Table 3

Model goodness of fit and association of lung cancer risk with alternative indicators of cumulative exposure to asbestos fibres, estimated by Poisson regression with adjustment for age, sex, race, calendar time and birth cohort

 Exposure indicator β SE (β) ∆ LR (df) p AIC Biologically-based indices* Modified Lippmann Index (0.25≤D≤1 μm and L≥10 μm)† 0.00283 0.00073 0.0279 11.1 (1) 0.001 2341.6 Berman Index 0.01880 0.00551 0.0326 8.8 (1) 0.003 2343.9 TEM fibres (D<0.25 μm and L≥10 μm) 0.00171 0.00054 0.0321 8.3 (1) 0.004 2344.4 Ad hoc indices (μm-y) Mean fibre length 0.00869 0.00257 0.0757 9.7 (1) 0.002 2343.1 Mean fibre diameter 0.15098 0.04558 0.0726 9.2 (1) 0.002 2343.5 Mean fibre length 0.01919 0.02400 0.1329 9.8 (2) 0.007 2344.9 Mean fibre diameter −0.18835 0.42987 −0.0735
• * Units are f-y/ml. All of the indices also include the criterion that the aspect ratio (length:diameter) is at least 3:1.

• Lippmann proposed minimum diameters of 0.15 μm or 0.3 μm, but we used a cut-off of ≥0.25 μm since that was the closest category in our TEM protocol.

• AIC, Akaike Information Criterion (smaller values indicate better fit); β and SE, regression coefficient and associated standard error; ∆, change in lung cancer risk for increment in exposure equal to 1 IQR; D, diameter; L, length; LR (df), likelihood ratio test statistic (equivalent to χ2) with degree of freedom (df) and associated p value; TEM, transmission electron microscopy.