Effects of co-exposure to noise and mixture of organic solvents on blood pressure.

OBJECTIVES Independent exposure to noise or organic solvents is reported to be associated with cardiovascular effects, but the effect of joint exposure is unclear. The present study aimed to investigate effects of noise, a mixture of organic solvents (N,N-dimethylformamide (DMF) and toluene) and their interaction on hypertension. METHODS We recruited 59 volunteers working in a synthetic leather manufacturing company during 2005-2006. Both personal noise exposure and airborne co-exposure to DMF and toluene at work were measured and used to calculate the mixed hazard index (HI). Multivariate logistic regressions were conducted to estimate between-group differences of hypertension by controlling for potential confounders. RESULTS We found that 18 co-exposure workers (82.22 +/- 2.70 dBA and a mixed HI of 0.53 +/- 0.20) had the highest prevalence of hypertension (55.6%) compared to 15 solvent-exposure workers (a mixed HI of 0.32 +/- 0.18; 46.7%), 9 noise-exposure workers (84.13 +/- 2.30 dBA; 44.4%) and 17 low-exposure workers (11.8%). The adjusted odds ratio (OR) of hypertension compared to low-exposure workers increased from 7.9 times (95% confidence interval (CI)=0.9-66.3; p=0.06) in solvent-exposure workers and 9.1 times (OR=9.1, 95% CI=1.0-81.1; p<0.05) in noise-exposure workers to 13.5 times (95% CI=1.5-117.8; p<0.05) in co-exposure workers. CONCLUSIONS Our findings suggest that co-exposure to noise, DMF and toluene is associated with hypertension in synthetic leather workers. Simultaneous exposure to noise and a mixture of organic solvents may have a sub-additive effect on the risk of hypertension.