Plastic plumbing systems, such as those made from PVC and cross-linked polyethylene, are more likely to deliver lead-laden drinking water than their copper counterparts, according to a new study published in the peer-reviewed Environmental Science & Technology.
It is a publication of the American Chemical Society in Washington.
The findings initially seemed counterintuitive, but researchers discovered the explanation.
``Brass is ubiquitous in domestic plumbing systems,'' said Marc Edwards, a professor of civil and environmental engineering at Virginia Tech University in Blacksburg, Va., in a June 2 telephone interview. ``It is an integral component in valves and faucets. Some of the brass has lead in it. In newer homes, brass is the primary source of lead in drinking water.''
Ironically, it is metal that is causing the problem in plastic plumbing systems, said Edwards, one of the study's lead researchers.
Lead is not leaching from PVC or PEX. However, the plastic pipe does indirectly create an environment for lead to contaminate drinking water, the study found.
Water utilities are increasingly treating water with chloramine to comply with disinfection regulations. Chloramine decay forms ammonia, which in turn supports ``autotrophic microbial nitrification,'' according to the study. The nitrification process can stimulate growth of heterotrophic bacteria, all of which lowers acidity levels, and can result in quality degradation while water sits stagnant in plumbing pipes.
``To oversimplify, the nitrifying bacteria grew very easily in PVC pipe and did not grow in copper,'' Edwards said. ``As a result, the pH was about one unit lower in PVC pipes. It's an indirect effect in that the presence of PVC allowed this bacteria to grow, which lowered the pH, which in turn caused the lead contamination.''
Kitchen and bathroom faucets are made mostly from brass and are ``undoubtedly the major sources of the lead,'' Edwards said.
Leaded brass also can be found in PEX fittings, shut-off valves and water meters, he said.
The findings are not cause for panic, but are cause for concern, he said.
``It doesn't pose nearly the hazard that lead paint, or lead in water from solder or lead pipe, causes,'' Edwards said. ``The levels we're talking about do exceed [Environmental Protection Agency] recommendation.
``There is no safe level of lead exposure.''
Lab testing on individual plumbing systems is available. One trusted source, Edwards said, is Asheville, N.C.-based Clean Water Lead Testing Inc.
Running water for 10-20 seconds before drinking is one way to effectively flush contaminated water from the system. Water filters are another safety method, Edwards said. Retrofitting of brass faucets and parts is also an option, he said.
``I'm not an advocate for any one type of plumbing material,'' he said. ``I'm a scientist. We were just trying to point out the strengths and weaknesses for each material in different situations. This explained some perplexing practical data that was out there.
``In general, each plumbing material has its strengths and weaknesses. Homeowners have to weigh those when making decisions.''