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Technetium did not arrive on earth in any appreciable amount until 1937 when a molybdenum atom was bombarded with deuterons by Carlo Perrier andEmilio Segrè.  This was not for lack of trying because element 43’s existence was predicted by Mendeleev in the mid 19th century (1). Technetium’s distinction as being a man made element, however, is only one of its curious aspects. As one might suspect it is also exclusively radioactive, being unstable in every form.  Still, technetium has  managed to be useful in several applications including chemical synthesis, nanoscale nuclear batteries, and nuclear medicine (1,2,3,4).

Bioavailability and Uptake

Although Technetium has isotopes with mass numbers ranging from 85 to 118 only 10 are regularly seen and of those only 3 are abundant, those being 97Tc, 98Tc, 99Tc. Technetium-99 is the most abundant of all isotopes since it is a major fission product in nuclear reactors (5). Moreover, the use of Technetium-99m in nuclear medicine is increasing Technetium-99 abundance. Technetium-99m is a metastable isotope that is a gamma decay product of Molybdenum-99, another abundant fissile product.  Indeed the amount of Tc in the environment is going up in all its forms but especially Tc-99.  Besides industry professionals who may handle Tc or encounter it in their work, the most common form of uptake is through water and food and even at that there is very little data to support how much is taken up. Since Tc-99m is a nuclear medicine tool, this is how it is most often encountered in humans. It is often intravenously injected in a molecular form that is best suited for a certain diagnostic purpose.  Technetium’s characteristics, however, allow it to pass through the body with ease and quickly (2,4).

Tc-99m/Tc99

Technetium-99m is the most prevalent diagnostic agent in nuclear medicine. It accounts for 85% of all diagnostic scans and is used around 20 million times per year (1). It is through its unique characteristics as a metastable radioactive isotope that gives it this dominance in the field. The first thing to note is that it is a powerful tool for looking inside a person because it emits gamma radiation that is easily detected (140.5 KeV) and provides a high resolution.

More importantly, the amount of radiation it gives off is low enough that it is not detrimental to the patient. A common injection for a diagnostic test is 250 MBq which would give a radiation dose of 0.05 Sv,  far below the demarcation for radiation poisoning or harm.

Techentium-99m has a half-life of around 6 hours so there is plenty of time for any test and then the agent loses most of its radiation, furthermore the biological half-life of Tc in general is about 1 day so there is little time for it to do any damage at all. An added benefit to the entire process is that Tc-99m is produced from the decay of Mo99 which has a half-life of 66 hours, giving the agent a form in which it can travel and have some shelf-life.

There has even been ome debate as to the positive effects of low-level radiation, like the kind that Tc-99m gives, because it activates DNA repair mechanisms in the body that can fix existing mutations (2). A final reason for its selection as the premiere diagnostic agent is Tc-99m non-specificity in the human body giving it the ability to identity many different organs depending on the molecular structure that is attached to Tc.  In one application, Tc-99m is even being used as a diagnostic for cancer by conjugating the metal with an antibody that is adept at identifying certain carcinomas (3). Some designs look for increased mitochondrial activity, others for certain macrophages or various immunological markers, all depending on the goal of the diagnostic. Ironically, capabilities are limited only by the knowledge of human disease.

Harmful Effects, Toxicology, Radiation

With the discussion of Tc-99m it seems like it is almost too good to be true and that it must have its drawbacks somewhere.  Indeed there is one drawback and that is that it still produces Tc-99 eventually and its half-life is 210,000 years.

Indeed, we may getting ahead of ourselves with all the applications of nuclear physics, in that the problem of what to do with the waste is not yet solved or even really seriously being considered. The radiation from external Tc, however, is not harmful unless in close proximity or really internally present. The key issue is then that it may not be a problem now but its accumulation in the environment can do unexpectedly disastrous things. Internally Tc99 is the only real threat and Tc-99 is easily taken up into plants and animals but does not seem to do any damage as it is just as easily metabolized by biological chelating agents. In humans the same is true where metallothionens take care of the metal efficiently. According to the EPA, the cancer coefficient for Tc-99 and Tc-99m, through food and water ingestion, is 4.28 E-11 and 1.22 E-12 (Bq-1), this epidemiological figure “takes into account age and gender dependence of intake, metabolism, dosimetry, radiogenic risk and competing causes of death in estimating the risks to health from internal or external exposure to radionucleotides (7). Unfortunately this is only understandable to those well versed in epidemiology or radiation in general, so for reference, K40 a radioactive isotope of potassium that is regularly ingested and currently resides in the human body in high amounts (~140g ) has a cancer coefficient of 4.30 E-10, a whole order of magnitude higher and it is in us all the time for our entire lives (8).  The matter of radiation is general is somewhat perplexing as relatively unstudied. Indeed this is the case for technetium where internal threat is cautioned but does not really seem to be a threat.

