question: How do things like asbestos cause cancer?
comment: There are certain irritants that are known to cause cancer. The exact mechanisms behind this is still unknown and it is something which is hard to study. Irritants like asbestos is killing cells. When cells are killed neighboring cells will have to divide to fill the void. So there is likely something with that process that can go wrong causing cancer. It could be that the DNA does not copy correctly which can cause a mutation. It is possible that during the copy process the helix is unwound which makes it more vulnerable to the regular causes of mutation. It could be that the genes responsible for cell division may become stuck in the on position sometimes. It is possible that the frequent cell divisions can easier mask the presence of a cancer allowing it to grow uncontrolled. We do not know yet. All we know is that according to the statistics people who worked with asbestos got certain cancers at a higher rate then the average population.
passages: Some substances cause cancer primarily through their physical, rather than chemical, effects. A prominent example of this is prolonged exposure to asbestos, naturally occurring mineral fibers that are a major cause of mesothelioma (cancer of the serous membrane) usually the serous membrane surrounding the lungs. Other substances in this category, including both naturally occurring and synthetic asbestos-like fibers, such as wollastonite, attapulgite, glass wool and rock wool, are believed to have similar effects. Non-fibrous particulate materials that cause cancer include powdered metallic cobalt and nickel and crystalline silica (quartz, cristobalite and tridymite). Usually, physical carcinogens must get inside the body (such as through inhalation) and require years of exposure to produce cancer.
   As an environmentally triggered malignancy, mesothelioma tumors have been found to be polyclonal in origin, by performing a X-inactivation based assay on epitheloid and biphasic tumors obtained from female patients. These results suggest that an environmental factor, most likely asbestos exposure, may damage and transform a group of cells in the tissue, resulting in a population of tumor cells that are, albeit only slightly, genetically different.
  
  Section::::Pathophysiology.:Immune system.
   Section::::Biological interactions.
  
  Section::::Biological interactions.:Mechanisms of carcinogenicity.
  
  Stanton and Layard hypothesized in 1977–78 that toxicity of fibrous materials is "not" initiated by "chemical" effects; that is, any trigger-effects of asbestos must presumably be "physical", such as mechanical damage which might disrupt normal cell activity—especially mitosis.
  
  There is experimental evidence that very slim fibers (60 nm, 0.06 μm in breadth) tangle destructively with chromosomes (being of comparable size). This is likely to cause the sort of mitosis disruption expected in cancer.
  
  Section::::Biological interactions.:Chemistry.
   BULLET::::- P14
  
  Asbestos has also been shown to mediate the entry of foreign DNA into target cells. Incorporation of this foreign DNA may lead to mutations and oncogenesis by several possible mechanisms:
  
  BULLET::::- Inactivation of tumor suppressor genes
  
  BULLET::::- Activation of oncogenes
  
  BULLET::::- Activation of proto-oncogenes due to incorporation of foreign DNA containing a promoter region
  
  BULLET::::- Activation of DNA repair enzymes, which may be prone to error
  
  BULLET::::- Activation of telomerase
  
  BULLET::::- Prevention of apoptosis
   Some substances cause cancer primarily through their physical, rather than chemical, effects on cells. A prominent example of this is prolonged exposure to asbestos, naturally occurring mineral fibers which are a major cause of mesothelioma, which is a cancer of the serous membrane, usually the serous membrane surrounding the lungs. Other substances in this category, including both naturally occurring and synthetic asbestos-like fibers such as wollastonite, attapulgite, glass wool, and rock wool, are believed to have similar effects. Non-fibrous particulate materials that cause cancer include powdered metallic cobalt and nickel, and crystalline silica (quartz, cristobalite, and tridymite). Usually, physical carcinogens must get inside the body (such as through inhaling tiny pieces) and require years of exposure to develop cancer. Common occupational carcinogens include:
   Section::::Malignant asbestos-related diseases.:Asbestos-related lung cancer.
   Section::::Malignant asbestos-related diseases.
  
  Section::::Malignant asbestos-related diseases.:Malignant mesothelioma.
   Section::::Society and culture.
  
  Section::::Society and culture.:Legal issues.
   Many building materials used in both public and domestic premises prior to the banning of asbestos may contain asbestos. Those performing renovation works or DIY activities may expose themselves to asbestos dust. In the UK, use of chrysotile asbestos was banned at the end of 1999. Brown and blue asbestos were banned in the UK around 1985. Buildings built or renovated prior to these dates may contain asbestos materials.
  
