Minggu, 01 Mei 2011

Mesothelioma may be caused by exposure to ultramafic rock

Everyday exposure to naturally occurring asbestos increases the risk of developing malignant mesothelioma, according to a study by UC Davis researchers.

The study - the largest to examine the question - will be published this fall in the American Journal of Respiratory and Critical Care Medicine.

Exposure to asbestos in the workplace, particularly in shipyards, has long been recognized as a risk factor for mesothelioma, a rare form of cancer affecting the lining of the lung. But in the new study, researchers found a consistent and dose-dependent association between mesothelioma and residential proximity to ultramafic rock, the predominant source of naturally occurring asbestos.

"Our findings indicate that the risks from exposure to naturally occurring asbestos, while low, are real and should be taken seriously," said Marc Schenker, professor and chair of the UC Davis Department of Public Health Sciences and the study's senior author. "This study provides important supportive evidence that naturally occurring asbestos causes mesothelioma - and public efforts should now shift to understanding the risk and how we can protect people from this preventable malignancy."

To put the mesothelioma risk in perspective, the disease kills about the same number of Americans each year as passive smoking. About 2,500 people a year die from mesothelioma in the United States, according to National Institute of Occupational Safety and Health statistics. About 3,000 deaths a year are attributed to exposure to secondhand tobacco smoke, according to U.S. Environmental Protection Agency statistics.

Ultramafic rock is distributed throughout the Sierra Nevada, Coast Ranges and Klamath Mountains in Northern and Central California, and has been a source of increasing concern as new housing developments cut through these areas. Of most concern are the areas of ultramafic rock associated with tremolite asbestos.

In their ambitious study, Schenker and his colleagues used California Cancer Registry data to identify 2,908 cases of malignant mesothelioma diagnosed between 1988 and 1997 in adults ages 35 and older. In most cases, the registry also provided occupational history. As a control group, an equal number of age- and gender-matched pancreatic cancer cases was selected (since pancreatic cancer has no known association to asbestos exposure). For both the mesothelioma and pancreatic cancer cases, the researchers employed sophisticated geographic information system mapping to pinpoint home or street addresses for every diagnosed individual. A map from the California Department of Conservation, Division of Mines and Geology, served as the reference for ultramafic rock deposits. Finally, statistical adjustments were made for sex, occupational asbestos exposure and age at diagnosis.

The researchers found that the risk of developing malignant mesothelioma was directly related to residential proximity to a source of ultramafic rock. Specifically, the odds of having mesothelioma fell by 6.3 percent for every 10 kilometers (about 6.2 miles) farther a person lived from the nearest asbestos source. The association was strongest in men, but was also seen in women. No such association showed up in the pancreatic cancer group. The study was not designed to determine the "ground zero" risk for those living closest to an asbestos source - only to test for a relationship between proximity and risk.

"This is very creative, painstaking epidemiology," said Jerrold L. Abraham, professor and director of environmental and occupational pathology at SUNY Upstate Medical University in Syracuse, New York, and a leading authority on mesothelioma. "The UC Davis researchers have shown a significant association between living near deposits of naturally occurring asbestos and mesothelioma. This is the strongest evidence possible without conducting one-on-one interviews with each diagnosed mesothelioma patient or his or her family."

Laurel Beckett, professor and vice chair of the UC Davis Department of Public Health Sciences and a study co-author, said the findings are important. "We showed that breathing asbestos in your community is not magically different from breathing asbestos in an industrial setting. It would have been a surprise to find otherwise."

Similarly, she said, it was no real surprise to scientists when passive smoking was found to cause lung cancer. "Like smoking, exposure to asbestos appears to be very dose-dependent," Beckett said. "Day-in, day-out occupational exposures are more dangerous than intermittent exposures in the community. But the more you can do to reduce your personal exposure, the safer you will be."

While the overall mesothelioma rate was about one case per 100,000 people per year in the California study, the rate varied markedly by gender and age. For white males, the rate was 2.29 cases per 100,000. For white females, it was 0.49. People over age 60 had ten times the rate of those ages 40 to 59.

