Environmental Biology

November 27, 1998

MERCURY POISIONING

THE MINAMATA TRAGEDY

In 1907 the Chisso Corporation built a factory in the small fishing village of Minamata, Japan along the shore of Minamata Bay. Fish populations began to decline in 1925, by 1950 fish began to float to the surface, shellfish and other aquatic organisms began to perish. Cats were the first land animals to show signs of distress, in 1952 they began having convulsions, whirling in violent circles, slobbering, becoming disoriented and throwing themselves into the sea. By 1953 dogs, pigs, birds and other animals started exhibiting the same strange behavior. Virtually no cats to be found in Minamata, Japan as of 1958.

A little girl age five years and eleven months old; who had been very bright suddenly showed signs of brain damage, and started having the same symptoms as the Minamata cats in 1956; this is the first documented case of human mercury contamination. Soon after her diagnosis, many more children began to demonstrate symptoms of the strange disease; babies were born with it and eventually adults started to show the same symptoms.

The Chisso Corporation was finally linked as the source of the disease because of their dumping of mercury into Minamata Bay and its contributory waters. Chisso began dumping mercury into the waters beginning in the 1930's and continued to dump through out most of the 1960's. Chisso denied all allegations for as long as they possibly could. The poisoning became known as Minamata Disease, and its victims rallied together and took the Chisso Corporation to court to sue for damages. It wasn't until March 20, 1973 that the victims triumphed and won their case. As of 1992 the number of people officially diagnosed as having Minamata disease totaled 2,252 people; 1,043 were dead and another 12,127 people were waiting to be tested. As recently as March of 1997, the number of people still waiting to be tested was 1,968.

Efforts were made to restore the bay; in 1974 a three-mile long net was placed around the bay to contain contaminated fish. After 53 years of being considered deadly waters, in 1998 the bay was declared safe again. Chisso finally took responsibility and have made their final payments.

HOW MERCURY ENTERS AND AFFECTS THE FOOD CHAIN

Mercury enters the atmosphere from a variety of sources, both natural and by humans. Natural mercury sources include volcano eruptions, groundwater seepage, and ocean evaporation. It is estimated that humans contribute a much greater amount. In the US alone it is estimated that we contribute approximately 243 tons of mercury into the air per year. It is believed that 85% of it is released from combustion sources that can be broken down into the following components:

27% Medical Waste Incineration

23% Municipal Waste Incineration

21% Utility Boilers

12% Commercial/Industrial Boilers

Once released into the environment, mercury can circulate through air, water and soil for extremely long time periods. The most toxic form of mercury is when it undergoes biological changes through its reactions with bacteria, producing methylmercury; it is this chronically toxic form that devastated the ecosystem of Minamata, Japan.

When methylmercury is present within aquatic ecosystems, organisms absorb the toxin, and then the toxins accumulate within their fatty tissues. An individual aquatic organism may contain only a very small amount of methylmercury, however as predators consume more and more fish, for example, the toxins build up within their fatty tissues. As we move up the food chain the levels of methylmercury magnifies. Once in the bodies of primarily mammals, methylmercury attacks the brain, liver and kidney causing rapid deterioration of these vital organs, resulting in severe irreversible damage. In the water, mercury has a half-life of approximately 200 days, once ingested the half-life is increased to over nine months. The only means of elimination are excretion through feces, breast milk and urination.

WHAT ARE THE RISKS?

Although everyone who consumes a lot of fish is at risk, pregnant women and their fetuses along with young children, are the greatest at risk of the human population.

Women exposed to the poison while pregnant have more miscarriages, and give birth to more babies with birth defects. The birth defects come in a wide variety and depend on the amount of exposure to methylmercury. The babies are born disfigured or missing limbs, mentally retarded and with nervous system dysfunction in most cases. Methymercury poisoning has also been linked as one of the main causes of Cerebral Palsy. Development is greatly slowed and in almost all cases the babies suffer from convulsive seizures. Other side effects do exist but are too numerous to mention.

