Archive for month: December, 2015

Lead is a bluish-white lustrous metal. It is very soft, highly malleable, ductile, and a relatively poor conductor of electricity. It is very resistant to corrosion but tarnishes upon exposure to air. Lead isotopes are the end products of each of the three series of naturally occurring radioactive elements.

Applications

Lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. Alloys include pewter and solder. Tetraethyl lead (PbEt₄) is still used in some grades of petrol (gasoline) but is being phased out on environmental grounds.
Lead is a major constituent of the lead-acid battery used extensively in car batteries. It is used as a coloring element in ceramic glazes, as projectiles, in some candles to threat the wick. It is the traditional base metal for organ pipes, and it is used as electrodes in the process of electrolysis. One if its major uses is in the glass of computer and television screens, where it shields the viewer from radiation. Other uses are in sheeting, cables, solders, lead crystal glassware, ammunitions, bearings and as weight in sport equipment.

Lead in the environment

Native lead is rare in nature. Currently lead is usually found in ore with zinc, silver and copper and it is extracted together with these metals. The main lead mineral in Galena (PbS) and there are also deposits of cerrussite and anglesite which are mined. Galena is mined in Australia, which produces 19% of the world’s new lead, followed by the USA, China, Peru’ and Canada. Some is also mined in Mexico and West Germany. World production of new lead is 6 million tonnes a year, and workable reserves total are estimated 85 million tonnes, which is less than 15 year’s supply.

Lead occurs naturally in the environment. However, most lead concentrations that are found in the environment are a result of human activities. Due to the application of lead in gasoline an unnatural lead-cycle has consisted. In car engines lead is burned, so that lead salts (chlorines, bromines, oxides) will originate.
These lead salts enter the environment through the exhausts of cars. The larger particles will drop to the ground immediately and pollute soils or surface waters, the smaller particles will travel long distances through air and remain in the atmosphere. Part of this lead will fall back on earth when it is raining. This lead-cycle caused by human production is much more extended than the natural lead-cycle. It has caused lead pollution to be a worldwide issue.

Health effects of lead

Lead is a soft metal that has known many applications over the years. It has been used widely since 5000 BC for application in metal products, cables and pipelines, but also in paints and pesticides. Lead is one out of four metals that have the most damaging effects on human health. It can enter the human body through uptake of food (65%), water (20%) and air (15%). Foods such as fruit, vegetables, meats, grains, seafood, soft drinks and wine may contain significant amounts of lead. Cigarette smoke also contains small amounts of lead. Lead can enter (drinking) water through corrosion of pipes. This is more likely to happen when the water is slightly acidic. That is why public water treatment systems are now required to carry out pH-adjustments in water that will serve drinking purposes. For as far as we know, lead fulfils no essential function in the human body, it can merely do harm after uptake from food, air or water. Lead can cause several unwanted effects, such as: – Disruption of the biosynthesis of haemoglobin and anaemia – A rise in blood pressure – Kidney damage – Miscarriages and subtle abortions – Disruption of nervous systems – Brain damage – Declined fertility of men through sperm damage – Diminished learning abilities of children – Behavioural disruptions of children, such as aggression, impulsive behavior and hyperactivity Lead can enter a foetus through the placenta of the mother. Because of this it can cause serious damage to the nervous system and the brains of unborn children.

Environmental effects of lead

Not only leaded gasoline causes lead concentrations in the environment to rise. Other human activities, such as fuel combustion, industrial processes and solid waste combustion, also contribute. Lead can end up in water and soils through corrosion of leaded pipelines in a water transporting system and through corrosion of leaded paints. It cannot be broken down; it can only converted to other forms. Lead accumulates in the bodies of water organisms and soil organisms. These will experience health effects from lead poisoning. Health effects on shellfish can take place even when only very small concentrations of lead are present. Body functions of phytoplankton can be disturbed when lead interferes. Phytoplankton is an important source of oxygen production in seas and many larger sea-animals eat it. That is why we now begin to wonder whether lead pollution can influence global balances. Soil functions are disturbed by lead intervention, especially near highways and farmlands, where extreme concentrations may be present. Soil organisms than suffer from lead poisoning, too. Lead is a particularly dangerous chemical, as it can accumulate in individual organisms, but also in entire food chains. For more effects on freshwater ecosystem take a look at lead in freshwater

