Mercury: A Hidden Threat in Everyday Life, part 1

Mercury is a unique substance: it is the only metal that exists in a liquid state at room temperature. Thanks to its unusual properties, it has fascinated people since ancient times. It was used in medicine as a remedy, in alchemy as an “element of transformation,” and later in industry—for making mirrors, thermometers, lamps, and other products.

However, over time, it became clear that behind its outer “magic” lies a serious danger: mercury is one of the most toxic elements on Earth, capable of wreaking havoc on the nervous, immune, and other systems of the body even in minimal doses. Understanding its toxicity marked an important turning point in both medical and environmental history.

How Humanity Learned About Mercury’s Dangers

The history of mercury use stretches back thousands of years. In ancient Chinese, Egyptian, and Greek medical texts, it was described as a universal cure, capable of driving out disease and prolonging life. It was used for skin conditions, parasites, and syphilis long before the discovery of pathogens. Side effects, including severe poisoning, were seen as an acceptable price for healing.

In the Middle Ages and the Renaissance, mercury became a central substance in alchemy. Its fluidity and metallic sheen symbolized spirit and the transition between worlds. Alchemists believed mercury was a prime element capable of linking matter and spirit. Many of them, including well-known physicians, suffered from chronic mercury poisoning but considered it a necessary sacrifice in pursuit of the “philosopher’s stone.”

From the 17th to the 19th century, mercury saw widespread use in both industry and medicine. It was added to medications and used in the production of mirrors, textiles, and hats. It was during this period that the phenomenon later known as “mad hatter syndrome” emerged—chronic poisoning among workers who processed felt with mercury. Symptoms included tremors, insomnia, irritability, and sometimes hallucinations and behavioral changes. This phenomenon was later immortalized in the character of the Mad Hatter in Lewis Carroll’s Alice in Wonderland.

True awareness of mercury’s extreme toxicity came only in the 20th century, after the tragedy in the Japanese city of Minamata. In the 1950s, a local chemical factory had been dumping mercury compounds into the sea for decades. These compounds accumulated in sediments and were transformed into methylmercury—the most dangerous organic form. Fish contaminated with the toxin were a staple in the diet of local residents. As a result, people developed severe neurological disorders: convulsions, blindness, impaired speech and coordination. Children were born with profound congenital abnormalities. Thus was born the term “Minamata disease,” which became a symbol of industrial poisoning and a turning point in the field of toxicology.

By then, it had become clear that mercury was not a local but a global issue. Other tragedies followed Minamata—some of which we will now discuss. These events confirmed that mercury knows no borders, and its impact can be devastating even in remote parts of the world. Each new incident increased pressure on governments to introduce stricter mercury regulations and pushed scientists to search for alternatives and new purification methods. In 2013, decades after the tragedy in Japan, the Minamata Convention was adopted—the first global agreement regulating the use of mercury, signed by more than 130 countries.

How Mercury Enters Our Environment

Mercury is a heavy metal that naturally resides deep within the Earth’s crust and, under natural conditions, rarely comes into contact with living organisms. Our bodies are not adapted to its presence, as biological evolution occurred without constant exposure to this element. It is humans who extract mercury from the Earth and release it into the biosphere, where it begins to circulate freely, accumulate, and poison the environment.

One of the main pathways of mercury pollution is through the atmosphere. When coal — especially high-sulfur “dirty” coal — is burned, and to a lesser extent oil and petroleum products, mercury is released into the air in the form of vapor and fine particles. At the same time, sulfur compounds are emitted, which, when deposited into water bodies, create favorable conditions for the conversion of mercury into methylmercury — its most toxic form. This combination of mercury and sulfur emissions results in a “double whammy” for ecosystems. Mercury then settles with precipitation, enters the soil, rivers, and water bodies — and eventually reaches the oceans. This process affects even the most remote areas of the planet.

