Relationship between pleural plaques and biomarkers of cumulative asbestos dose. A necropsy study.

BACKGROUND

The relationship between pleural plaques and cumulative asbestos exposure is controversial.

OBJECTIVES

To evaluate the relationship between lung asbestos bodies (AB) and fibres (AF) and plaques presence and extension.

METHODS

In a necropsy series of shipyard workers with asbestos-related diseases, we measured counts (per g of dry lung tissue) of AB (thousands) and AF>1 µm (millions). Pleural plaques were classified into three extension grades. We fitted univariate and multivariable linear (dependent variables: AB and AF, log10 transformed) and multinomial (dependent variable: plaques grade) regression models.

RESULTS

We analysed 124 subjects, 13 without plaques 20 with grade 1, 69 with grade 2, and 22 with grade 3 plaques. Geometric means (GM) of AB were 10.6, 23.3, 126, and 140 in the four groups respectively (P=0.0001). GMs for AF (mostly amphiboles) were 1.2, 1.4, 7.3, and 12.9 (P=0.0001). AB and AF were strongly correlated (r=0.81). The likelihood of no plaques and grade 1 plaques decreased with increasing AB and AF doses, with a corresponding increase of grade 2 and 3 plaques. Plaque presence and extension was also associated with histologically verified asbestosis (P<0.001).

CONCLUSIONS

Our study showed a strong positive relationship between pleural plaque presence and extension and both lung asbestos burden and asbestosis.