Mercury is a natural element with the symbol Hg that is found in air, water and soil.
This material is also known as quicksilver in Greek .
Exposure to even small amounts may cause serious health problems and is a threat to the development of the child in the womb and early life.
Hg may have toxic effects on the nervous system, digestive system, immune system, lungs, kidneys, skin and eyes.
According to the WHO (World Health Organization), mercury is one of the top ten chemicals or groups of chemicals important to public health.
People are mainly exposed to methylmercury, an organic compound, when they eat fish and shellfish containing this compound.
Methylmercury is very different from ethylmercury. Ethyl mercury is used as a preservative in some vaccines and does not pose a health risk.
mercury
Mercury exists in different forms:
- Elemental (or metallic) and inorganic (to which people may be exposed through occupation).
- Organic (eg, methylmercury, which people may be exposed to through the diet).
Its different forms differ in terms of the degree of toxicity and its effect on the nervous, digestive and immune systems of the body and the lungs, kidneys, skin and eyes.
This substance occurs naturally in the earth’s crust.
This material is released in the environment from volcanic activities, weathering of rocks and as a result of human activities.
Human activities are the main cause of this substance, including:
- Coal-fired power plants
- Residential coal burning for heating and cooking
- Industrial processes
- Garbage incinerators
- Mining of mercury, gold and other metals.
Once in the environment, mercury can be converted to methylmercury by bacteria.
Under different conditions, people may be exposed to this substance in any way.
However, exposure occurs mainly through the consumption of fish and shellfish contaminated with methylmercury and through the inhalation of its original vapors by workers during industrial processes. Cooking does not destroy mercury.
Exposure to mercury
All humans are exposed to some level of mercury.
Most people are exposed to low levels of this substance, often through chronic exposure (long-term continuous or intermittent contact).
However, some people are exposed to high amounts of Hg.
including acute exposure (exposure for a short period of time, often less than a day). An example of acute exposure can occur due to an industrial accident.
What are the factors that determine the health effects and severity of this substance:
- type of mercury
- dose
- The age or developmental stage of the exposed person (the fetus is most sensitive).
- Duration of exposure
- Route of exposure (inhalation, ingestion or skin contact).
In general, two groups are more sensitive to the effects of this substance.
The fetus is more affected by this substance because it is growing. And it can negatively affect the development of the child’s brain and nervous system.
The primary health effect of methylmercury is the disruption of neural development.
Thus, cognitive thinking, memory, attention, language, and visuospatial motor skills may be affected in children exposed to methylmercury as fetuses.
The second group is people who are regularly exposed to high levels of mercury (such as populations that rely on subsistence fishing or people who are exposed to this substance through their jobs).
Among the selected subsistence fishing populations, 17,000 children showed cognitive impairment (mild mental retardation) caused by consuming fish containing this substance.
A notable example of exposure to this substance affecting public health occurred in Minamata, Japan, from 1932 to 1968.
where the acetic acid production plant discharged liquid waste into Minamata Bay.
The discharge contained high concentrations of methylmercury. The bay was rich in fish and oysters and provided the main livelihood for local residents and fishermen from other areas.
For many years, no one knew that the fish was contaminated with Hg, and this caused a strange disease in the local community and other areas.
At least 50,000 people were partially affected, and more than 2,000 cases of Minamata disease were confirmed.
Minamata disease peaked in the 1950s, with severe brain damage, paralysis, incoherent speech, and delirium.
Health effects of mercury exposure
Elements and methylmercury are toxic to central and peripheral nervous system.
- Inhaling its vapor can cause harmful effects on the nervous, digestive and immune systems of the body, lungs and kidneys.
- It may be fatal.
- Inorganic salts of mercury are corrosive to the skin, eyes and digestive system.
- If swallowed, it may cause kidney poisoning.
Neurological and behavioral disorders may be observed after inhalation, ingestion or skin exposure in its various compounds.
Symptoms of neurological disorders
- Includes vibration
- insomnia
- Memory loss
- Neuromuscular effects
- Headache
- Cognitive and motor dysfunction
Mild, clinical signs of central nervous system toxicity can be seen in workers exposed to initial airborne mercury levels of 20 µg/m3 or more for several years.
Symptoms such as kidney effects have been reported, ranging from increased protein in the urine to kidney failure.
How to reduce human exposure to mercury sources
There are several ways to prevent adverse health effects, including:
- Promoting clean energy
- Stop using this substance in gold mining
- Eliminate extraction of Hg
- Gradual removal of unnecessary products containing this substance
- Promote the use of clean energy sources that do not burn coal.
Burning coal for power and heat is the main source of mercury.
Coal contains mercury and other hazardous air pollutants that are emitted by burning coal in electric power plants, industrial boilers, and household stoves.
Eliminate mercury mining and its use in gold mining and other industrial processes
This substance is an element that does not disappear. Therefore, the existing mercury is in use and can be recycled for other essential uses, and it does not need to be mined anymore.
The use of mercury in artisanal and small-scale mining, especially gold, is dangerous and has health effects on vulnerable populations.
Non-Hg (non-cyanide) gold mining techniques should be promoted and implemented, and where this material is still used, safer work practices should be used to avoid exposure.
Eliminate the use of unnecessary products containing this substance and carry out the safe transport, use and disposal of products containing Hg.
It is found in many products, including:
- Batteries
- Measuring devices, such as thermometers and barometers
- the switch
- Electric relay in the equipment
- Lamps (including some types of lamps)
- dental amalgam (for tooth filling)
- Skin lightening products and other cosmetics
Mercury in battery manufacturing
Pharmacology
A wide range of measures are being taken to reduce the level of this substance in products or to phase out products containing mercury.
In healthcare, thermometers and barometers containing mercury are being replaced by other devices.
Dental amalgam is used in almost all countries.
A WHO expert consultation in 2009 concluded that a global ban on amalgam would be problematic in the short term for public health and the dental health sector.
But disease prevention and amalgam alternatives should be promoted, such as:
- Research and development of cost-effective options
- Training of dental professionals
- Increase public awareness
Inorganic mercury is added in significant amounts to some skin lightening products.
Many countries have banned skin lightening products containing mercury because it is dangerous to human health.
Use of mercury in vaccines and pharmaceuticals
This substance, like thiomersal (ethylmercury), is used in very small amounts as a preservative in some vaccines and medicines.
Mercury in vaccine production
Compared to methylmercury, ethylmercury is very different.
Mercury is quickly broken down by the body and does not accumulate.
WHO has closely monitored the scientific evidence for the use of thimerosal as a vaccine preservative for more than 10 years and has consistently reached the same conclusion:
There is no evidence that the amount of thimerosal used in vaccines poses a health risk.