(TIME.com) -- Chlorine is supposed to take care of most of the microbes floating around in pools, but human waste, it seems, is stubbornly resistant to being sanitized.
That's the conclusion of a group of researchers from the Centers for Disease Control (CDC), who collected water samples from 161 filters in public and private swimming pools, as well as water parks in Atlanta last summer.
What they found trapped in those filters was enough to make swimmers think twice before logging their laps. More than half of the samples were contaminated with E. coli, which the investigators say comes from one primary source -- swimmers pooping in the pool.
The study, published in the latest Morbidity and Mortality Weekly Report, specifically looked at pools in Atlanta, but the researchers say such contamination is likely a widespread problem in U.S. pools, thanks to swimmers not washing themselves off before taking a dip.
According to the scientists, each of us carries about 0.14 grams of fecal material into the pool -- and that doesn't include accidents or cases of diarrhea.
Among municipal pools, the genetic testing for pathogens detected E. coli in 70% of the filters, while 66% of the water parks contained the bacteria and 49% of pools in private clubs showed evidence of the contamination.
"These findings indicate the need for swimmers to help prevent introduction of pathogens, e.g., taking a pre-swim shower and not swimming when ill with diarrhea, (for) aquatics staff to maintain disinfectant level and pH according to public health standards to inactivate pathogens, and state and local environmental health specialists to enforce such standards," the authors write in their report.
When a pool is properly chlorinated, however, bacteria like E. coli should be killed off, since proper pH levels typically take care of the issue. According to the CDC, it takes less than a minute for E. coli to be inactivated if chlorine levels are adequate, about 16 minutes to control Hepatitis A virus, about 45 minutes to kill off the Giardia parasite and over 10 days for a Crypto parasite.
But just one diarrhea accident can cause an infection for anyone who gets a mouth full of pool water. Fortunately, the testing did not reveal strains of E. coli 0157, a particularly virulent form of the bacteria that was responsible for several outbreaks, and deaths, from serious foodborne illnesses.
According to NPR, because the researchers only analyzed the samples for genetic signatures of different pathogens, they couldn't determine whether the bugs were alive, and potentially reproducing in the water, but there were no pool-related diseases reported in Atlanta during the summer the samples were gathered.
Thomas Lachocki, the CEO of the National Swimming Pool Foundation, says that in order to be properly chlorinated, pools should contain 1-4 parts per million of chlorine and pH levels should be within 7.2--7.8.
"You can go to any mass market store and go into the pool chemical aisle and buy test stripes. All of these have chlorine and pH tests. In five seconds, you can do a quick analysis yourself and have an idea of what the various levels are," he says.
But if you don't have the time to do your own testing, look for clear water. "You should always be able to see the bottom of the pool clearly. Usually if the water is cloudy, something with the filter or chemicals isn't right," says Lachocki. "Clear water doesn't mean everything is alright, but cloudy water is an absolute positive sign that something is not right."
Here are some additional recommendations from the CDC for ensuring a bug-free dip:
-- Don't swim when you have diarrhea.
-- Shower with soap before you start swimming.
-- Take a shower to rinse off before you get back into the water.
-- Take bathroom breaks every 60 minutes.
-- Wash your hands after using the toilet or changing diapers.
-- Try not to swallow the pool water.
If you have young children:
-- Take children on bathroom breaks every half-hour to hour or check diapers frequently.
-- Change diapers in the bathroom or diaper-changing area and not at poolside where pathogens can rinse into the water.
There may be no way to completely sanitize a pool, but the latest analysis of what could be lurking in the water should motivate lifeguards and pool managers to be more vigilant about testing those waters more frequently.
Women who discover they carry a hereditary gene mutation that dramatically increases their risk of breast and ovarian cancers face big decisions and the possibility of tens of thousands of dollars in medical costs.
Carriers of the BRCA gene mutation have up to an 85% chance of getting breast cancer and a 60% chance of getting ovarian cancer in their lifetime, according to FORCE, a nonprofit for people affected by hereditary breast and ovarian cancers. Those who make the tough decision to remove as much of the breast and ovarian tissue as possible can significantly decrease their risk of cancer, but doing so isn't cheap.
Initial genetic testing for mutations on the BRCA1 and BRCA2 genes, which typically serve as tumor suppressors, costs roughly $4,000 when not covered by insurance, according to Myriad Genetics, the only laboratory that analyzes the tests. Subsequent tests for family members of a mutation carrier tend to be cheaper because the initial mapping has already been done.
If someone tests positive, doctors recommend they have a mammogram and M.R.I scans at least once a year, which can add up to several thousand dollars. And if they opt for a preventive ovary removal surgery or double mastectomy with reconstructive surgery, the costs can climb to tens of thousands of dollars or more, though insurance usually covers at least part of the bill.
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While most insurance companies will also pay for genetic testing, patients have to be deemed "high-risk" first.
For women, that often means they either have to be diagnosed with breast cancer before age 45 or have multiple close blood relatives (like an aunt, mother or sister) who have been diagnosed with breast or ovarian cancer. Men who are diagnosed with breast cancer at any age are typically covered. Yet some insurers have broader criteria than others, said Lisa Schlager, vice president of community affairs and public policy at FORCE.
"We do have people who shouldn't get tested and end up getting it covered," said Schlager. "And then we have people who should be tested and they get denied."
Medicare, for instance, is stricter than most private insurers and will only cover testing for women who have already been diagnosed with cancer.
According to Myriad, 95% of eligible patients receiving the tests are insured and out-of-pocket costs are typically less than $100. Under the Affordable Care Act, BRCA genetic testing is now classified as preventative care, requiring no out-of-pocket cost for those who are deemed eligible, although some plans still don't recognize that requirement yet, said Myriad spokesman Ron Rogers.
The company also offers a financial assistance program for low-income patients -- those who earn less than two times the federal poverty limit, which is $22,980 for a single-person household -- without health insurance.
But for those who are uninsured and don't qualify, the costs can be prohibitive.
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"It has got to be a priority to ensure that more women can access gene testing and lifesaving preventive treatment, whatever their means and background, wherever they live," actress Angelina Jolie wrote in a New York Times editorial announcing she had undergone a preventive double mastectomy after testing positive for a BRCA1 mutation.
Claudia Gilmore, who underwent a preventive double mastectomy in 2011 at the age of 23, spent roughly $2,500 out of pocket for her surgeries, which she said would have cost around $100,000 without insurance coverage. She also took a month of paid time off work using her employer's short-term disability policy, something she said not all workers would be able to do.
"The point of getting a BRCA genetic test is so you can do something with that information," said Gilmore, now a public health graduate student at the University of California Los Angeles. "If a woman doesn't have health insurance, how could she even consider preventive surgery or ongoing medical surveillance for the rest of her life?"
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Uninsured patients could receive genetic testing by participating in research studies or seeking out financial assistance programs at hospitals and local nonprofits. Some surgeons are also able to arrange free preventative surgeries for uninsured patients who test positive, said Ellen Matloff, director of Cancer Genetic Counseling at Yale Cancer Center and a plaintiff in a lawsuit challenging Myriad's patent for the BRCA gene.
Still, many simply choose to go without the test.