ELi ON EARTH: Mercury Matters in East Lansing
Image: Metal mercury, courtesy of the Centers for Disease Control
Mercury—the metal not the planet—has been in the East Lansing news since a spill at the East Lansing Wastewater Treatment plant and an ELi scoop about continuing concerns among city workers regarding exposure.
Should East Lansing residents worry about mercury? The short answer is yes, East Lansing residents should worry about mercury.
Each year, the Michigan Department of Community Health (MDCH) collects laboratory tests from Michigan patients with high levels of the heavy metals mercury, arsenic, and cadmium. These results are analyzed and published in cooperation with the Division of Occupational and Environmental Medicine in the Department of Medicine at Michigan State University. (Disclosure, the author is a member of that department and trained under and played soccer with the division’s director, Ken Rosenman, MD.)
Each year people in Michigan test positive for high levels for heavy metals. In 2012-13, eight people in Ingham County were known to have had high levels of one of these substances.
How do people get high mercury levels in their bodies?
There are several different forms of mercury to consider when talking about human exposure: mercury metal (which can exist in a liquid or gaseous form), mercury salts, and “organic mercury.”
Let’s first talk about mercury metal, which is a heavy, shiny metal and is unique among the metal elements in that it is liquid at room temperature. Most people have seen metallic mercury in a thermometer or, after a thermometer has broken, as a shiny ball on a table top. Metallic mercury is also used in its liquid state in switches and thermostats. It is used as a vapor in compact fluorescent lights.
This metallic form of mercury is the material that spilled in the East Lansing Wastewater Treatment Plant. Generally, metallic mercury is not absorbed by intact skin and is poorly absorbed by the body if it is eaten. The most common way to absorb metallic mercury is by breathing the small amount of vapor that comes off the liquid metal at room temperature.
There is mercury vapor in all fluorescent lights including in the spiral and folded compact fluorescent lights that people use in their lamps at home and in the long fluorescent lamps used in offices and workshops. In a fluorescent light, electricity is used to excite the mercury vapor, which gives off light, including a large amount of ultraviolet light that people can’t see. The ultraviolet light from the excited mercury causes the phosphorescent coating inside the glass tube to glow with a white light visible to humans. In terms of power consumption, converting the ultraviolet light from excited mercury vapor to visible light from the phosphorescent powder in the tube is very efficient. That’s why people use mercury in light bulbs—because it makes for an efficient light source. Breaking a fluorescent light immediately releases the small amount of mercury vapor in the glass tube of the light bulb.
What then about mercury salts? Historically, many people have been poisoned by ingesting mercury salts found in medications like calomel, which is a mercury-chloride salt. While the metal form of mercury is not well absorbed by the human gastrointestinal system, mercury salts like calomel are well absorbed orally. Calomel is a linear molecule of two chlorine atoms (Cl) and two mercury atoms (Hg) arranged in a line: Cl-Hg-Hg-Cl.
As a medicine, calomel was used as a treatment for syphilis, as a laxative, a purgative, for yellow-fever, and as part of a teething powder for babies and toddlers into the 1950s and 1960s. People still occasionally ingest mercury salts through skin whitening treatments.
So what is “organic mercury”? Chemicals with carbon atoms are called “organic” molecules, and mercury can form a bond with carbon to form organic mercury. With the help of bacteria, mercury in the water and soil can form the carbon-mercury molecule methylmercury, which can wash into rivers, lakes, and oceans.
Once in the water, methylmercury can enter the food chain by contaminating the meaty flesh of fish. Small fish ingest the methylmercury, which gets stored in their muscles. Larger fish eat the smaller fish, and the levels of methylmercury increase in larger, older fish if they eat other fish. The progressive increase in mercury levels in animals higher and higher on the food chain is called bioaccumulation. Bioaccumulation can also happen with other toxins like dioxin and PCBs, which accumulate in the fat of animals. People are at the top of the food chain in East Lansing, and toxins like mercury can accumulate in our bodies if we eat other animals contaminated with methylmercury.
The Michigan Department of Environmental Quality tests fish for mercury in Michigan lakes and rivers. In Ingham County, Fidelity Lake, Lake Lansing, the Red Cedar River, and the Grand River are regularly tested. The fish in each of these lakes and rivers have concerning levels of mercury and people should limit themselves to eating as little as six servings of fish per year for the largest species in the most polluted waters. (There are other pollutants, like PCBs and dioxin tested for in Ingham County and found to be a concern as well.)
How is mercury potentially harmful to East Lansing residents?
For all of the concerns about mercury and the relationship between pollution and mercury levels in our air and food, the fact is that mercury has always been around humanity and our bodies can get rid of small amounts of mercury without apparent disease.
The evidence is that current medical sources of mercury probably don’t cause illness. Most dental fillings no longer include mercury, which was potentially bad for the workers who made them, but even if you have mercury-amalgam fillings, there is not evidence that you should replace them. Thimersol, which is a mercury containing preservative, is no longer used in vaccines (except for influenza vaccines), although there has been significant research done to show that thimersol has not caused autism or other harm to children or adults.
The spectrum of disease attributed to actual mercury poisoning is large and diverse. When mercury metal vapor (like that which would have likely been produced in the East Lansing spill and improper clean-up) is inhaled, it enters the blood stream and it binds to proteins. From the blood stream, mercury crosses into the brain and crosses the placental barrier between mother and fetus. Mercury can also be present in breast milk.
Wherever it goes, mercury binds to proteins. People with enough exposure can develop many problems, but the nervous system is particularly vulnerable to mercury, leading to tremors, sensory loss, and changes in mental function including extreme shyness and timidity.
Other mercury salts can accumulate in the kidneys and cause kidney failure. Workers who use organic mercury compounds have developed renal failure, mental disorders, muscle problems, and loss of sensation.
Mercury is particularly bad for children whose developing brains appear to be more sensitive than adults’ to the effects of mercury.
The teething powders that once contained calomel were found to cause hand and foot rashes and pain from an allergic reaction to the mercury salt.
In Michigan, 80% of high mercury and arsenic levels are attributed to eating fish, but there are controversies about how much disease is caused by methylmercury ingested from fish. Studies of people consuming typical amounts of ocean fish do not demonstrate much negative impact compared to people who do not eat ocean fish. (JAMA. 1998 Aug 26;280(8):701-7) All the same, methylmecury is known from occupational exposures to be dangerous.
How can East Lansing residents avoid mercury exposure?
If you break a fluorescent light, ventilate the room, and follow this MDCH guide.
Do not overindulge your appetite for fish. Fish is a great source of protein, but people who eat large amounts of some fish (like shark, tuna, and salmon) and other animals high on the ocean food chain (like seals and whales) can accumulate high levels of mercury.
You can safely dispose of household mercury (from thermometers and thermostats) through the Ingham County Health Department’s Household Hazardous Waste Collection. Batteries can be safely disposed of locally thanks to the City of East Lansing’s recycling partnership with Battery Giant.
If you work with or around mercury, make sure you and your co-workers have the training and equipment to deal with any toxins in your workplace. As you’ll be reading about in ELi’s upcoming reports, a lack of preparedness for dealing with mercury spills was one reason the problem at the Wastewater Treatment Plant ended up much bigger than it would have otherwise been.
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