Inside Chlorine's Staying Power

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For all of the criticism and market pressure brought to bear on traditional chlorination, proponents point out that despite popular concerns and a spectrum of available alternatives, chlorine has remained indispensable for many professionals and consumers alike — a fact that is not likely to change anytime soon.

In 1908, Jersey City, N.J., became the first city in the U.S. to apply full-scale chlorination to its drinking water. Within a few short years, other major cities including Philadelphia and Chicago would follow, and as the technology spread, waterborne diseases such as typhus, typhoid fever and dysentery virtually disappeared. According to some estimates, the advent of chlorinated drinking water led to a 50-percent increase in overall life expectancy within the first 20 years.

To Karen Rigsby, a chemist, business support manager and R&D specialist for BioLab, it's tough to overstate the impact chlorine has had on society.

"I always go back to the quote from Life magazine many years ago that said, 'Chlorine in drinking water is the most significant public health advancement of the last millennium.' As big as that sounds, it's hard to argue with. To this day, when you look at places in the world that don't have chlorinated drinking water and the horrible problems they battle, it's obvious how much we benefit from chlorine. Of course it's important to swimming pools, but there's so much more it than that."


Still, for all of its brilliant success in drinking water, where its use is practically unchallenged, the swimming pool industry has met with constant pressure to reduce or even eliminate chlorine use. Some objections are more intuitive; many people don't like the idea of swimming in a chemical they use to make their whites brighter. Others have a more scientific basis — chlorine in pools reacts to form disinfection by-products, which are a suspected cause or contributor to a number of maladies.

As Dr. Andrew Weil, a well-known health and nutrition expert and advocate of holistic medicine and nutrition, said in a 2009 online essay: "Chlorine used to disinfect swimming pools is widely recognized as a health hazard. New research suggests that children who swim frequently in chlorinated pools may have increased risks of developing allergies or asthma. Among adults, exposure to chlorine in swimming pools has been linked with other health problems including bladder and rectal cancer and, possibly, an increased risk for coronary heart disease."

Advocates of chlorine use are quick to counter that those types of hyperbolic statements are misleading — that swimming in properly chlorinated pools actually lowers the risk of illness. Jerry Wallace, president of Swim Chem, a service firm based in Sacramento, Calif., is very much a traditionalist when it comes to chemical treatment. The company, founded by his father, John Wallace, has been relying on chlorine use for 46 years, a practice Jerry plans on maintaining.

"We've always used chlorine," he says. "We started out using gas chlorine, but that was regulated to the point that the cost of compliance became too much. So we switched to liquid chlorine and have been just as successful. It's effective for us because of our thought process of how we want to treat pools. The problem with a lot of pools isn't chlorine, but inadequate overall treatment. Proper water balance, filtration, cleaning, circulation, shocking, backwashing, all of those things together are what determines whether or not you have quality water.

"If you apply the fundamentals of proper maintenance," he adds, "you won't have problems associated with disinfection byproducts."

One of the lingering misconceptions about chlorine, Rigsby says, is the smell, even though that concern is easily addressed: "It's counterintuitive," she says. "People think they're smelling too much chlorine when in fact the smell comes from the byproducts because there's not enough oxidation. Well-maintained pools don't typically have problems with smell."

Be it concerns over smell, possible carcinogenic effects of some byproducts or the question of whether or not chlorine turns hair green, Wallace is skeptical of chlorine critics: "You always want to consider science and new technologies," he says. "At this point, we do know for sure that chlorine has been used in pools and public water treatment for a hundred years, and it's always worked and worked well," he says. "Now people are coming up with causes for problems that we'd never even considered before, but oftentimes the data isn't that convincing.

"Fortunately," he adds, "we don't hear it much from our customers even though many of them are very well informed these days. Most are very happy with the way we're maintaining their pools with chlorine."


Chlorine-related concerns, be they real or supposed, have led to the rise of the many now-familiar alternative sanitizers. Although most tout an array of non-chlorine benefits, very few if any ever make the claim that pools and spas should be run with no chlorine at all.

Whether motivated purely by the market or by science (or both), manufacturers of ozone, UV, ionizers and other alternatives continue to push the idea that less chlorine is better, and have data to back up those claims. Manufacturers of ozone and UV in particular have made significant inroads based on product performance as well as peer reviewed science.

With so much pressure put on chlorine from the public and competing market interests, it begs the question of whether chlorine use has, in fact, been diminished.

"I don't think it has," Rigsby says. "We see technologies from time to time that do make some outstanding claims, and we do investigate those. We're certainly not closed-minded to anything new that will make people's lives better. While yes, we manufacture chlorine, we care about maintaining the pool as a whole because ultimately that's in the interest of both the industry and our consumers. But when you consider the claims made by different manufacturers, you have to focus on the science to fully understand all the implications."

With Swim Chem's successful reliance on traditional chlorination, alternative sanitizing methods have a very high bar to clear before Wallace would consider turning to them.

"We're approached all the time about this, that and the other, the next best thing, but we always ask, 'How is that going to make us more profitable and more important, our pools better and customers happier?' And I've not been shown a way yet," he says.

