Pneumoconiosis is caused by the accumulation of dust in the lungs and the tissue reaction to its presence.
The appearance of pulmonary disability from pneumoconiosis is related to the amount of dust that has been inhaled. This amount will vary with the fibrogenicity of the dust. A dust which has a high fibrogenic potential is capable of incapacitating a larger amount of lung tissue following a shorter exposure than a dust having a low fibrogenic potential. In general, a very small percentage of workers exposed to a dust with a low fibrogenic potential (such a soft-coal miners) become incapacitated solely because they have developed simple pneumoconiosis. However, breathlessness and incapacitation may develop when simple pneumoconiosis becomes converted into the complicated variety and an excessive amount of functioning lung tissue is destroyed by progressive massive fibrosis. Of the pneumoconioses caused by fibrogenic dusts, silicosis and asbestosis are the most important. Silicosis is characterized by multifocal nodular fibrosis whereas asbestosis is typically a non-uniform diffuse pulmonary fibrosis that tends to be more pronounced in the basilar portions of the lungs. Silica and asbestos workers as well as coalminers and workers in non-dusty trades may develop breathlessness from chronic bronchitis or emphysema or both. The cause of this breathlessness is most often ascribable to the destruction of lung tissue or inflammation of the air passages (or both) by cigarette smoke. Cigarette smoke is also the main factor in the production of lung cancer in asbestos workers.
The Encyclopedia of World Problems and Human Potential is a collaboration between UIA and Mankind 2000, started in 1972. It is the result of an ambitious effort to collect and present information on the problems with which humanity is confronted, as well as the challenges such problems pose to concept formation, values and development strategies. Problems included are those identified in international periodicals but especially in the documents of some 60,000 international non-profit organizations, profiled in the Yearbook of International Organizations.
The Encyclopedia includes problems which such groups choose to perceive and act upon, whether or not their existence is denied by others claiming greater expertise. Indeed such claims and counter-claims figure in many of the problem descriptions in order to reflect the often paralyzing dynamics of international debate. In the light of the interdependence demonstrated among world problems in every sector, emphasis is placed on the need for approaches which are sufficiently complex to encompass the factions, conflicts and rival worldviews that undermine collective initiative towards a promising future.
Non-profit, apolitical, independent, and non-governmental in nature, the UIA has been a pioneer in the research, monitoring and provision of information on international organizations, international associations and their global challenges since 1907.