Children who are exposed after birth also suffer side effects from the poisoning. The list of symptoms include:

· Impairment of peripheral vision

· Disturbances in Sensations (pins and needles and/or numbness)

· Uncoordinated Movements (as in writing, fine motor skills, etc.)

· Speech Impairment

· Hearing Impairment

· Walking Impairment

· Delays in Motor and Language Development

· Mental Disturbances

· Impacts on the Central Nervous System

· Death, in extreme cases

· Other suspected side effects that have not been proven yet include effects on the reproductive system, immune system and to have genotoxic effects.

MERCURY CONCERNS IN THE UNITED STATES

Currently 40 states have advisories issued against eating fish that comes from more than one their lakes, rivers and streams. North Carolina is no exception. In 1993, North Carolina had advisories on 10 separate water bodies statewide and 27 advisories against all pollutants, species and groups. By 1996 this had increased to 15 advisories on separate water bodies statewide and 46 advisories against all pollutants, species and groups. From 1993 to 1996 there has been a 50% increase in the total advisories issued statewide.

Portland, Oregon; the Great Lakes Region; areas under going heavy deforestation and several other areas throughout the United States are dealing with a steady increase of methylmercury poisonings; if not stopped it could lead to another disaster like the one that occurred in Minamata, Japan.

Recently the EPA (Environmental Protection Agency) has been trying to devise a plan of action to combat the mercury pollution problem in the United States. Some standards and regulations have been set for medical and municipal waste incineration processes, however they fall short of what is needed. At the request of Congress coal burning energy production plants are exempt from the standards and regulations even though they are the leading point source of the contamination. The National Resource Defense Council (NRDC) has recently filed a lawsuit against the EPA demanding that higher standards and better regulation practices be employed, they are claiming that the EPA is falling short of its responsibilities.

The FDA (Food and Drug Administration) has declared that fish containing 1ppm or less of mercury is safe for consumption; this calculation is referred to as the Reference Dose (RfD). The EPA also uses this formula to determine their calculations of the effects of daily exposure to the human populations. They are continuing studies and have been adjusting the RfD according to those findings. The studies have been on going for years in areas where know high mercury accumulations have been reported.

CONCLUSION

Throughout the onset of industrialization and modernization mercury poisoning has been a problem. Severe out breaks of Minamata disease have occurred in various parts of the world, including Iraq, Canada and New Zealand; just to name a few. The United States is now facing the possibility of an outbreak of this devastating "Disease". We must employ higher standards and regulations to reduce the vast amounts of mercury we are placing into our environment on a daily basis. We must identify all point sources we can and find a way to reduce their mercury emissions; means to clean up existing pollution must also be placed into action. Public education and awareness must also be addressed if we are to have any hopes of avoiding a similar disaster like the one that took place in Minamata, Japan. The time is now to learn from our mistakes of the past.

SOURCES:

Smith; W. Eugene and Aileen M. - Minamata - (An Alskog-Sensorium Book) Holt, Rhinehardt and Winston, New York © 1975

U.S. News 08/11/97: A Bay, and People Safe Again http://www.usnews/issue/970811/11wrbr.htm

Mercury Poisoning: The Legacy of Minamata, Japan http://www.essential.org/orgs/cchw/ehm/mar97.html

MINAMATA Tokyo Exposition http://www.tama.or.jp/~sena/minamata/tokyoten/ehome.html

Science Behind the Mercury Study http://www.cnt.org/air/hg_sci.htm

NRDC Pro: Contaminated Catch - Executive Summary http://www.nrdc.org/nrdc/nrdcpro/fppubl.html

Populations at risk of Methylmercury http://www.cnt.org/air/hg_risk.htm

Methylmercury poisoning: The Minamata Bay disaster http://www.idrc.ca/books/reports/1997/19-02e.html

The Toxic Cycle http://www.portland.com/mercury/mainchrt.htm

Mercury Facts http://www.research.fsu.edu/RinR/Fal_Wn97/merc_fac.htm

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Sandra Justus

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