As a materials science expert with a focus on metallurgy, I can provide you with a detailed explanation of the composition of brass and its lead content, as well as the regulations and concerns surrounding its use, particularly in the context of plumbing fixtures and their potential impact on drinking water quality.
Brass is an alloy made primarily of copper and zinc. The specific ratio of these two metals can vary, which in turn affects the properties of the brass, such as its hardness, color, and corrosion resistance. In addition to copper and zinc, brass may also contain small amounts of other elements, including lead.
The lead content in brass can vary significantly depending on the type of brass and its intended use. For instance, in the United States, the Safe Drinking Water Act (SDWA) has regulations that limit the amount of lead that can be present in materials that come into contact with drinking water. According to the regulations, the lead content in brass used for plumbing fixtures must not cause the water to exceed a lead concentration of 15 parts per billion (ppb) when tested under specific conditions.
However, it's important to note that the SDWA does not specify a maximum lead content for brass itself. Instead, it focuses on the end result: the lead levels in the drinking water. This means that a brass alloy with a higher lead content can still be used in plumbing fixtures as long as it does not contribute to elevated lead levels in the water when tested.
The reference you provided mentions that brass in the United States can contain up to 8 percent lead, as long as it doesn't leach more than 11 ppb of the metal into drinking water. This is a specific case where the lead content is regulated based on the potential for lead to leach into water, rather than a direct limit on the lead content in the brass material itself.
It's also worth mentioning that the standard test for evaluating how much lead will leach from a brass fixture is conducted using a water solution that simulates typical drinking water conditions. The reference suggests that this standard recipe may be "remarkably tame," implying that it might not fully represent the aggressive conditions that can occur in some water systems, which could potentially lead to higher levels of lead leaching than what is predicted by the standard test.
In summary, the lead content in brass can vary, and while there are regulations in place to ensure that brass used in plumbing fixtures does not contribute to unsafe levels of lead in drinking water, the specific lead content in a given piece of brass is not directly regulated by the SDWA. Instead, the focus is on the water quality after contact with the brass. The potential for lead to leach from brass into water is a concern, and the testing methods used to evaluate this risk are subject to ongoing discussion and potential refinement to ensure they accurately reflect real-world conditions.

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In the United States, that brass can contain up to 8 percent lead -- as long as it doesn't leach more than 11 ppb of the metal into drinking water. The problem, Edwards -- and now UNC -- has found: The standard recipe for the water used to evaluate how much lead will leach from a brass fixture is remarkably tame.Oct 30, 2008read more >>