A landmark federal commitment to fund the elimination of a toxic national legacy—lead drinking water pipes—promises to improve the public health outlook for millions of people across the U.S. But it also presents communities with a thorny choice between replacement pipes made of well-studied metals such as copper, steel or iron and more affordable but less-studied pipes made of plastic.
Under a $15-billion allocation in last year’s Bipartisan Infrastructure Law, dedicated funding has started flowing to U.S. states to pay for removing and replacing so-called lead service lines—pipes that connect underground water mains with buildings and their plumbing systems. The funds could cover the replacement of about a third of the nation’s estimated six million to 10 million such lines.
In March the anticipated surge of lead-pipe-replacement work prompted a group of 19 health and environmental advocacy organizations headed by the nonprofit Natural Resources Defense Council (NRDC) to publish a set of guiding principles for lead-line replacement. Amid numerous recommendations related to community involvement, safety and economic justice, the document takes a stand against swapping in pipes made of plastic and calls for copper lines instead.
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Although there is a consensus in the health and biomedical community that lead service lines should be replaced, many water quality and health questions about plastic drinking water pipes in the U.S. are unresolved or have yet to be addressed, a number of experts say. Some industry representatives disagree with recent findings that suggest links between plastic drinking water pipes and health issues. The situation could prove frustrating and confusing for utilities and consumers as communities receive federal funds for replacements—and must then consider the many dimensions of choosing the safest and most suitable new pipes for their region.
Service lines are commonly made of copper, iron, steel or one of several types of polyethylene or polyvinyl chloride (PVC), according to various sources. In the next decade up to 35 percent of U.S. utilities’ spending on drinking water distribution will go toward plastic pipes, says Bluefield Research, a firm that provides analyses of global water markets. Plastic materials such as PVC and high-density polyethylene (HDPE) are typically less expensive to purchase up front than more traditional materials such as copper, ductile iron and steel. So when measured in miles of distribution pipe, plastic is forecast to make up nearly 80 percent of the nation’s water pipe inventory by , according to Bluefield.
It is very clear that there is no safe level of lead exposure, according to the U.S. Centers for Disease Control and Prevention and many medical and public health leaders. Taking in even low levels of lead from paint and drinking water causes several types of health issues, including intellectual deficits, particularly in children, as well as neurological and reproductive problems and increased risk of cardiovascular death.
With plastic pipes, the matter of potential drinking water contamination is less clear-cut. In the NRDC-led group’s lead-line-replacement principles, the copper-not-plastic item points to recent research suggesting that plastic pipes can potentially contaminate drinking water in three ways. The first is the release of chemicals into water from the pipe material, a process called leaching, which has been documented in severalstudies. The second route, called permeation, involves pollutants such as gasoline that can seep from groundwater or soils through the walls of plastic pipes, which has been noted in reports by the Environmental Protection Agency and the Water Research Foundation (formerly the Awwa Research Foundation). And finally, plastic pipes exposed to the high heat of wildfires are at risk for melting and other thermal damage. Plastic pipes damaged in wildfires could release toxic chemicals into drinking water, the NRDC document suggests, citing an October EPA fact sheet. The high heat of fires can degrade plastic pipes, valves and meters in drinking water distribution systems, potentially releasing volatile organic compounds (VOCs) into drinking water, the EPA document states. A study arrived at more explicit findings by revealing in lab tests that plastic pipes exposed to wildfire temperatures can release benzene, a carcinogen, and other VOCs into water.
Pipe material-related factors beyond those in the principles document can also contaminate drinking water. A July laboratory study by civil and environmental engineer Marc Edwards of Virginia Tech and his colleagues revealed that the growth of Legionella pneumophila, the water-borne bacterium that causes Legionnaires’ disease, varied with the pH of water, whether that water was in contact with cross-linked polyethylene (PEX) or copper pipes, and the presence of phosphate, which is used to control corrosion.
