Hazards of Mercury – Safety Perspectives and Measures

Abstract

Mercury is one of the most hazardous contaminants emitted to the atmosphere due to its toxic effects on the environment and human health. Anthropogenic and geological sources account for 30 % and 10 % respectively, whereas the rest is from re-emissions. Consumption of fossil fuels for power generation and heating purposes is still the main source of anthropogenic emissions of mercury. The mercury emissions from industrial sources not only affect equipment and processes but are also a potential hazard for plant and operator’s safety. High reactivity and volatility of mercury make its capture rather difficult. Mercury in the atmosphere is in three primary forms i.e. elemental, inorganic and organic. Gaseous elemental mercury is the most common in anthropogenic and natural emissions to the atmosphere. The transport and deposition of atmospheric mercury depend greatly on whether it is elemental or oxidized. The global cycle of mercury is mainly controlled by oxidation–reduction reactions in the atmosphere and aquatic ecosystem that readily convert volatile Hg⁰ into soluble Hg²⁺ and vice versa. A small fraction of mercury is converted to methyl mercury by bacteria in anoxic environments. Exposures to mercury can affect the human nervous system and harm the brain, heart, kidneys, lungs, and immune system. The only way to reduce mercury pollution is to capture it from emission sources by effective technologies and safety measures. The paper highlights the mercury sources, which increase health hazards in Europe and Asia along and discusses the transport of mercury and viable preventive measures. The progress in mercury removal technologies is also discussed with their limitations.