• Mercury is a naturally occurring element that is found in air, water and soil.
• Exposure to mercury – even small amounts – may cause serious health problems, and is a threat to the development of the child in utero and early in life.
• Mercury may have toxic effects on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.
• Mercury is considered by WHO as one of the top ten chemicals or groups of chemicals of major public health concern.
• People are mainly exposed to methylmercury, an organic compound, when they eat fish and shellfish that contain the compound.

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Mercury exists in various forms: elemental (or metallic) and inorganic (to which people may be exposed through their occupation); and organic (e.g., methylmercury, to which people may be exposed through their diet). These forms of mercury differ in their degree of toxicity and in their effects on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.

Mercury occurs naturally in the earth’s crust. It is released into the environment from volcanic activity, weathering of rocks and as a result of human activity. Human activity is the main cause of mercury releases, particularly coal-fired power stations, residential coal burning for heating and cooking, industrial processes, waste incinerators and as a result of mining for mercury, gold and other metals.

Once in the environment, mercury can be transformed by bacteria into methylmercury. Methylmercury then bioaccumulates (bioaccumulation occurs when an organism contains higher concentrations of the substance than do the surroundings) in fish and shellfish. Methylmercury also biomagnifies. For example, large predatory fish are more likely to have high levels of mercury as a result of eating many smaller fish that have acquired mercury through ingestion of plankton.

People may be exposed to mercury in any of its forms under different circumstances. However, exposure mainly occurs through consumption of fish and shellfish contaminated with methylmercury and through worker inhalation of elemental mercury vapours during industrial processes. Cooking does not eliminate mercury.

Exposure to mercury

All humans are exposed to some level of mercury. Most people are exposed to low levels of mercury, often through chronic exposure (continuous or intermittent long term contact). However, some people are exposed to high levels of mercury, including acute exposure (exposure occurring over a short period of time, often less than a day). An example of acute exposure would be mercury exposure due to an industrial accident.

Factors that determine whether health effects occur and their severity include:

• the type of mercury concerned;
• the dose;
• the age or developmental stage of the person exposed (the foetus is most susceptible);
• the duration of exposure;
• the route of exposure (inhalation, ingestion or dermal contact).

Generally, two groups are more sensitive to the effects of mercury. Foetuses are most susceptible to developmental effects due to mercury. Methylmercury exposure in the womb can result from a mother’s consumption of fish and shellfish. It can adversely affect a baby’s growing brain and nervous system. The primary health effect of methylmercury is impaired neurological development. Therefore, cognitive thinking, memory, attention, language, and fine motor and visual spatial skills may be affected in children who were exposed to methylmercury as foetuses.

The second group is people who are regularly exposed (chronic exposure) to high levels of mercury (such as populations that rely on subsistence fishing or people who are occupationally exposed). Among selected subsistence fishing populations, between 1.5/1000 and 17/1000 children showed cognitive impairment (mild mental retardation) caused by the consumption of fish containing mercury. These included populations in Brazil, Canada, China, Columbia and Greenland.

A significant example of mercury exposure affecting public health occurred in Minamata, Japan, between 1932 and 1968, where a factory producing acetic acid discharged waste liquid into Minamata Bay. The discharge included high concentrations of methylmercury. The bay was rich in fish and shellfish, providing the main livelihood for local residents and fishermen from other areas.

For many years, no one realised that the fish were contaminated with mercury, and that it was causing a strange disease in the local community and in other districts. At least 50 000 people were affected to some extent and more than 2000 cases of Minamata disease were certified. Minamata disease peaked in the 1950s, with severe cases suffering brain damage, paralysis, incoherent speech and delirium.

