Drinking Water from Plastic Pipes May Not Be Safe, Chemical Additives Found

2011-11-09 12:19
Drinking water from plastic bottle

Drinking water from plastic pipes is used more often in construction than traditional copper piping for delivering water to homes and within homes to the faucet. Previous studies on plastic pipe safety for drinking water were limited to issues regarding taste and odor. Today, however, a recent study reveals its findings on not only the taste and odor of drinking water from plastic pipes, but also on leakage products consisting of residues from chemical additives used in the manufacture of plastic pipe.

Drinking water in the U.S. is provided by approximately 161,000 public water systems. Most of our drinking water comes from community water systems that serves roughly 268 million people and is monitored by the Environmental Protection Agency (EPA). The water comes from either surface water sources such as lakes and reservoirs or from groundwater sources such as aquifers.

After water from a source is processed through a treatment plant, it travels up to thousands of miles though complex piping systems before it finally arrives in your home and through your faucet. The average American home uses approximately 90 gallons of water a day, which many consider excessive in comparison to the average European who uses 53 gallons a day and an individual in the sub-Saharan desert who uses only 3.5 gallons per day.

In recent years, the price of copper has forced builders to switch to plastic pipes for delivering water to homes. The types of plastic piping used include polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polypropylene, high-density polyethylene (HDPE) and more recently a form of polyethylene called cross-linked polyethylene known by its abbreviation PEX. Prior to using plastic for water systems, all of the types were approved and certified by NSF International, an independent certification, standards and testing organization, and the American National Standards Institute (ANSI).

The popularity of using PEX over copper is that it has proven to be just as reliable as copper, is more flexible, easier to install and of course—much cheaper. However, with some consumers, the use of PEX or other forms of plastic pipe for drinking water has met with resistance. Chief among the claims against plastic piping is that it can cause the water to have an odor or taste that has been described as being fruity, waxy or plastic-like in character.

When chemical experts were called upon to assess the complaints, they determined that at times—especially with a new plastic pipe water system—that the water can have an odor or taste to it that differs significantly from a tasteless test control water sample. However, in almost all cases, the malodor and bad taste of the water disappeared after two months of use in a home. They said that why some homes may be affected and others not could be due to differences in the water itself dependent upon the water treatment plant that supplies the water.

Another concern of using plastic pipe for drinking water is that chemical additives used in the manufacture of plastic pipes may leach out and contaminate the water. In a recent study published in the Journal of Water and Health, researchers from the Norwegian Institute of Public Health decided to examine ten different types of PEX pipes used in delivering drinking water for odor and taste as well as evidence of leached chemicals from the plastic.

Using standardized laboratory tests, they placed water samples into samples of plastic pipes for 72 hours and then analyzed the water samples for chemical breakdown products from the pipes. The results of the study are listed as follows:

• No health risks associated with drinking water from PEX pipes.
• A few types of PEX pipe may cause prolonged undesirable taste and odor if the water remains in the pipes over time.
• Although the taste and odor usually dissipate with use, water from two of the PEX types still had an unpleasant smell and taste after a year.
• The level of volatile organic compounds that leaked from new PEX pipes was generally low.
• The level was further reduced with use.
• No correlation was found between production method and leaking products.
One of the volatile organic compounds detected, however, was methyl-tert-butyl ether (MTBE). MTBE is widely known as a chemical additive that had previously been used in
gasoline to make gasoline in cars burn cleaner.

MTBE was outlawed by the U.S. government in recent years due to the discovery that it was contaminating ground water when gasoline storage tanks leaked at service stations or when gasoline was spilled on the ground by users. Animal studies have shown that exposure to MTBE causes liver and kidney damage and increases the risk of developing cancer.

While there is no federal standard for MTBE in public drinking water, the US Environmental Protection Agency has set a drinking water advisory level of 20-40 micrograms per liter for public water. However, due to a lack of conclusive data demonstrating that these levels of MTBE have adverse health effects, the advisory level is based on taste and odor concerns. They contend that MTBE levels below this range should not cause water to have an unpleasant taste or odor.

Some states, however, set their limits higher depending on the water source. In Connecticut for example, well water is allowed a limit of 70 micrograms per liter in privately owned wells.

The authors of the paper note that the concentration of MTBE detected was higher than that recommended by the U.S. government, but did reduce to levels below the U.S. standard after the plastic tubes had been used for a while. Their final conclusion as to whether drinking water from plastic pipes is safe was that for the chemicals detected there is very little or no concern regarding leached chemicals. However, malodors from some pipe types can persist for up to 1 year.

Source: Journal of Water and Health Vol. 9 No 3 pp. 483–497, 2011 doi:10.2166/wh.2011.165
Image: Drinking water from Plastic - Wikipedia

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