Research by Purdue University has found that some types of plastic pipes leach chemicals into drinking water that can cause odours and sometimes exist at levels that may exceed health standards, once again raising the issue of transparency when it comes to green building materials.
Plastic pipes are generally less expensive, lighter and easier to install than metal pipes. They also require less energy to manufacture – generating less carbon dioxide compared to metal pipes – and have a longer life cycle, making them ideal for green buildings.
“The green building industry has been fighting a lonely fight to encourage transparency in building materials and disclosure of chemicals of concern to consumers,” said Rebecca Dunn Bryant, Passive House consultant and managing principal of Watershed LLC. “The American Chemistry Council and many other industry groups have strongly resisted disclosing building material ingredients. The US Green Building Council (USGBC) in particular has been quite embattled as they try to promote consumers' right to know more about the materials in their buildings.”
The discussion, Bryant said, has been likened to the first debates around nutritional labeling for food products. In those debates, manufacturers argued that disclosure would ruin their businesses and that competitors would steal their "secret recipes.” The same argument stands today with building materials.
“Crosslinked polyethylene (PEX) piping has been differentiated as a greener alternative to other piping materials on a life cycle basis,” Bryant said. “However, there has been very little to no publicly available information on chemical leaching from PEX. The Purdue University research is extremely pertinent to green building professionals, and all building professionals, for that reason.”
Andrew Whelton, an assistant professor of civil engineering in Purdue University's Lyles School of Civil Engineering and Division of Environmental and Ecological Engineering, and his team have looked at a number of plastic pipe varieties including PEX, high-density polyethylene (HDPE), polyvinylchloride (PVC), chlorinated PVC (cPVC) and polypropylene (PP) pipes.
In a study for the journal Water Research, published in September, drinking water was tested from a PEX plumbing system in a “net-zero energy” building in Maryland six months after the system had been installed. The testing revealed the presence of 11 chemicals that were PEX pipe ingredients and ingredient degradation products.
Research with PEX pipes in the laboratory also showed that six brands caused drinking water to exceed the US Environmental Protection Agency's maximum recommended drinking water odour limit, Whelton said. The US EPA's maximum drinking water odour limit is a "threshold odor number" of three, or 3 TON. Compliance is voluntary because the standard is based on aesthetic - not health - considerations.
Odour and chemical levels were monitored with and without chlorine treatment over a 30-day period for the six pipe brands. Chlorine, the most popular disinfectant chemical used in the United States, protects drinking water from disease-causing organisms as it travels to the tap. When chlorine reacted with chemicals leached by the plastic pipes, odour levels for one brand of PEX pipe tripled.
“While the total mass of chemicals leached by PEX pipes was found to decline after 30 days of testing, odours generally continued as the pipes aged” said Whelton.
One PEX pipe brand also caused drinking water to exceed the ethyl-tert-butyl ether (ETBE) drinking water health standard.
Findings also showed some chemicals released by plumbing pipes can be transformed into carcinogenic chemicals regulated by the EPA; chemicals leached by certain plastics are conducive to bacterial growth; and plumbing system cleaning practices described in some, but not all, plumbing codes can cause PEX pipe chemical leaching to worsen.
“The issue is that our building codes and testing protocols are not sufficient to address the complex interactions between plastic pipes, water, and disinfectants,” said Bryant. “We want to encourage the green building community to lead the charge on this issue, since there is a lot of energy focused on removing toxics from our built environment right now.”
“Additionally, if we are trying to create net zero water buildings, it is even more important that we maintain a strong focus on water quality, and fully understand how the material choices, design, and operations of our potable water delivery systems within our buildings affect water quality at the tap.”
In the Materials and Resource credit category of LEED v4, the goal of the USGBC is to change the paradigm for how decisions are made in building design and make new information available to decision makers.
“Instead of stating there are good materials and bad materials, we have incentivised information to help designers make good decisions for their specific situation and perform intentional trade-off analyses,” said Sara Cederberg, technical director at the USGBC
The LEED v4 credits are built on a life cycle approach (LCA). There is a credit that addresses environmental impacts of how a product is made through EPDs, and then, since LCA cannot yet fully address health, social issues and ecosystem disruption, there is a credit related to what is inside the product and chain of custody for origin.
The Material Ingredients credit rewards manufacturers who have disclosed the contents of their product and have performed a hazard screen in the first option of the credit. The second half of the credit is intended to reward products whose hazards have been fully characterized and phased out priority chemicals or found alternatives.
“We have found red list approaches problematic and instead intend to drive alternatives assessments, innovation and promote green chemistry along the supply chain. The credit does not ban the use of any specific material,” said Cederberg.
“Fostering a better understanding of the impact of buildings on health is a huge priority for our designers, developers and property managers. This year at Greenbuild, there was an entire education track devoted to the topic. The advent of the WELL building standard and the AIA ‘Materials Matter’ work are further evidence of this development.”
Cederberg said the USGBC has also seen most of the large architecture firms in the US begin to demand transparency from building product suppliers. In that context, LEED v4 has taken huge steps to advance the understanding of the health impact of buildings and the materials that go into buildings.
“Transparency alone does not equate performance, but we see it as a first step. We hear from some parts of the building industry that disclosing confidential business information will hurt business. This is an ongoing conversation -- negotiating the market demand for information and the real need to protect intellectual property, when it is truly a trade secret,” Cederberg said. “I can't speak specifically to the health impacts of PEX, but this is a great example of the types of trade-offs our designers are wrestling with and the more accurate information at their disposal the better.”
In Australia, too, there are Green Star credits that encourage better behaviours in the area of materials in relation to Life Cycle Impacts, Sustainable Products, Construction and Demolition Waste and Responsible Building Materials.
In fact, it is making the point with respect to transparency when it comes to Sustainable Products, stating that up to three points can be achieved in recognition of “the specification of transparent, sustainable products. This includes re-used and recycled products, products with an environmental product declaration, or products with a recognised eco-label.”
In terms of PEX, plumbing and piping materials are subject to standards published by Standards Australia and Standards New Zealand.
“The National Health and Medical Research Council (NHMRC) Australian Drinking Water Guidelines 2011 state that materials, such as pipes and fittings, should comply with Australian Standard which is AS/NZS 4020:2005 – ‘Testing of products for use in contact with drinking water’,” a spokesperson for the NHMRC stated.
The Purdue University work is funded by a National Science Foundation grant entitled Towards a Safer and Greener Indoor Environment: Chemical Liberation from Polyethylene Plumbing Pipe.