Some organizations associated with the plastic pipes industry are skeptical or dismissive of findings that link these pipes with potential drinking water quality and health concerns. Bruce Hollands, executive director of the Uni-Bell PVC Pipe Association, points to a environmental product declaration (EPD) that followed an assessment of seven PVC water and sewer pipe products by the International Organization of Standardization (ISO), a voluntary, nongovernmental standards organization. The declaration states, “PVC pipe and fittings are resistant to chemicals generally found in water and sewer systems, preventing any leaching or releases to ground and surface water during the use of the piping system. No known chemicals are released internally into the water system. No known toxicity effects occur in the use of the product.” An update due out in a few months will contain the same statement, Hollands says.
A similar position is held by a nonprofit organization called NSF (originally founded as the National Sanitation Foundation), which is one of several organizations to offer testing that can lead to certification of manufacturers’ drinking water pipes and other system components under a standard called NSF/ANSI/CAN 61 Drinking Water System Components–Health Effects, or Standard 61. “We are not aware of credible evidence that would discourage the use of plastic pipe or other products that are certified to NSF/ANSI/CAN 61 in drinking water systems,” NSF said in a statement to Scientific American.
Standard 61 is determined by a committee of manufacturers, toxicologists, water utilities and federal and state regulatory officials, said NSF (which is unrelated to the U.S. National Science Foundation). The standard is recognized by the nonprofit American National Standards Institute (ANSI) and the Standards Council of Canada (a federal “Crown corporation”). The EPA says it “has supported the development of independent third-party testing standards for plumbing materials” under Standard 61, the agency says. The EPA’s only safety requirement for pipes and other plumbing materials is that they are free of lead. Nearly all U.S. states require utilities to use pipes and other water distribution system products that are certified to Standard 61.
Consumers with questions about the safety of pipes that are in contact with drinking water should focus on individual products that are certified to appropriate standards rather than the materials that pipes are made of, NSF wrote in its statement to Scientific American. Some material-related trends have emerged in examinations of specific contamination routes, however.
Permeation of metal pipes is “extremely rare,” says Edwards, who in pinned down the cause of high lead levels amid Flint, Mich.’s water crisis. In contrast, gasoline and solvents can permeate polyethylene pipes, and pure benzene and other dangerous organic compounds also permeate PVC pipe without rubber gaskets (although gasoline does not), a Water Research Foundation report states. In a document, the Plastics Pipe Institute, a trade organization, called the conclusions of the report “inconclusive and perhaps misleading.”
All pipes can leach their constituent materials to some extent, according to a National Research Council report. Corrosion control can help to manage copper that leaches from pipes made of that metal, Edwards says. Various types of plastic pipes can release compounds that are potentially toxic or carcinogenic, studies have found. Yet the EPA has set no legally enforceable federal standards for many of these contaminants if they turn up in drinking water (under the Safe Drinking Water Act, state standards for contaminants must be at least as stringent as federal ones). The current questions that need to be answered are which pipe-related contaminants get into drinking water, the extent to which they might affect water quality and human health, and whether any industry-independent researchers or government regulators are looking for specific concerning contaminants at all, especially in the case of plastic pipes.
Rather than advocating for one material over another for these service lines, many U.S. environmental engineers say the choice of material for any given underground water pipe should depend on factors such as whether a pipe will be flushed before use; how regularly the pipe will be used; whether the pipe is going in near an underground tank storing gasoline, sewage or other harmful material; and conditions such as the water pH and temperature.
For example, in a study funded by the EPA, environmental engineer Patrick Gurian of Drexel University and his colleagues found statistically significant higher concentrations of total organic carbon (TOC), a nonspecific water quality measure, in some PEX pipes than in copper ones. Organic carbon in a water supply can come from decaying leaves and other natural sources and can leach from synthetic sources such as a plastic pipe.
But the characteristics of the study’s two individual water systems (in Philadelphia and Boulder, Colo.) varied by water source, disinfectant used and average pH, among other factors. Such variations are unavoidable across water systems. “Plastic pipe can leach TOC, but this can be addressed through quality control measures such as proper testing and certification,” Gurian says. “Engineering is about managing risks and making tradeoffs. I am not aware of information that would justify banning all plastics from use as pipe materials.” The Plastic Pipe and Fittings Association, a trade association, wrote in a statement to Scientific American that “plastic pipe has been extensively studied for all sorts of supposed maladies since the early s.”
