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The day after I posted my last blog entry ("A tale of two exposures"), highlighting the silica sunflower seed snafu at the Tate Modern Museum in London, the front page of the New York Times arts section featured a major report on Ai Weiwei's ill-fated installation. This included not only a first-hand account of the clouds of dust generated by the visitors allowed to traipse over the interactive field of fake seeds, but also a detailed technical explanation of precisely why the show was so particularly problem-ridden. To achieve just the right seed-like effect Weiwie desired, it seems the artist first cast the porcelain seeds and then fired them with a black liquid clay slip rather than a standard glaze. This is not usually done with porcelain, we are informed by the Time's report, because slip on porcelain does exactly that: it easily slips off the underlying ceramic. This explains why the art reporter, overlooking the exhibit from a balcony even before it was closed off from direct contact with the public, mused that is was "an upper-respiratory disaster waiting to happen" (http://www.nytimes.com/2010/10/19/arts/design/19sunflower.html). A lower-respiratory disaster might be more precise, but no point in quibbling. This report did make me start thinking, though, about other potentially informative news updates touching on the subject matter of previous blog entries of mine.
In late August, I had written about the likely aftermath of the BP Gulf of Mexico oil disaster ("Black gold, tainted gold, and rare earth"). Consumers' concerns over oil slick-contaminated shrimp seem to have abated, or at least dropped from the news, but this past week the story broke that flawed cement could have been a major contributor to the oil well failure. Per reports, the subcontractor for the cement had run tests prior to the Deepwater Horizon rig explosion indicating that the material was unstable (http://www.reuters.com/article/idUSTRE69R4DZ20101028). This "instability" in the foam slurry cement may have allowed hydrocarbons to come up the drill pipe and then reach the floor of the rig, where they ignited. Perhaps the fear over tainted shrimp was misdirected, but a little well-placed corporate paranoia may not be overdoing it. The familiar name of the cement supplier: Halliburton Co.
Rare earth metals, also featured in the same blog entry, have similarly been in the news this past week http://www.nytimes.com/2010/10/30/business/global/30rare.html?src=busln). Actually, such reports have been in the news repeatedly, often in the business pages. In late September, China began blocking the export of all rare earth metals. Initially this was on the pretext of an unrelated diplomatic flap with Japan, but then China extended the ad hoc embargo more generally. Of great note is China's position as nearly the sole worldwide exporter of these strategic metals, in high demand for a variety of high-tech industrial applications. As it turns out, however, it is not that China hit the geological jack-pot and sits on all of the world's reserves of Yttrium, Lanthanum, Cerium, Neodymium, and their Periodic Table buddies. It's just that the Chinese (or at least Chinese decision-makers) are willing to put up with the severe environmental degradation tied to the exploitation of these materials. In mining "clean" deposits of rare earths, this means acid-laden extraction wastes. But most of China's (and the rest of the world's) rare earth deposits are naturally laced with radioactive Thorium.
Thorium is not a substance that we would want supplemented to our food or water supplies. Although trace amounts of radioactive Thorium are widely distributed naturally, human background exposure under normal scenarios is fairly minimal. Nonetheless certain practices, such as the German penchant for ingesting "healing soil" (aka, packaged dirt) have been studied as a potential source of excess Thorium intake. The problem with Thorium is that once it enters the body, it tends to be taken up by immune cells in the liver where it then resides for a very long time, all the while emitting dangerous radiation. We know this because for many years thorium was used a medial contrast agent, leading to a very rare human cancer (angiosarcoma) decades later. Perhaps aware of this problem, the Chinese have been shoring up an artificial waste lake linked to its rare earth mining operations, a lake far larger than the one that burst in Hungary and less than 10 miles from the Yellow River. Closer to home, a rare earth mine near the California-Nevada border is hoping to re-open next summer. It operator, Molycorp, prefers to call rare earth elements "green metals" (http://www.molycorp.com/greenelements.asp).
