Method for estimating objectively the comparative merits of biological tests of lead exposure.

with positive smears histological sections failed to reveal asbestos bodies in over 50%.Histological evidence of minimal asbestosis was found in 10 cases.There were no cases of classical asbestosis.The series includes one case of mesothelioma of pleura.There was no significant excess of positive smears in patients dying from gastrointestinal or lung carcinoma.The incidence was higher in patients living in urban areas (25.6%) than in those from rural areas (3.5%).Twenty-nine patients definitely or probably were exposed to asbestos dust at work and two further patients had non-occupational exposure.Neighbourhood contamination with asbestos dust is probably not important in this series.When compared with a series of 23 cases of mesothelioma of pleura or peritoneum, 21 (91%) of which showed asbestos bodies in histological sections of lung, the greater incidence of asbestos bodies in the cases of mesothelioma is statistically highly significant.This survey was suggested by Professor A. G. Heppleston, and I am indebted to him for valuable criticism and advice during the work.My thanks are also due to Professor D. J. Newell for statistical advice, to the late Mr. L. Hall and Mr. W. Brine for assistance in preparing the smears, and to Miss Joyce Ward for assistance in interviewing patients' relatives.