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There are concerning carcinogens in Western Pennsylvania water

A national report finds cancer-causing chemicals in Pittsburgh's drinking water, including a disinfection byproduct at levels 3 times the national average

Some contaminants in Pittsburgh's drinking water—including disinfectant byproducts and industrial chemicals—are at unsafe levels and could contribute to the region's higher than average cancer rates, according to a new report.


A just-updated national tap water database tracks contaminants detected in drinking water throughout the country, and compares their levels against legal limits, safe limits, and state and national averages.

The database, published by the Environmental Working Group (EWG), a public health advocacy nonprofit, compiles all contaminant testing data conducted by nearly every water utility in the country through 2017, and provides details about the levels of pollutants detected and what health risks are associated with them.

The information provided in the database goes beyond what customers get in their annual reports from their water utilities, and reveals that a number of cancer-causing contaminants are being detected in drinking water throughout the U.S. EWG experts warn contaminated drinking water—most of which currently meets legal quality standards—could cause an estimated 100,000 cancer cases in the U.S.

The new database also reveals that several cancer-causing contaminants are found at levels significantly higher than national and state averages in Pittsburgh's drinking water.

For example, Bromodichloromethane is one of several trihalomethanes that can form when chlorine is added to water as a disinfectant and it combines with organic compounds. The chemical, which is categorized as a "probable human carcinogen" by the Environmental Protection Agency, was detected in water from the Pittsburgh Water and Sewer Authority (PWSA) at 16.8 ppb (parts per billion). That's nearly three times higher than the national average of 5.7 ppb, and double the state average of 8.34 ppb.

This level is also 280 times above EWG's Health Guideline of 0.06 ppb, which was derived from the California Office of Environmental Health Hazard Assessment in 2018. The number represents the level at which one in a million people exposed to that level over their lifetime will get cancer as a result. One in a million is generally considered an "acceptable" level of risk by the EPA when it comes to environmental exposures. Any level higher than that would lead to a greater number of people than one in a million getting cancer as a result of exposure to the chemical.

There is no legal limit for Bromodichloromethane in drinking water.

PWSA told EHN that the level of Bromodichloromethane cited in the EWG database was reported in 2016, and that more recent testing has shown reduced levels of the chemical. In 2018, the most recent full year available, they reported 14.3 ppb of Bromodichloromethane, and their year-to-date level for the first three quarters of 2019 is 13.9 ppb.

"While the levels of disinfection byproducts, including bromodichloromethane and other trihalomethanes in PWSA's drinking water are fully compliant with all applicable federal and state standards, we are aware of the concerns about these compounds raised in the EWG analysis, and are proactively taking steps to further reduce these levels," Robert A. Weimar, Executive Director of PWSA, told EHN.

Weimar added that upgrades currently underway planned in consultation with the Pennsylvania Department of Environmental Protection will allow PWSA to use activated carbon filtration, which will improve its ability to lower levels of disinfection byproducts, and that they're working with the American Water Works Association's Partnership for Safe Water to explore additional strategies to improve Pittsburgh's water quality.

Hexavalent chromium, which is commonly found in dye, paint, wood preservatives, and chrome plating waste, was also detected in PWSA's water. At 0.535 ppb, the contaminant is consumed by Pittsburghers at a rate 27 times higher than EWG's Health Guideline of 0.02 ppb. That level slightly exceeds the national average of 0.492 ppb, and is more than double the state average of 0.227 ppb. For the broader U.S., most of the cancer risk from water contaminants is due to arsenic and disinfection byproducts. Other major contaminants included radioactive elements such as uranium and radium.

"It's important for people to realize that legal doesn't necessarily mean safe," Sydney Evans, a Science Analyst at EWG, told EHN. "People tend to take the safety of their tap water for granted because it's being monitored, tested, and treated. But there's a big discrepancy between what's legal and what science says is safe."

