Mercury
5/20/2011
In Greek mythology, Mercury is the fleet-footed messenger of the Gods. He was the cleverest of the Olympians, patron of translators and interpreters. He ruled over wealth, good fortune, commerce, fertility. . . and thievery. He brought the souls of the dead to the underworld, and was honored as a god of sleep. As a physical substance in the living organism, however, mercury is the antithesis of the fleet-footed messenger’s finer qualities. In the body, mercury disrupts cellular function at all levels, robbing the body of health and escorting the victim to the underworld of neurological dysfunction.
Mercury, also widely known as quick-silver, has the chemical symbol, Hg – coming from the Latinized form of the Greek word, hydrargyros, meaning “water-silver.” As this ancient name implies, mercury is a liquid at standard temperature and pressure; the only metal with this property), becoming a solid at -38.83 ̊C (at this temperature, degrees Fahrenheit and Celsius have similar numerical values). Because it is an element (number 80 on the Periodic Table) mercury occurs naturally, comprising an average 0.08 parts per million (ppm) of the earth’s crust. Mercury is usually found as an ore, such as cinnabar (HgS) or Livingstonite (named after the African explorer, David Livingstone and is comprised of mercury, antimony and sulfur). These ores have a mercury content that typically range from 0.1% – 2.5% and are most commonly found near hot springs or volcanic regions where high density rocks are forced to the Earth’s crust.
Mercury is routinely used in the manufacture of industrial chemicals and electronics while being recognized as a health concern during many types of soil remediation and building deactivation and decommissioning projects. Of course we all know of mercury’s presence in thermometers, thermostats and manometers where we can all recall playing with this material in our younger years when its glass container broke and we rolled it around in our hands, dividing it into little spheres and then recombining them, giving us hours of amusement. And while elemental mercury can be absorbed through the skin, its primary route into the human body is inhalation. Yet, ingestion of elemental mercury can occur without any (or minimal) uptake followed by excretion without causing adverse health effects (but please don’t try this at home!). As a matter of fact, elemental mercury was used as a laxative in the 1800’s.
Another major form of mercury falls under the classification of inorganic compounds; of which mercuric nitrate is most notable. This material was used in the production of felt hats in the mid-18th to mid-19th centuries whereby mercuric nitrate was used to separate animal fur from its pelt and matted it together. The vapors emitted during this process were extremely toxic, causing severe psychological symptoms and was probably the reason for the descriptive phrase we still use today – Mad as a Hatter. It is probably the reason for the play on words by Lewis Carroll for the character, the Mad Hatter, in his novel, “Alice’s Adventures in Wonderland.”
The most toxic form of mercury is organic mercury, sometimes referred to as methylated mercury. Generally human intake of this contaminant occurs due to our consumption of fish. As huge amounts of elemental mercury is continuously being released into the environment (it has been estimated that over 11,000 tons of mercury are released into the environment annually), fish and other sea creatures ingest the elemental form of mercury and during their metabolic process it combines with organic molecules and thus becomes an organic compound. Once in this form, entry into the human biologic system through ingestion is rapid and has the potential to cause serious health effects as the organic mercury has the ability to enter cells, causing destruction of the various cellular components. The toxicity of methylated or organic mercury first came to the attention of the international community in the 1950s, when many of the inhabitants of the Japanese fishing village, Minamata, on Kyushu Island developed neurological damage and terotogenic (embryonic deformation) effects. These unfortunate cases were the result of a nearby petrochemical plant that manufactured plastics and dumped elemental mercury into the local waters which were then ingested by the indigenous water life, resulting in the methylation process, and consumed by the local population as their main dietary staple.
Today, many of our environmental clean-up projects involve concerns with mercury. Though mercury has a low vapor pressure (and therefore having a reduced the ability to become airborne) the current occupational airborne exposure limits are quite stringent (ACGIH TLV is 0.025 mg/m3). Therefore, when handling mercury or mercury-contaminated soils, it is important to wear the right personal protective equipment. Not too long ago, a chemist at Dartmouth College died from skin absorption of dimethyl mercury. Even though the researcher was wearing gloves, they were latex and therefore allowed the dimethyl mercury to penetrate its barrier and contact the skin where the contaminant was absorbed through the skin resulting in severe central nervous system disorders. It was reported (based on the researcher’s lab notes) that only a few drops of dimethyl mercury caused this unfortunate incident. A more appropriate glove, such as SilverShield® would have provided the right hand protection (PVC and neoprene gloves also would not have provided the right protection).
As we can see, exposure to mercury is a complicated subject. It is important to understand what class of mercury may be present and to make sure that the right PPE is selected. Other things that need to be considered include having a medical surveillance program that incorporates pre and post blood-mercury levels. As many occupational physicians have witnessed, persons that consume a can of tuna fish on a regular basis (i.e. daily) will show elevated mercury levels in their blood (however, adverse health effects from the daily consumption of tuna has not resulted in unusually health conditions). Therefore, appropriate medical screening can identify these persons and appropriate steps may be implemented. The initial step will always be to get your Safety and Health Professional involved so that proper protective measures and exposure assessments can be applied – Your safety and health demands it!
“If you don’t know where you are going, any road will get you there.”
Lewis Carroll – Author of “Alice’s Adventures in Wonderland”