To a large extent, he says, it's a matter of value to the customer. Given that chlorination is working at an affordable price, Wallace simply doesn't see the benefit in moving in a different direction: "When I look at the ROI, I just don't see it," he says. "Say you have an ozone or UV system, or both, neither of which I'm opposed to at all. But you're still going to need some chlorine for bather-to-bather contact, but now you have the costs of maintaining the UV or ozone systems. I've never seen an economic side that pays off for the consumer. By contrast, pure chlorine use is economical, it's efficient, it works and you have to use it anyway."


The reasons behind chlorine's enduring nature include its ability to work as both a sanitizer, oxidizer and an algaecide, added to the fact that it readily stays in solution, especially when stabilized using cyanuric acid. To date, no alternative exists that meets all those criteria.

Ozone, for example, is an extremely effective oxidizer and sanitizer, but does not stay in solution for more than few minutes. UV is an effective sanitizer, but provides no residual and does not oxidize organic compounds. Ionizers stay in solution and kill some forms of algae and bacteria, but do not oxidize organic compounds. Bromine is an effective sanitizer, oxidizer and does create a residual, except it can't be as effectively stabilized in sunlight.

"We find that alternatives are not sustainable over time," Rigsby says. "You might be able to run a pool for a short period of time on an ozone system, for example, but without chlorine at some point you're most likely going to run into water-quality issues, especially in a pool or spa that's used on a regular basis, and chlorine is going to be the solution. If you want an ozone system, that's fine, all we're saying is to be realistic about what you expect it to do."

While eliminating chlorine altogether is arguably a bridge too far, there are many in the industry who do, in fact, believe that incorporating alternative treatments in combination with chlorine provides the best of all possible worlds.

Long Island-based builder and service professional Steve Kenny has immersed himself in studying and applying combinations of technologies to create what he calls "resilient" water. "But it's never been about eliminating chlorine," he explains. "I use a combination of ozone and UV along with chlorine, in my case, calcium hypochlorite in a feeder, but the reason for that really is to enable chlorine to do its job. It will always be a pillar of water treatment, it's just that now we have technologies that can make it even better."

Kenny developed his approach after his kids experienced severe respiratory problems after using an indoor pool at the local YMCA. "The problem wasn't chlorination, per se," he says, "but the fact that the system wasn't keeping up with the demand and harmful byproducts were forming and making people sick.

"The idea is to use these technologies so they all make each other more effective," he adds. "Ozone reduces oxidizing demand while the UV also sanitizes. That leaves the chlorine residual in the water to safely handle all the bather-to-bather contact issues. And, when you're constantly oxidizing organic compounds and removing chloramines, you don't have the water quality issues associated with poorly maintained pools."

He's quick to point out that proper water balance, filtration and basic cleaning regimens are equally critical. "The health of our customers, our neighbors and our families depend on wholesome, quality water, which is why we have to make it as bullet proof as possible," he says. "When you use a combination of treatment approaches combined with all the other fundamentals of good treatment, including dilution from time to time, you create a situation where the water can withstand the use without turning into a green, cloudy and smelly mess."


Kenny is among many aquatic professionals who have applauded the advent of the Model Aquatic Health Code, a voluntary set of recommendations published in 2014 by the Centers for Disease Control that defines proper treatment techniques for public aquatic environments. Among those recommendations is the use of primary and secondary treatment "pillars" including ozone and UV, along with chlorine.

Whether or not the MAHC will have any measurable impact on the state of the art of pool and spa treatment remains to be seen.

"It's too early to tell," Rigsby says. "I think it's great that people are getting together, looking at the research and having these conversations. So the fact that the MAHC is raising awareness can only help. Still, because it's an entirely voluntary set of recommendations, it's always going to be up to the individual to do their research and become educated about what is and isn't proper water treatment. That hasn't changed."

While Rigsby is a proponent of peer-reviewed research when it comes to understanding water treatment, and chlorination in particular, she also is the first to caution that looking at any one report or study can lead to a skewed and possible erroneous perspective. For example, on the subject of cyanuric acid and the effect that different concentrations have on chlorine performance, she believes that laboratory research doesn't tell the whole story.

"When you look at all the peer-reviewed data and the studies that have caused concern regarding the build-up of cyanuric acid, you find it's those that are done in laboratories with beakers using distilled water, which has no chlorine demand," she explains. "Those studies are great as a theoretical foundation, but when you add organic compounds and chlorine demand, like you do in an actual swimming pool, then the whole thing changes. The published data in those settings clearly shows that cyanuric acid has no practical effect on chlorine's ability to sanitize."

Within the chlorine industry, issues such as stabilizer levels, feeder technology, shocking products and methods, ORP control technology, testing practices and especially the use of saltwater chlorination, remain points of discussion, if not controversy. Even those who are strong advocates of chlorine say it pays to be cautious and weigh different types of information and resources.

But while reading through the tremendous amount of literature on chlorine sanitization, Wallace says, it's important to keep perspective on proven technology. "Being informed is a good thing, but when it comes to chlorination, the information that's out there can sometimes lead you to an inaccurate conclusion. On the other hand, when you step back and consider what really works and the science behind it, chlorine is still, in my opinion, the most affordable, available and reliable option we have."

Comments or thoughts on this article? Please e-mail [email protected].

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