Low level exposure to asbestos: is there a cancer risk?
In the early days of asbestos use when its harmful potential was not understood hygiene standards at the workplace were extremely low. Airborne dust concentrations were uncontrolled and fibre levels in excess of
100 per ml were not unusual. This type of exposure led to the discovery that inhalation of asbestos produced
pulmonary fibrosis,¹ bronchial carcinoma² and mesothelioma³. Efforts to reduce concentrations of asbestos fibre began in the 1930s and, since the 1950s, increasingly stringent limits have been imposed by law. Some countries have banned many uses of asbestos, although it remains almost essential for some special packing and friction products. Various fibre substitutes have been introduced in advanced countries, especially for plastic or cement products, though these are generally less durable and more costly. The latter point is a serious matter in third world countries where asbestos cement products are well-nigh essential for water and drainage pipes and for building construction. In addition, it now seems possible that some manmade mineral fibres could carry similar risks to health.
What conclusions may be drawn from a synthesis of these experimental and epidemiological findings? We cannot say, and it may be impossible to prove or disprove that at very low levels of exposure to asbestos the risk of cancer is zero. None the less, further statistical analyses are needed to test the linearity of risk in relation to intensity of exposure. So far as lung cancer is concerned, clearly any increase in risk at exposure below today's control limits, even in men who smoke more than they now do, would not be detected.
Glossary:
carcinoma - tumor maligno epitelial ou glandular, que tende a invadir tecidos circundantes, originando metástases.
increasingly - cada vez mais
stringent - rigoroso
100 per ml were not unusual. This type of exposure led to the discovery that inhalation of asbestos produced
pulmonary fibrosis,¹ bronchial carcinoma² and mesothelioma³. Efforts to reduce concentrations of asbestos fibre began in the 1930s and, since the 1950s, increasingly stringent limits have been imposed by law. Some countries have banned many uses of asbestos, although it remains almost essential for some special packing and friction products. Various fibre substitutes have been introduced in advanced countries, especially for plastic or cement products, though these are generally less durable and more costly. The latter point is a serious matter in third world countries where asbestos cement products are well-nigh essential for water and drainage pipes and for building construction. In addition, it now seems possible that some manmade mineral fibres could carry similar risks to health.
What conclusions may be drawn from a synthesis of these experimental and epidemiological findings? We cannot say, and it may be impossible to prove or disprove that at very low levels of exposure to asbestos the risk of cancer is zero. None the less, further statistical analyses are needed to test the linearity of risk in relation to intensity of exposure. So far as lung cancer is concerned, clearly any increase in risk at exposure below today's control limits, even in men who smoke more than they now do, would not be detected.
Glossary:
carcinoma - tumor maligno epitelial ou glandular, que tende a invadir tecidos circundantes, originando metástases.
increasingly - cada vez mais
stringent - rigoroso
harmful - prejudicial
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