Many drinking water limits for harmful contaminants haven't been updated in 20 to 40 years, Evans explained, and when those limits were set, regulators took into account not only the health effects of contaminants, but also the cost of removing them from drinking water and limitations of available technology, most of which has changed dramatically in recent decades.

"And beyond that," Evans added, "a lot of them don't even have legal limits yet. For example, hexavalent chromium, which is a potent carcinogen, has no federal legal limit in drinking water."

Regional problem

PWSA isn't the only water authority in the region with problems.

The following chemicals—all known, probable or possible carcinogens—were found in at least one of the 10 largest municipal drinking water systems in Allegheny County (which encompasses Pittsburgh):

  • Bromodichloromethane
  • Bromoform
  • Chloroform
  • Hexavalent chromium
  • Dibromochloromethane
  • Nitrate
  • Dichloroacetic acid
  • Trichloroacetic acid
  • Total trihalomethanes

These types of contaminants can get into drinking water in a number of ways. Some are the result of pollution from industries or municipal waste, but most occur when chemicals used to disinfect drinking water combine with organic compounds like those found in algae, agricultural runoff, or wastewater from the oil and gas industry.

Many carcinogenic contaminants were detected at levels significantly above national or state averages in the Pittsburgh region. A few examples:

  • Dibromochloromethane, another byproduct of chlorine disinfection, was detected at levels nearly four times the national and state averages at Moon Township Municipal Authority

Fossil fuel connection

A spokesperson for Pennsylvania American Water stated, "We take water quality and safety very seriously. The Environmental Protection Agency (EPA) sets water quality standards intended to protect public health and Pennsylvania American Water treats and delivers water that meets or surpasses all EPA and Pennsylvania drinking water standards."

Myron Arnowitt, Pennsylvania state director for the national environmental advocacy group Clean Water Action, said many of the carcinogens in Pittsburgh's drinking water come are the result of all the fossil fuel extraction in the region.

"Much of the research on this has found that brominated disinfection byproducts are the most dangerous of this group of carcinogens, and those are a number of the ones we have considerably higher levels of here than in other places," he told EHN.

"We don't add bromide," Arnowitt explained, "so the bromide is coming from the source water. There are several different sources, but certainly oil and gas wastewater has been a prominent one in Southwestern Pennsylvania. It's incredibly salty. Most of it is chloride, but a portion is bromide, and that portion is leading to higher levels of brominated disinfection byproducts for all the water systems in our region."

Arnowitt added that research suggests suggests coal plants may also be adding brominated materials to source water, and that as a region, we're taking on additional cancer risk as a result of being home to these fossil fuel industries. He also noted that these particular compounds are a difficult problem to treat at home.

"These contaminants are not something you can solve with a pitcher filter," he said. "These compounds are volatile, so the primary exposure around your house actually comes from breathing in steam from your shower."

Both Arnowitt and Evans at EWG emphasized the importance of protecting source water from these types of contaminants.

"The burden falls on treatment plants to get these contaminants out of the water, but they're not the ones putting them there in the first place," Evans said. "This is why regulations are so important—it costs a lot less to prevent the pollution in the first place than it does to try and clean it up down the line."

Cumulative exposures

Allegheny County is also in the top 2 percent of all U.S. counties for cancer risk from air pollution. All these exposures add up.

"When legal limits were being set for most of these contaminants in drinking water 20 or 40 years ago, they were looked at in isolation instead of in the mixtures we're all exposed to," Evans explained. "But that was just for those 22 contaminants, and just for drinking water," she added.

"When you start looking at all the different ways we're exposed, they're all going to make a difference." She also noted that some studies suggest exposure to a variety of carcinogens not only adds up, but the contaminants can also combine to become even more potent than they are in isolation.

A chart detailing which types of filters can remove each of the contaminants from drinking water is included in the page for each utility. The database also includes information on how residents can talk to their elected officials about the safety of their water.

"Ultimately, we want to see the process of reviewing these regulations streamlined, since it's currently inefficient, slow, and not health protective," Evans said. "To get there, we need to get people engaged on this issue in their communities."

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