Mr E. A. Walker said: The lungs may not be the only tissues exposed to asbestos. In a working environment one might reasonably anticipate some oral intake. Is there any evidence of an excess of oesophageal or gastric cancer in the industries where the pneumoconioses occur? If this were the case it might bring into question the use of asbestos as a filter, e.g. in the production of beer.

The Author, in reply, said that a number of asbestos feeding experiments had been undertaken in this country and in the United States, and none had produced any tumours.

Professor P. C. Elmes added that gastro-intestinal cancers are reported in excess only in heavily exposed working groups and even then not consistently. When asbestos dust is inhaled the bulk of it is cleared from the airways and lungs and swallowed, so that the alimentary dose is very much higher in dust-exposed groups than from drinking liquids cleared with asbestos. The epidemiological evidence does not support a real risk from beverages.

Dr J. N. M. Firth posed the following questions:

( a ) Does silicified crocidolite, used in the preparation of semi-precious jewellery, cause the same problems as the pure mineral?

( b ) ‘Pele hair’ is a common product of volcanic activity. Do the fibres have the right dimensions to cause problems?

( c ) Vesicular basalts occur in many areas of the world, and I recall collecting a suite of zeolites from N Skye which contained many fibrous varieties. Would

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