Health effects of mercury exposure

Elemental and methylmercury are toxic to the central and peripheral nervous systems. The inhalation of mercury vapour can produce harmful effects on the nervous, digestive and immune systems, lungs and kidneys, and may be fatal. The inorganic salts of mercury are corrosive to the skin, eyes and gastrointestinal tract, and may induce kidney toxicity if ingested.

Neurological and behavioural disorders may be observed after inhalation, ingestion or dermal exposure of different mercury compounds. Symptoms include tremors, insomnia, memory loss, neuromuscular effects, headaches and cognitive and motor dysfunction. Mild, subclinical signs of central nervous system toxicity can be seen in workers exposed to an elemental mercury level in the air of 20 μg/m3 or more for several years. Kidney effects have been reported, ranging from increased protein in the urine to kidney failure.

How to reduce human exposure from mercury sources

There are several ways to prevent adverse health effects, including promoting clean energy, stopping the use of mercury in gold mining, eliminating the mining of mercury and phasing out non-essential mercury-containing products.

Promote the use of clean energy sources that do not burn coal.

Burning coal for power and heat a major source of mercury. Coal contains mercury and other hazardous air pollutants that are emitted when the coal is burned incoal-fired power plants, industrial boilers and household stoves.

Eliminate mercury mining, and use of mercury in gold extraction and other industrial processes.

Mercury is an element that cannot be destroyed; therefore, mercury already in use can be recycled for other essential uses, with no further need for mercury mining. Mercury use in artisanal and small-scale gold mining is particularly hazardous, and health effects on vulnerable populations are significant. Non-mercury (non-cyanide) gold-extraction techniques need to be promoted and implemented, and where mercury is still used safer work practices need to be employed to prevent exposure.

Phase out use of non-essential mercury-containing products and implement safe handling, use and disposal of remaining mercury-containing products.

Mercury is contained in many products, including:

• batteries
• measuring devices, such as thermometers and barometers
• electric switches and relays in equipment
• lamps (including some types of light bulbs)
• dental amalgam (for dental fillings)
• skin-lightening products and other cosmetics
• pharmaceuticals.

A range of actions are being taken to reduce mercury levels in products, or to phase out mercury-containing products. In health care, dental amalgam is used in almost all countries. A 2009 WHO expert consultation concluded that a global near-term ban on amalgam would be problematic for public health and the dental health sector, but a phase down should be pursued by promoting disease prevention and alternatives to amalgam; research and development of cost-effective alternatives; education of dental professionals and the raising of public awareness.

Mercury use in some pharmaceuticals, such as thiomersal (ethyl mercury), which is used as a preservative in some vaccines, is very small by comparison with other mercury sources. There is no evidence that suggests a possible health hazard resulting from the amounts of thiomersal currently used in human vaccines.

Inorganic mercury is added to some skin-lightening products in significant amounts. Many countries have banned mercury-containing skin-lightening products because they are hazardous to human health.

Political agreement

The continued release of mercury into the environment from human activity, the presence of mercury in the food chain, and the demonstrated adverse effects on humans are of such concern that in 2013 governments agreed to the Minamata Convention on Mercury. The Convention obliges government Parties to take a range of actions, including to address mercury emissions to air and to phase-out certain mercury-containing products.

WHO response

The World Health Organization publishes evidence about the health impacts of the different forms of mercury, guidance on identifying populations at risk from mercury exposure, tools to reduce mercury exposure, and guidance on the replacement of mercury-containing thermometers and blood pressure measuring devices in health care. WHO leads projects to promote the sound management and disposal of health-care waste and has facilitated the development of an affordable, validated, non-mercury-containing blood pressure measuring device.

The name platinum is derived from the Spanish “platina”, meaning “little silver”.

Platinum is a lustrous silvery-white, malleable, ductile metal and a member of group 10 of the periodic table of the elements. It has the third highest density, behindosmium and iridium. Platinum is unaffected by air and water, but will dissolve in hotaqua regia, in hot concentrated phosphoric and sulphuric acids, and in molten alkali. It is as resistant as gold to corrosion and tarnishing. Indeed, platinum will not oxidize in air no matter how strongly it is heated.

