Introduction the Mercury Issue UNEP Promotes Environmentaly Sound Practices Globally and Its Own Activities
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Introduction The Mercury Issue UNEP promotes environmentaly sound practices globally and its own activities. This magazine is printed on 100% recycled paper, using vegetable-based inks and other eco- friendly practices. Our distribution policy aims to reduce UNEP’s carbon footprint. UNEP_Intro_UK_B_int_01-20_ARP 06/05/10 16:59 Page1 Introduction The Mercury Issue UNEP_Intro_UK_B_int_01-20_ARP 06/05/10 16:59 Page2 Introduction to the Mercury Problem KEY MESSAGES ■ Mercury has been used in various products and processes for hundreds of years due to its unique chemical properties; namely, mercury is in liquid form at room temperature. ■ Mercury and mercury-containing compounds are highly toxic and have a variety of significant adverse effects on human health, wildlife and the environment. ■ In recent years, environmental mercury levels have risen. ■ Once released, mercury can persist in the environment where it circulates between air, water, sediments, soil and biota in various forms. Atmospheric mercury can be transported long distances in the atmosphere, incorporated by microorganisms and may be concentrated up the food chain. ■ Localized hot spots exist from the use of mercury in industrial processes, mining, waste sites and other air emission sources. ■ Bacterial processes convert some of the mercury deposited in bodies of water into methylmercury, a form that can bioaccumulate up the food chain, becoming concentrated in larger, predatory marine mammals and fish, such as seals, swordfish, shark, marlin, mackerel, walleye, sea bass and tuna. ■ In the human body, mercury damages the central nervous system, thyroid, kidneys, lungs, immune system, eyes, gums and skin. Neurological damage to the brain caused by mercury cannot be reversed. There is no known safe exposure level for elemental mercury in humans, and effects can be seen even at very low levels. ■ The most common exposure to mercury is through ingestion of fish and other marine species contaminated with methylmercury. There are two general types of subpopulations particularly susceptible to mercury health effects from 2 mercury in food: those who are more sensitive to the effects of mercury (the foetus, newborn babies and children) and those who are exposed to higher levels of mercury through their livelihood and/or culture (anglers, subsistence fishers). ■ People may also be exposed to elemental or inorganic mercury through inhalation of mercury vapour during occupational activities or spills or through direct contact from mercury use. ■ Over the past 50 years mercury’s toxicity has been well documented and many countries have taken steps to reduce its uses and releases, and to protect their citizens from exposure to mercury. UNEP_Intro_UK_B_int_01-20_ARP 06/05/10 16:59 Page3 What is mercury? Mercury is a natural element. In its pure form, mercury is a shiny silver-white metal that is liquid at room temperature. Where does mercury come from? Trace amounts of mercury exist in air, land and water due to the weathering of rock and from volcanic activity. Pure mercury is rarely found in nature, but the pure metal is extracted from cinnabar. Mercury has always been present in our environment from natural sources (such as forest fires and volcanic eruptions) and therefore in varying amounts in the foods we consume. Human activities, however, substantially contribute to the mercury in the environment and in the food chain. Mercury has been used in a wide range of products and industrial processes over the years, but currently most of it is employed in: > Industrial processes that produce chlorine (mercury chlor-alkali plants) and/or vinyl chloride monomer (for polyvinyl chloride (PVC) production, and polyurethane elastomers); > Artisanal and small scale gold mining; > Products such as electrical switches (including thermostats) and relays, measuring and control equipment, energy-efficient fluorescent light bulbs, batteries and dental amalgam; > Mercury is also sometimes used in laboratories, cosmetics, pharmaceuticals including vaccines as a preservative, paints, and jewellery. Mercury is also released unintentionally from other industrial processes, such as coal-fired power and heat generation, cement production, mining and other metallurgic activities such as non-ferrous metals production. Coal-fired power production is today deemed the single largest global source of atmospheric mercury emissions. Waste from products and industrial processes containing mercury can be a significant source of mercury release 3 Different forms of mercury travel different distances. Some forms deposit within a few kilometers of release, while others are transported throughout the hemisphere before