ASU engineers lead research on water contaminants and their impacts
When people think about water contamination, images of oil spills or gunk spurting out of a kitchen faucet might jump to mind. But contaminants in our water are often undetectable to the naked eye.
Researchers at Arizona State University are working to identify these unseen contaminants and to measure their effects on human and environmental health.
Some of those unnoticed pollutants are directly linked to consumer practices. Chemicals in the products we use often end up in the water supply. For example, many stain and stick resistant products are made with something called perfluorinated compounds. Their chemistry, which makes them useful in the home, also makes them persistent in the environment. They simply do not degrade.
Nature is full of hydrocarbons – strings of carbon atoms that hold onto hydrogen atoms. In perfluorinated compounds, those hydrogen atoms get replaced with fluorine. These new chemicals are not seen in nature.
“The fluorine-carbon bond is the strongest bond in organic chemistry. There is no organism known that can make a living pulling these fluorines back off the carbon skeleton. And we’ve decided to mass produce these chemicals and put them into the environment, where they will linger for decades, centuries, if not millennia,” says Rolf Halden.
Halden is director of the new Center for Environmental Security in the Biodesign Institute at ASU, a senior sustainability scientist for the Global Institute of Sustainability, and a professor in the School of Sustainable Engineering and the Built Environment, one of ASU’s Ira A. Fulton Schools of Engineering.
Perfluorinated compounds are found in grease-resistant food packaging, non-stick cookware and water-resistant clothing. Halden describes these compounds as “schizophrenic” in their behavior, which makes it difficult to predict their environmental fate.
“One half of the compound repels water, while the other embraces it; and the high fluorine content renders the compound almost indestructible,” says Halden. “It’s beautiful chemistry, really. But if you don’t use it prudently, you create pollution that’s impossible to clean up.”
Other pollutants that have proved resistant to degradation are antimicrobial compounds. These are designed to kill or stop the growth of bacteria and fungi. Like perfluorinated compounds, polychlorinated antimicrobials do not break down easily and instead simply accumulate in the environment.
By taking sediment cores from the Chesapeake and Jamaica Bays and dating them using radioactive fallout from atmospheric nuclear tests conducted in the ‘50s, Halden and his colleagues were able to find antimicrobials used and disposed of by Americans as far back as the 1960s.
“The stuff is still there, awaiting degradation,” says Halden. “There are organisms living in these aquatic environments now, including many microbes, that have been exposed to antimicrobials throughout their entire lifecycle and over multiple generations. How do they react to that pressure?”
Since these compounds don’t break down, they create an environment that fosters the emergence of drug-resistant bacteria. As they build up in the environment, these antimicrobials cycle back to us, first accumulating in algae and worms and then in fish that people eat.
In a 2007 study published in the journal Food and Chemical Toxicology, the chemical triclosan was found in 60 out of 62 breast milk samples collected from women in California and Texas. Triclosan is an antibacterial and antifungal agent that is widely used in deodorants, soaps, toothpaste and cleaning supplies.
“These polychlorinated antimicrobials are everywhere,” says Halden. “If I swipe up dust on my finger, it can contain up to two parts per million of triclosan.”
Other than successfully combating gingivitis, there is no evidence that triclosan provides any other health benefits, according to a consumer update by the U.S. Food and Drug Administration. The New York Times reported in August 2012 that Johnson & Johnson, a personal care product company, is phasing out the use of triclosan in their products. But many companies resist making changes.
While manmade pollution is an evolving problem, many natural contaminants still get into our water sources, as well. Some of these natural chemicals can cause pretty serious problems, says Paul Westerhoff.
Westerhoff is a professor in the school of Sustainable Engineering and the Built Environment and associate dean of research for the Ira A. Fulton Schools of Engineering. He studies water contamination and its impact downstream.
He notes that a wide range of natural contaminants exist. Arsenic can naturally occur in surface and ground water, and presents a host of health risks. And algae that grow in water can make toxic byproducts. Algae also produce compounds that can make water taste and smell funky.
“The two that we’ve been focused on in the Phoenix metro area for the last 15 years are called Methylisoborneol, or MIB, and Geosmin. These are produced by algae in the reservoirs and the canals and are responsible for making our drinking water have an earthy-musty taste or odor,” says Westerhoff.
Other contaminants actually come from our efforts to purify water. When chlorine is added to the water to kill bacteria and pathogens, it can react with dissolved organic matter to form carcinogens.
“Things like chloroform, bromoform and a large list of other regulated compounds are formed, as well as many that aren’t regulated,” says Westerhoff. “They regulate about nine of these chemicals out of about 900. These all are derived from reactions of disinfectants with natural organic matter.”
While it may seem that our water is chock full of deadly toxins, it’s important to remember that exposure to something does not automatically create a health risk. For example, passing a smoker on the street and inhaling a puff of second-hand smoke is much different from the constant exposure of living with a smoker. We need more information about what effects certain chemicals have on humans and what levels of exposure we can tolerate without risk.
As an engineer, Westerhoff also examines the effectiveness of methods to filter and purify drinking water, such as activated carbon. Activated carbon is processed to be porous and absorb unwanted contaminants, acting as a filter.
“If you have activated carbon under your sink, it removes the flavors of MIB, Geosmin and chlorine, but only a few of the chlorinated organics” says Westerhoff. “If you did that on a municipal treatment scale, say for the city of Phoenix, it’s far more cost-effective. So we’ve been looking at the efficiency of activated carbon to remove a broad range of chemicals beyond those that are currently regulated.”
While some methods are available to clean up our drinking water, perfluorinated and antimicrobial compounds have permeated the environment and present significant hurdles in cleaning them up. Halden believes the best route to dealing with these resilient chemicals is informing the public about what’s in the products they use.
“What’s needed is a combination of more foresight in the way we pick and produce chemicals and then education of the consumers,” says Halden. “Right now, people are completely in the dark – they don’t even know what they’re buying. If you work with pollution control, the best, most effective way to deal with pollution is to not create pollution.”
Rolf Halden is also a senior sustainability scientist in the Global Institute of Sustainability, and a professor in the Ira A. Fulton Schools of Engineering.
Written by Pete Zrioka, Office of Knowledge Enterprise Development. This article first appeared on ASU Research Matters.