Conclusion

This investigation in general has brought about the knowledge that radiation poisoning is relatively unstudied and little is known about what is tolerable and what is detrimental. But currently Tc-99m is an overwhelmingly powerful medicinal tool that seems to help more people than it hurts. With more research and understanding it can only be solidified as a truly entirely beneficial material.

Niobium is a rare, soft, malleable, ductile, gray-white metal. It has a body-centered cubic crystalline structure and in its physical and chemical properties it resembles tantalum. It must be placed in a protective atmosphere when processed at even moderate temperatures because it tends to react with oxygen, carbon, the halogens,nitrogen, and sulfur. The metal is inert to acids, even to aqua regia at room temperatures, but is attacked by hot, concentrated acids, and expecially by alkalis and oxidizing agents.

Applications

Niobium is used for the production of high-temperature-resistant alloys and special stainless steels. Small amounts of niobium impart greater strenght to other metals, especially those that are exposed to low temperatures. Niobium carbide is used in cutting tools. It is used in stainless steel alloys for nuclear reactors, jets, missiles, cutting tools, pipelines, super magnets and welding rods.

Niobium-tin and niobium-titanium alloys are used as wires for superconducting magnets capable of producing exceedingly strong magnetic fields. Niobium is also used its pure form to make superconducting accelerating structures for particle accelerators. Niobium alloys are used in surgical implants because they do not react with human tissue.

Niobium in the environment

Plants generally show only traces of niobium and many have none at all, although some mosses and lichens can contain 0.45 ppm. However, plant growing near niobium deposits can accumulate the metal to levels above 1 ppm.

Niobium was mined chifely as columbite, and is formerly known as colombium (Cb). Another mined metal is pyrochlore and this is now the most important. The main mining areas are Brazil, which produce more than 85% on the world’s niobium, Zaire, Russia, Nigeria and Canada. World production is around 25.000 tonnes per year. The amount of unmined reserves is not known, but there are extensive deposits of pytochlore.

Health effects of niobium

Niobium and its compounds may be toxic (niobium dust causes eye and skin irritation) , but there are no reports of human being poisoned by it. Apart from measuring its concentration, no research on niobium in humans has been undertaken.

Niobium, when inhaled, is retained mainly in the lungs, and secondarily in bones. It interferes with calcium as an activator of enzyme systems. In laboratory animals, inhalation of niobium nitride and/or pentoxide leads to scarring of the lungs at exposure levels of 40 mg/m³.

Environmental effects of niobium

No negative environmental effects have been reported.

Yttrium is a highly crystalline iron-gray, rare-earth metal. Yttrium is fairly stable in air, because it is proteced by the formation by the formation of a stable oxide film on its surface, but oxidizes readily when heated. It reacts with water decomposing it to release hydrogen gas, and it reacts with mineral acids. Shavings or turnings of the metal can ignite in air when they exceed 400 °C. When yttrium is finely divided it is very unstable in air.

Applications

The largest use of the element is as its oxide yttria, Y₂O₃, which is used in making red phosphors for color television picture tubes. Yttrium metal has found some use alloyed in small amounts with other metals and It is used to increase the strength of aluminium and magnesium alloys. When added to cast iron it make the metal more workable. Although metals are generally very good at conducting heat, there is an alloy of yttrium with chromium and aluminium which is heat resistant. Yttrium oxide in glass makes it heat- and shock-resistant, and is used for camera lenses. Yttrium oxide is suitable to making superconductors, which are metal oxides which conduct electricity without any loss of energy.