Some researchers say plastic pipes in the U.S. have not yet undergone the same degree of water quality and health scrutiny as pipes made of copper, iron, steel and cement. With these so-called legacy materials, methods to prevent or remedy leaching, permeation and other issues are well known, says environmental engineer Andrew Whelton of Purdue University. But that is not the case with plastic pipes. Colleges and graduate schools that train civil engineers and public health researchers have historically ignored the chemistry and manufacturing of plastic in their curricula on water quality issues, Whelton says.
Scott Coffin, a research scientist at California’s State Water Resources Control Board, studies the impacts of microplastics in drinking water on human health, as well as the potential health impacts of endocrine-disrupting additives in water distribution systems. He agrees that more research is needed on water quality and plastic drinking water pipes. “Drinking-water-distribution-system contaminants resulting from plastic pipes are not explored very often,” Coffin says. “It’s sort of forgotten about, honestly, in the water industry.”
Whelton and his colleagues have actively pursued questions about potential contaminants in the water carried in plastic and other types of drinking water pipes. In a study, the team identified 11 PEX-related organic compounds, including toluene—one of 90 or so contaminants for which the EPA has set legal limits in drinking water—in the water that was in contact with PEX pipes installed in a six-month-old “net-zero energy” building. The compounds were not found in water entering the building. Two years later the team published a study that compared contaminants released by copper pipes and by 11 brands of a total of four types of plastic pipes. Microbial growth thresholds were exceeded in water in contact for the first three days of exposure with three of the brands of PEX pipe. Then, in a study, Whelton and other colleagues found that heavy metals, including copper, iron, lead and zinc accumulated as sediment and formed scales inside PEX drinking water pipes in a home’s one-year-old plumbing system.
None of these three studies, all funded by the U.S.’s NSF (the National Science Foundation) and performed with pipes marked as certified to Standard 61, was designed to make direct health claims, Whelton says. Instead they were meant to reveal potential contaminants—some of which could hold implications for water quality and health—that could be produced by interactions between drinking water and plastic pipes.
Each of the studies, however, drew the pointed attention of the other NSF (the nonprofit testing and certifying organization), which reported $123 million in revenue in . On a voluntary basis, manufacturers of products ranging from water system components to microwave ovens may pay fees to NSF, or any of several other competitors, to assess whether products meet standards (which are often set in collaboration with NSF) and whether they merit certification. Such certification indicates that “an independent organization has reviewed the manufacturing process of a product and has independently determined that the final product complies with specific standards for safety, quality or performance,” according to NSF’s website.
In NSF released a document addressing Whelton and his colleagues’ , and studies of plastic drinking water pipes, stating that the conclusions and data “have contributed to misinformation and confusion about these products.”
Whelton says there is no misinformation in the studies, each of which was peer-reviewed. NSF “claimed information was not included in the studies when it actually was,” he says, adding that the organization’s document itself “is an example of misinformation and should be ignored.”
When it comes to drinking water safety and plastic, that is largely what the organizations that signed onto the lead-service-line-replacement principles headed by NRDC have done, putting their trust elsewhere than the plastic industry and pipe testing and certification organizations. The NRDC-led group’s document of principles links to studies and reports by the EPA, the Water Research Foundation and academic researchers. And the document states that its call for copper replacement pipes rather than plastic ones draws on recommendations and concerns from the Healthy Building Network, the International Association of Fire Fighters and United Association, a plumbers’ and pipe fitters’ union. As Yvette Jordan of the Newark Education Workers Caucus, an organization that signed the document, puts it, “When you have so many people—so many organizations, especially—when they agree..., shouldn’t you take notice and say, ‘Okay, we should probably reexamine this ... and use copper and not plastic’?”
Plastics Reckoning: PVC Is Ubiquitous, But Maybe Not for Long
By one estimate, lifetime exposures to plastic chemicals cost the U.S. $249 billion in health care in .
PVC was first synthesized in the mid-s and started to become popular in the early s as an alternative for natural rubber. The addition of other chemicals made PVC more flexible (useful for, say, waterproof coatings on clothing), more durable (when exposed to UV rays, for example), and fire resistant. The construction industry’s use of PVC for flooring, siding, pipes, and more doubled between and .
