Occupational exposure to machining fluids and laryngeal cancer risk: contrasting results using two separate control groups.

This death certificate-based case-control study linked Connecticut Tumor Registry and Connecticut Division of Vital Statistics death data to determine whether machining fluid exposure is associated with laryngeal cancer risk. Laryngeal cancer cases were compared with oral cancer controls and general population controls. Level of exposure to machining fluids was imputed from the usual occupation and industry on the death certificate. Because exposure was infrequent among females, analysis was limited to males. When cases were compared to oral cancer controls, high exposure to machining fluids was associated with laryngeal cancer (odds ratio = 1.48; 95% confidence interval = 1.01-2.16), with a p-value for trend of 0.08. When cases were compared to population controls, no association between machining fluid exposure and laryngeal cancer was observed. A possible reason for the contrasting results, other than chance, is that exposure data quality for the cases and oral cancer controls may have differed from that of the population controls.