It seems the section that my organization wishes to comment on is not open for comment, although that certainly was not clear in our review of the draft. I would also note that trying to submit comments via the USGBC site has been a dreadful experience. See input from the North American Metals Council below:

December 10, 2012

Via Online Submission

The North American Metals Council (NAMC) provides these comments on the latest version of the Leadership in Energy and Environmental Design (LEED) Green Building document, specifically the chapter “PBT SOURCE REDUCTION—LEAD, CADMIUM, AND COPPER.” The title and intent of this chapter should be modified to remove the reference to persistent, bioaccumulative, and toxic (PBT) as a descriptor for the metal substances listed.

Metals exhibit unique characteristics that make it inappropriate to evaluate or characterize metal substances using the general hazard evaluation principles, such as PBT, that are applied to organic chemicals. For this reason, the stated intent of the draft LEED document -- “To reduce the release of persistent, bioaccumulative, and toxic (PBT) chemicals associated with the life cycle of building materials” -- is inaccurate and not scientifically justified if it is to be applied to metals or metal substances.

Characterization of persistence for metals is problematic because all metals and other elements on the periodic table are conserved and hence, persistent -- although the form and availability of the metal can change (thereby affecting its potential bioavailability and toxicity) depending on the environmental conditions. Applying persistence criteria designed for organics to metals, therefore, can result in misleading assessments of potential hazard. A more discriminating approach is needed.

The same is true of bioaccumulation. Unlike organic substances, the bioaccumulation potential of metals cannot be estimated using octanol-water partition coefficients (Kow). For metals, bioconcentration and bioaccumulation factors (BCF and BAF) are inversely related to the concentration of the metal in the surrounding environmental medium and are not reliable predictors of chronic toxicity, food chain accumulation, or hazard. The inverse relationship between exposure concentration and BCF means that organisms from the cleanest environments (i.e., background) have the largest BCF or BAF values, even though they are least at risk of toxic insult. This inverse relationship does not exist for organic substances. Thus, it is counterintuitive to use BCF/BAF and log Kow -- which were originally derived for hazard evaluation of organic substances -- to evaluate hazard and risk for metals.

The U.S. Environmental Protection Agency (EPA) has recognized this and related points in its Framework for Metals Risk Assessment, noting that metals and metal substances must be assessed differently than organic chemicals. Thus, as EPA states in its Fact Sheet on Framework for Metals Risk Assessment, “the latest scientific data on bioaccumulation do not currently support the use of bioconcentration factors and bioaccumulation factors when applied as generic threshold criteria for the hazard potential of metals.”

To avoid confusion and incorrect or inappropriate references to PBT, NAMC recommends that the title of this section simply refer to the chemicals listed, and the intent of the section be removed.

Thank you for the opportunity to provide this input.