In the s, though, researchers began to document liver cancers in PVC plant workers and traced their exposure to vinyl chloride monomer (the starting ingredient of PVC), now classified as a carcinogen. In the s, people began campaigning against the use of PVC in children’s toys, concerned particularly about exposure to certain PVC additives called phthalates, some of which are known endocrine disruptors, capable of affecting development and reproduction. Calls for bans began to ramp up.
Regulations that limit the use of PVC or some of its additives have mounted, as companies, cities, and nations have enacted dozens of restrictions over the past decades. In , Austria became one of the first countries to ban certain phthalate plasticizers from children’s toys; other nations followed suit, including the United States, in . The U.S. Plastics Pact — a group that works to eliminate single-use and non-recyclable plastics and counts among its members companies that produce 33 percent of U.S. plastic packaging — has identified PVC as one of a handful of problematic and unnecessary materials and has committed to take measures to eliminate it from packaging by .
Last November, a coalition of non-governmental organizations called on the European Commission to phase out PVC by . And in December, the U.S. Environmental Protection Agency kickstarted a chemical safety evaluation process for five toxic chemicals, including vinyl chloride, which could be a first step toward a national ban. “We are working to ban vinyl chloride full stop,” says Enck. “It’s going to take the EPA at least eight years to get through the process. But we’re in it for the long haul.”
The Vinyl Institute, a U.S. industry trade group, says it is providing data to the EPA. “Our members continue to tout the many benefits of PVC and defend the vital material against calls for bans,” the institute said in a statement. “We believe this risk evaluation will further assure that the production and uses of vinyl chloride are safe.”
It can be notoriously difficult to tally up the medical and environmental effects of any given chemical. People are likely exposed to 30,000 chemicals a day, often at low concentrations, so linking cause and effect is difficult, says Bethanie Carney Almroth, an ecotoxicologist at the University of Gothenburg who studies plastic toxicity in the marine environment and is a steering member of the Scientists’ Coalition for an Effective Plastics Treaty, an independent group aiming to advise treaty-makers.
A study of toys made before found some were up to 40 percent phthalates by weight.
“It’s death by a thousand cuts,” she says. The net impact, though, is thought to be huge. A February study by Leonardo Trasande, an environmental health researcher at New York University, found that lifetime exposures to plastic chemicals cost the U.S. $249 billion in health care in , thanks to everything from pre-term births to obesity, heart disease, and cancer.
The European Chemicals Agency (ECHA) published a report last November on PVC, along with 63 key chemicals commonly used to make it heat stable, flexible, and flame retardant. Its conclusions salve some concerns but amplify others. Regarding liver cancer from worker exposure to vinyl chloride — the original and highest-profile concern about PVC — the ECHA report noted that strict exposure limits for workers in Europe have stamped out reports of this kind of cancer.
Of course, says ECHA chemist Jesus Vazquez-Rodriguez, “accidents can happen.” In , a train carrying 115,000 gallons of vinyl chloride in addition to other chemicals derailed and caught fire in Ohio; responders released and burned the remaining vinyl chloride to keep it from exploding. The dramatic incident and its black plume of smoke attracted widespread attention and concern about possible chemical exposures. The non-profit Toxic-Free Future estimated in a report last month that at any given time there are 36 million pounds of vinyl chloride on the move over 2,000 miles of U.S. railways, raising the specter of future disasters.
In terms of PVC additives, the ECHA report highlights phthalates — specifically, short-chain orthophthalates — as a primary concern. While a few specific phthalates have been weeded out in Europe and in the U.S., they are still widely used, ECHA notes, in parts of Asia, the Middle East, Africa, and Latin America.
Even in places where phthalates are regulated, says Carney Almroth, the rules can have holes and limitations. A study in her home country of Sweden, for example, found that certain phthalates and other chemicals that had been banned from children’s toys still showed up in eight out of 10 tested food containers (including cereal boxes and kids’ cups), where they were allowed. Carney Almroth herself looked at children’s toys made before , purchased at second-hand stores, and found some were up to 40 percent phthalates by weight. “They’re endocrine disruptors. And your kids suck on them,” she sighs. These compounds aren’t chemically bound within the plastic, she notes, so they easily leak out.