  Section::::Causes.:Genetic disposition.
   Health impact of asbestos
  
  All types of asbestos fibers are known to cause serious health hazards in humans. Amosite and crocidolite are considered the most hazardous asbestos fiber types; however, chrysotile asbestos has also produced tumors in animals and is a recognized cause of asbestosis and malignant mesothelioma in humans, and mesothelioma has been observed in people who were occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos factories and mines.
   Pleural contamination with asbestos or other mineral fibers has been shown to cause cancer. Long thin asbestos fibers (blue asbestos, amphibole fibers) are more potent carcinogens than "feathery fibers" (chrysotile or white asbestos fibers). However, there is now evidence that smaller particles may be more dangerous than the larger fibers. They remain suspended in the air where they can be inhaled, and may penetrate more easily and deeper into the lungs. "We probably will find out a lot more about the health aspects of asbestos from [the World Trade Center attack], unfortunately," said Dr. Alan Fein, chief of pulmonary and critical-care medicine at North Shore-Long Island Jewish Health System.
   When asbestos-containing material is damaged or disintegrates, microscopic fibers are dispersed into the air. Inhalation of asbestos fibers over long exposure times is associated with increased incidence of lung cancer, in particular the specific form mesothelioma. The risk of lung cancer from inhaling asbestos fibers is significantly greater to smokers, however there is no confirmed connection to damage caused by asbestosis . The symptoms of the disease do not usually appear until about 20 to 30 years after the first exposure to asbestos.
   Mesothelioma development in rats has been demonstrated following intra-pleural inoculation of phosphorylated chrysotile fibers. It has been suggested that in humans, transport of fibers to the pleura is critical to the pathogenesis of mesothelioma. This is supported by the observed recruitment of significant numbers of macrophages and other cells of the immune system to localized lesions of accumulated asbestos fibers in the pleural and peritoneal cavities of rats. These lesions continued to attract and accumulate macrophages as the disease progressed, and cellular changes within the lesion culminated in a morphologically malignant tumor.
   Asbestos-related diseases
  
  Asbestos-related diseases are disorders of the lung and pleura caused by the inhalation of asbestos fibres. Asbestos-related diseases include non-malignant disorders such as asbestosis (pulmonary fibrosis due to asbestos), diffuse pleural thickening, pleural plaques, pleural effusion, rounded atelectasis and malignancies such as lung cancer and malignant mesothelioma.
   Asbestos from natural geologic deposits is known as "naturally occurring asbestos" (NOA). Health risks associated with exposure to NOA are not yet fully understood, and current US federal regulations do not address exposure from NOA. Many populated areas are in proximity to shallow, natural deposits which occur in 50 of 58 California counties and in 19 other US states. In one study, data was collected from 3,000 mesothelioma patients in California and 890 men with prostate cancer, a malignancy not known to be related to asbestos. The study found a correlation between the incidence of mesotheliomas and the distance a patient lived from known deposits of rock likely to include asbestos; the correlation was not present when the incidence of prostate cancer was compared with the same distances. The risk of mesothelioma declined by 6% for every that an individual had lived away from a likely asbestos source.
   Asbestos is a mineral which was extensively used in the United States to fireproof buildings and textiles, among other items, in the 1950s-1980s. Workers are frequently exposed to asbestos during demolition and renovation work, which can cause asbestosis and/or mesothelioma. Asbestos exposure can also cause pleural effusion, diffuse pleural fibrosis, pleural plaques, and non-mesothelioma lung cancer. Smoking greatly increases the lung cancer risk of asbestos exposure.
  
  Residents and workers of asbestos mining centers such as the town of Asbest, Russia suffer dangerous exposure to asbestos and asbestos dust.
  
  Section::::Occupational environmental exposure.:BCME.
   Section::::Pathophysiology.:Intracellular.
  
  Analysis of the interactions between asbestos fibers and DNA has shown that phagocytosed fibers are able to make contact with chromosomes, often adhering to the chromatin fibers or becoming entangled within the chromosome. This contact between the asbestos fiber and the chromosomes or structural proteins of the spindle apparatus can induce complex abnormalities. The most common abnormality is monosomy of chromosome 22. Other frequent abnormalities include structural rearrangement of 1p, 3p, 9p and 6q chromosome arms.
  
