Possible metabolic interaction between hexane and other solvents co-exposed at sub-occupational exposure limit levels

Objective: To investigate whether metabolic interactions exist between hexa ne (HEX) and other solvents when co-exposed at the levels below occupationa l exposure limits. Methods: Workers, 219 men in ten workshops in total, vol unteered to participate in the study. They were occupationally exposed to m ixtures of HEX and one or more of toluene (TOL), ethyl acetate (EA) and ace tone (ACE). Time-weighted average intensity of vapor exposures was monitore d by diffusive personal sampling. 'Free'- and 'total'-2, 5-hexanedione (HD) levels in the end-of-shift urine samples were determined by gas chromatogr aphy (GC) before and after acid hydrolysis of urine, respectively, and expr essed as observed (HDob) or after correction for creatinine concentration ( HDcr) or urine specific gravity (HDsg). Possible interaction was examined b y multiple regression analysis (MRA), taking either free- or total-HD as a dependent variable, and the four solvent concentrations as independent vari ables. Results: In most cases, exposure intensity did not exceed the curren t occupational exposure limits even when additiveness was assumed. In addit ion that HEX was the most influential independent variable in all cases as expected, the MRA showed that, in cases of free-HD, ACE was also influentia l to HDob although weakly, but not to HDcr or HDsg. With regard to total-HD , ACE was weakly influential to HDob and HDsg, and EA also weakly to HDcr. The effect of ACE on free- or total-HD was not detected, however, when 22 m en exposed only to HEX and ACE were subjected to the same analysis. Similar ly, the effect of EA on total-HD was not observed among the remaining 197 m en exposed to HEX, TOL and EA only. Conclusions: When the exposures were be low occupational exposure limits, the free-HD levels in urine after HEX exp osure will not be modified by co-exposures to TOL, EA or ACE.