With a single fiery Facebook post, environmental activist Erin Brockovich sparked a local movement of people now fearful of the chemicals used to treat their tap water.

The North Texas Municipal Water District has assured its nearly 1.7 million customers that their water meets federal standards and is safe. Those assurances, however, haven’t convinced many in the Safer Water, North Texas Facebook group, which formed three weeks ago and now has more than 12,500 members.

The initial Facebook post targeted Plano water, although accusations were broadly against the larger water district. Now the claims and questions are a swirl of different issues, mostly about how the district is disinfecting the water and what chemicals are left when that water reaches residents' taps.

The water for much of Collin County and parts of Dallas, Denton and other counties has been blamed for rashes, skin irritation, nose bleeds, coughs and other health problems. Brockovich, claims the local utility has "FAILED" and is raising questions about dangerous chemicals that could be lurking.

That debate is expected to escalate this week as Brockovich, famous for exposing water contamination in California and the movie she inspired, attends a rally Thursday with concerned residents at Frisco Celebration Hall. Tickets cost $20 and are available in limited numbers for the 6 p.m. event.

Chlorine vs. Chloramine

Outside scientists familiar with current research aren’t likely to clear up these murky waters completely. They say that, by and large, the water from major utilities are safe. But new research shows there may be reason to worry about chemicals used to disinfect drinking water and the byproducts the use of those chemicals may create.

"It’s never so clear cut," said Marc Edwards, the Virginia Tech professor who helped expose the Flint, Mich., lead water crisis. "It comes down to picking, I guess, your poison in this case. The reality is that use of those disinfectants is so important to public health that we live with the drawbacks."

McKinney resident Kelly Broussard poses for a portrait with tap water at her home, Tuesday, April 3, 2018. She and her daughters have experienced itchy, aggravated skin that they fear could be a result of high chlorine levels in their water. She's part of a group on Facebook that organized after environmental activist Erin Brockovich's criticized Plano's water on Facebook. Brockovich is in town Thursday to talk to local residents and also meet with the North Texas Municipal Water District, which supplies water to Plano and dozens of other cities. (David Woo / Staff Photographer)

The outcry started a few weeks ago when the utility began its annual 28-day chlorine “maintenance,” also known as a chlorine burn. For the month, they use chlorine rather than their typical combination of chlorine and ammonia, known as chloramine.

The district has done this each year, just before spring, for the last decade. But this common treatment hadn’t generated widespread public opposition previously.

“Something this year feels different,” said Jamie Stephens, co-founder of the Safer Water Facebook group. “My entire living room, it smells like an indoor swimming pool.”

North Texas Municipal Water District officials said chlorine levels during this maintenance period, which ended March 26, were consistent with the levels in earlier months and also with the maintenance period a year ago.

Elizabeth Turner, a special-projects manager for the district, said there were a couple of possibilities. The heavy rainfall could have changed the composition of the lake water and caused the chlorine to dissipate more slowly. Also, lower water consumption during that period could have had an effect.

The North Texas Municipal Water District has used chloramine since the utility started in 1956. About 45 percent of the U.S. — including the city of Dallas — gets water from utilities that use the mixture to disinfect their water.

In her Facebook post, Brockovich described the use of chloramine as a “cheap dirty trick and a really bad idea.”

For many, the switch was defensible. As a disinfectant, chloramine is longer lasting, which is helpful in a large, complex system such as the one served by the North Texas Municipal Water District. It now provides water to about 80 cities and communities in 10 counties.

But Environmental Protection Agency rules also played a role nationally in water districts’ decision to switch to chloramine. In the 1970s, scientists discovered that chlorine created byproducts — such as trihalomethanes — that are considered probable carcinogens. The EPA set water exposure levels for those byproducts in 1979 and has since updated the standard.

Michael Plewa, education director of the Safe Global Water Institute at the University of Illinois at Urbana-Champaign, said not enough is known even about the regulated byproducts.

"You want to have high-quality water,” he said. “The EPA has a protocol to ensure that utilities, by following certain guidelines, are producing uniform, high-quality drinking water. The job of scientists like myself and other colleagues is to try to make good water better."

Many water utilities decided that chloramine would help reduce levels of byproducts regulated by EPA and meet the federal agency's clean water standards.

The city of Plano hired an independent lab to conduct tests and found levels of disinfection byproducts slightly higher than the EPA’s maximum level. However, the maximum level is set for an average rather than a single reading, and those sites had much lower levels during previous tests.

Chloramine: The 'cheapest approach'

"Chloramines is the cheapest approach to meeting the disinfection byproduct regulations," Edwards said. "It has proven to be effective over the decades of use. But it does have some drawbacks sometimes that we're learning more about. Everything you do has drawbacks."

Chloramine isn’t as potent as chlorine and sometimes more biofilm harboring dangerous bacteria could build up inside the pipes. Particularly in warm weather areas, a “chlorine burn” is used to chemically flush the system before summer.

Also, the burn helps reduce the potential for a bacterial process called nitrification, which increases the amount of nitrogen in the water.

But recent studies have found that chloramine has its own set of disinfection byproducts, and they are generally more toxic than trihalomethanes, said Susan Richardson, a chemistry professor at the University of South Carolina and former EPA scientist. However, none of those chloramine byproducts are regulated by the EPA.

It’s these types of byproducts that Brockovich alluded to in her Facebook post. She also rallied opposition to the use of chloramine in Tyler, Stockton, Calif. and other cities.

Not all water is as susceptible to the creation of these disinfection byproducts, though.

"There's this trade off," said Richardson. "It all depends on what you have in your source water. You can't have a recommendation that's one size fits all."

She said that water high in iodide can generate more toxic disinfection byproducts when chloramine is used. That can be a problem in coastal areas where there is salt water intrusion or inland where salt from underground formations can seep into water supplies.

Chloramine has also been a problem for older systems — unlike those in North Texas — that still have a large amount of lead. Edwards found that the switch to chloramine was responsible for lead levels spiking in Washington, D.C., water in the early 2000s.

'Reduce organic matter in water'

Scientists say an important way to reduce the disinfection byproducts is to cut down the amount of plant matter and other organic material that leaches into the water. One option is to use granular activated carbon filters, which is more expensive but still feasible. Cincinnati uses that technology for its drinking water and says it needs two-thirds less chlorine now.

Officials with the North Texas Municipal Water District considered granular activated carbon. Instead, they decided to adopt what would be a more expensive approach that they said would reduce byproducts and also kill some smell and taste problems when there are summer algae blooms in the lakes.

"We went with ozone simply because we got more benefits," said Mike Rickman, the district’s deputy director of operations and maintenance.

He said that $130 million project, installed in 2014, was the first step. The district is also transitioning to biologically active filtration by 2020, which officials expect will make the system even more efficient.

"You do have to look at your raw water sources to see what is going to be the best treatment options available," Turner said. "All those are unique as a fingerprint."

Even as scientists continue to look more closely at how tap water is disinfected, they remind the public of how far water supplies have come. Since Jersey City, N.J., started chlorinating its tap water 110 years ago, countless deaths have been prevented.

“The greatest public health achievement of the 20th century was the disinfection of water,” Plewa said.