey stated that a typical swimming pool sand filter removes only about 25 percent of oocysts each time the water is filtered (typically every 4-6 hours). Fortunately, there are several chemical and design factors that can be tweaked to achieve much greater removal rates. For this, the researcher recommended all three of the following techniques already employed by the drinking water industry:

  • Slowing the rate of filtration (≤ 10 gallons per minute per square foot of filter area)
  • Increasing the filter depth (≥ 24 inches of 0.5 mm effective size sand)
  • Using coagulants (0.1 mg aluminum per liter of water with alum or polyaluminum chloride)

The first two factors make intuitive sense: Slowing the rate of pool water filtration and increasing the filter depth increase the odds of oocysts being caught in the matrix of a pool filter. Most importantly, however, Dr. Amburgey emphasized that coagulants dramatically enhance filtration. As filter media and oocysts are both negatively charged, there are no electrical attractions between them to enhance filtration. Positively charged coagulants added to swimming pool water, however, can effectively promote oocysts sticking to filter media. It is important to note that optimizing coagulation for Crypto removal can be complicated and is best left to researchers.

Other options suggested to enhance filtration include replacing sand with at least 18” of Ceraflow-70 (an ultrafine granular ceramic media), ceramic membrane filters, and the use of “precoat filters” where a woven material is precoated with at least 0.15 pound of diatomaceous earth (a fine powder) per square foot of filter area (forming a layer that is roughly 1/8” thick) that has pores small enough to trap Crypto particles. With pore sizes in the range of 1 micron (0.001 millimeter), diatomaceous earth can remove 99.99% of oocysts of diameter 4 microns in pool water.

Time will tell if swimming pool filtration is more widely optimized to help prevent future US Crypto outbreaks. As the recent World Aquatic Health Conference demonstrates, one thing is for sure: The right discussions are taking place.

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1 Yoder, J.S, Wallace, R.M., Collier, S.A., Beach, M.J. and Hlavsa, M.C., “Cryptosporidiosis Surveillance-United States, 2009-2010,” Morbidity and Mortality Weekly Report, September 7, 2012. On line, available: http://www.cdc.gov/mmwr/preview/mmwrhtml/ss6105a1.htm

2 Whitehead, W.E., Borrud, L., Goode, P.S., Meikle, S., Mueller, E.R., Tuteja, A., Weidner, A., Weinstein, M., Ye, W., (2009). “Fecal incontinence in US adults: epidemiology and risk factors,” Gastroenterology, 137(2): 512-7.


Crypto Outbreaks in Aquatic Facilities

Left to right: Cryptosporidium in the oocyst stage; emerging from its resistant shell; fully emerged
Photo courtesy of the Centers for Disease Control & Prevention


Over 250 people in central Ohio and over 100 in Arizona have been sickened in summer outbreaks of cryptosporidiosis, a diarrheal illness caused by the microscopic parasite Cryptosporidium, or “Crypto.” These parasites are found throughout the US and abroad, and settle in the intestines of infected humans and animals, making Crypto one of the most well-known zoonotic diseases. According to the Centers for Disease Control & Prevention (CDC), millions can be released in the feces of an infected person. Only 10 to 30 are needed, however, to cause infection in a healthy person, according to Yoder and Beach (2010).1

Crypto spreads in aquatic facilities when people inadvertently swallow water contaminated with the feces of infected individuals. Understanding Crypto and how to avoid infection can help your family enjoy the fun and health benefits of swimming pools and other aquatic facilities.

Chlorine Resistance

Crypto is the leading cause of recreational water outbreaks in the US. You may be wondering why chlorine, a mainstay of swimming pool treatment, doesn’t destroy Crypto. The gold standard for disinfectants, chlorine helps reduce the public’s exposure to a wide array of waterborne bacteria, viruses and parasites. Crypto, however, is chlorine-resistant as a result of the protective shell of the parasite’s “oocyst” stage, the stage at which it is shed in the feces of those infected (see photo above). Crypto can survive in water at CDC-recommended chlorine levels (1–3 mg/L) and pH (7.2–7.8) for over 10 days, according to Shields et al. (2008)2 . The protective shell also allows Crypto to survive outside the body for long periods of time.

