Laryngeal and hypopharyngeal cancer and occupational exposure to asbestos and man-made vitreous fibers: Results of a case-control study

Background The data from a case-control study performed in France between 1 989 and 1991 were used to test whether exposure to either asbestos or to ma n-made vitreous fibers (MMVF) is a risk factor for cancer of the larynx or the hypopharynx. Methods This study involved 315 incident cases of laryngeal cancer 206 case s of hypopharyngeal cancer; and 305 hospital-based controls with other type s of cancer; all recruited in 15 hospitals in six French cities. The subjec ts' past occupational exposure to asbestos and to four types of MMVF (miner al wool, refractory ceramic fibers, glass filaments, and microfibers) was e valuated based on their job history, with the aid of a job exposure matrix. Odds ratios were calculated with unconditional logistic regression, with a djustment for smoking and drinking levels. Results Exposure to asbestos resulted in a significant increase in the risk of hypopharyngeal cancer (OR = 1.80, 95% CI: 1.08-2.99) and a nonsignifica nt increase in the risk of laryngeal cancer (OR = 1.24, 95% CI: 0.83-1.90). Risk was highest for the epilarynx (highest cumulative level of exposure: OR = 2.22, 95% CI: 1.05-4.71). Exposure to mineral wools was of borderline significance for the risk of hypopharyngeal cancer (OR = 1.55, 95% CI: 0.99 -2.41), and nonsignificantly associated with the risk of larngeal cancer (O R-1.33, 95% CI: 0.91-1.95). The risk was again highest for the epilarynx (O R = 1.85, 95% CI: 1.08-3.17). No significant results were observed for the other MMVF. Conclusions These results suggest that asbestos exposure increases the risk of epilaryngeal and hypopharyngeal cancers. It is difficult to reach a con clusion about the effects of mineral wools, because nearly all the exposed subjects were also exposed to asbestos. The possible effects of other MMVF were difficult to assess in this study, because of the paucity of exposed s ubjects.