CHAPTER 2 LEAD LEACHING FROM IN-LINE BRASS DEVICES: A CRITICAL EVALUATION OF THE EXISTING STANDARD
The ANSI/NSF 61, Section 8 standard is relied on to protect the public from in-line brass plumbing products that might leach excessive levels of lead to potable water. Experiments were conducted to examine the practical rigor of this test. Contrary to expectations, the test was not highly protective. Rather, it was determined that small devices made of pure lead can easily pass the leaching protocol. Reforms are needed to help prevent such unacceptable outcomes in the future. In the meantime, there is no assurance that brass devices passing this test are safe.
With the recent crisis of confidence arising from excessive lead in potable water of the nation’s capital (Nakamura, 2004), a comprehensive national review of lead standards is inevitable. That comprehensive review should consider the adequacy of existing standards and sampling protocols, regulatory oversight and response, issues of simultaneous compliance and resolution of knowledge gaps (Edwards, 2004).
It is widely accepted that minimizing the extent of lead leaching to drinking water from plumbing materials is a worthy public health goal and the EPA Lead and Copper Rule (LCR) has achieved great progress in this area (Federal Register, 1991). The amount of lead leached to public drinking water is a function of two key factors that are under societal control. The first factor is the type of plumbing material used—some plumbing products have a relatively high tendency to contaminate drinking water with lead. The second factor is the corrosivity of the water supply that contacts plumbing products. Achieving the goal of very low lead in drinking water requires progress in both areas.
The EPA LCR has been designed to assess the lead leaching tendency of public water supply in the context of existing plumbing. Lead present in the one liter « first draw » EPA LCR sample can come from: 1) lead present in the source water, 2) lead leached to water as it quickly passes through service lines at high flow rates, and 3) lead leached to water as it contacts the home plumbing system during prolonged stagnation (Figure 2-1). The EPA LCR also requires monitoring of lead leaving the treatment plant and has very limited sampling provisions to detect “spikes” of lead that might build up in water from prolonged stagnation in service lines. If 90% of first draw samples are not below the 15 ppb lead action limit, the LCR prescribes steps to minimize corrosivity of the water. For example, by manipulating the chemistry of public drinking water through adjustment of pH, alkalinity, or by addition of corrosion inhibitors such as orthophosphate, it is often possible to greatly reduce leaching of lead to public water supplies at relatively modest cost (Schock, 1989a; Schock et al, 1996; Edwards, 2002a). Such corrosion control steps can often reduce lead leaching to water from many lead-bearing plumbing products including pure lead pipe, lead solders and brass.
Progress has also been made in phasing out potentially harmful plumbing products. Pure lead pipe, leaded solders and brass with > 8% lead content were deemed such a potential hazard, they were explicitly banned in the 1986 SDWA as amended in 1996 (40 CFR Part 141, §141.43). More recent progress has been driven by Proposition 65 in California, which has led to use of very low lead brass residential water meters and required a more stringent standard for lead discharge from consumer faucets. Proposition 65 has also impacted standards for products that are available nationally (Maas et. al., 2002a-e). However, the definition of “lead free” brass still allows sale of devices containing up to 8% lead by weight as long as they are in compliance with performance standards established in accordance with 42 U.S.C. 300g-6(e).
To illustrate the potential magnitude of the problem, we note that a typical gate valve has at least 100 g of brass that could uniformly corrode away before the product failed. At 5% lead content, the lead leached to water from corrosion could contaminate every drop of water (to the 15 ppb lead action limit) used by a typical family of four in a year. Of course, this amount of brass corrosion does not occur in a year, but is spread over the product lifetime. But considering that multiple brass devices are installed between the water main and the home, there can be an additive effect. There is also potential for “spikes” of lead in drinking water coming from the tap, attributable to the water that sat inside these devices during stagnation.
These considerations illustrate a societal need for a test that prevents installation of brass products that could leach excessive lead to water. What are the desirable characteristics of a test? On the practical side, those selling plumbing products are correct to argue that the test should be of reasonable duration and expense. If the test were too expensive or required too much time, improved plumbing products might be excluded from market, which is not in the public interest. It is also critical that the test be reasonably reproducible in different laboratories around the country and at different times. Finally, it is critical that the test be prospective, such that products leaching problematic levels of lead can be excluded from the pool of products that is installed in homes (or schools) before they pose a direct public health threat. Obviously, many of the home or institutional plumbing products in question are not visible or even readily accessible once installed, so a “recall” of dangerous products would be practically impossible.
Some have argued that the EPA Lead and Copper Rule (LCR) itself can protect the public from brass products that may leach excessive lead. This argument logically fails for many reasons. In the case of new in-line products, this would require installation of potentially dangerous untested products in consumers’ homes, sampling according to an as yet undetermined protocol, and exposing consumers to potentially dangerous levels of lead throughout the test. The EPA LCR would also have to be modified extensively to test leaching from in-line devices. At present the LCR does not 1) intend to make sure that homes are sampled with every type of plumbing product that has ever been made, 2) attempt to document the presence of specific types of brass products present in the homes which are sampled in the EPA LCR, or 3) purposefully detect spikes of lead that might occur from brass installed near the service lines. In short, the LCR was not designed, nor can it rationally be used, to protect the public from potentially harmful plumbing products.
