What is Mercury & Methylmercury?

What is Mercury?

Mercury is a heavy metal that occurs in liquid form at room temperature. Aristotle, a Greek scholar, named it quicksilver over 2000 years ago because at room temperature it is a silver-coloured liquid. Early physicians used it for medicinal purposes to treat diseases such as syphilis, and problems affecting the intestines, as well as other conditions.

Mercury poisoning was written about as early as the 15th century.  Until the mid-1800s, poisoning resulted mostly from inhaling mercury vapours. In the 1840s, other man-made chemicals were known to cause poisoning.

Some workers were especially vulnerable to this poison, or toxin. Mercury was used by mirror makers. Chemists who came into contact with it in their labs were affected. Hatters, workers who were involved in the production of felt hats in the mid-19th century, were exposed to mercury nitrate. It was used to treat fur skins, such as beaver and rabbit, to make felt hats, thus perhaps the saying, “mad as a hatter”. The children’s book, Alice in Wonderland, is said by some to refer to these victims of mercury poisoning.

Methylmercury – A Dangerous Chemical

Mercury is an element. An element is a substance that cannot be broken down chemically into a simpler form, for example, hydrogen, or oxygen. These elements can be changed by a scientist, who has special knowledge, to form water. They can also be changed by a totally natural process. Water is a compound. It is a substance formed when more than one element is changed chemically, as happens when hydrogen, an element, is combined with another element, oxygen, to form water, a compound. In the case of methylmercury, mercury joins with carbon and hydrogen to form methylmercury.

This transformation, or change, happens by a process called methylation. Bacteria in river sediment cause mercury deposited in wastewater from chemical plants, such as the Dryden Mill, to change into this poisonous compound. Live creatures, such as fish and shellfish, eat it. Humans and animals in turn eat them. If the poisons are of a sufficiently high concentration, they can be harmful to both.

Animals and humans, who had eaten a lot of fish over a long period of time, were seriously affected. The Dryden Mill dumped a lot of chemical waste, or effluent, into the rivers. The poison that resulted was very harmful to the food in the food chain eaten by residents of the English – Wabigoon River systems.

Major Methylmercury Outbreaks

Methylmercury is a substance made from mercury when it is combined with other chemicals, such as chlorine. Fish ate polluted foods poisoned by these substances.  Grain treated with chemicals to control diseases affecting its kernels also poisoned people who ate them.

Some of the countries hit by this disease include Japan, 1953-65, Iraq, 1971-72, Pakistan, 1969, and Ghana, 1969. The most notable outbreaks occurred in Japan and Iraq.

The first recorded large-scale outbreak happened in Japan. The first four cases of the then mysterious disease were presented at the Minamata Health Centre in 1956. Mercury was involved in the process used by the industrial plants. They allowed the release of mercury-contaminated wastewater into Minimata Bay. Fish and shellfish were poisoned. Humans who ate them were consequently subject to this disease, now known as the Minimata disease. As of 1995, 2,200 people have been officially recognized as having this disease and over 10,000 displayed its symptoms. These were the first recorded cases of mercury poisoning contracted through the aquatic, or water food chain.

The world’s use of mercury has increased dramatically since World War II. It is used in many industries: agriculture, electrical, paint, leather tanning as well as paper production, to name just a few. Dentists used it for tooth fillings. Thermometers were made, using this compound.

In 1969 and 1970, scientists discovered that various kinds of fish from many lakes and rivers in Ontario, Quebec, Saskatchewan and Manitoba tested positive for unsafe levels of methylmercury. Lakes in Ontario mentioned regularly at this time included Lake St. Clair, Lake Erie, Clay Lake, as well as others. Over 200 lakes, scientists reported, were being monitored by Ontario government agencies.

People working and living on the English-Wabigoon River systems, studies showed, were being affected in ways similar to that of people in other parts of the world. The Royal Commission on the Northern Environment, 1977-78, established by the Ontario government, drew attention to the plight of those living on the two reserves under study. This was only one of the reasons that favourable legislation was finally passed in 1986.

Mercury Status in Fish

The study reports on mercury levels and other contaminants in fish at various selected sites in the province, including those affecting the two First Nations in question. The levels are still above the Health Canada guidelines of 0.5 parts per million for safe consumption, e.g. northern pike. Others, such as whitefish, are safe for the human diet. Health Canada suggests that populations that consume fish on a regular basis should consider the safer guideline of 0.2 parts per million. It is important that people should refer to the Ontario guidelines for the consumption of mercury-contaminated freshwater fish.

Unfortunately, science cannot yet say how long the poisonous mercury will last in affected waters, but it could be several decades. Almost forty years have gone by since mercury poisoning was first discovered in the area studied in the Cosway Report. This toxin remains a serious health threat.


Little new information on a definition of methylmercury poisoning contamination has shown up in studies on the subject.

Of concern is that the Mercury Disability Board does not have access to data gathered by Health Canada on levels of methylmercury in hair and blood samples of inhabitants tested in both communities. The data is not shared.

It is well established in various studies that child development problems occur in many children in both communities. This is evident in learning and behavioural problems. Studies should be conducted to determine the reality and extent of these problems.

There are other issues with regard to the study of data contained in clinical assessment forms. Important information on various aspects of the after-effects of contamination could become evident.

Mercury Disability Board

A Historical Report: 1986-2001

The full report (available here) consists of three volumes. It was written by a university student, Sylvia Cosway, who was working on her Ph.D. at the University of Manitoba. The entire study covers over 400 pages in a language more suited to readers with special training in medicine and chemistry. This booklet is written in a simpler style. It avoids many highly technical terms as well most of the details useful primarily to professionals.