Mercury Poisoning and Minamata Convention on Mercury

The Minamata Convention on Mercury is named after Minamata, a city in Japan where serious health damage occurred as a result of mercury pollution in the mid-20th Century. Minamata is known worldwide due to Minamata disease, a neurological disorder caused by mercury poisoning. The disease was discovered in 1956. It was caused by the release of methylmercury in the industrial wastewater from a local chemical factory, which continued from 1932 to 1968. This highly toxic chemical bioaccumulated in shellfish and fish in Minamata Bay and the Shiranui Sea, which when eaten by the local populace resulted in mercury poisoning.

The disease caused deaths of humans along with cat, dog, and pig. The animal effects were severe enough in cats that they came to be called “dancing cat fever.

The Minamata disease is included in the four Big pollution diseases of Japan, which have been summarized in the following table:

The Minamata Convention

The Minamata convention provides controls and reductions across a range of products, processes and industries where mercury is used, released or emitted. These range from medical equipment such as thermometers and energy-saving light bulbs to the mining, cement and coal-fired power sectors.

The convention was has been four years in negotiation and will be open for signature at a special meeting in Japan in October. It will take effect once it has been ratified by 50 countries. The scope of the new treaty which puts in controls and also reduction measures in respect to mercury is as follows.

It has been agreed that production, export and import of a range of (Not all) mercury containing products will be banned by 2020. These products to be banned include:

• Batteries, except for ‘button cell’ batteries used in implantable medical devices
• Switches and relays
• Certain types of Compact Fluorescent Lamps (CFLs)
• Mercury in cold cathode fluorescent lamps and external electrode fluorescent lamps
• Soaps and cosmetics

Certain kinds of non-electronic medical devices such as thermometers and blood pressure devices are also included for phase-out by 2020.

The devices which have been given exemptions are some large measuring devices where currently there are no mercury-free alternatives.

Vaccines where mercury is used as a preservative have been excluded from the treaty as have products used in religious or traditional activities

The dental fillings using mercury amalgam will be phased out.

Artisanal and Small-Scale Gold Mining

The booming price of gold in recent years has triggered a significant growth in small-scale mining where mercury is used to separate gold from the ore-bearing rock. Emissions and releases from such operations and from coal-fired power stations represent the biggest source of mercury pollution world-wide.

Workers and their families involved in small-scale gold mining are exposed to mercury pollution in several ways including through inhalation during the smelting. Mercury is also being released into river systems from these small-scale operations where it can contaminate fish, the food chain and people downstream.

Governments agreed that the treaty will require countries to draw up strategies to reduce the amount of mercury used by small-scale miners. Nations with artisanal and small-scale gold mining operations will draw up national plans within three years of the treaty entering into force to reduce and if possible eliminate the use of mercury in such operations. Public awareness campaigns and support for mercury-free alternatives will also be part of the plans.

From Power Stations to Cement Factories

The new treaty will control mercury emissions and releases from various large industrial facilities ranging from coal-fired power stations and industrial boilers to certain kinds of smelters handling for example zinc and gold.

Waste incineration and cement clinker facilities are also on the list.

Nations agreed to install the Best Available Technologies on new power plants and facilities with plans to be drawn up to bring emissions down from existing ones.

Does this treaty seek to reduce natural emissions of mercury?

No. This treaty does not seek to reduce natural emissions, because mercury exists naturally on our planet. The objective is to limit anthropogenic emissions generated by the use of mercury in man-made products or processes.

What are sources of mercury?

The most common ore of mercury is Cinnabar or vermilion (HgS). To produce liquid mercury (quicksilver), crushed cinnabar ore is roasted in rotary furnaces. Pure mercury separates from sulfur in this process and easily evaporates. The top sources of anthropogenic emission of mercury include

• Coal-fired power plants (largest aggregate source of mercury emissions). This includes power plants fueled with gas where the mercury has not been removed.
• Gold Production: This is the second largest source of mercury emission.
• Non-ferrous metal production, typically smelters.
• Cement production.
• Waste disposal, including municipal and hazardous waste, crematoria, and sewage sludge incineration.
• Caustic soda production.
• Pig iron and steel production.
• Production of batteries.

How Bioaccumulation of Mercury takes place?

Fish and shellfish have a natural tendency to concentrate mercury in their bodies, generally in the form of methylmercury, a highly toxic organic compound of mercury. Species of fish that are high on the food chain, such as shark, swordfish, king mackerel, albacore tuna, and tilefish contain higher concentrations of mercury than others. As mercury and methylmercury are fat soluble, they primarily accumulate in the viscera, although they are also found throughout the muscle tissue. When this fish is consumed by a predator, the mercury level is bioaccumulated.