Mercury’s many toxicities

Shiny, liquid metal mercury has fascinated people for centuries. However, it is now well known to be highly toxic, with the World Health Organisation (WHO) designating it a top ten chemical of major public health concern.

In this article, we give an overview of the different forms of mercury, how they get into the human body, and their effects on its systems. We touch on who’s most vulnerable, the tragic mercury poisoning epidemic that precipitated global action, and explain why mercury monitoring is a necessity to protect individuals across places and generations. Enviro Technology are proud to offer a range of solutions for mercury monitoring – get in touch with us today to find out more.

Forms of mercury

People can be exposed to different types of mercury:

• Elemental mercury is the silvery, metallic liquid that you might recognise. However, it also vaporises readily into a toxic, odourless gas. Sources of elemental mercury are usually industrial processes that burn coal or otherwise involve mercury-containing materials; breakage of products or equipment with mercury components; or dentistry, if mercury-containing dental amalgam is used.
• Inorganic mercury refers to mercury salts that have been formed when mercury reacts with other elements such as chlorine, sulphur, or oxygen. Inorganic mercury is used in the production of batteries, synthetic materials, and prohibited skin-lightening products.
• Organic mercury is created when mercury combines with carbon, either as a result of biological or human activity. The most common type of organic mercury is methylmercury, which is produced when bacteria metabolise mercury present in the environment. Highly toxic methylmercury can build up in larger animals (such as fish) when they eat other organisms that have themselves consumed the compound. People are at a high risk when they eat fish and shellfish that have been contaminated in this way. Organic mercury can also be human-made. For example, it was once commonly used in agricultural pesticides and in paints.

Routes of exposure

The different forms of mercury are associated with different pathways into the body. The main route of exposure to elemental mercury is inhalation after it has vaporised. Inorganic and organic mercury are usually absorbed in the digestive tract, the latter principally following ingestion of contaminated fish. However, absorption through the skin is also possible for these forms.

Health impacts

Mercury intoxication has been associated with over 250 symptoms. The health effects experienced depend on the form of mercury a person is exposed to (see the graphic below), the level of exposure, and the person’s vulnerability or health status. An academic article published in a public health journal details the toxic effects of mercury on some of the body’s systems. We provide a summary here.

• Effects on the nervous system
  • The nervous system is the primary casualty of mercury poisoning. Mercury accumulates in nervous tissue and impairs nerve and brain cell energy generation, maintenance, and detoxification. This results in psychological, sensory, and motor control symptoms.
• Effects on the pulmonary and cardiovascular systems
  • Inhalation of mercury vapours can cause chemical stress in lung cells, leading to coughing, wheezing, and chest tightness, and potentially inducing lung disease. Mercury can also pass into the blood, where it may reduce oxygen-carrying capacity, or accumulate in the heart and impair its ability to pump blood.
• Effects on the renal system
  • As the organs responsible for filtering the blood, mercury can reach high levels in the kidneys. It can damage the tubules and other structures that regulate the body’s fluid levels and wastes, potentially leading to kidney failure.
• Effects on the digestive system
  • Mercury’s toxic effects on the digestive system are less understood. However, the element and its compounds have been found to inhibit enzyme production and destroy intestinal bacteria, leading to digestive disturbance.
• Effects on the immune system
  • Mercury can alter the production and function of immune cells, making the body less able to fight disease-causing agents. This can increase susceptibility to infections. Immune dysregulation may also lead to autoimmune conditions, where the immune system targets the body’s own cells and tissues.

Image source: The International Labour Organisation

Children are particularly vulnerable

Mercury toxicity is extremely harmful to children both before and after birth. Mercury can pass through the placenta to the unborn foetus, while young children may inhale larger doses of mercury than adults due to their larger lung area relative to body weight, faster breathing, and the tendency for heavy mercury to accumulate at lower heights, near a child’s breathing zone. Many health impacts are similar to those seen in adults. However, the effects on the nervous system are more profound given that unborn and young children are undergoing intensive development. Infantile exposure can irreversibly damage the structure and function of the growing brain. This can lead to life-long problems with cognition, communication, sensory perception, and coordination.

Minamata disease

Minamata disease was originally used to describe the mysterious neurological symptoms exhibited by residents of the Japanese coastal city of Minamata during the 1950s. These symptoms included a lack of muscle coordination, speech impairment, narrowed vision and, in severe cases, coma and rapid death. A congenital form of the disease was also identified, affecting foetuses in the womb.

Investigations revealed that the residents were being poisoned by organic mercury. The source was pinpointed to a local factory that had been discharging mercury-containing wastewater into the sea for over two decades. Over that time, the mercury had been ingested by sea animals of increasing size, eventually accumulating to dangerous levels in the fish that were the Minamata residents’ staple food. Shockingly, the factory in question continued utilising mercury for twelve years after the first case of Minamata disease was observed.

While some symptoms of the disease are treatable, especially if exposure has been low, others are largely irreversible. Furthermore, the congenital form of Minamata disease means that future generations were directly implicated in the tragedy. Needless to say, the effects are still felt today. In 2013, the United Nations established a new convention dedicated to eradicating mercury-related harm and named it after the Japanese city.

Is mercury still a health concern?

The two most notable mercury poisoning incidents both involved consumption of contaminated foodstuffs. They occurred in Japan (as discussed) and in Iraq in the 1970s, when people fell ill after baking bread with grain that had been treated with a mercury fungicide. Fortunately, mercury agrochemicals have been banned in many countries since, including in the UK. The UK also has rules in place to ensure that food businesses take measures to maintain food safety and acceptable levels of contaminants, if they’re present. In addition, The Food Standards Agency conducts its own research and undertakes official monitoring of high-risk products, such as certain types of shellfish.

Efforts are ongoing under the 2013 Minamata Convention to phase out widely-used mercury-containing products. This means that exposure is increasingly most likely to occur in workplaces that handle mercury. Because of the prevalence of artisanal and small-scale gold mining (which uses mercury) and industrial developments in sub-Saharan Africa, South America, and East and South-east Asia, the situation is most critical in these regions.

All the same, the UN Environment Programme state that everyone is exposed to some level of mercury. Indeed, it persists in the environment and can travel far from the site of emission. Atmospheric mercury concentrations are currently 450% above natural levels, and, if the substance builds up in an ecosystem, it can be passed dangerously up the food chain, as happened in Minamata. Experts warn that it is very likely that no safe level of exposure to mercury exists. This is why, if activities might involve the element, monitoring is vital to protect public and environmental health, now and in the future, no matter the context.

Enviro Technology’s Paul Keeling can help find the right mercury monitoring solution for you.