Health Problems from Radiation Exposure

What are the health problems associated with radiation exposure?

Depending on length of exposure and how much radiation is involved, the effect can be acute in the form of radiation poisoning, or more long term in the form of increased risk of cancers.

The workers at the plant who are trying to cool overheated fuel rods and and prevent a meltdown are likely to experience the highest levels of exposure in the shortest period of time. They are at highest risk for radiation sickness, or acute radiation syndrome, which can damage tissues, cause the bone marrow to stop generating new blood and immune cells, and lead to periods of severe illness or eventually death. People exposed to high levels of radiation are also at greatest risk of infection, so they need to be kept in isolation wards in sterile environments to protect them from bacteria and viruses.

To reduce their risk, regulatory agencies set limits for the amount of time nuclear-plant workers can be exposed to situations that carry a risk of excessive radiation exposure. These limits are generally calculated in the form of cumulative yearly exposure, so once workers reach that amount, they cannot be re-exposed to radiation for another year. In the U.S., the Nuclear Regulatory Commission restricts workers to 50 millisieverts of radiation exposure per year. At the Fukushima plant's No. 2 reactor, radiation levels had hovered at about 73 microsieverts (0.073 millisieverts), before a blast sent the amount soaring to 11,900 microsieverts (11.9 millisieverts) three hours later.

Longer term health consequences of exposure include cancer, particularly thyroid cancer, since the gland is especially sensitive to the effects of radiation. Again, the risk varies depending on distance, dose and duration of exposure.

People in and immediately around the crippled reactors are likely to have higher long-term cancer risks than others. For the majority of Japanese, however, that additional risk is likely to be relatively small, according to Dr. David Brenner, director of the center for radiological research at Columbia University. "The exposures [most] people are getting — as opposed to those right outside the plant — is still pretty low," he says. "It's important to stress that the risk of cancer under normal circumstances is already big anyway, and what we're talking about here is a pretty small increase over and above that very big cancer risk. We're not talking about a doubling of risk or anything like that."

The difference between the ongoing Fukushima incident and the explosion of the Chernobyl nuclear facility in Ukraine in 1986 is that the latter released a more dangerous cloud of radioactive material — which eventually drifted as far as Western Europe — and which some studies suggest could have contributed to as many as 2000 additional cancers, and possibly more, in the ensuing years.

There may yet be more radioactive material released from the Fukushima plant, but so far the material that has been released appears to have mostly dissipated into the atmosphere, Dr. Kirby Kemper, nuclear physicist and physics professor at Florida State University, tells CNN.

People near the plant are being told to stay indoors. Can that really reduce radiation exposure?

Yes. Staying indoors and sealing your house is a way to prevent ingesting or carrying around any radioactive material that may have attached to dust or other airborne particles and to keep it from landing on skin, clothing or hair. How long people should stay indoors depends on the half-life of the radioactive material (how long it takes radioactivity to dissipate by half): the health danger could be largely reduced in as soon as a week in the case of radioactive iodine, or many years in the case of cesium.

Will the food supply be contaminated?

According to Japanese officials, the explosions in the four reactors have released radioactive iodine 131 and cesium 137. Because iodine has a half-life of just over a week, any grasses, crops or animals exposed to it should be cleared of any residual material in a matter of weeks. If no more radioactive material is released into the air, Brenner says, there would not be much radioactive contamination to worry about when it comes to the food supply.

Cesium 137 is a different story, since it has a longer half-life, of 30 years. But both forms of radioactive material are heavier than air, and their ability to disperse rapidly is limited.

Still, in the meantime, at least for a few weeks, says Brenner: "Don't drink the milk [from the nearby area]. The pathway for radioactive iodine to get into human beings is via milk. The iodine hits the ground, gets on the grass, cows eat the grass, and it is concentrated in the milk, and people drink the milk."

Is there a safe distance to be when a nuclear disaster occurs?

That's hard to say, since it depends on currents and winds as well as the radioactive half life of potentially dangerous materials released into the air. Fortunately, it appears that the prevailing winds are pushing materials from Fukushima out to sea and away from more populated Japanese cities.

Are the effects of radiation exposure cumulative?

Yes. That's why regulatory agencies set yearly thresholds of acceptable exposure for employees who regularly work around radioactive material.

Can radioactive particles be transmitted from person to person?

Yes, in two ways. Most commonly, radioactive material that attaches to dust or other small particles and settles on skin or clothing can be transferred during physical contact.

In addition, an individual who is internally contaminated can emit particles in urine, blood or sweat, and coming into contact with these fluids can transmit exposure.

If you are contaminated, how do you get rid of the radioactive material?

External particles of radioactive material can be washed away, but you have to be careful not to spread tiny bits of material onto your skin when removing contaminated clothing.

If the thyroid is contaminated, it can be treated with potassium iodide, which counters some of radiation's effects on that tissue. The Japanese government has distributed about 230,000 units of iodine to evacuation centers where residents closest to the Fukushima plant have been moved, as a precaution.

Read more: http://healthland.time.com/2011/03/15/japans-next-nightmare-health-problems-from-radiation-exposure/#ixzz1GieJHE8L

Source: http://healthland.time.com/2011/03/15/japans-next-nightmare-health-problems-from-radiation-exposure/

STEM CELLS CURE THE UNCURE ILLNESS

Stem cells have the remarkable potential to develop into many different cell types in the body. Serving as a sort of repair system for the body, they can theoretically divide without limit to replenish other cells as long as the person or animal is still alive. When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell.

What are the unique properties of all stem cells?

