Task 1—Metal and Mineral Commodities in the Built Environment
Many metal and mineral commodities are present in the built environment. Most are used intentionally in building or household products. Well-known examples include copper pipes and wiring, cement and aggregate used to make concrete and concrete–based products, zinc solder or galvanized coatings, and gypsum wallboard. Less well-known examples are antimony used as a fire retardant in building materials, hexavalent chromium used as a pigment in plastics and fabrics, and clays used as strengtheners in plastics.
The types, amounts, and forms of metal and mineral commodities used in the built environment have changed over time as a result of: changing technology (i.e., shifts from tungsten filament bulbs to mercury bearing compact fluorescent light bulbs); safety concerns (fire troubles with aluminum electrical wiring); substitution by cheaper or more durable materials (e.g., use of cement backer board rather than gypsum wallboard in showers), and; recognition of potential environmental or health concerns (e.g., curtailed use of asbestos in insulation or linoleum, and of lead in paints or solders).
Many metals and minerals are also present as natural trace constituents or anthropogenic contaminants in many products in the built environment, but are often undocumented or unrecognized. For example, amphibole asbestos was found prior to the early 2000s as a natural accessory mineral in many commercial vermiculite products produced from Libby, Montana, and used as house insulation.
There has not been a systematic or detailed approach taken to understanding the concentrations and forms of metal or mineral commodities in the built environment. Particularly for metal or mineral commodities that are present at low levels in large volume materials, understanding more details about their concentrations and forms will help provide a broader understanding of metal and mineral commodity usage in society. It also helps provide a better accounting for the amounts of these commodities that are being sent to landfills, or that potentially might be appropriate for recycling.
A number of the metal or mineral commodities in the built environment can potentially be toxic to humans or other organisms. For example, abrasion or weathering of lead-based paints in older houses has been demonstrated as a major source of lead toxicity to children. Fortunately in more modern buildings, many potential toxicants generally are either present in low enough amounts to not pose a toxicity risk, are present in non-toxic forms, or are ensconced within materials that under normal conditions prevent excessive exposures to humans or other organisms. However, disasters such as floods, earthquakes, and fires can drastically alter the forms of and/or risk for exposures to potential toxicants from the built environment. For example, toxicants can be leached from building materials by floodwaters, pulverized by earthquakes into dusts, or combusted by fires. Being able to understand details of the built environment as a source for potential mineral or metal toxicants is therefore key to be able to anticipate better the potential environmental or health issues that may develop in future disasters.
This task conducts literature surveys and collects new data to examine the uses, characteristics, and disaster-related environmental health implications of mineral and metal commodities present in the built environment. The primary focus is on trace metals and minerals that are contained within materials used in large volumes in the built environment, such as concrete, gypsum wallboard, cement cinder blocks, ceiling tiles, and selected electronics. Because of the potentially significant differences in composition of a given material by use, manufacturing process, region, country, age, and other parameters, we are obtaining information on as many different samples as possible of each material studied.
A literature survey has searched for existing data on metals and minerals present in these materials. Samples of these materials have been collected from various ages and types of buildings, obtained from colleagues, dumpsters, recyclers, or landfills, or as a last resort purchased commercially. We have also collected debris generated by building demolition.
The samples are being analyzed by methods we have used to characterize potential environmental and health characteristics of a wide range of earth materials and disaster materials. These include mineralogy and phase composition (via X-Ray Diffraction, Scanning Electron Micrscopy, and [LA-ICP-MS]), bulk composition (via ICP-MS, XRF, and CVAFS), reflectance spectroscopy, solid-phase metal speciation using synchrotron-based techniques. Samples have also been collected for analysis of organic chemical composition (e.g. polycyclic aromatic hydrocarbons, organohalogen fire retardants, pesticides, termiticides, etc.), but few analyses have been done due to the high cost per sample of these analyses.
Appropriately prepared samples (e.g. broken or pulverized to simulate earthquake effects or ashed in the lab to simulate fire effects) are being tested for bulk chemistry, freshwater and seawater leachability using the USGS Field Leach Test, landfill fluid leachability using modified EPA Method 1311, and bioaccessibility in simulated gastrointestinal fluids and simulated lung fluids. Leachate fluids are analyzed for chemical composition using ICP-MS, CVAFS, and ion chromatography, for oxidation-state speciation of specific metalloid toxicants.