As the story of the incident unfolded, some of the comments associated with the health effects of mercury included:
“With mercury, although it's not something you want to ingest or something you want on (an) open wound, by itself as it sat there ... it wasn't anything that could cause immediate danger…' KCRA, Sacramento, January 19, 2007
“Officials believe the small amount of mercury spilled would be harmful only if someone touched it or drank it.” Fox News, January 19, 2007
“Officials said none of those exposed appeared to have been sickened by the mercury, which can cause severe health problems if it is inhaled, ingested or comes in contact with an open wound.” LA Times, January 20, 2007
As someone who deals with mercury on a daily basis, these comments are typical of those I hear and seem to be contradictory in meaning. In fact, these statements are not wholly accurate. What most people hear about mercury comes from many different sources, including the internet where myths and false information is presented and continually repeated. Sometimes information does come from well-meaning sources who believe in what they are saying, but usually they do not possess accurate knowledge of mercury or the science behind the element.
Aside from the incident in L.A., the whole “mercury issue” is quite political given the debates and confusing information surrounding contaminated fish, coal burning power plant emissions, dental fillings, vaccines and other potential sources of mercury. Undoubtedly, education is the key to better understand these issues. As a component of my work, I seek to inform both the public and professionals about mercury, relying upon sound science and personal experience from cleaning up mercury spills and consulting on mercury related projects. A basic understanding of the principles of the nature of mercury can easily assist in reversing many of the myths commonly referenced today.
What is mercury?
Mercury is an element found in many forms. Most people are familiar with the “elemental” form of mercury, which is silver in color and has a shiny, fluid appearance. Mercury is also called “quicksilver” because it is very hard to contain and when spilled, it typically fractures into very small beads (some invisible to the naked eye) which can travel great distances. Because of mercury’s high surface tension, these tiny beads act more like marbles with a round shape rather than drops of water, which tend to attach themselves to surfaces and not travel very far.
Elemental mercury is commonly used in fever thermometers, blood pressure cuffs, heating and cooling thermostats and hundreds of other common devices. Elemental mercury is also very good at what it does; it conducts electricity (thermostats & other electrical devices), expands and contracts predictably with temperature changes (fever thermometers) and has very low vapor pressure (manometers, barometers). Also, silver fillings used to repair cavities in human teeth contain around 50% elemental mercury.
The primary hazard associated with elemental mercury is inhalation, or breathing the vapors emitted from the uncontained element. Mercury vapor is odorless, colorless and tasteless and cannot be seen without special mercury vapor analyzers which measure the concentration of mercury vapor in the air.
Contained, elemental mercury poses little risk of exposure. However, when a mercury containing device is broken and the element is spilled, the risk of exposure increases. Potential symptoms of elemental mercury exposure (by inhalation) include:
- Extremity tremors (shaking, twitching)
- Mood swings (emotional changes, irritability)
- Muscle weakness and/or atrophy
Kidney effects, breathing difficulty and respiratory failure, as well as death have occurred with higher exposures.
Many medical reports suggest ingested mercury, or mercury that is swallowed, passes through the intestinal tract with very little absorption into the body tissues. Likewise, with skin contact, elemental mercury absorbs very little into unbroken skin, although a thorough washing with warm, soapy water is necessary should contact occur.
Inhaled mercury vapor is absorbed through gas exchange in the lungs and readily passes the blood-brain barrier, potentially causing the adverse health effects listed above. Although everyone reacts differently, generally it takes a very high dose of mercury vapor over a long period of time to manifest adverse effects to its exposure, although a short-term, high dose exposure may cause significant health effects.
Anyone exposed to enough mercury over a long period of time can begin to show signs of mercury poisoning. However, the most at-risk populations include small children, pregnant and/or nursing mothers and the elderly. Also, those with previous mercury poisoning are more likely to be affected by lower subsequent doses of mercury vapor.
It should be noted that even if exposure has occurred, human health effects may not necessarily result. Again, everyone is different and every spill is unique. Exposure assessments take into consideration many different conditions and there are treatment options available for treating mercury poisoning.
Living with Mercury & Mercury spills
There are hundreds of mercury and mercury compound containing devices and products throughout society, found in many different locations. Some of these mercury compounds are added to the product, while others are simply a byproduct of manufacturing.
An example of a form of mercury that is frequently in the news is methyl-mercury. This form is created by the “methylization” of elemental mercury by bacterial organisms in the environment, creating a mercury compound. This compound “bio-accumulates,” or builds up, as more organism consume each other until the mercury compound is at its highest potential concentration at the top of the food chain. This mercury compound is why many areas around the country have issued advisories against eating certain fish caught in particular waters. Although not a vapor emitting form of mercury, methyl-mercury poses serious potential health hazards as well if ingested.
Ultimately, many factors influence spilled elemental mercury’s effects, as well as its cost for cleanup and potential for human exposure. These factors include, but are not limited to:
- Amount and type of mercury spilled
- The surface on which it spills
- Where the spill occurred
- Indoors: Will the vapor be distributed through heating & cooling ventilation? Could it be tracked to satellite locations? Is the mercury accessible?
- Drains & Sewers
- The distance the mercury falls, if at all
- Whether or not the mercury is tracked by humans, pets, vehicles, etc.
- The time between the spill and the cleanup
- Is the mercury use associated with religious or cultural use?
- Knowledge and experience of those performing the cleanup
The latest spill
The form of mercury released in the L.A. subway was elemental in nature. It was reported that 5 fluid ounces of mercury was spilled in the incident. The Reportable Quantity of a spill of mercury that must be reported to the Environmental Protection Agency is 1 pound, or about 2 tablespoons. Five fluid ounces - the amount spilled in L.A. - is about 5 pounds of mercury. It’s a big deal. Unfortunately, in my experience, I have seen less than this amount of spilled mercury cause significant damage to property and cause human health problems.
The Agency for Toxic Substances and Disease Registry (ATSDR), an agency of the U.S. Department of Health and Human Services, has stated in a Health Consultation, “Very small amounts of metallic mercury (approximately one-half teaspoon or the amount contained in one oral thermometer) can raise air concentrations to levels harmful to human health. This is why persons working with or around metallic mercury should avoid tracking metallic mercury into the home where vapors can be released over a long period of time.”
Spilled mercury is a hazard to human health and the environment. It was reported by KNBC-TV on January 19, 2007 (regarding the recent L.A. mercury spill), “...in just the five minutes of videotape the MTA released, as many as six people walked through the spill, including one man who stopped to touch it.” This information, if true, is very troubling given the nature and behavior of mercury and its potential health effects. I believe statements made by officials regarding a potential terrorist threat are valid and worthy of investigation. However, an equally important message in this case includes education regarding mercury, limiting its impact and the potential for human exposure and adverse health effects.
In the end, all mercury spills are different and cannot be judged from outsiders as to their severity. The only thing that is certain is that each spill must be handled immediately as to assess the potential exposure and begin an effective cleanup. Educating the public and those impacted is also critical when dealing with a mercury incident. Only then can we be sure that human safety is not at risk and property damage is minimized.