[From Healing the Harm, Section One: "The Pollution Problems Created by Medical Waste"]

Mercury is a persistent, bioaccumulative toxin that has been linked to numerous health effects in wildlife and humans. Its natural state under ambient temperature is a silvery-white liquid that changes easily from solid to liquid to gas, allowing it to circulate in the atmosphere and the environment. There are three major forms of mercury that circulate in the atmosphere but the one of most concern for humans and wildlife is methylmercury, because it builds up in the muscle tissue.

Health Effects

Mercury is a potent neurotoxin, which means it attacks the body's central nervous system; it can also harm the brain, kidneys and lungs. It can cross the blood-brain barrier as well as the placenta. Neurotoxic risks to developing fetuses and young children are primary reasons for fish-consumption advisories, aimed at discouraging pregnant women, women of child-bearing age, and young children from eating too much fish. Studies done on women who ate methylmercury-contaminated fish or grain showed that even when the mothers showed few effects of exposure, their infants demonstrated nervous-system damage.

Symptoms of Mercury Poisoning:

* Impairment of the peripheral vision;

* Disturbances in sensations ("pins and needles" feelings, numbness) usually in the hands feet and sometimes around the mouth;

* Lack of coordination of movements, such as writing;

* Impairment of speech, hearing, walking;

* Muscle weakness;

* Skin rashes;

* Mood swings;

* Memory loss;

* Mental disturbances.

Methylmercury has been shown to cause tumors in mice at high doses. It is classified as a reproductive toxin, because data indicate that methylmercury could increase the frequency of mutation in human eggs and sperm. Methylmercury is also an endocrine-disrupting chemical, impairing normal thyroid functions, but these effects appear only at very high exposures.

Many animals are also affected by mercury. Fish accumulate mercury in their muscle tissue. Animals which rely on fish for a large portion of their diets, such as loons, eagles, mink and osprey are at risk from contaminated fish and may suffer neurological impairment as a result.

Exposure

Humans are most likely to be exposed to mercury through the consumption of fish. Exposure can also take place through the ingestion of water and other food sources and through the skin. In some workplaces (such as in a health care setting), there is also a risk of mercury inhalation.

Methylmercury accumulates in the environment and in wildlife, but the highest concentrations appear in the muscle tissue of fish, particularly fish at the top of the aquatic food chain.

Measured values of methylmercury in fish from various areas of the U.S. range from less than 0.1 parts per million (ppm) to 8.94 ppm; typical values are between 0.11 and 0.26 ppm.

Tuna 0.206

Shrimp 0.047

Pollock 0.15

Salmon 0.035

Cod 0.121

Catfish 0.088 &.16

Clam 0.023

Flounder 0.092

Crab 0.117

Scallop 0.042

Source: MERCURY STUDY REPORT TO CONGRESS, Volume I: Executive Summary, SAB Review draft, USEPA, June 1996.

According to the US EPA, fish consumption advisories for mercury increased 46% from 1993 to 1995 (899 to 1,308). The number of states that have mercury advisories has risen steadily from 27 in 1993 to 37 in 1996. Ten states have issued 90% of the 1,308 mercury advisories in effect: Minnesota, Wisconsin, Florida, North Dakota, Massachusetts, New Jersey, Michigan, New Mexico, South Carolina and Georgia.

Note that about one gram of mercury will contaminate a twenty-acre lake with enough mercury to cause fish advisories. For comparison, a teaspoon of mercury weighs about 70 grams. One thermostat contains about 3 grams of mercury, one electrical switch about 3.5 grams of mercury, and 100 fluorescent lamps contain about 4 grams of mercury.

Elemental mercury can be inhaled easily and is readily absorbed into the bloodstream. This can occur when an item containing elemental mercury (like a thermometer or a sphygmomanometer) breaks, spilling the mercury into the open. This type of exposure allows the mercury to penetrate the blood-brain and placental barriers in humans and wildlife.

Another controversial source of human exposure to mercury is dental amalgam. Amalgams, or mixtures, of mercury, silver, copper and tin have been commonly used to fill cavities. Studies have shown that mercury vapor is released from mercury amalgam fillings.

The half-life of mercury, or the time needed to excrete half of a dose to which one is exposed at any one time, is 44 to 80 days. Mercury is excreted via feces, urine and breast milk.

Where Does Mercury Pollution Come From?

Mercury has been widely used in many industrial processes because of its diverse properties: it responds to temperature and pressure changes (making it useful for thermometers and blood-pressure devices), conducts electricity, and forms alloys with other metals. Numerous studies show that mercury contamination of the environment is taking place due to atmospheric transport and deposition of mercury coming from incinerators. The Mercury Report to Congress listed medical waste incinerators as the number-two emitter of mercury.

Some Sources Of Mercury In Health Care & Their Alternatives

Mercury is used in number of medical products. The good news is that there are alternatives for most of those items. The following is a list of some mercury-containing medical products, and their safer counterparts:

Sources: MERCURY IN THE HEALTH CARE SECTOR: THE COST OF ALTERNATIVE PRODUCTS (Draft), Pollution Probe, November 1996, p. 15. Personal Communication with Dr. Paul Kirkegaard, DDS, St. Paul, MN, April 1997.

* It must be noted that one common alternative dental amalgam contains Bisphenol A, an endocrine disrupting chemical. However, there are other amalgams available which contain neither mercury nor Bisphenol A.