Worldwide, epidemiological studies of mesothelioma have found occupational causes for most but not all cases of the disease. In some undeveloped areas of the world, including parts of Greece and Turkey, mesothelioma cases have been linked to use of naturally occurring asbestos in household materials such as whitewash. The UC Davis study suggests naturally occurring asbestos also causes mesothelioma in developed countries, through incidental, non-occupational exposures.

California has required statewide cancer reporting since 1985 and established the California Cancer Registry in 1988. One of the largest cancer databases in the world, the registry is responsible for collecting cancer incidence and mortality statistics for more than one tenth of the United States population. An estimated 98.9 percent of all mesothelioma cases diagnosed in California are reported to the registry.

The registry's size enabled researchers to identify an association that might not have been apparent in a smaller study.

Needed now are field studies to more accurately characterize determinants of exposure to asbestos fibers among residents in areas with naturally occurring asbestos, Schenker said. In addition, he said more must be learned about the types and size of fibers in asbestos deposits, the types of human activities that disturb asbestos fibers and the determinants of cancer risk in exposed populations.

"Because mesothelioma takes 20 to 30 years to develop, what we learn today will allow us to protect Californians from this preventable cancer decades into the future," Schenker said.

Nanotech could cause mesothelioma

Carbon nanotubes

3D model of three types of single-walled carbon nanotubes. (Wikipedia: Michael Stroeck, file photo)

In the 1990s scientists found a way to roll carbon atoms into a cylinder, called a nanotube. Now US researchers have found that the lungs of mice respond to some fibres from nanotubes as they would to asbestos, forming lesions and becoming inflamed.

Dr Andrew Maynard from the Woodrow Wilson International Centre for Scholars told AM nanotubes are excellent at conducting heat and electricity. They're already being used in sports equipment because of their strength.

"Almost like a miracle material. If only we could make it in large quantities in high purity, we could use it to do things that we have only dreamt of before," he said.

"If you look out in the market place, it is beginning to appear. So you can buy things like baseball bats, you can buy tennis racquets, you can buy golf clubs with this material, but I think those are probably just the tip of the iceberg."

Dr Maynard says at the moment there is no requirement to disclose that nanotubes are being used.

"In fact if you look at the safety guidelines for the material, most people are treating it just as graphite, the sort of stuff that you find in your pencil," he said.

He says the new study shows there is strong evidence that if carbon nanotubes get into the wrong place, they can cause mesothelioma.

"So we've got one piece of the puzzle here," he said.

"There are a couple of other pieces of the puzzle which still need to be filled in and those are asking whether exposure to this material actually will occur.

"Whether people can breathe it in and if they do, whether these fibres can work their way to the outer edge of the lung and then cause an effect.

"But we knew that if those two things happened, there is a very strong change that the prolonged carbon nanotubes will eventually lead to this disease."

Nanotubes used in sporting equipment are safely encased. Dr Maynard says the greater risk is to people involved in manufacturing them and disposing of them.

He hopes his findings aren't seen as fear-mongering, but he warns nanotechnology could become as widely used as asbestos once was.

"Carbon nanotubes are seen very much as the poster child of nanotechnology," he said.

"Some of the predictions are that by the year 2014 we are going to see goods sold around the world something like $2.6 trillion that are based in some way on different types of nanotechnology."

Dr Maynard also agrees there's a lack of knowledge about the safe use of nanotechnology in food, and is calling for more research.

"We are in a position where we could actually do great things with this technology if we had the knowledge to be able to use it safely," he said.

"Unfortunately, a lot of that knowledge is lacking at the moment. We need the research to fill in those information gaps."

Dr Maynard's findings are published today in Nature.

Newest technique which can help diagnose mesothelioma

A new technique may help clinicians hone in on a diagnosis in patients presenting with a pleural effusion of unknown cause.

The study will appear in the Sept. 1 issue of the American Journal of Respiratory and Critical Care Medicine.

"Pleural effusion, or the accumulation of fluid in the pleural cavity, can be maddeningly difficult to diagnose as a wide variety of malignant and benign causes exist," said Helen Davies, specialist registrar and research fellow at the Oxford Center for Respiratory Medicine and Oxford University, lead author of the study. "One of the causes, malignant pleural mesothelioma, is a relatively rare cancer, but its incidence is rapidly increasing on a global scale."