Temporarily elevating chlorine levels in Crypto-contaminated swimming pools—a process known as super-chlorination—can destroy the parasite, but it must be done when the facility is closed to swimmers.3 Crypto infections may spread regionally when infected swimmers who are unwilling to wait for a pool to reopen following super-chlorination visit neighboring pools. Pool water filtration is another strategy for removing Crypto. The factors affecting the efficiency of removal of Crypto and other parasites by filtration is an important subject of ongoing study. According to CDC’s Model Aquatic Health Code, UV (ultraviolet) radiation (light sanitization) following filtration may be the most cost-effective disinfection strategy (see the Code’s Annex, p. 131). UV inactivates Crypto so that it can no longer reproduce.

Cryptosporidiosis Symptoms

Symptoms of cryptosporidiosis include: watery diarrhea, stomach cramps or pain, dehydration, nausea, vomiting, fever and weight loss. Some people with cryptosporidiosis have no symptoms at all, and may unknowingly spread the illness in aquatic facilities. Symptoms are likely to last from one to two weeks, but can persist sporadically for up to 30 days. Immunocompromised persons may develop “serious, chronic, and sometimes fatal illness,” according to CDC. Such people include people with AIDS, those with inherited diseases that affect the immune system, and cancer and transplant patients who are taking certain immunosuppressive drugs.

Most people with healthy immune systems recover from cryptosporidiosis without treatment. CDC reports Nitazoxanide may be prescribed for treatment of diarrhea caused by Crypto in people with healthy immune systems. Nitazoxanide is not approved for treatment of immunodeficient individuals because it has not been shown to be effective for that population.

Tips for Reducing Your Risk of Cryptosporidiosis at Aquatic Facilities

Remember the saying, “When Swimming, Don’t Discount Sanitary Conditions”

  • Wash hands thoroughly after using the bathroom, and instruct children to do the same.
  • Shower with soap and water (especially the perianal area) before entering the aquatic facility.
  • Diarrhea: Do not use aquatic facilities if you are experiencing diarrhea; if you were diagnosed with cryptosporidiosis, do not use aquatic facilities until two weeks after diarrhea has stopped.
  • Diaper Changing: Do not change diapers poolside; use designated facilities, and wash hands thoroughly afterwards.
  • Swallowing water: Avoid swallowing water while in the aquatic facility.
  • Children: Take young children on frequent bathroom breaks (every hour); check diapers frequently (every 30–60 minutes).

The tips above are important, not only for the residents of Ohio and Arizona who are experiencing Crypto outbreaks currently, but for everyone who frequents aquatic facilities. Don’t wait for an outbreak—help avoid one!

Chris Wiant, M.P.H., Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council.

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1 Yoder, J.S. and Beach, M.J. (2010). Cryptosporidium surveillance and risk factors in the United States. Experimental Parasitology 124:31–39.

2 Shields, J.M., Hill, V.R., Arrowood, M.J., and Beach, M.J. (2008). Inactivation of Cryptosporidium parvum under chlorinated recreational water conditions. Journal of Water and Health 6:513–520.

3 A recent update to the Model Aquatic Health Code recommends that for Crypto inactivation in pools (that use cyanuric acid stabilizer), a dosage of 20 ppm free chlorine is needed for 28 hours, representing a doubling of the previous concentration x time, or “CxT” recommendation.

Your Guide to Removing Swimming Pool Stains

The swimmers at the summer games inspired awe in all who viewed those exciting events, including the littlest backyard pool athlete who has dreams of winning gold.  Recently, the sparkling blue of the dive pool in Rio was transformed into a deep green, sparking fears of algae.  In fact, the color change was blamed on a decline in alkalinity, caused by insufficient levels of chemicals that buffer pool water pH.  A significant drop in pH can make the water corrosive to metal fixtures and equipment, which could cause metal leaching and discoloration of the water.

If you are maintaining a backyard pool for your family, you may be wondering about the appearance of stains in your pool – not only in the water, but on pool surfaces.  What causes them and how should they be treated?  A recent article1 by Terry Arko in The IPSSAN (The Independent Pool & Spa Service Association, Inc., July, 2016) newsletter provides many helpful answers.

As Arko notes, “Not all stains are the same, so it’s important to diagnose the stain before providing a broad-spectrum treatment.”  Arko also makes the point that when addressing a pool stain, the first thing to do is to ensure the water chemistry is balanced.  He notes, “A lot of staining in pools is from the pH dropping down and aggressively dissolving the metals into solution.”  Regarding pool surfaces, vinyl and fiberglass pools usually respond better to stain treatment than plaster pools, which are more porous.  The quality of paint on plaster, concrete or cement plastered pools also affects how easily stains are removed.  Arko recommends brushing pool walls regularly and adding a sequestering agent (to prevent metal staining) at a frequency (e.g., weekly, biweekly, or monthly) that fits your needs.

