Recreational Water Illness Outbreaks Spur Interest in Supplemental Disinfection
The calls came in slowly at first. In the early weeks of August 2005, a handful of recent patrons of a sprayground at upstate New York's Seneca Lake State Park began complaining to local health and parks departments of gastrointestinal illness. By Aug. 15, there were 100 such reports, prompting the state's top health and parks officials to issue a public advisory and order the Seneca park sprayground closed. Within two days, the casualty report had increased eightfold. And only a week after the public advisory was released, that figure tripled.
©Russell Kightley rkm.com.au
All told, nearly 4,000 people from 35 counties across the state were sickened that summer. By the end of August, tests conducted on the sprayground's two storage tanks had confirmed what health officials suspected all along: Cryptosporidium, the parasite behind a highly contagious waterborne infection (cryptosporidiosis) often known to cause severe diarrhea and occasionally death, was the culprit of the largest recreational water illness outbreak in New York's history. In a typical year, the state records fewer than 500 cryptosporidiosis cases.
For its part, the New York state health department acted quickly and decisively in the wake of the 2005 crypto outbreak. Sidestepping its typical bureaucratic process, officials invoked an emergency rule-making procedure and by November of that year had written water quality and design guidelines governing spraygrounds. (Originally available in draft form, the final version of these regulations was permanently adopted in January.) Spraygrounds hadn't been covered by existing rules because, as Douglas Sackett explains it, they weren't "quote-unquote regular pools."
"We did not have regulations in place at the time to cover spraygrounds because there's no standing water, so they didn't meet our definition of a pool," says Sackett, assistant director of New York's Bureau of Community Environmental Health & Food Protection. "But we recognized that these are the types of pools frequented by toddlers and younger children, where fecal accidents are more likely to occur. So we evaluated the situation and came up with what we thought were appropriate design criteria to provide sanitary water quality."
Sackett and his colleagues included in those criteria filter and disinfectant mandates specifically intended to prevent future crypto outbreaks. The most notable rule, however, is one requiring all water circulating through a sprayground's system to be disinfected by ultraviolet light — widely recognized by aquatic industry experts as the most effective means by which to inactivate chlorine-resistant crypto.
Although Sackett says that relatively few spraygrounds are currently operating in his state, he acknowledges the potential logistical and financial challenges facing sprayground operators — particularly those who have to retrofit their existing facilities to meet the new codes. "UV is not an inexpensive treatment. It's effective if properly designed, but with larger flow rates, there are some considerable costs in putting it in," says Sackett, noting his challenge in balancing operational burdens with public protection. "We have to walk carefully."
As the incidence of crypto and other recreational water illnesses (RWIs) continues to rise — 34 total outbreaks were reported in the United States in 2004, compared to just seven in 1997 — aquatic industry professionals and health officials everywhere are feeling increasingly compelled to devise practical solutions to combat what some say is this generation's most serious aquatic health issue.
"Based on the data, in the long term we're seeing the emergence of crypto-sporidium as the major pathogen in chlorinated pools in this country, and this is expanding in other countries as well," says Michael Beach, an epidemiologist at the U.S. Centers for Disease Control and Prevention and the nation's preeminent RWI researcher. "At chlorinated venues, about two-thirds of illnesses are due to cryptosporidiosis. And because it's chlorine-resistant, it's clearly the pathogen about which we have to think about doing something different."
For the CDC, that process starts with raising awareness of RWIs in general. In recent years, the agency has dedicated an entire web site solely to this issue (www.cdc.gov/healthyswimming) to help educate facility operators about RWIs such as crypto. Using everything from easy-to-read downloadable posters to detailed statistics and charts, the site not only defines the various bugs, it also tells where they are commonly found and how they are spread, offers tips on how to prevent transmission, and provides recommendations on appropriate local responses to fecal accidents and outbreaks.
"When we've done focus groups with facility operators, for a lot of people it's an 'Aha!' moment as opposed to, 'We knew about this, but we just don't care.' They didn't have a clue that this was an issue they should be thinking about," says Beach. "Aquatics is a risk-prevention business. Operators just need to add RWIs to the list of other things that they already deal with — from lightning to drowning to bloodborne illnesses and injuries. We've neglected this facet for too long."
The CDC feels just as strongly about reaching out to swimmers, which it does in earnest during National Recreational Water Illness Week. This year's observance, the third annual, will be held during the week preceding Memorial Day, the traditional opening of the summer swim season (not coincidentally, this is the period when almost all RWI outbreaks are reported).
"We don't see evidence that educating swimmers about the potential for the spread of illness decreases swimming," says Beach, noting that last year more than 250 Air Force facilities used the opportunity to hold RWI education programs for their patrons. "In return, they got a lot of positive feedback. People don't like to be kept in the dark. The ostrich syndrome is not going to work with this bug. Due diligence dictates that we get out in front and let people know about this."
The CDC's Healthy Swimming project has been supported by nearly $350,000 in grants, courtesy of the National Swimming Pool Foundation — which last year also funded a $100,000 Purdue University study of the ancillary chemical effects of using UV light in recreational water settings.
