Southwest Environment

Stories written by University of Arizona students

Department of Soil, Water and Environmental Science
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What’s wrong with Tucson tap water?

By Nathan Blevens

Glass of waterPhoto by Joost Nelissen [ ]
Filling up a glass with tap water is not something every Tucson resident feels comfortable doing

By all accounts, Tucson Water has met the U.S. Environmental Protection Agency’s standards for clean drinking water.  Yet residents of Tucson spend millions of dollars every year on bottled water, water filters, and water services such as Sparkletts.  So, why do many Tucson residents refuse to drink water directly from the tap?

For one thing, many people in Tucson and throughout the country are becoming increasingly concerned with what is not being tested on a regular basis.  Impurities such as pharmaceuticals, personal care products, and cleaning products are categorized as “emerging contaminants” and are not currently regulated by the EPA.

“It is not feasible for a utility  to go out and monitor for every single emerging contaminant that people might be concerned with,” said Channah Rock, water quality specialist and assistant professor of the Soil, Water, and Environmental Science Department at the University of Arizona, who points out the amounts are generally negligible. “It’s extremely expensive, requires high tech equipment, highly trained personnel and is also time consuming" she added. “It is not realistic that every utility have a lab on-site that could test for all of them.”

By using chlorine as a disinfectant, Tucson Water has essentially rid the drinking water of harmful bacteria delivered to the nearly 740,000 people it serves.  However, issues with the by-products of chlorine and the thousands of miles of piping distributing the water raise concern even among the scientific community.

Long-term Tucson residents might distrust tap water for another reason: TCE, short for trichloroethylene. TCE became a well-known chemical throughout Tucson in the 1980s when people in South Tucson became ill or even died from years of drinking from contaminated wells.

Tucson residents have also been hesitant to use water from the Colorado River via the Central Arizona Project, commonly known as the CAP.

Regulating chemicals

Tucson Water officials are required by the EPA to test for 90 regulated contaminants, including known carcinogens such as TCE.  They are also required to test for unregulated contaminants, which, according to Tucson Water’s website, rarely cause health effects but pertain to properties like taste and color.  Out of the 115 contaminants tested, only 22 were detected in 2009, according to Tucson Water’s most recent Annual Water Quality Report.  None of these were above the levels permitted by the EPA. (See related table.)

“We collect samples monthly from all these areas,” explained John Kmiec, referring to the 267 total Tucson Water distribution sampling points. Kmiec is the environmental and regulatory compliance supervisor for Tucson Water.

Yet these 115 contaminants are only a drop in the bucket compared to the hundreds of thousands of other chemicals, organics, microbes and derivatives that make their way into our water supplies, Rock indicated.

Tucson Water doesn’t test for pharmaceuticals as part of their regulatory program. However, the utility has tested for pharmaceuticals in a select number of locations for research purposes, Kmiec said, and plans to work with the UA Arizona Laboratory for Emerging Contaminants program in future studies.

A 2008 investigation by the Associated Press found three pharmaceuticals present in trace amounts in some Tucson water.  The news agency found carbamazepine, a seizure medication; dehydronifedipine, a heart medication; and sulfamethoxazole, an antibiotic. 

Kmiec noted that these compounds are persistent in the environment – that is, they do not break down easily. But when found in the environment, the levels are generally minute.

“When we talk about pharmaceuticals in the environment,” said Kmiec, “were talking about things measured in the part per trillion.” 

Although in high doses these contaminants may be harmful, the concentrations within the water pose little risk to human health. One part per trillion amounts to about a drop of ink in 26 Olympic-size swimming pools.

Most emerging contaminants are seen as an acceptable risk by scientists, but not necessarily by members of the public.   

“People are a lot less accepting of even a very, very small risk when they’re not in control of the risk,” she said. For example, she noted that smoking has been shown to pose serious health risks, but people do it anyway because they are in control of that risk.

Most scientists concerned about pharmaceuticals have focused more on ecological changes rather than human health issues, Kmiec said.  Pharmaceuticals and endocrine disruptors like estrogen, that may affect animals are typically a concern in fish or amphibians. 

“They’re in it 24/7, 365,” said Kmiec. “With those types of exposures for those types of creatures, it’s a heck of a lot different than human exposure.”


