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 χ^{2}) with degree of freedom (df) and associated p value; TEM, transmission electron microscopy.