Tuesday, August 23, 2011
Wednesday, August 3, 2011
Asbestos
Asbestos from Greek ἄσβεστος, "unquenchable" or "inextinguishable") is a set of six naturally occurring silicate minerals exploited commercially for their desirable physical properties. They all have in common their asbestiform habit, long, (1:20) thin fibrous crystals.
The inhalation of asbestos fibers can cause serious illnesses, including malignant lung cancer, mesothelioma (a formerly rare cancer strongly associated with exposure to amphibole asbestos), and asbestosis (a type of pneumoconiosis). Long exposure to high concentrations of asbestos fibers is more likely to cause health problems. The European Union has banned all use of asbestos and extraction, manufacture and processing of asbestos products.
Asbestos became increasingly popular among manufacturers and builders in the late 19th century because of its sound absorption, averagetensile strength, and its resistance to fire, heat, electrical and chemical damage. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement(resulting in fiber cement) or woven into fabric or mats. Commercial asbestos mining began in the Eastern Townships of Quebec, Canada and the world's largest asbestos mine is located in the town of Asbestos, Quebec.
Asbestos
Asbestos
Monday, August 1, 2011
Cancer
Cancer (medical term: malignant neoplasm) is a large, heterogeneous class of diseases in which a group of cells display uncontrolled growth, invasion that intrudes upon and destroys adjacent tissues, and often metastasizes, wherein the tumor cells spread to other locations in the body via the lymphatic system or through the bloodstream. These three malignant properties of cancer differentiate malignant tumors from benign tumors, which do not grow uncontrollably, directly invade locally, or metastasize to regional lymph nodes or distant body sites like brain, bone, liver, or other organs.
Researchers divide the causes of cancer into two groups: those with an environmental cause, and those with a hereditary genetic cause. Cancer is primarily an environmental disease, though genetics influence the risk of some cancers. Common environmental factors leading to cancer include: tobacco use, poor diet and obesity, infection, radiation, lack of physical activity, and environmental pollutants.
These environmental factors cause or enhance abnormalities in the genetic material of cells. Cell reproduction is an extremely complex process that is normally tightly regulated by several classes of genes, including oncogenes and tumor suppressor genes. Hereditary or acquired abnormalities in these regulatory genes can lead to the development of cancer. A small percentage of cancers, approximately five to ten percent, are entirely hereditary.
The presence of cancer can be suspected on the basis of clinical signs and symptoms, or findings after medical imaging. Definitive diagnosis of cancer, however, requires the microscopic examination of a biopsy specimen. Most cancers can be treated, with the most important modalities being chemotherapy, radiotherapy and surgery. The prognosis in cancer cases can be greatly influenced by the type and location of the cancer and the extent of disease.
While cancer can affect people of all ages, and a few types of cancer are more common in children than in adults, the overall risk of developing cancer generally increases with age, at least up to age 80-85 yr. In 2007, cancer caused about 13% of all human deaths worldwide (7.9 million). Rates are rising as more people live to an old age and as mass lifestyles changes occur in the developing world.
Subscribe to:
Posts (Atom)