Prevalence and incidence of benign asbestos pleural effusion in a working population

Abstract

Benign asbestos effusion was defined by exposure to asbestos, confirmation by roentgenograms or thoracenteses, no other disease related to pleural effusion and no malignant tumor within 3 yr. There were 34 benign effusions among 1135 exposed workers compared with no otherwise unexplained effusions among 717 controls. Prevalence was dose related with 7.0%, 3.7% and 0.2% effusions with severe 3, indirect 2 and peripheral exposure, respectively. The latency period was shorter than for other asbestos-related disorders. Benign effusion was the most common asbestos-related abnormality during the 1st 20 yr after exposure. Incidence studies showed 9.2 effusions/1000 person yr for level 3 exposure, 3.9 for level 2 and 0.7 for level 1. Most effusions were small, 28.6% recurred and 66% were asymptomatic. There was 1 mesothelioma 6 yr after effusion. Asbestos exposure should be carefully searched for in patients with idiopathic pleural effusion.