Complaints about the use of chloramines in the city's water supply have already come trickling in, according to Bob Bledsoe, a Tulsa city spokesman.

"We've had several calls. We've got people saying, 'I've got this ailment, [or] the glasses are spotting in the dishwasher,'" Bledsoe said.

But as far as the introduction of new chemicals to the city's water supply, "Well, we haven't put them in yet," Bledsoe said.

July is when the city plans to introduce ammonia as a secondary disinfectant for tap water, resulting in chloramine-treated water. Postcard mailings will be sent this month to notify customers of a change first announced in 2010.

The change results from a federally-mandated effort to better regulate a certain class of harmful chemicals formed as byproducts of the disinfectant process.

Some of these chemicals, known as trihalomethanes, or THMs, have been linked to an increased risk for cancer.

"Bladder cancer risk was associated with long-term exposure to THMs in chlorinated water at levels regularly occurring in industrialized countries," concluded researchers in a 2007 article published in the American Journal of Epidemiology.

How big is the risk? Scientists continue to study the link. The Environmental Protection Agency, however, estimates that their new national monitoring mandate will prevent 280 cases of bladder cancer yearly.

Chlorine -- the city's primary disinfectant for drinking water, as it is in the majority of U.S. cities, according to a 2007 survey -- helps prevent the spread of diseases like cholera and typhoid fever when used to disinfect a water supply. It also, however, reacts with naturally-occurring materials in the water, leading to the formation of byproducts.

Trihalomethanes can be reduced by adding ammonia to chlorine, which the city says it will do in trace amounts. Previously, EPA limits were based on the averaging of samples taken from different spots in a water system. This allowed for some spots to have levels of byproducts above EPA limits, so long as other spots had low enough levels for the average to be under EPA limits. Under this testing system, Tulsa water had levels of trihalomethanes within EPA limits.

But under new EPA regulations, water authorities had to identify sites with high levels of trihalomethanes.

For customers farthest away from treatment plants, "it takes two to four days for water to get there," noted Joan Arthur, senior special projects engineer with the city. The longer water sits in the approximately 2,200-mile-long water system, the higher the levels of disinfectant byproducts, she said. Areas with higher levels have generally been in the southern and western fringes of Tulsa, Arthur said. Now, all monitoring locations must have trihalomethanes below specified levels.

About one-third of utilities use chloramines. However, some Tulsa citizens protested the change. A high-profile water expert, Bob Bowcock, who has worked with community activist Erin Brockovich, expressed concerns at an October meeting of the Tulsa City Council.

"You have one of the best water qualities I've seen in the United States," Bowcock told the council, arguing that the city should not make changes to blindly follow federal regulations because "the EPA is really behind on the curve on this one."

Bowcock can be counted among skeptics who question chloramines and say they can be harmful to people's health. City staffers prepared a document rebutting Bowcock's claims, and the Tulsa Metropolitan Utility Authority approved the change in December.

It's a pattern that occurs not just in Tulsa. One study about chloramines and lead exposure in the academic journal Environmental Health Perspectives described research in Wayne County, North Carolina, where one water system used chlorine and another recently changed to chloramines.

The "change to chloramines was associated with an increase in children's blood lead levels," researchers concluded, though they noted that the effect was hardly noticeable in children living in homes built after 1950. Only children living in older homes had blood lead level averages above the 2012 established safety threshold.

But was lead really tied to chloramines, or even drinking water? The area's utility director told the Raleigh News and Observer after the research became public in 2006 that the utility had always been in compliance with lead testing regulations for drinking water; the area continues to use chloramines, according to a website for the local utility district.

Arthur said pilot tests done with chloramines showed no problems with corrosion. With the change to chloramines, the city will increase lead testing.

One of Bowcock's claims was that other harmful byproducts besides those regulated by the EPA are associated with chloramines. City officials have said they plan to test for one such byproduct, N-nitrosodimethylamine, or NDMA, after implementing the change to chloramines (city tests in 2008 and 2009 did not detect the chemical).

"EPA has indicated NDMA is an emerging disinfection byproduct and that they may develop a standard for it in the future," Arthur wrote in an email.

It's part of a larger question about water regulation, with only some chemicals currently regulated. A 2010 editorial in Environmental Health Perspectives noted that "increased emphasis on DBPs, or any class of contaminants, will be balanced against the need for research and risk assessment for chemicals not currently addressed by regulations."

Bowcock advised the city to consider alternatives to chloramines, but acknowledged they could be costlier.

City estimates put the cheapest alternative at nearly 40 times the cost of the chloramines project, which will cost about $1 million, said Arthur.

While water rates are increasing by 7 percent for consumers, Arthur said the rate hikes have little to do with the chloramines project. The city's annual budget for water supply, treatment and distribution is about $107 million.

"Generally, the rate increases have more to do with capital needs and rising fuel costs," Arthur said.

Arthur said the most frequent complaint about Tulsa's water has been a chlorine taste, which should decrease.

In most communities that have made the change, "their customers actually think that the water tastes better," Arthur said.

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