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Case Study 3: Asbestos Toxicity
Pages 168-188

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From page 168...
... EN Asbestos exposure is associated with asbestosis, mesothelioma, arid lung cancer, and may cause cancer at extrathoracic sites. This monograph is one in a series of self-instructional publications designed to increase the primary care provider's knowledge of hazardous substances in the environment and to aid in the evaluation of potentially exposed patients.
From page 169...
... A chest X ray is normal.
From page 170...
... Although many applications have been phased out of production, uses of asbestos have included the following: Commercial Boilers and heating vessels Cement pipe Clutch, brake, transmission components Conduits for electrical wire Corrosive chemical containers Electric motor components Heat protective pads Laboratory furniture Paper products Pipe covering Roofing products Sealants and coatings Textiles (including curtains) Homes and Bulidings Duct insulation Fire protection panels Fireplace artificial logs or ashes Furnace insulating pads Fusebox liners Heater register tape and insulation Joint compounds Patching plaster Pipe or boiler insulatior: Sheet vinyl or floor tiles Shingles Textured acoustical ceiling Underlayment for sheet flooring Asbestos fibers may result from mining, milling, and weathering of asbestos-bearing rock, and from the manufacture, wear, and disposal of asbestos-containing products.
From page 171...
... Fibrous tremolite, the asbestos commonly found in talc, has also been found in play sand. Drinking water supplies may become contaminated with asbestos from erosion of natural land sources, discarded mine and mill tailings, asbestos cement pipe, and from disintegration of other asbestos-containing materials transported via rain.
From page 172...
... Cigarette smoking and exposure to other carcinogens greatly increase the risk of asbestos-associated lung cancer. A comparison of the experiences of 17,800 asbestos insulation workers with matched controls showed that asbestos workers who did not smoke suffered 5 times the number of lung cancer deaths than controls who neither smoked nor worked with asbestos (55 deaths per 100,000 man-years for asbestos workers who did not smoke compared with 1 1 deaths per 100,000 man-years for controls who were neither asbestos workers nor smokers)
From page 173...
... There is evidence that cigarette smoking in asbestos workers is also associated with increased risk of cancer of the esophagus, oropharynx and buccal cavity, and larynx. Cancers of the stomach, colon-rectum, and kidney, however, do not appear to be synergistically affected by smoking and asbestos exposure since smoking and nonsmoking asbestos workers suffer equal incidences of these health effects.
From page 174...
... Data do not clearly relate Gl tumors or peritoneal mesotheliomas to direct ingestion of asbestos fibers, although persons exposed to asbestos by inhalation have been reported to have a twofold greater risk of colorectal cancer than unexposed persons. Some investigators believe this malignancy is caused by fibers removed from the lungs' upper respiratory regions by ciliary mechanisms and then swallowed.
From page 175...
... Exposure to other carcinogens, dose and duration of exposure, individual susceptibility, and elapsed time since initial exposure all may play a role in disease development. Chronic low-level asbestos exposure has been associated with lung cancer, mesothelioma, and pleural diseases, including pleural asbestosis; higher doses are more likely to produce parenchymal asbestosis.
From page 176...
... Pleural plaques are not lung cancer precursors, although persons with pleural plaques have an increased incidence of lung cancer. Migration of inhaled asbestos to the pleura is the most likely cause of plaques.
From page 177...
... O It is unclear whether a threshold asbestos dose exists for lung cancer. O Increased incidence of gastrointestinal cancers has been reported among asbestos workers.
From page 178...
... Cardiovascular Effects Fibrosis of the lung can lead to increased resistance to blood flow through the capillary bed, resulting in cor pulmonale. This condition may also occur with less severe fibrotic disease, especially if chronic obstructive lung disease is simultaneously present, as commonly seen in cigarette-smoking asbestos workers.
From page 179...
... signs and Symptoms Significant clinical syndromes include asbestosis, lung cancer, and mesothelioma. Asbestosis The most common finding in asbestos-induced pulmonary disease is pleural thickening, often manifested as discrete pleural plaques.
From page 180...
... Fibrotic lung disease due to asbestos inhalation is often associated with pleural plaque formation, which eliminates other etiologic possibilities such as drugs, radiation, sarcoidosis, collagen vascular disorders, Goodpasture's syndrome, hemosiderosis, idiopathic pulmonary fibrosis secondary to lung infections, and inhaled silica, coal dust, or organic dusts. Lung Cancer Lung cancer caused by asbestos exposure cannot be differentiated from cancer caused by other environmental factors.
From page 181...
... The association of pleural thickening and calcification enhances diagnostic accuracy; however, open lung biopsy is the only definitive diagnostic test for asbestosis. The radiologic appearance of asbestos-induced lung cancer does not differ from that of other cancers.
From page 182...
... Sputum cytology remains useful as a diagnostic test for neoplasia and lung cancer, however. Other Tests Recent studies suggest that lymphocyte abnormalities {particularly T-cell)
From page 183...
... Persons exposed to asbestos should be advised of the increased risk of lung cancer and the synergistic effects of cigarette smoking, although smoking does not affect the development of mesothelioma. Explaining environmentally related cancer risk is difficult because extrapolation of risk from workplace data is impossible in many cases.
From page 184...
... City/ (7) if examination of the father of the child described in the case study is entirely normal except for bilateral pleural plaques, what follow-up will you recommend?
From page 185...
... EPA's proposed maximum contaminant level (MCL) for asbestos in drinking water is 7 million fibers (larger than 10 microns in length)
From page 186...
... Declining relative risks tor lung cancer after cessation of asbestos exposure. J Occup Med 1984;26:422-6.
From page 187...
... A thorough medical and occupational history; a physical examination, including auscultation of the head and lungs; chest X ray; and spirometryto assess possible restrictive and/orobstructive pulmonary disease may be indicated. Stool hemoccult testing is also advised.
From page 188...
... A respected physician in the community is often able to put the risk of disease due to asbestos into perspective for such an audience. Before making public statements, however, it would be advisable to consult with state and local public health officials on the potential for asbestos exposure in local schools.


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