Office of the administrator science advisory board
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Dr. William StubblefieldComments on Chapter 7 - Ecological Effects of Lead Chapter 7 is a discussion of the ecological effects of Pb. Effects on terrestrial and aquatic ecosystems are first considered separately. They are then integrated by classes of endpoints (bioaccumulation, growth, mortality, hematological effects, development and reproduction, neurobehavior, community and ecosystem effects). Does the panel consider this approach appropriate? Chapter 7 provides an excellent synthesis of the available toxicity data for lead. The chapter is well-written and well-organized and does an adequate job of addressing “new” published data (post-2006). The separation of terrestrial and aquatic ecosystem data is appropriate and the subsequent organization by endpoints and levels of biological complexity is good. Some questions may be raised regarding the inclusion of some data and endpoints; however, this will be discussed in greater detail below. Is it appropriate to derive a causal determination for bioaccumulation as it affects ecosystem services? This question is a bit difficult to address as posed. The process of bioaccumulation, i.e., the uptake and accumulation of environmental pollutants, may or may not have any effects on ecosystem services. Therefore, bioaccumulation should not necessarily be thought of as an adverse or toxic effect. Bioaccumulation as a result of environmental exposure can result in adverse effects to the exposed organism or to consumers of the organism but only if concentrations of the contaminant are sufficient to elicit a toxic response at a given “site of action.” In many cases bioaccumulation of metals, such as lead, in select tissues is a normal metabolic process by which an organism is able to sequester and ultimately eliminate metals, e.g. metal granule formation in mollusks. It may very well be possible to derive a “causal” relationship between exposure and the presence of metals in tissues. However, due to the non—linear relationship between exposure concentration and tissue concentration with metals, developing a quantitative relationship would be doubtful. Similar concerns exist when evaluating possible food chain related effects. Available data suggest that little tissue bound lead is bio-accessible when consumed by predators, thus leading to “biodilution” of lead concentrations as one moves up the food chain. Has the ISA adequately characterized the available information on the relationship between Pb exposure and effects on individual organisms and ecosystems, as well the range of exposure concentrations for the specific endpoints? The ISA has done an excellent job of synthesizing and discussing the relationship between lead exposure and effects on individual organisms and ecosystems since 2006. Since the document relies on data that existed prior to 2006 and does not provide a summary of the extant data it is somewhat difficult to assess how adequately the document characterizes all of the available information. Summarization of all of the available data would be helpful; however, presentation of all of the available data would make the document unwieldy. Presentation of the available data in the form of a species sensitivity distribution (SSD) that identifies new versus old data would be helpful to the reader. Also, the ISA relies solely on published toxicity data available in the open literature. Additional unpublished toxicity information may be available from the lead industry given all of their efforts over the past 5+ years in developing data for compliance with the European REACH regulations. This information is likely to be available either directly from the lead industry or from the European Chemicals Agency. It should also be pointed out that the US EPA Ambient Water Quality Criteria for lead is based on 1985 or older science. In 1999 the US EPA Office of Water announced its intent to revise the existing lead criteria to reflect newer science; to date this has not been done. Clearly, based on the data summarized in the ISA, there is substantial “new” information available upon which to revise the criteria document. In moving forward with the lead air quality criteria it will be necessary for the Office of Air to consider the available new science in deriving their assessment of possible effects to organisms in the aquatic environment. Are there subject areas that should be added, expanded upon, shortened or removed? The ISA does a good job of covering the vast majority of post-2006 published data relating to let effects on aquatic and terrestrial organisms. It is interesting, however, that a number of endpoints such as physiological stress, hematological effects, and neurobehavioral effects are considered in this document. Traditionally the US EPA has limited their interpretation of environmental effects to those effects that can be directly related to population and community level concerns. This approach has limited endpoints considered for criteria and standards to those associated with organism survival, growth, and reproduction. Alternative biochemical or physiological level endpoints are considered only when a direct link can be made to population or community level concerns. Therefore, since no direct linkages can be made between an observation of a biochemical, behavioral, or physiologic endpoint and a population or community level concern it may be appropriate to eliminate discussion of these types of endpoints from the ISA. If the ISA was expanded to consider dose-response in terrestrial systems, should we limit data to field soils? I would recommend the data should be limited to “natural” soil data. Testing can be conducted under either laboratory or field conditions but the test matrix should be a “true soil.” If the ISA were expanded to consider dose-response in aquatic systems, how might we most efficiently present toxicity data that varies greatly by organism, and environmental parameters that influence bioavailability (pH, dissolved organic carbon etc.)? The best approach for presenting wide differences in sensitivity among organisms is through a species sensitivity distribution (SSD) approach. Environmental parameters that influence bioavailability are best discussed in terms of a description of the biotic ligand model. Application of the BLM to natural waters is best described by presenting the results of calculations using a series of natural waters or waters that exhibit a range of composition and chemical/physical parameters found across the United States. By presenting the data in this fashion the reader can easily ascertain the relative importance of each of the parameters on assessing lead toxicity. This applies to both the aquatic environment as well as to the terrestrial environment. Directory: sab -> sabproduct.nsf sab -> History honours thesis, 1986 – 2013 sab -> University rankings new method sab -> Is a decision by world banks to step in and provide cut-price dollar funding to eurozone banks a credible solution to the debt crisis? The Environment Agency says a drought that has affected parts of England since June could last until next sab -> David A. 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