Currently, the first-line test for mesothelioma in patients with a pleural effusion is pleural fluid cytology, but this test is not very sensitive. Dr. Davies and her colleagues undertook the study to determine whether there would be additional clinical benefit to looking at pleural fluid mesothelin, a protein released in high quantities into the pleural fluid of most patients with mesothelioma.

They obtained pleural fluid samples from 209 patients referred to a specialized respiratory clinic. Levels of soluble mesothelin were measured in all samples.

Their results demonstrated median pleural fluid mesothelin levels were over six times greater in patients with mesothelioma than in patients with metastatic carcinomas, and ten times greater than in patients with benign effusions.

Using mesothelin levels at a cut-off of 20nM, they found that it had an overall negative predictive value of 95 percent, meaning that a patient with a mesothelin level less than the cut-off of 20nM could be 95 percent confident they did not have malignant mesothelioma.

There were 12 false positive results with metastatic adenocarcinomas accounting for over 90 percent of these cases. However, all patients with pleural fluid cytology suspicious for mesothelioma and an elevated mesothelin level had mesothelioma.

"This study suggests a way for clinicians to more readily identify these cases from the start," said Dr. Davies.

Obtaining a prompt diagnosis of mesothelioma has benefits for patients and physicians alike. "Because mesothelioma has a median survival time of 12 months, minimizing the number of invasive procedures and tests patients require is crucial to reduce morbidity and the time they need to spend in hospital," said Dr. Davies. "An earlier diagnosis also allows speedier interventions to relieve symptoms as well as initiation of other treatments such as chemotherapy or radiotherapy if appropriate."

Exposure to asbestos is the main risk factor and accounts for the majority of mesothelioma cases. Legislation to prevent occupational exposure to asbestos has been enforced in the developed world; however, unrestricted contact continues in developing countries.

Over 90 percent of patients with mesothelioma present with a pleural effusion and its incidence is predicted to peak within the next two decades.

"Pleural fluid mesothelin provides a valuable adjunct in the diagnostic assessment of patients presenting with pleural effusions, especially when cytological examination is not definitive, and can improve clinical practice," said Dr. Davies.

Sabtu, 16 April 2011

Causes of Cancer

Cancer is a class of disease characterized by out-of-control cell growth. With more than 200 different types of cancer, one can develop it in virtually any organ of the body. Research states that there are more than 60 different organs in the body where cancer can develop.

Typically, one form of cancer will develop in certain areas of the body. However, since cancer can develop from almost any type of cell, it is also possible that more than one type of cancer can develop in any one part of the body. For example, one can develop pleural mesothelioma or pericardial mesothelioma, two different types of cancer, even though they both form in, and around, cardiac muscles.

Ultimately, cancer is the result of cells that grow uncontrollably and do not die. Whereas normal cells in the body go through life stages of growth, division and death, cancer cells do not complete this cycle. Programmed cell death is called apoptosis, and when this process begins to weaken, cancer can form. Since cancer cells do not die, they continue to grow and divide, causing a mass of abnormal cells to develop, eventually causing cancer.

Cancer is a complex group of diseases with numerous causes. Genetic factors, smoking, diet and physical activity, certain infections and exposure to different types of chemicals and radiation, such as asbestos, are all linked to the development of cancer.

In this section, one can learn more about the known causes of cancer and educate themselves on how to better prevent this disease from developing in themselves or their loved ones.

Genetics and Cancer: Some types of cancer are known to run in certain families’ histories. However, most cancers are not linked to genes. Therefore, one does not literally inherit the disease from their parents. This section uncovers the links between genes and cancer, as well as genetic testing and how it is used.

Tobacco and Cancer: This section relates tobacco usage with cancer and provides resources for those interested in quitting smoking. It also touches on the synergistic effects of smoking and exposure to asbestos.

Diet and Physical Activity: Learn how diet, physical activity, lifestyle choices and alcohol use may affect one’s risk of developing cancer.

Sun and UV Exposure: This section connects excessive sun exposure to cancer. It also provides resources and ways to protect oneself from harmful UV rays.

