Safe Swimming: Chlorine does not always mean clean

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July 25, 9:20 AM

by Doctor Lissa, Health Care Examiner

 

 

                                        Look before you leap

We have noted that in any pool or park with large numbers of bathers, there are probably pathogens in the water which cannot be controlled with disinfection.  Cryptosporidium and Giardia are the two most easily spread.  This is true because of the following:

1. The huge number of pathogens a single infected person can spread (1trillion)
2. The low number of pathogens it takes to be infected (10)
3. The extended period after clinical recovery in which others can be infected (weeks to months)
4. The moderate chlorine resistance of Giardia (30-60 minutes) and high chlorine resistance of Cryptosporidium (11 days)
5. The prevalence of poor pool maintenance and water filtration design

So you're probably wondering what chlorine does and if it works against anything worth noting.  The answer is yes.  Conventional chlorination and filtration in well-maintained pools and water parks are effective against at least three bugs that make us really sick:

• E.coli
• Shigella
• norovirus

And of course, it does kill Giardia after 30-60 minutes.  Not great, but not as bad as Cryptosporidium (11 days).

So chlorine does some good as long as the pool is properly maintained (the best maintained pools with adequate chlorine levels have 1ppm-3 ppm free available chlorine).  This is amazine considering that fecal accidents in pools are not uncommon and each day up to 2 to 3 pounds of feces can be found in the water of an average-sized public pool from accidents and swimmers' bodies that have been improperly cleansed after bowel movements.  (I know, this is not pleasant for me either).  Even so, most people are not infected.  It's just the one's who are that we need to be concerned about.

Unfortunately, during the last 3 years, the number of Cryptosporidium cases reported to the CDC has risen.  in 2005, the number of nonoutbreak cases increased 41%, in 2006, 24% and in 2007, there was an increase of 66% (this translates to about 100,000 cases as a conservative estimate).   This is not a new phenomenon.  In 1993 an outbreak in Milwaukee sickened over 400,000 residents when their drinking water was contaminated.  Since then there are new federal drinking water guidelines and outbreaks in municipal drinking water has decreased.  Although pool and water outbreaks have not sickened as many people, they occur with much more frequency.

Last year the largest outbreak related to swimming pools and water parks occurred in Utah with almost 2,000 cases reported.  It is estimated that only about 8% of the cases were reported leading to the hypotheses that as many as 23,000 people may have been infected.  And the news is full of recent closings of pools across the country.  (Stay tuned)

Who is at greatest risk?

• Children 5 and under (more likely to have accidents in the water and swallow water)
• People with compromised immune systems such as the elderly and those whose immune systems are weakened.

So our main concerns are still Giardia and Cryptosporidium, with Cryptosporidium taking first place simply because it is virtually without effective treatment and is so hard to eliminate from the water. 

The CDC has a program you might want to take a look at called, "Healthy Swimming" where you can find out more about ideas to keep yourself safe.  Again, the best defense is to be informed and to be alert.

By following the CDC guidelines, visits to water parks and swimming pools can continue to be fun and a great way to beat the heat!

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