Stem cells differ from other kinds of cells in the body. All stem cells—regardless of their source—have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types.

Scientists are trying to understand two fundamental properties of stem cells that relate to their long-term self-renewal:

1. why can embryonic stem cells proliferate for a year or more in the laboratory without differentiating, but most adult stem cells cannot; and
2. what are the factors in living organisms that normally regulate stem cell proliferation and self-renewal?

Discovering the answers to these questions may make it possible to understand how cell proliferation is regulated during normal embryonic development or during the abnormal cell division that leads to cancer. Importantly, such information would enable scientists to grow embryonic and adult stem cells more efficiently in the laboratory.

Stem cells are unspecialized. One of the fundamental properties of a stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions. A stem cell cannot work with its neighbors to pump blood through the body (like a heart muscle cell); it cannot carry molecules of oxygen through the bloodstream (like a red blood cell); and it cannot fire electrochemical signals to other cells that allow the body to move or speak (like a nerve cell). However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells.

Stem cells are capable of dividing and renewing themselves for long periods. Unlike muscle cells, blood cells, or nerve cells—which do not normally replicate themselves—stem cells may replicate many times. When cells replicate themselves many times over it is called proliferation. A starting population of stem cells that proliferates for many months in the laboratory can yield millions of cells. If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of long-term self-renewal.

The specific factors and conditions that allow stem cells to remain unspecialized are of great interest to scientists. It has taken scientists many years of trial and error to learn to grow stem cells in the laboratory without them spontaneously differentiating into specific cell types. For example, it took 20 years to learn how to grow human embryonic stem cells in the laboratory following the development of conditions for growing mouse stem cells. Therefore, an important area of research is understanding the signals in a mature organism that cause a stem cell population to proliferate and remain unspecialized until the cells are needed for repair of a specific tissue. Such information is critical for scientists to be able to grow large numbers of unspecialized stem cells in the laboratory for further experimentation.

Stem cells can give rise to specialized cells. When unspecialized stem cells give rise to specialized cells, the process is called differentiation. Scientists are just beginning to understand the signals inside and outside cells that trigger stem cell differentiation. The internal signals are controlled by a cell's genes, which are interspersed across long strands of DNA, and carry coded instructions for all the structures and functions of a cell. The external signals for cell differentiation include chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment.

Therefore, many questions about stem cell differentiation remain. For example, are the internal and external signals for cell differentiation similar for all kinds of stem cells? Can specific sets of signals be identified that promote differentiation into specific cell types? Addressing these questions is critical because the answers may lead scientists to find new ways of controlling stem cell differentiation in the laboratory, thereby growing cells or tissues that can be used for specific purposes including cell-based therapies.

Adult stem cells typically generate the cell types of the tissue in which they reside. A blood-forming adult stem cell in the bone marrow, for example, normally gives rise to the many types of blood cells such as red blood cells, white blood cells and platelets. Until recently, it had been thought that a blood-forming cell in the bone marrow—which is called a hematopoietic stem cell—could not give rise to the cells of a very different tissue, such as nerve cells in the brain. However, a number of experiments over the last several years have raised the possibility that stem cells from one tissue may be able to give rise to cell types of a completely different tissue, a phenomenon known as plasticity. Examples of such plasticity include blood cells becoming neurons, liver cells that can be made to produce insulin, and hematopoietic stem cells that can develop into heart muscle. Therefore, exploring the possibility of using adult stem cells for cell-based therapies has become a very active area of investigation by researchers.

The Promise of Stem Cells

Studying stem cells will help us understand how they transform into the dazzling array of specialized cells that make us what we are. Some of the most serious medical conditions, such as cancer and birth defects, are due to problems that occur somewhere in this process. A better understanding of normal cell development will allow us to understand and perhaps correct the errors that cause these medical conditions.

Another potential application of stem cells is making cells and tissues for medical therapies. Today, donated organs and tissues are often used to replace those that are diseased or destroyed. Unfortunately, the number of people needing a transplant far exceeds the number of organs available for transplantation. Pluripotent stem cells offer the possibility of a renewable source of replacement cells and tissues to treat a myriad of diseases, conditions, and disabilities including Parkinson's and Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis.

Have human embryonic stem cells successfully treated any human diseases?

Scientists have been able to do experiments with human embryonic stem cells (hESC) only since 1998, when a group led by Dr. James Thomson at the University of Wisconsin developed a technique to isolate and grow the cells. Moreover, Federal funds to support hESC research have been available since only August 9, 2001, when President Bush announced his decision on Federal funding for hESC research. Because many academic researchers rely on Federal funds to support their laboratories, they are just beginning to learn how to grow and use the cells. Thus, although hESC are thought to offer potential cures and therapies for many devastating diseases, research using them is still in its early stages.

Adult stem cells, such as blood-forming stem cells in bone marrow (called hematopoietic stem cells, or HSCs), are currently the only type of stem cell commonly used to treat human diseases. Doctors have been transferring HSCs in bone marrow transplants for over 40 years. More advanced techniques of collecting, or "harvesting," HSCs are now used in order to treat leukemia, lymphoma and several inherited blood disorders.

The clinical potential of adult stem cells has also been demonstrated in the treatment of other human diseases that include diabetes and advanced kidney cancer. However, these newer uses have involved studies with a very limited number of patients.

Participating in Research Studies

Scientists are testing the abilities of adult stem cells to treat certain diseases. You can search for clinical trials using stem cells (or other methods) to treat a specific disease at ClinicalTrials.gov.