Other Carcinogens: Some environmental causes may be lurking in one’s home or at work. This section helps individuals understand and identify possible pollutants in the air.


American Cancer Society

Cancer Myths and Misconceptions

Myths can cause hypochondriacs and the like to unnecessarily worry about their health. Frightening claims on the internet circulate daily about new products causing cancer. Besides most of the claims being bogus, many of these accusations cause people to worry about their health, and the health of their families for no reason. One should get all the facts before jumping to conclusions. Below is a list of common myths about cancer and whether or not there’s any truth to them.

Myth: Deodorant can cause breast cancer.

Fact: Although a few reports have suggested that some deodorant products contain harmful substances such as aluminum compounds and parabens that can be absorbed through the skin, there’s no conclusive evidence linking the use of underarm antiperspirants with breast cancer. According to the National Cancer Institute, no clinical studies have yet to link these products with breast cancer.

If someone is still concerned about using deodorants that contain substances such as aluminum compounds and parabens, they can certainly find natural products that do not contain those chemicals.

Myth: Microwaving food in plastic containers releases harmful, cancer causing substances.

Fact: Microwave-safe plastics and wraps do not leak harmful chemicals into food.

However, the Food and Drug Administration (FDA) states that plastic containers produced with no intention of being used in a microwave can melt and potentially leak chemicals into food. Things such as margarine tubs and similar containers should not be put into a microwave to heat up food. It is important to check to see that the container being used in a microwave is labeled microwave-safe.

Myth: People diagnosed with cancer should not eat sugar, since it can cause cancer to grow faster.

Fact: Sugar does not make cancer grow faster. Just like healthy cells, cancer cells depend on blood sugar (glucose) for energy. However, giving more sugar to cancer cells does not speed their growth. Likewise, denying cancer cells sugar will not impede their growth.

This misconception may be due in part to a misunderstanding of positron emission tomography (PET) scans, which use a small amount of radioactive tracer – typically a form of glucose. Since cancer cells use more energy, they absorb a greater amount of this tracer. For this reason, people have concluded that cancer cells grow faster on sugar, but it is simply not true.

Myth: Good people don’t get cancer.

Fact: In the days of old, it was a common belief that illness was a punishment associated with a person who did bad things. As a matter of fact, some cultures still uphold those beliefs. However there is absolutely no evidence whatsoever to prove you can get cancer simply because you deserve it. To test how crazy this theory is, try explaining why a newborn or young child would deserve cancer.

Myth: Cancer is contagious.

Fact: Unlike a cold, a person cannot catch cancer from someone who has it.

That being said, there is no need to avoid someone who has cancer. In fact, a loved one touching, and spending more time with someone who has cancer could be more beneficial than not.

Although cancer itself is not contagious, some viruses, which are contagious have been known to cause cancer. Examples of these viruses are:

  • Human papillomavirus (HPV): a sexually transmitted disease – that can cause cervical cancer among other forms of cancer.
  • Hepatitis C: a virus transmitted through sexual intercourse, or contracted through infected intravenous (IV) needles. Hepatitis C can cause liver cancer.

One should talk to a doctor about ways to protect themselves from these viruses.

Myth: Grilled meats can cause cancer

Fact: It has been proven that eating grilled, or pan fried meat can increase a person’s risk of cancer.

When meat is grilled a harmful chemical called heterocyclicamines are created. Research suggests that since a greater quantity of this chemical is found in meats cooked well done or burnt, to either limit the amount of time the meat is spent on the grill, and or just cut off the burnt pieces altogether. They also recommend marinating and precooking meats in a microwave safe container prior to cooking meat elsewhere. Keep in mind grilling foods such as fruits and veggies are safe and healthy.


Mayo Clinic Staff, . "Cancer causes: Popular myths about the causes of cancer." Mayo Clinic 16 May 2009: n. pag. Web. Retrieved 8 Apr 2011 by Mayo Clinic.

Breast Cancer

Breast cancer is the second most common cancer among women in the United States. While men have been diagnosed with this cancer, women are 100 times more likely to develop breast cancer over men.

