Background

Mercury widely occurs in the environment, owing to natural and anthropogenic processes. It is present in three forms, namely elemental (metallic) mercury, inorganic or organic mercury. This review will focus on metallic and inorganic mercury only. Elemental mercury is a shiny, silver-white liquid metal at room temperature. It evaporates to form mercury vapour, which is the predominant form of mercury in the atmosphere. Inorganic mercury compounds contain mercury combined with other elements such as sulphur, oxygen or chlorine. They are mostly white powders or crystals.

Most of the mercury released from man-made activities is elemental mercury released into the air due to mining ore containing mercury, burning fossil fuels and incinerating waste. Mercury also enters the soil from fertilizers, fungicides and from solid waste i.e. thermometers or electrical switches. 

Elemental mercury is used in the electrolysis of sodium chloride to make caustic soda and chlorine and used to make lamps, batteries, electrical switches, thermometers and barometers. Dental amalgam contains elemental mercury mixed with a silver-tin alloy. Inorganic mercury compounds have been used in pharmaceuticals, fungicides and antiseptics.

People working in factories making equipment containing mercury or in chemical processing plants that use mercury may be exposed to mercury vapour. Dentists may also breathe in mercury vapour whilst making amalgam fillings.

If exposed to mercury, the harmful effects that may occur largely depend on the way people are exposed and the type of mercury they are exposed to. After swallowing small amounts of elemental mercury, very little enters the body, whereas after breathing elemental mercury vapour, about 80 % enters the blood from the lungs. Inorganic mercury compounds do not vaporise hence are not generally breathed in and only small amounts may pass through the skin. If swallowed, up to 40 % may enter the body.

Breathing in elemental mercury vapour for a short time affects the nervous system and lungs leading to tremors, walking difficulties, chest pains and breathlessness, respectively. After longer periods, the lining of the mouth and lungs may be damaged. Kidney damage may also occur as well as stomach irritation, nausea, vomiting and diarrhoea. Eating food or drink contaminated with inorganic mercury damages the kidneys, stomach and intestines and nervous system.

The International Agency for Research on Cancer could not classify mercury and its compounds as to their carcinogenicity to humans.

 

Key Points       Production and Uses

• Mercury - Production and Uses
  Added/updated: 16 October 2008