Source: How does toxic mercury get into fish? (WHOI)

Medical and household products also remain sources of mercury. Dental amalgam fillings, which contain around 50% metallic mercury, are still used in some countries. When old fillings are removed or medical waste is incinerated, mercury is released into the environment. On average, about 100 tons of mercury from dental amalgams enter the environment globally each year. According to WHO, 30–40% of this mercury ends up in solid waste, accumulating in water, soil, and air without decomposing. In the U.S. alone, dental offices discharge around 5.1 tons of mercury annually into wastewater treatment systems. In Canada, around 1.3 tons of new amalgam fillings are placed each year, and the number of old fillings being removed has increased by about 70% since 2000. The good news: the introduction of ISO-certified amalgam separators in dental offices across Canada has significantly reduced mercury discharges into wastewater—by up to 95%.

Industrial dumping is another ongoing problem. In the second half of the 20th century—especially from the 1950s to the 1970s—industrial waste containing heavy metals, including mercury, was dumped into the ocean in metal containers that were considered sealed. This practice was widespread both in Western countries and the USSR. Over time, the walls of these containers corroded, and toxic substances began to leak into seawater and marine sediments. These “burials” still pose a serious threat to ocean health.

Once in water, mercury undergoes biochemical transformations. Once mercury enters the water, it undergoes biochemical transformations. Although it is mostly released into the environment in a relatively harmless inorganic form, it can convert into methylmercury in marine environments—a much more toxic and easily absorbed compound. This process occurs under low-oxygen conditions, both in seabed sediments and in deeper ocean layers where specialized anaerobic bacteria reside. These bacteria use sulfate for respiration and, in the process, methylate mercury—especially when organic particles carrying mercury from the surface are present. The resulting methylmercury accumulates in plankton, then in small fish, and eventually in large predators such as tuna, shark, and swordfish. The higher a fish is in the food chain and the longer it lives, the more mercury it tends to accumulate. Ultimately, mercury returns to humans through food—now in its most dangerous form.

An official seafood Recommendations: Regular consumption of large amounts of seafood increases the risk of mercury poisoning, especially for children and pregnant women. The U.S. EPA and FDA recommend that women who are pregnant, nursing, or may become pregnant, as well as young children, avoid swordfish, shark, king mackerel, and tilefish entirely. White (albacore) tuna should be limited to 6 ounces (170 g) per week, and other fish and shellfish to 12 ounces (340 g) per week. If these limits are exceeded one week, intake should be reduced the next to maintain safe averages. Adults are also advised to limit consumption of large predatory fish and check local advisories on the safety of fish from lakes, rivers, and ponds.

Another route is via wastewater and industrial runoff. For decades, chemical, pulp and paper, metallurgical, and rubber manufacturing facilities—including plants like “Radikal” in Kyiv—discharged mercury-containing waste into water bodies. Mercury compounds were used as catalysts, especially in rubber production. In the absence of purification and oversight, these industries became local hotspots of heavy pollution, with consequences still felt today.

Environmental Disaster in the USSR (Modern-Day Ukraine)

The “Radikal” plant in Kyiv is one of the most severe mercury contamination cases in Eastern Europe. After production was halted in 1996, the facility became a long-term and dangerous source of environmental pollution.

Founded in 1951, the plant produced chlorine and caustic soda using mercury-cell technology. Dozens of tons of metallic mercury were used in the process. After closure, most of this material remained onsite—not sealed in containers, but literally spilled across the floors of industrial buildings. This dramatically increases the risk of evaporation and leakage into the environment.

According to environmental agencies, around 200 tons of metallic mercury and mercury sludge are still present on the grounds of the “Radikal” site. Air, soil, and groundwater contamination extends beyond the plant boundaries. Due to the site’s proximity to the Dnipro River and the local drainage system, toxins may have spread to nearby residential neighborhoods, including high-rise apartment areas.

Attempts at demercurization have been made, but a significant amount of mercury remains exposed. Proper disposal requires substantial financial and technical resources—resources that are entirely lacking at the local level.