Breast cancer is a type of cancer that forms in tissues of the breast. It usually originates in the ducts (tubes that carry milk to the nipple) but it can also form in the lobules, the glands that produce milk. Most breast lumps are benign (not cancerous), however some may need to be sampled under a microscope to make certain that they are not cancer.

Certain women are at higher risks of getting breast cancer than others. Age, family history and genetic makeup are not things that can be altered; however there are external risk factors that can be controlled. These risks include:

  • Drinking more than two alcoholic beverages per day
  • Bearing children after the age of 30 (or never having children at all)
  • Taking the drug diethylstilbestrol (DES) to prevent miscarriages
  • Obesity (thought to trigger excess estrogen production)
  • Receiving hormone replacement therapy (HRT)
  • Receiving radiation therapy to the chest

Asbestos and Breast Cancer

Environmental factors may play a role in breast cancer as well. The correlation between breast cancer and mesothelioma is uncertain. Conversely, studies have shown a link to higher rates of breast cancer in women that were exposed to environmental toxin asbestos. There is not enough evidence to indicate that this is a causal relationship, but it could suggest that long-term asbestos exposure may be associated with higher risks of breast cancer.

A study of British factory workers who were diagnosed with cancer found a slight increase in breast cancer diagnoses in female factory workers who were exposed to asbestos in the workforce for two or more years. Another British study examined 178 females for the presence of asbestos. The fiber was prevalent in the lungs of 30 percent of all women in the study, yet the bulk of the females found with asbestos were found in the subgroup of women who had been diagnosed with breast cancer. Of the 82 women with breast cancer, 38 were found to have asbestos in their lungs.

The second study suggests that asbestos fibers may have pierced the lungs and passed through the muscles covering the chest wall, eventually reaching the breast tissue. While there is not enough evidence to support the implication, there is a potential link between breast cancer and asbestos exposure.


Wagner, J. "Mortality from all cancers of asbestos factory workers in east London 1933-80." Pub Med n. pag. Web. 11 Apr 2011. Retrieved by Pub Med.

Cancer Overview

There are more than 100 diseases that fall under the broad umbrella of “cancer.” The uniting feature of these diseases is abnormal cell division – cancerous cells are those that grow out of control. Though cell division is an important bodily process that allows for growth and repairing injuries, when the DNA safeguards that control division rates fail, cancer develops. These cancerous cells often invade other, healthy tissues, something normal cells cannot do.

Damage to a cell’s DNA may cause it to replicate instead of die when it is no longer needed, creating more cells with damaged DNA. A variety of factors can cause this damage, from genetic abnormalities to environmental causes like smoking or asbestos exposure. However, the cause is not always known. If cancerous cells spread to other parts of the body through blood or lymph vessels, the cancer is said to have metastasized. This is often a sign that the cancer is in its later stages and makes the disease more difficult to treat.

Though in common speech, “tumor” is sometimes used as interchangeable with “cancer,” these words refer to two different things; not all cancers cause tumors, and not all tumors are cancerous. Leukemia, for example, causes cancer cells to develop in the blood and blood-forming organs like bone marrow, but does not form tumors. Benign tumors are noncancerous and cannot invade other tissues or metastasize. However, a benign tumor can cause health problems if it continues to grow and presses into other organs, disrupting their function.

Cancers can be divided into broad categories based on the locations where they originate. Carcinomas are cancers that begin in the skin or lining of the internal organs, whereas sarcomas are those that start in bone, cartilage, fat, muscle, blood, vessels, or other connective tissue. Leukemia, as noted above, begins in blood-forming tissues, and lymphoma and myeloma are cancers of immune system tissues and organs. Finally, central nervous system cancers are those that develop in the brain or spinal cord.

Unfortunately, cancer has become an extremely common phenomenon. The American Cancer Society projects that one-third of all women and half of all men in the United States will develop cancer at some point during their lifetimes. According to the National Cancer Institute, over 1.5 million new cases of cancer, not including melanoma, were reported in 2010, and 569,490 people died of cancer. Risk factors vary from region to region as well as person to person. Factors known to increase risk of developing cancer include smoking, heavy drinking, exposure to ultraviolet rays and sunlight, and poor diet.