For new brass plumbing products, there are two current standards designed to provide protection. The first is NSF 61 Section 9, which tests « end point » devices that can contact water collected in the first draw sample during stagnation (Figure 2-1). Plumbing products that pass NSF Section 9 have explicit recognition from the EPA in terms of limiting lead leaching to water (EPA, 2004). All other brass devices fall under NSF 61 Section 8 including backflow preventers, building valves, check valves, compression fittings, corporation stops, meter couplings, water meters, strainers, pressure regulators and many other devices. These are termed “in-line” devices. There is presently no national legal requirement that in-line devices brass devices meet NSF 61 Section 8 standards. However, 44 states had legislation requiring conformance to these standards by 2001, and the remaining states had intentions to do so (ASDWA, 2001)
While many in the drinking water industry are familiar with the general reputation of NSF 61 in certifying plumbing products as safe for drinking water usage, detailed knowledge of the test protocol is not readily accessible nor understood. Few appreciate that there are important differences between the test protocols for end-point devices such as faucets versus those for in-line devices such as meters and shutoff valves as detailed by Hazan (1994). In-line devices are tested in two waters henceforth termed the “NSF pH 5” and “NSF pH 10” water. After the devices are exposed to the test waters for up to 14 days conditioning, lead leached to the test water is quantified after a 12-16 hour stagnation period. The measured concentration of lead from the test is then normalized to “determine the level of contaminants projected “at the tap” based on the level of contaminants identified during laboratory analysis” (e.g. NSF, 2002). If the normalized concentration is less than 15 ppb the product passes the protocol and can be NSF certified, as long as the product also contains less than 8% lead by weight as specified by law (EPA, 2004).
Products that pass the test can be labeled « ANSI/NSF 61-8 Clean Water for Our Future” in the marketplace and other prominent displays indicate that devices have passed the standard (Figure 2-2). A purchaser would be further reassured to read NSF literature which indicates the NSF 61 Section 8 standard was developed by a consortium of: NSF International, The American Water Works Association Research Foundation, the Association of State Drinking Water Administrators, The American Water Works Association with support from The U.S. Environmental Protection Agency under cooperative agreement #CR-812144 (e.g. NSF, 2000). In the preface on page v of the original 1988 NSF 61 Standard, it states: “Standard 61 was developed to establish minimum requirements for the control of potential adverse human health effects from products which contact drinking water.”
The point of this discussion is that conscientious members of the public and the water industry have been give every reason to believe that NSF 61, Section 8 certification protects against products that would leach excessive concentrations of lead to drinking water. It is recognized that compromises are necessary in developing a test, and that the actual concentrations of lead measured during the test are controlled by the test protocol. Key factors in the protocol include chemistry of the test water, duration of the test, duration of the contact time of test water and material before sampling, normalization factors, and reproducibility. This research will carefully examine only the chemistry of the test waters, normalization factors, and whether the existing test is sufficiently protective.
MATERIALS AND METHODS:
Sixteen hose bibs that were ANSI/NSF 61 Section 8 certified were purchased from a local hardware store. While hose bibs themselves do not normally require NSF 61 Section 8 testing, as they are not specifically intended to produce water for human consumption, they were convenient for testing scientific principles related to aggressivity of the test waters. The hosebibs were covered at one end with a threaded PVC cap and at the other end with a non-threaded cap (Figure 2-3). During testing the hose bibs were set horizontally with the outlet directed upwards. Twelve identical sections of 12 cm long 1.7 cm inner diameter pure lead pipe were also used to examine the aggressivity of the test solutions to pure lead. One end of the pipes was plugged with a rubber stopper that did not leach lead, whereas the other end of the lead was loosely covered to exclude dust from entering the device.
The leaded samples were rinsed twice with de-ionized water and then washed twice with exposure solution. Each type of lead bearing material was filled with water from one of four different solutions:
- NSF pH 5.0 water: 203.25 mg/L MgCl2 (51.82 mg/L as Mg) and 347.25 mg/L NaH2PO4 (77 mg/L as P) with 2 mg/L as Cl2.
- NSF pH 5.0 water without phosphate: same recipe as pH 5 water but without NaH2PO4.
- NSF pH 10 water: 476.75 mg/L sodium borate (110.4 mg/L-B) at pH 10 dosed with 2 mg/L as Cl2.
- Aerated NSF pH 10 water: Same recipe as NSF pH 10 water but aerated for an hour.
For comparison, some leaded materials were exposed to a relatively non-aggressive tap water containing 30.5 mg/L alkalinity as CaCO3, pH 8.6, 40 mg/L of Cl– and 50 mg/L of SO4-2. Fresh solutions were prepared weekly. pH was precisely adjusted to the target value using 1 N HCl or 1 N NaOH base. Water was changed in the devices as per the ANSI/NSF 61, Section 8 schedule. Samples of water were collected from each plumbing specimen for analysis on the 2nd, 9th, 25th and 58th day after a 16 hour stagnation. The same schedule was followed for the pure lead pipes except that the experiments were terminated after the 25th day. On occasion, samples collected from the pure lead pipes were passed through a 0.45 µm pore size nylon syringe filter to quantify soluble lead.
CHAPTER 1: ROLE OF CHLORINE AND CHLORAMINE IN CORROSION OF LEAD BEARING PLUMBING MATERIALS
Results and Discussions
CHAPTER 2: LEAD LEACHING FROM IN-LINE BRASS DEVICES: A CRITICAL EVALUATION OF THE EXISTING STANDARD
Materials and Methods
Results and Discussions.
Consideration of Test Water Chemistry.
CHAPTER 3: GALVANIC CORROSION OF LEAD BEARING PLUMBING DEVICES.
Materials and Methods
Galvanic relationship between current and lead leached
GET THE COMPLETE PROJECT
RECONSIDERING LEAD CORROSION IN DRINKING WATER: PRODUCT TESTING, DIRECT CHLORAMINE ATTACK AND GALVANIC CORROSION