Though the testing of water is thorough, there have been health incidents in Tucson’s past involving the public drinking water. Tucson Water now tests for TCE specifically because of a past incident.

In 1981, the cancer-causing agent trichloroethylene trickled into the drinking water supply around Tucson International Airport.  The problem was discovered and the water is being treated to remove the TCE.  Although this water is treated and tested more than any water in the Tucson area, some residents are still concerned that Tucson Water adds some of it back to the drinking water after treatment, Kmiec said.

CAP water

Ongoing concerns about another water source, Colorado River water, has led Tucson Water to use other options – namely, recharging into groundwater supplies – rather than distribute it directly in tap water, Kmiec noted.

In 1992, the Central Arizona Project canal extended its reach to Tucson and the city began treating the Colorado River water for drinking.  Although this newfound allotment of water was welcomed without much hesitation to this dry desert community, opinion quickly shifted once some residents started receiving the surface water. 

“We received a lot of complaints of red water and dirty water,” Kmiec said. “This was deemed to be because of the CAP water.”

By 1994, just two years after the CAP water was introduced, the “uproar” of residents led the city to order Tucson Water to stop piping in CAP water, he said. Now, he added, the city uses the surface water only for aquifer recharge and recovers the water with a mix of native groundwater.  Faucets at treatment centerPhoto by Nathan Blevens
A line of faucets at Tucson Water’s Hayden-Udall treatment center once provided operators with quality control for CAP water. Now that the city no longer distributes CAP water, only the faucet from the groundwater source runs constantly.

Chorine: Good and bad

A long-term concern among all water utilities is the amount of potentially dangerous bacteria and other microbes growing in their water distribution systems.

Harmful bacteria such as E. Coli are of high importance when purifying city water.  For its water treatment, Tucson Water uses chlorine, one of the most successful methods in killing waterborne bacteria. 

Scientists are generally confident in most water utilities’ ability to produce clean water. 

“The reason I’m so confident is because they’re highly regulated in most states,” Rock said.  “They’re required to treat and produce water to a very high standard and if it’s not, then they’re not allowed to discharge that water to the environment or for other specific uses in the community where it may pose a health threat.”

Rock’s biggest worry about any city water supply is what happens once the treated water enters the distribution system.  Officials indicated that Tucson’s network consists of nearly 4,500 miles of piping.

“Although you chlorinate at the treatment plant to disinfect bacteria” and other microorganisms, said Rock, “over time that chlorine or other disinfectant will start to dissipate and the concentrations will start to drop.”

Once the chlorine concentrations go down, it leaves room for harmful bacteria to grow. Tucson Water has recognized this as a potential problem and has taken measures to prevent it. 

“They’ve been proactive about it,” said Rock. “They’ve introduced chlorine boosters that will shoot up the concentration of chlorine to a regulated standard so that you can prevent potential regrowth opportunities.” 

Tucson Water also does monitoring throughout its expansive distribution system, something she said is unique for a utility.

“The invention of chlorine as a water disinfectant to civilization itself is one of man’s greatest achievements,” said Kmiec.  However, it is not without its downsides. 

Although the chlorine levels used by water utilities are safe, Kmiec said, chlorine can form disinfection byproducts such as trihalomethanes, or THMs. These chemicals can cause cancer. However, they are regulated by the EPA and shown in the most recent Tucson Water Annual Water Quality Report to be under the permitted limits.

Water-borne diseases such as typhoid fever and cholera were prevalent in populations throughout the world for centuries, as Ruth Stringer notes in her book Chlorine and the Environment.

About 20 years after chlorine was first introduced into city drinking water in 1908, Jersey City saw typhoid fever death rates fall by more than 92 percent.

“The benefits of chlorine as a water disinfectant in the past hundred years,” Kmiec said, “have probably saved hundreds of millions of people’s lives around the world.”

The World Health Organization estimates that water-borne disease accounts for 1.8 million deaths each year.  Dying from diseases like typhoid fever or cholera after taking a casual sip from the home faucet is an issue Tucson residents will never have to worry about.

Nathan Blevens is an environmental science major at the University of Arizona. As a Midwesterner used to drinking water from the faucet, he has been puzzled about why so many local Tucsonans don’t drink the tap water.


City of Tucson on water quality

World Health Organization on water-borne diseases

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