It has a coefficient of expansion almost equal to that of soda-lime-silica glass, and is therefore used to make sealed electrodes in glass systems. Hydrogen and oxygengas mixtures explode in the presence of platinum wire.

There are six naturally occurring isotopes : the most abundant are platinum-194, which accounts for 33%, platinum-195 (34%) and platinum-196 (25%). The others are platinum-198 (7%), platinum-192 (1%) and platinum-190 (0.01%). The latter is weakly radioactive, with a half life of 700 billion years, while the other five are non-radioactive.

Applications

Platinum has many uses. Its wear- and tarnish-resistance characteristics are well-suited for making fine jewelry. Platinum and its alloys are used in surgical tools, laboratory utensils, electrical resistance wires, and electrical contact points. It is used (30%) as a catalyst in the catalytic converter, an optional component of the gasoline-fuelled automobile exhaust system. The largest use (50%) of platinum is for jewellery, another 20% is used in industry: platinum is used in the chemical, electrical, glass and aircraft industries, each accounting for about 10 tonnes of the metal per year. The glass industry uses platinum for optical fibers and liquid crystal display glass, especially for laptops.

Platinum in the environment

Platinum primary occurrence is with other metal ores associated with basic igneous rocks. Platinum nuggets occur naturally as the uncombined metal, as does an alloy of platinum-iridium. Three-quarters of the world’s platinum comes from South Africa, where it occurs as cooperite, while Russia is the second largest produced, followed by North America. World production of platinum is around 155 tonnes a year and reserves total more than 30.000 tonnes

Health effects of platinum

Platinum is a noble metal. The concentrations of platinum in the soil, water and air are very minimal. In some places deposits can be found that are very rich in platinum, mainly in South Africa, the Soviet Union and the United States. Platinum is used as a component of several metal products, such as electrodes and it can be used as a catalyser of a number of chemical reactions. Platinum bonds are often applied as a medicine to cure cancer. The health effects of platinum are strongly dependent upon the kind of bonds that are shaped and the exposure level and immunity of the person that is exposed. Platinum as a metal is not very dangerous, but platinum salts can cause several health effects, such as: – DNA alterations – Cancer – Allergic reactions of the skin and the mucous membrane – Damage to organs, such as intestines, kidneys and bone marrow – Hearing damage Finally, a danger of platinum is that it can cause potentiation of the toxicity of other dangerous chemicals in the human body, such as selenium.

Environmental effects of platinum

The application of platinum in metal products is not known to cause many environmental problems, but we do know that it can cause serious health conditions in the working place environment. Platinum is emitted into the air through the exhausts of cars that use leaded gasoline. Consequently, platinum levels in air may be higher on certain locations, for instance in garages, in tunnels and on terrains of trucking companies. What the effects of platinum on animals and the environment may be has not yet been researched very extensively. The only thing we know is that platinum will accumulate in the roots of plants after uptake. Whether eating platinum-containing plant roots can do any harm to animals and humans, is not yet clear. Microrganisms may be able to convert platinum substances to more dangerous substances in soils, but on this subject we also have little information.

Osmium is lustrous, silvery metal, one of the so-called platinum group of metals. It is the densest metal known, althoung only by the narrowest margins. Osmium is uneffected by water and acids, but dissolves with molten alkalis. Osmium powder reacts slowly with the oxygen of the air and gives off detectable amounts of osmium tetroxide vapour.

Applications

The metal is used in a few alloys and in industry as a catalyst. At one time it was to be encountered in the nibs of high-quality fountain pens, compass needles, long-life gramophone needles and clock bearings, thanks to its extreme hardness and corrosion resistance.

Osmium in the environment

Osmium is mainly found alloyed with other platinum metals, from which it is recovered commercially. The most important ores are either iridosmine and osmiridium. Iridosmine is a rare mineral found in Russia and in North and South America. Less of 100 kg are produced each year. There is little demand for the metal, which is difficult to fabricate.