Mercury and Environmental Disasters in Canada

Like other industrialized countries, Canada has faced serious consequences from mercury contamination. One of the most well-known cases is the discharge of mercury-laden waste into the Wabigoon River (Ontario) by Dryden Chemicals Ltd. between 1962 and 1970. Approximately 10 tons of mercury were released into the river, leading to widespread poisoning among the Grassy Narrows and Whitedog First Nations, whose traditional lifestyle depended heavily on fishing.

The affected individuals developed typical symptoms of chronic methylmercury poisoning: tremors, impaired coordination, and memory loss. This case became known as the “Ontario Minamata disease,” in reference to the tragedy in Japan, and is considered one of the worst environmental disasters in Canadian history.

Even after 50 years, the river sediments remain hazardous, and fishing in the area is still restricted. A full-scale cleanup has never been carried out.

Another example is the city of Trail (British Columbia), where the Teck Cominco smelter discharged mercury-containing slag into the Columbia River for decades. It is estimated that 1.6 to 3.6 tons of mercury entered the river each year, with part of the contamination flowing downstream into the United States—making the incident transboundary in nature.

Since the late 1990s, cleanup operations have been implemented and ongoing environmental monitoring has been established. According to official reports, mercury levels in the water have decreased to meet regulatory standards, but monitoring continues.

These cases illustrate how devastating and long-lasting mercury contamination can be—and why strict environmental oversight and systemic restoration efforts are essential after such spills.

Historical and Modern Uses of Mercury

For centuries, mercury has been widely used in various fields—from medicine and metallurgy to cosmetics and religious practices. Despite growing knowledge of its toxicity, many applications persisted for decades—and in some countries, they are still in use today.

In Medicine:

• Dentistry: Amalgam fillings with high metallic mercury content are still in use (e.g., in Canada and developing countries), although in the European Union, all amalgam fillings will be completely banned starting January 1, 2025.
• Medical devices: Mercury-containing thermometers, sphygmomanometers, and manometers were once standard and are now being gradually phased out.
• Vaccines: Thimerosal (ethylmercury), a preservative used in multi-dose vials, is still in limited use today.
• Pharmacology (historically): Mercuric chloride (corrosive sublimate) and calomel were once used as antiseptics and laxatives.
• Topical treatments: Previously used in antibacterial ointments; in some countries, skin-lightening creams containing mercury salts are still available.

In Industry:

• Chemicals: Used as a catalyst or in electrolysis for the production of chlorine, plastics, and rubber.
• Gold and silver mining: The amalgamation method is still used in illegal and small-scale mining operations.
• Lighting and equipment: Fluorescent lamps, mirrors (previously coated with amalgam).
• Electronics: Older button batteries (mercury oxide).

In Daily Life and Culture:

• Household items: Mercury thermometers, lamps, and vintage electrical devices can still pose a hazard if broken.
• Tooth powder with mercury: In the 19th–20th centuries, mercuric chloride was added to tooth powders for hygiene. These were later banned due to their toxicity.
• Traditional practices: Liquid mercury (“azogue”) has been used in rituals in parts of Latin America and Asia.
• Food risks: Methylmercury formed in aquatic environments accumulates in fish—today, this is the main source of mercury exposure in humans.

Understanding the potential sources of mercury in daily life helps reduce the risk of chronic intoxication. Mercury tends to accumulate in body tissues, and symptoms may develop subtly—making it especially important to make conscious choices when it comes to food, cosmetics, and even old household items.

Conclusion

Tragedies such as “Minamata disease” in Japan and poisonings in Canada have revealed how devastating mercury exposure can be to both health and the environment. These events became turning points that led to international agreements aimed at reducing mercury use.

Modern understanding of mercury toxicity is the result of many mistakes, tragedies, and scientific efforts. If we have truly learned from the past, the next step must include not only the disposal of accumulated waste but also a re-evaluation of all sectors where mercury is still used—especially in medicine and healthcare.