Yttrium in the environment

Yttrium never occurs in nature as a free element. It is found in almost all rare earth minerals and in uranium ores. The yellow-brown ore xenotime can contain as much as 50% yttrium phophate (YPO4) and is mined in Malaysia. Yttrium is found in the rare-earth mineral monazite, of which it makes 2.5%, and in smaller quantities in other minerals such as barnasite, fergusonite and smarskite. The output of yttrium is about 600 tonnes per year, measured as yttrium oxide, and world reserves are estimated to be around 9 million tonnes.

Health effects of yttrium

Yttrium is one of the rare chemicals, that can be found in houses in equipment such as colour televisions, fluorescent lamps, energy-saving lamps and glasses. All rare chemicals have comparable properties. Yttrium can rarely be found in nature, as it occurs in very small amounts. Yttrium is usually found only in two different kinds of ores. The use of yttrium is still growing, due to the fact that it is suited to produce catalysers and to polish glass. Yttrium is mostly dangerous in the working environment, due to the fact that damps and gasses can be inhaled with air. This can cause lung embolisms, especially during long-term exposure. Yttrium can also cause cancer with humans, as it enlarges the chances of lung cancer when it is inhaled. Finally, it can be a threat to the liver when it accumulates in the human body.

Effects of yttrium on the Environment

Yttrium is dumped in the environment in many different places, mainly by petrol-producing industries. It can also enter the environment when household equipment is thrown away. Yttrium will gradually accumulate in soils and water soils and this will eventually lead to increasing concentrations in humans, animals and soil particles.

Rubidium is present in the earth’s crust, in seawater, and in the human body. Our body contains about 350 mg. It has not yet been shown to be essential. Chemically, it is like potassium, and in some animals it can replace potassium in certain functions, though this does not seem to be the case in humans. Rubidium can possibly be a potassium antagonist in regard to absorption and utilization, though this needs further investigation.

Rubidium is absorbed easily from the gut, about 90 percent. It is found generally throughout the body, with the least in the bones and teeth; it is not known to concentrate in any particular tissue. Excess rubidium is eliminated mainly in the urine.

Sources: Food sources of rubidium have not been researched very well as yet. Some fruits and vegetables have been found to contain about 35 ppm. Rubidium may also be found in some water sources.

Functions: There are currently no known essential functions of rubidium. In studies with mice, rubidium has helped decrease tumor growth, possibly by replacing potassium in cell transport mechanisms or by rubidium ions attaching to the cancer cell membranes. Rubidium may have a tranquilizing or hypnotic effect in some animals, possibly including humans.

Uses: There are no clear uses for rubidium as yet. Because of its possible tranquilizing effect, it could help in the treatment of nervous disorders or epilepsy.

Deficiency and toxicity: There is no known deficiency or toxicity for rubidium.

Requirements: There is no RDA for rubidium. The average dietary intake may be about 1.5 mg. daily.

Water Purification One of the major uses of bromine is as a water purifier/disinfectant. Brominated compounds are used for water treatment in swimming pools and hot tubs. They are also used to control algae and bacterial growth in industrial processes.

 

	Agriculture Bromine compounds are effective pesticides, used both as soil fumigants in agriculture, particularly fruit-growing, and as a fumigant to prevent pests from attacking stored grain and other produce. Significant volumes of world trade in agriculture goods depend on the use of bromine compounds to ensure compliance with mandatory rules on quarantine.

 

	Cars – past and future In the past, bromine compounds were used in leaded fuel, as a constituent of “anti-knock fluid”. However, this use has declined as lead has gradually been removed from fuel. Bromine compounds are now being tested in batteries for electric cars, designed to produce zero emissions. Such batteries can also be used as electricity storage devices.

 

Healthcare A key use of bromine compounds is in the manufacturing of pharmaceuticals. Brominated substances are important ingredients of many over-the-counter and prescription drugs, including analgesics, sedatives, and antihistamines. In fact, bromine compounds are active ingredients in several drugs that treat pneumonia and cocaine addiction. Currently, several drugs containing bromine compounds are undergoing trials for treatment of Alzheimer’s disease and new generations of anti-cancer and AIDS drugs.

 

	Photography Bromine compounds have a number of applications in photography. Several compounds are used to make the light-sensitive component of a photographic emulsion; without bromine compounds photographs would not capture sufficient light. Other bromine compounds are used as an ingredient in photo development.