Health effects of osmium

Osmium tetroxide, OsO₄, is highly toxic. Concentrations in air as low as 10^-7 g m^-3can cause lung congestion, skin damage, and severe eye damage. The oxide, in particular, should only ever be handled by a properly qualified chemist.

Osmium tetroxide can be absorbed into the body by inhalation of its vapour, by inhalation of its aerosol and by ingestion.

Inhalation risk: A harmful contamination of the air can be reached very quickly on evaporation of this substance at 20°C.

Inhalation: Burning sensation. Cough. Headache. Wheezing. Shortness of breath. Visual disturbances. Symptoms may be delayed. Skin: Redness. Skin burns. Pain. Skin discoloration. Blisters. Eyes: Redness. Pain. Blurred vision. Loss of vision. Severe deep burns. Ingestion: Abdominal cramps. Burning sensation. Shock or collapse.

Chemical dangers: The substance decomposes on heating producing fumes of osmium. The substance is a strong oxidant and reacts with combustible and reducing materials. Reacts with hydrochloric acid to form toxic chlorine gas. Forms unstable compounds with alkalis.

Effects of short-term exposure: Tear drawing. The substance is corrosive to the eyes, the skin, and the respiratory tract. Inhalation of this substance may cause lung oedema. Exposure to high concentrations may result in death. The effects may be delayed.

Effects of long-term or repeated exposure: Repeated or prolonged contact with skin may cause dermatitis. The substance may have effects on the kidneys.

Environmental effects of osmium

No information found in our select references. However we expect osmium ecotoxicity to be very low because of its strength as an oxidizer, that makes it be readily converted to the dioxide, a form of the metal that is reasonably innocuous.

Tungsten is a lustrous and silvery white metal. The bulk metal resists attack by oxygen, acids and alkalis. Tungsten has the highest melting point of any metal.

Applications

Tungsten is used in filaments in incandescent light bulbs, it is also used in electric contacts and arc-welding electrodes. Tungsten is used in alloys, such as steel, to which it imparts great strength. Cement carbide is the most important use for tungsten: its main component is tungsten carbide (WC). It has the strength to our cast iron and it makes excellent cutting tools for the machining of steel. X-ray tubes for medical use have a tungsten emitter coil and the screen used to view X-rays rely on calcium and magnesiumtungstate phosphors to convert X-rays into blue visible light. Tungsten is also used in microchip tecnology and liquid crystals displays.

Tungsten in the environment

Very little tungsten has been detetced in the dew soils that have been analysed for it, although around an ore-processin plant in Russia levels as high as 2000 ppm were found. The concentration of the element in natural waters is very low.

There are several minerals of tungsten, the most important are scheelite and wolframite. The main mining area is China, which today accounts for more than two-thirds of the world’s supply. Other places with active tungsten mines are Russia, Austria, Bolivia, Peru and Portugal. World production is around 40.000 tonnes per year and reserves are estimated to be around 5 million tonnes. Tungsten is also recycled and it meets 30% of demand.

Health effects of tungsten

Tungsten has been shown to act by antagonizing the action of the essential trace element, Molybdenum. Long industrial experience has indicated no pneumoconiosis to develop among workers exposed solely to W or its insoluble compounds (at air concentrations of the order of 5 mg/m3).

Acute health effects: Irritating to the skin and eyes on contact. Inhalation will cause irritation to the lungs and mucus membrane. Irritation to the eyes will cause watering and redness. Reddening, scaling, and itching are characteristics of skin inflammation. Follow safe industrial hygiene practices and always wear protective equipment when handling this compound.

Chronic health effects: This product has no known chronic effects. Repeated or prolong exposure to this compound is not known to aggravate medical conditions.

All tungsten compounds should be regarded as highly toxic. The metal dust presents a fire and explosion hazard.

Effects of tungsten on the Environment

Tungsten metal powder administered to animals has been shown in several studies as not altogether inert. One study found that guinea pigs treated orally or intravenously with tungsten suffered from anorexia, colic, incoordination of movement, trembling, dyspnea and weight loss. This product is not expected to be hazardous for the environment. No specific ecotoxicity data is available for this product.