The table below is based on Arko’s recommendations for specific pool stain removal:

Stain Color Likely Source Treatment Notes
Blue-green stain on pool surfaces or in water (but water is not cloudy) Copper from algaecides, heat exchangers, fill water, older copper plumbing Granular treatments, such as citric acid and ascorbic acid used directly on the stain; an additional sequestering agent can help the filtration system trap removed metals.  If treatment includes phosphoric and/or phosphonic acid, these must be removed at a later time.  Generally, non-phosphate treatments are only effective on stains that have not yet set into the surface. If water is blue-green and also cloudy, the likely source of the stain is algae, in which case an algaecide is needed; algae will also be evident by slimy walls and floor.

In the Rio dive pool example, the alkalinity of the pool water had to be restored with chemicals such as sodium bicarbonate and sodium carbonate.

Purple precipitate on pool water surface, tile line, skimmers and pool cleaner Copper cyanurate when the cyanuric acid level is over 100 ppm Reduce cyanuric acid level to about 50 ppm by draining water. Draining water also addresses copper in the water, but it is important to test the water for any remaining copper.
Brown stain on pool surfaces or in water The most common source is well water that contains dissolved iron or manganese; other potential sources are pool heater headers or lawn fertilizers Same as for copper; if the source of iron is well water, begin a maintenance program of adding a sequestering agent weekly; use a non-phosphate sequestering agent to preclude elevating phosphate levels.
Brown stains, some of which may be shaped like leaves and other organic debris Leaves and other natural materials that settle to the pool bottom; often found after uncovering the pool at the start of pool season Stains may disappear as pool chlorine levels are established or shock treatment is applied; alternatively, citric acid or ascorbic acid work well to lift these stains.
Metal corrosion Salt generators corrode metals, such as pool ladders and light rings Add a sacrificial anode, such as zinc; use a non-phosphate sequestering agent.


Bruce Bernard, PhD, is President of SRA Consulting, Inc., and Associate Editor of the International Journal of Toxicology, and lives in Cambridge, MD.

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1 “Pool staining—identify before you treat,” by Terry Arko, The IPSSAN, July, 2016, p. 9, 13, and 17.



How to Interpret Pool Chlorine Readings

Pool chlorine levels are easily measured by dipping a test strip in the pool for a few seconds and then matching the resulting color of the strip to a chart linked to “parts per million” chlorine levels. Here’s the rub: Some pool test kits measure “free chlorine,” whereas others measure both “free chlorine” and “total chlorine.” There is a difference between “free” and “total” chlorine. That may be breaking news to an investigative reporter who recently confused the two in a news segment about possible contaminants in swimming pools.

Why Measure Chlorine?

This summer, the Centers for Disease Control and Prevention (CDC) is recommending the public check the chlorine level and pH of pool water before enjoying a refreshing swim. Why? A new CDC report finds that one in five pools in five states in 2013 had to be closed due to serious safety violations, including improper pH or chlorine readings. That prompted an investigative reporter for NBC News and the Today show, to measure pathogen and chlorine levels at several public aquatic facilities. At one pool, the reporter described a “sky-high” total chlorine reading of 10 parts per million. He compared the reading to the appropriate range of free chlorine levels (1-3 parts per million), saying, “Three is ideal, so it is way over.” Needless to say, that created consternation in the news room, not to mention fear and confusion among the viewing public.

There’s Chlorine, and Then, There’s Chlorine!

Without getting too technical, the reading that is a measure of how much chlorine is available in pool water to destroy germs is known as the free chlorine level. But not all chlorine in the pool is available to destroy germs. As the Water Quality and Health Council discussed in its article of May 27, 2016, some chlorine may be unavailable because it has chemically reacted with impurities brought into the pool on the bodies of swimmers. Chlorine that reacts with swimmer perspiration, urine, body oils and cosmetics produces “combined chlorine,” which is mostly unavailable to destroy germs.

The total chlorine level is the sum of the free chlorine and combined chlorine levels in the pool. Reporting a total chlorine level of 10 parts per million, as the reporter did, only tells us that the free chlorine level is likely less than that.

Total Chlorine = Free Chlorine + Combined Chlorine.

I hope this explanation helps you interpret chlorine level reports! This summer, you can order a free pool test kit—that measures pool water free chlorine and pH—at www.healthypools.org.

Linda F. Golodner is President Emeritus of the National Consumers League and Vice Chair of the Water Quality & Health Council.

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