they are deposited. A BRIEF HISTORY OF MERCURY Mercury was one of the first known metals and has been used since ancient times for reasons both practical and mystical. For example, mercury has been used as the mineral cinnabar (HgS) as a red pigment. Archeologists have found mercury in an Egyptian tomb dating from 1500 BC. The Greeks knew of mercury and used it as a medicine, and as recently as the 20th century mercury compounds were used to treat syphilis. The dangers of mercury have become more widely acknowledged over the past several centuries. Mercury’s neurological effects on hat-makers, who used mercuric nitrate to make felt for hats, were so widely recognized that it led to the expression, “mad as a hatter.” UNEP_Intro_UK_B_int_01-20_ARP 06/05/10 17:00 Page4 How are people exposed to mercury? Most individuals are exposed to mercury through certain food sources. People are exposed to methylmercury mainly through their diet, especially from consumption of fish and other marine species. Elemental mercury carried in the atmosphere is eventually deposited and taken up in bacteria in aquatic environments and converted from elemental mercury into methylmercury. Methylmercury bio- accumulates up the food chain and is the primary source of mercury in our food. In addition, people may be exposed to elemental or inorganic mercury through inhalation of ambient air. Approximately 80% of inhaled mercury vapour is absorbed by the body. Potential exposure routes include mercury spills, breakage of mercury containing products, occupational exposures and/or living close to a facility/industry that emits mercury in its processes. Other potential exposures can come from: > exposure to some products such as paints, pesticides or fungicides that contain mercury; > other mercury products such as soaps or cosmetics that are applied directly to people’s skin. For examples of mercury exposure, see Case Studies 1 and 2 at the end of this booklet. Who are at risk? All humans are exposed to some low levels of mercury. The factors that determine whether or not adverse health effects will occur and how severe the health effects include: the chemical form of mercury; the dose; the age or developmental stage of the person exposed (the foetus is the most susceptible); the duration of 4 exposure; the route of exposure - inhalation, ingestion, dermal contact. In particular, individuals and communities who are directly exposed to mercury through their occupation or local industry may be at risk. There are a few general types of susceptible subpopulations in terms of methylmercury found in food; those who are more sensitive to the effects of mercury and those who are exposed to higher levels of mercury: > The foetus, the newborn and young children are especially sensitive to mercury exposure because of the sensitivity of the developing nervous system. In addition to in utero exposures, neonates can be further exposed by consuming contaminated breast milk. Thus, new mothers, pregnant women, and women who might become pregnant should be particularly aware of the potential harm of methylmercury. > Individuals with diseases of the liver, kidneys, nerves, and lungs are at higher risk of suffering from the toxic effects of mercury. UNEP_Intro_UK_B_int_01-20_ARP 06/05/10 17:00 Page5 > Other subpopulations may be at greater risk to mercury toxicity because they are exposed to higher levels of methylmercury due to high fish and seafood consumption such as recreational anglers and subsistence fishers, as well as those cultures that tend to regularly eat fish and other seafood. What are the signs and symptoms of mercury poisoning? The earliest effects of methylmercury poisoning in adults are non-specific symptoms such as paresthesia, malaise, and blurred vision. It can cause nausea, lack of appetite, weight loss, abdominal pain, diarrhea, skin burns and irritation, swollen gums and mouth sores, as well as drooling. With increased exposure, more severe symptoms appear such as numbness and tingling in the lips, mouth, tongue, hands and feet, tremors and lack of coordination, vision and hearing loss, memory loss, personality changes, respiratory distress and kidney failure. Acute exposure to elemental mercury and vapour can result in acrodynia or “pink disease”, which is characterized by bright pink peeling palms, fingers, and soles of the feet, excessive perspiration, itchiness, rashes, joint pain and weakness, elevated blood pressure and heart palpitations. Methylmercury readily crosses the placenta from mother to baby, and also the blood-brain barrier. Methylmercury can also cause mental impairments and learning disabilities, cerebral palsy, seizures, spasticity, tremors, and lack of coordination, along with eye and hearing damage in the unborn baby as a result of the mother's exposure. In addition, methylmercury can also pass into