One of the group of so-called heavy metals which accumulate in the body, mercury has been described as one of the most toxic substances known to man, particularly the organic forms of mercury such as methylmercury and ethylmercury. These forms are created by micro-organisms in the sea and lakes, from inorganic mercury salts which have been discharged in industrial effluent. Fish consume the plankton which contain these toxic forms of mercury, and humans can be poisoned by the fish, especially the larger varieties such as tuna, which can accumulate quite large quantities of mercury from eating many smaller fish. In 1953, when mercury was accidentally discharged into Minamata Bay in Japan, 46 people died after eating mercury-contaminated fish. Poisoning by organic mercury has also occurred in Iraq, Guatemala and Pakistan, when people consumed grains which had been dressed with mercury fungicides. These grains were not intended for human consumption but for planting. Humans also suffered mercury poisoning after eating animals which had been fed with such grains.
Other sources of mercury include:
- Accidental breaking of thermometers, discarded batteries and mercury vapour lamps
- Amalgam in silver tooth fillings
- Coal burning
- Fungicides sold for use on lawns and gardens
- A wide variety of industrial processes.
- Medicines such as calomel talc
- Some ethnic cosmetics and medicines
As shown by studies on animals given amalgam tooth fillings, mercury mainly accumulates in the kidneys; the minute amounts of mercury which come out of the teeth during chewing and are then swallowed, can in time result in a loss of 50 per cent of kidney function. (Drasch G et al: Quecksilberkonzentration in der Nierenrinde. 6th International Trace Element Symposium, Leipzig, 1989.)
A large number of enzymes in the body can be inactivated by mercury, and toxicity symptoms can include insomnia, dizziness, chronic fatigue and weakness, depression, tremors, nervousness, poor co-ordination and dermatitis. Mercury alters protein structure, rendering it unusable. It interferes with sulphur binding sites and can therefore impair insulin synthesis and haemoglobin function. These symptoms may progress to kidney damage and brain damage. Insanity is a typical sign of severe mercury poisoning. The mental illness known as ‘general paralysis of the insane’ or tertiary syphilis, was very common before the advent of modern treatments for syphilis, and is now known to have probably been caused by poisoning due to the old-fashioned anti-syphilis treatments which were based on mercury, antimony and arsenic.
Some individuals can develop a sensitivity to mercury which makes them susceptible to it in different ways. Many cases of auto-immune diseases such as multiple sclerosis, diabetes and systemic lupus erythematosus have responded to the removal of mercury amalgams from teeth. An increasingly common condition known as multiple allergy syndrome (in which the sufferer is allergic to many different foods and other substances) may also respond to the removal of mercury amalgams. These successes may be explained by the fact that the mercury acts as a constant source of stress to the body’s detoxification system, which may recover and work normally once this stress has been removed.
Dentists are at particular risk of mercury poisoning, since they are exposed to mercury vapour, which when inhaled through the nose quickly reaches the brain. The trace element selenium helps to protect against mercury’s toxic effects.