NSPF chief executive officer Tom Lachocki is confident that researchers at the CDC, Purdue and elsewhere will learn what those responsible for treating public drinking water have already discovered. "For years, UV has been used in a number of industries, in drinking water and wastewater treatment, and its greatest strength is that it inactivates chlorine-resistant pathogens like crypto-sporidium," he says. "The science behind UV inactivation is nothing new or controversial. It's substantiated by decades of research and validation."
UV light rays with wavelengths of at least 254 nanometers kill microorganisms such as crypto by altering their DNA structure, hampering their ability to grow cells and form biofilms. Yet, water containing undesired pathogens must receive a dose (or pass through a beam) of UV light with a concentration of at least 40 millijoules per square centimeter (mJ/cm2) (this unit measures the intensity of exposure). Entire bodies of water cannot be dosed at once, without risking harm to pool operators or patrons (human eyes and skin can only withstand up to 6 mJ/cm2 of 254-nm UV light). Therefore, UV lamps deliver their death sentences to pathogens from within sealed stainless steel chambers through which pool water is circulated.
For this very reason, Roy Fielding, director of aquatics at the University of North Carolina at Charlotte, has yet to jump on the UV bandwagon. "With UV, all the bad stuff has to get back to the unit. You can't deactivate it in the pool," he says. "Even though it's probably going to be in the shallow end of the pool, crypto is negatively buoyant, meaning it sinks to the bottom. In most pools — even if everything is working the way it's supposed to and you have perfect circulation — there is going to be some water that does not get back into the system for two days. But most pools aren't working perfectly. If you have bad circulation, how long is it going to take to get all the water back to the pump room?"
Fielding, a certified pool operator instructor who recommends chlorinating pools between 3 and 5 parts per million, would rather keep his pools well chlorinated than equip them with UV irradiation equipment. "Facility operators are so afraid of chlorine that they think it's going to kill people," says Fielding, who discredits such fears by recounting an anecdote told by the late Neil Lowry, a chemist and well-known aquatic industry consultant who died last June. "He spoke at the first World Aquatic Health Conference, where he said, 'A lot of people speak badly about chlorine. But I did a little experiment at home. I raised the chlorine in my backyard pool up to 30 ppm, threw my kids and the neighborhood kids in it, made them stay in there for three hours, got them out, hosed them off and they're still alive. Case closed.' "
Fielding says that if UNC-Charlotte pool patrons ever do get sick, it won't be because they drink the water in his pools. "You talk about scares with E. coli, but where do you get it? You get it from Taco Bell and salads from your grocery store," he says. "That type of E. coli is much more prevalent than what we have in swimming pools. And I'm not trying to take away the livelihood of UV salesmen. But if a flu pandemic hits our country, I'm going to be in my pool. With the chlorine, that's probably the safest environment I can be in."
Lachocki understands Fielding's apprehension to place all his trust in UV technology. "That's the issue with UV — as good as UV is, crypto has to go through the system to get inactivated," says Lachocki. "So if someone sick from crypto has a diarrheal accident in a pool, UV will not prevent an outbreak. It'll minimize an outbreak. If you ingest water that hasn't gone through the filtration system, you have the potential of contracting crypto. You're at risk. But if you swim the next day, you're pretty much free and clear. That's good news, but it's not perfect news."
The shortcomings of UV irradiation technology notwithstanding, it's likely that the days of attacking RWIs with simple chlorination and filtration are all but over. "At some point in the future, the aquatic facility won't have a two-stage protection program," predicts Lachocki. "I think it's just a matter of time before there will be three stages of protection: filtration and chlorination, as well as UV."
It should be noted that the New York state health department, while making clear its strong preference for UV systems, has left open the possibility for sprayground operators to install ozone or other supplemental disinfection systems as the respective technologies advance and "so long as they provide the equivalent level of protection," says Sackett.
New York health officials are also considering whether to expand the UV mandate to all 6,000 public pools statewide (shallow-water venues are receiving the first look, says Sackett).
Beach would laud such a step — or any step beyond the industry's decades-old notions of pool sanitation. "We have to expand our thinking from the traditional, rectangular pool with standing water," he says. "The designers are way ahead of the rest of us. Anywhere there's moving water — whether it's spraying, aerosolized, whatever — there's exposure, and pathogens can be transmitted."
Yet, it remains to be seen whether any states other than New York will implement public health codes mandating the use of UV irradiation systems at aquatic facilities. For now, Lachocki has his eyes on Florida, which he says is currently contemplating such a measure.
For the time being, CDC researchers continue to study the technology, recently focusing on whether higher doses of UV light (at least 60 mJ/cm2), in addition to inactivating crypto, can also help reduce chloramines and thus improve indoor air quality in aquatic environments. As of this writing, data was still being analyzed. "Whether UV does as much as people are saying it does is not clear right now," says Beach. "Will it be a panacea? Probably not."
But one thing is clear. "In the pool industry we are seeing a paradigm shift to supplemental disinfection — ozone, UV — these sorts of inline systems," Beach continues. "I think another level of protection, although it doesn't replace chlorine, will give pool operators increased security. Our major barriers in pool operations — chlorination and filtration — are no longer effective enough."
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