A second class of concern in ECHA’s PVC report is organotin: carbon- and tin-based compounds widely added to PVC in North America to help prevent it from decomposing, and more narrowly added to products in Europe when, for example, plastic needs to be transparent or stable at high temperatures. Those uses include blister packages for pills. Some organotin substances are neurotoxic, or they can interfere with the reproductive or immune system; they are regulated in European toys and were banned from use as anti-fouling paint on ships because of their impacts on marine life, including causing sex changes in whelks. The ECHA report finds there are risks to recycling facility workers from exposure to organotins.
Some PVC additives have alternatives, but those replacements might turn out to be worse for health.
Scientists continue studying PVC. One recent analysis concluded we should be paying more attention to volatile organic compounds degassing from vinyl home décor, like wallpaper and flooring (such compounds are responsible for “new car smell”). Others are trying to document what might be released from PVC pipes into water, or from PVC medical supplies burned in hospital incinerators.
Recycling is also a challenge. Special systems are needed to recover PVC; if it’s included with other types of plastics, “it ruins the batch,” says Carney Almroth. In Europe, where the rate of PVC recycling is relatively high, just 27 percent is recycled. Even if properly recycled, the mechanical grinding of PVC can release microplastics into the air. The impacts of that are largely unknown, but microplastics (of any polymer) appear to be increasingly problematic for human health and ecosystems. Plastic microbeads have already been banned from products like facial scrubs for these same reasons; the ECHA report notes there’s no reason to think that PVC microplastics generated by recycling would be any less problematic.
Fortunately, there are alternatives for PVC for most uses — including for vinyl records, medical devices, and construction material — though some of them cost more. ECHA estimates that polyethylene pipes, for example, are at least 20 percent more expensive than PVC, and ductile iron pipes 90 percent more expensive. But there are other considerations. “It’s not just the cost of the material itself. There’s the cost to society,” says Vazquez-Rodriguez.
Some of PVC’s more problematic additives also have alternatives. But some of those chemical replacements might turn out to be worse for the environment or health. Of the 16,000 chemicals known to be used in plastics, says Carney Almroth, 4,200 are known to be hazardous and 10,000 have insufficient data. That leaves plenty of scope for unknown harms. And these chemicals are everywhere. One study in the U.S. found “abundant” plasticizers in fast foods like hamburgers, having presumably leached in from packaging or food service gloves. “The human health implications of chronic exposures to replacement plasticizers are poorly understood,” wrote the authors, led by environmental health scientist Ami Zota of the Columbia University Mailman School of Public Health, noting that only a few animal studies have been done on replacement chemicals.
Limitations in both information and policies can make it easy for so-called “regrettable substitutes” to be adopted if they’re cheaper. Back in , lead- and cadmium-based stabilizers in PVC were singled out as problematic and toxic. Those heavy metals have fallen out of use, but some manufacturers outside of Europe switched to organotin, says Vazquez-Rodriguez.
The upcoming plastic treaty should help to sort out some of these issues, with an appendix listing problematic chemicals. Which ones will be singled out is very much under discussion, but PVC, says Carney Almroth, is “an easy one,” along with polystyrene, which has also been banned in some countries from some uses, including single-use disposable food containers.
Some worry the plastics treaty will focus on waste management rather than on stemming production.
The treaty’s rough draft contains different options for how this list might be structured and used. At the most stringent end of the spectrum would be an international commitment to ban certain chemicals and polymers by a specific date. At the more lenient end, it might simply lay out guidance for how to consider chemicals, and leave it up to nations to decide what actions to take.
“The chemical industry and the fossil fuel industry are playing a dominant role at the negotiations,” says Enck, who worries the treaty won’t be hard-hitting enough, and will focus too much on waste management rather than on stemming production and eliminating harmful products. The Vinyl Institute is among the industry groups that have been attending treaty negotiations.
Carney Almroth would like to see more radical ideas considered. One would be to create a list of allowable chemicals, rather than expanding a list of banned ones. “Right now, we’re in a situation where we have 350,000 synthetic chemicals, and we theoretically invent 70 chemicals an hour,” she says. “If we look at this complexity, and then try to imagine some way to regulate this, it becomes an impossible task.”
But imagine limiting the plastics market to a set number of polymers and additives with known and acceptable risks, she says. “That’s the dream scenario.”
