Inhalation of mineral dusts causes chronic, nonneoplastic lung diseases called pneumoconioses. This group of disorders includes diseases induced by organic and inorganic particulates as well as chemical fume-and vapor-induced nonneoplastic lung diseases. The most common pneumoconioses are caused by exposures to coal dust (in mining of hard coal), silica (in sandblasting and stone cutting), asbestos (in mining, fabrication, and insulation work), and beryllium (in mining and fabrication). Exposure to these agents nearly always occurs in the workplace. The increased risk of cancer as a result of asbestos exposure, however, extends to family members of asbestos workers and to other persons exposed outside the workplace. Pneumoconioses and their pathogenesis are discussed in Chapter 13.
Tobacco is the most common exogenous cause of human cancers, being responsible for 90% of lung cancers. The http://ebooksmedicine.net
Fig. 8.6 Theeffectsofsmokingonsurvival.Thestudycomparedage-specificdeathratesforcurrentcigarettesmokerswiththoseofindividualswhoneversmokedregularly(BritishDoctorsStudy).Thedifferenceinsurvival,measuredatage75betweensmokersandnonsmokersis7.5years.(Modified from Stewart BW, Kleihues P, editors: Worldcancerreport,Lyon, 2003, IARC Press.) main culprit is cigarette smoking, but smokeless tobacco in its various forms (snuff, chewing tobacco) also is harmful to health and is an important cause of oral cancer. Not only does the use of tobacco products create personal risk, but also passive tobacco inhalation from the environment (“second-hand smoke”) can cause lung cancer in nonsmokers. From 1998 to 2007 in the United States, the incidence of smoking declined modestly, but this trend failed to continue, and approximately 20% of adults remain smokers. In recent years, China has become the world’s largest producer and consumer of cigarettes. China has approximately 350 million smokers who in aggregate consume about 33% of all cigarettes smoked worldwide. Cigarette smoking causes, worldwide, more than 4 million deaths annually, mostly from cardiovascular disease, various types of cancers, and chronic respiratory problems. It is expected that there will be 8 million tobacco-related deaths yearly by 2020, the major increase occurring in developing countries. Of people alive today, an estimated 500 million will die from tobacco-related illnesses. In the United States alone, tobacco is responsible for more than 400,000 deaths per year, with one-third of these attributable to lung cancer.
Smoking is the most important cause of preventable human death. It reduces overall survival in a dose-dependent fashion. Whereas 80% of nonsmokers are alive at age 70, only about 50% of smokers survive to this age (
Fig. 8.6 ). Cessation of smoking greatly reduces the risk of death from lung cancer, and it even has an effect, albeit reduced, on people who stop smoking at age 60. Discussed
Fig. 8.7 Adverseeffectsofsmoking.Themorecommonareinboldface.Cancer of oral cavity Cancer of larynx Cancer of esophagus Cancer of lung Myocardial infarction Peptic ulcer Cancer of pancreas Systemic atherosclerosis Chronic bronchitis, emphysema
Cancer of bladder next are some of the agents contained in tobacco and diseases associated with tobacco consumption. Adverse effects of smoking in various organ systems are shown in
Fig. 8.7
The number of potentially noxious chemicals in tobacco smoke is vast;