  Common gene abnormalities in mesothelioma cell lines include deletion of the tumor suppressor genes:
  
  BULLET::::- Neurofibromatosis type 2 at 22q12
  
  BULLET::::- P16
   Section::::Non-malignant asbestos-related pleural diseases.
  
  Benign asbestos-related pleural abnormalities encompass four types of pleural changes:
  
  BULLET::::- Pleural plaques
  
  BULLET::::- Diffuse pleural thickening
  
  BULLET::::- Benign asbestos pleural effusions
  
  BULLET::::- Rounded atelectasis (folded lung)
  
  The pleura appears to be more sensitive than the lung parenchyma to the effects of asbestos fibres. Thus asbestos-related pleural diseases can result from much lower doses than the fibrotic changes in the lung.
  
  Section::::Non-malignant asbestos-related pleural diseases.:Pleural plaques.
   Asbestos are fibrous material that are found in many industrial buildings in Australia from the 1940's to 1987 . Exposure to asbestos occurs through inhalation of the particulates contained in these fibrous material, and they quickly become trapped and deposited in the airways and passages of the lungs. As such, the exposure to asbestos increases the risk of developing cancers in the lung, ovary and pharynx. The incidence of these cancers are said to occur decades after initial exposure to asbestos. Products containing asbestos were eventually phased out towards the end of the 1980's, and a complete ban on asbestos was initiated in 2003. State and federal law in Australia have guidelines in their duty of care conduct of both employers and employees to reduce the risk of asbestos exposure. 
   Trace amounts can be found in talc, which often contains asbestos fibers of various types. Studies into health risks associated with talc determined that with so many commercial varieties of talc being types of asbestine minerals, the resultant lung disease—talcosis, which can follow their prolonged inhalation, is usually a variety of asbestosis.
   Section::::History of health concerns and regulation.:1950s.
   All types of asbestos fibers are known to cause serious health hazards in humans and animals. Amosite and crocidolite are considered the most hazardous asbestos fiber types; however, chrysotile asbestos has also produced tumors in animals and is a recognized cause of asbestosis and malignant mesothelioma in humans, and mesothelioma has been observed in people who were occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos factories and mines.
   Experimental evidence suggests that asbestos acts as a complete carcinogen with the development of mesothelioma occurring in sequential stages of initiation and promotion. The molecular mechanisms underlying the malignant transformation of normal mesothelial cells by asbestos fibers remain unclear despite the demonstration of its oncogenic capabilities (see next-but-one paragraph). However, complete in vitro transformation of normal human mesothelial cells to a malignant phenotype following exposure to asbestos fibers has not yet been achieved. In general, asbestos fibers are thought to act through direct physical interactions with the cells of the mesothelium in conjunction with indirect effects following interaction with inflammatory cells such as macrophages.
   Asbestos can cause lung cancer that is identical to lung cancer from other causes. Exposure to asbestos is associated with all major histological types of lung carcinoma (adenocarcinoma, squamous cell carcinoma, large-cell carcinoma and small-cell carcinoma). The latency period between exposure and development of lung cancer is 20 to 30 years. It is estimated that 3%-8% of all lung cancers are related to asbestos. The risk of developing lung cancer depends on the level, duration, and frequency of asbestos exposure (cumulative exposure). Smoking and individual susceptibility are other contributing factors towards lung cancer. Smokers who have been exposed to asbestos are at far greater risk of lung cancer. Smoking and asbestos exposure have a multiplicative (synergistic) effect on the risk of lung cancer. Symptoms include chronic cough, chest pain, breathlessness, haemoptysis (coughing up blood), wheezing or hoarseness of the voice, weight loss and fatigue. Treatment involves surgical removal of the cancer, chemotherapy, radiotherapy, or a combination of these (multimodality treatment). Prognosis is generally poor unless the cancer is detected in its early stages. Out of all patients diagnosed with lung cancer, only 15% survive for five years after diagnosis.
   Toxic wastes often contain carcinogens, and exposure to these by some route, such as leakage or evaporation from the storage, causes cancer to appear at increased frequency in exposed individuals. For example, a cluster of the rare blood cancer polycythemia vera was found around a toxic waste dump site in northeast Pennsylvania in 2008.
  