March 1, 2008
Breathe easy when you're in the swim
Ernest Blatchley III and colleagues at Purdue University, Illinois, are learning how to reduce the production of irritating and unhealthy volatile compounds in swimming pools by turning to ultraviolet technology to complement the use of chlorinated disinfectants.
Most swimmers are familiar with the odour of their pool. That strong smell of "chlorine" is not, however, due to chlorine gas at all. Instead, it is the smell of volatile byproducts formed when chlorinated disinfectants react with sweat and urine in the water.
These volatile chloramines and other contaminants have in recent years been targeted as a possible risk factor for respiratory problems not only in pool users but among poolside staff, such as lifeguards and attendants. Understanding how these volatile contaminants are formed in various reactions could take us a stroke closer to making indoor swimming pools healthier.
"If the concentrations of those volatile byproducts gets high enough, then they can become an irritant to your respiratory system, to your skin and to your eyes," explains Blatchley. The issue received widespread media coverage in the US in 2007 when the U.S. National Swimming Championships in Indianapolis were interrupted after swimmers experienced difficulty breathing.
Unfortunately, the conventional chemical tests carried out on the poolside to evaluate pH and "chlorine" levels in the water, do not test for organic compounds, such as chloramines. However, Blatchley, working with post-doctoral research associate Jing Li in Purdue's School of Civil Engineering, published details last year in the journal Environmental Science & Technology explaining why these organic contaminants ought to be tested and outlining how this might be done. They now have new data, based on work by graduate students William Weaver and Yuli Wen and undergraduate student Jessica Johnston, which is scheduled to appear later this year in ES&T and will be presented to the World Aquatic Health Conference in Colorado Springs, Colorado during October.
Michael Beach, of the Centers for Disease Control and Prevention's National Center for Zoonotic, Vector-borne and Enteric Diseases, explains that the research is part of an effort to bring the scientific rigour of drinking-water chemistry to the wider aquatics industry. "If you don't understand what's in the soup, you can't know how to treat the water," he says, "The Purdue research is finding all sorts of compounds that could have potential health effects." He adds that as a major public health issue, such research is critical but more data are needed.
"It's amazing how little we know about swimming pool chemistry," Blatchley said. "And that's why we have pools being shut down for reasons that are probably avoidable. We want to solve this problem so that businesses and municipalities can operate their swimming pools in a manner that doesn't cause people to get sick." It is not just about byproducts of disinfectants reacting with sweat and urine, Blatchley and his team are also investigating the byproducts of personal care products, such as makeup, deodorants and perfume that for some reason many swimmers see fit to apply prior to taking a dip.
Using membrane introduction mass spectrometry, the researchers analysed swimming pool water for the presence of organic compounds formed from creatinine, urea and amino acids, which are found in human urine and sweat. Their results suggest possible mechanisms by which these compounds are formed. "We focused on a couple of the amino acids that we believe are representative of those that are present in sweat and urine and likely to be present at high concentrations in swimming pool water," Blatchley explains. They have tested numerous public pools and are building up a profile of volatile disinfection byproducts.
The next stage of the process is to figure out how these various byproducts might be broken down. After all, there is only so much policing of pool users that can be done to ensure they shower before swimming, not urinate in the pool and remove cosmetics and deodorants before diving in. The new research focuses on whether ultraviolet radiation might be used to degrade disinfection byproducts quickly and safely.
Blatchley explains that most are broken down to nitrates and nitrous oxide. "Currently, we know where about 75 percent of the nitrogen goes, and we think we know where most of the rest of it goes, but we need to do some experiments to confirm that," he concedes.
The same results may also have implications for drinking water quality in places where UV is used in conjunction with chlorinated disinfectants. "The chemistry is very similar in both settings," says Blatchley, "so our interest is broader than just swimming pools."
• Environ Sci Technol, 2007, 41, 6732-6739
• World Aquatic Health Conference 2008
• Blatchley Page
Article by David Bradley