Wednesday, December 29, 2010

Guest Post - Naturally Harmful Metals and Minerals

Next up in the in the guest blog domain is Eric Stevenson who wanted to write about how natural "stuff" could be potentially hazardous to one's health. Check it out below:

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Naturally Harmful: The Modern and Historical Use of Asbestos, Lead, and Mercury


When a substance is known as “naturally-occurring,” we have a tendency to think of it as something that is possibly beneficial, or at the very least benign – certainly not harmful. However, many metals and minerals that occur naturally in the Earth’s crust are toxic to humans. In some cases, their deadliness was known from the beginning; in others, their usefulness obscured or outweighed the symptoms that warned of their toxicity.

Asbestos
Asbestos was once considered a “miracle mineral.” Ancient Greek writers told stories of tablecloths that could simply be tossed in the fire after use, emerging not only unscathed, but cleaner and whiter than before. Medieval alchemists were so entranced with this material that they hypothesized it came from the hair of salamanders, which could walk through fire and survive. By the time of Marco Polo, however, people knew that asbestos was mined from the earth.

In 1820, an Italian scientist became the first to run a successful business based on asbestos products – fireproof clothing sold all over Europe. Soon after, many items began to incorporate asbestos into their design: stage curtains, gaskets and packing for steam engines, paint and tar paper, and cement. The inclusion of asbestos in construction materials would continue into the 1970s for the simple reason that asbestos was an incredibly effective flame retardant. No doubt countless lives were saved from fire.

However, this “miracle mineral” was not the safety boon it appeared to be. When asbestos-containing products sustain damage, tiny, needle-like fibers are released into the air. Once inhaled, these fibers can cause serious health problems, including lung scarring, asbestosis, and mesothelioma, a rare and deadly form of cancer. One reason this cancer is so dangerous is that mesothelioma symptoms can take anywhere from 20-50 years to surface after exposure, by which time the disease is often in its final stages. Because of these dangers, asbestos has largely been replaced with alternative fire-resistant substances in newly-manufactured construction materials.

Lead
A soft, malleable metal, lead is useful for its low melting point, high density, and resistance to corrosion. It was accessible and easily worked with, and therefore made the ideal medium for the famed plumbing system of the Roman Empire. Lead was not only used for pipes, but also as a component in coins, flatware, cosmetics, spermicide, and food seasonings.

However, even the ancient Romans understood that exposure to lead had serious health-related consequences. As we now know, even low levels of exposure can cause chronic lead poisoning. The dangers of acute lead poisoning were apparent in Renaissance Europe, where it may have been used in some royal assassinations. In modern times, lead was used as a fuel additive, despite early evidence that the vapors were toxic to the workers producing it.

Though lead was removed from gasoline – as well as other products like pipes and house paint – beginning in the mid-1970s, the metal continues to be used in products from car batteries to radiation shielding. Unlike asbestos, lead can still be found in many construction materials because it usually has to be ingested to be poisonous. Initial symptoms of lead poisoning – including headache, abdominal pain, memory loss, and kidney failure – may be confused with other conditions, though more severe neurological problems soon follow. Like asbestos, there is no amount of lead ingestion, however small, that is considered “safe.”

Mercury
Mercury is notable for being one of the few metals that exists as a liquid at room temperature. Historically, mercury had a wide variety of applications, from the practical (preserving wood, developing daguerreotypes) to the recreational (handheld games, fishing lures). Amazingly, both the ancient Chinese and the ancient Greeks thought of mercury as a substance that promoted good health and long life, and doctors continued to use it into the 20th century to treat conditions ranging from depression to constipation to syphilis.

In modern times, most people know mercury as the liquid in thermometers, though it is also found in other measurement devices such as barometers (air pressure) and sphygmomanometers (blood pressure). Thimerosal, an organomercury compound, has been used as a component in dental amalgam and a preservative in vaccines. The latter use triggered a controversy over the possible role of thimerosal in the development of autism, though the most recent studies do not support a link between the two. Regardless, the FDA reports that thimerosal has been phased out of nearly all vaccinations required for young children.

However, parents are right to be concerned about exposing their children to any form of mercury. The substance is extremely dangerous if ingested, inhaled, or absorbed through the skin. Like lead, mercury poisoning affects the central nervous system, resulting in symptoms as diverse as sensory impairment, lack of coordination, hallucinations, and social phobia. Despite the dangers, small amounts of mercury can still be found in certain cosmetics, fluorescent lamps, neon signs, and telescopes.

If you would like more information about any of these substances, please visit:

James E. Alleman and Brooke T. Mossman. “Asbestos Revisited.” Scientific American, 1997.
http://virlab.virginia.edu/Nanoscience_class/lecture_notes/Lecture_14_Materials/Asbestos_CNT/Sci%20Am%20-%20Asbestos%20Revisited%20-%20July%201997.pdf

Jack Lewis. “Lead Poisoning: A Historical Perspective.” EPA Journal, 1985.
http://www.epa.gov/history/topics/perspect/lead.htm

U.S. Food and Drug Administration. “Thimerosal in Vaccines.” FDA.org, 2010.

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