Effect of welding fume on heart rate variability among workers with respirators in a shipyard.

Welding fume exposure is associated with heart rate variability (HRV) reduction. It is still unknown whether respirator can reduce effect of welding fume on HRV among welding workers in a shipyard. We recruited 68 welding workers with respirator and 52 welding workers without respirator to measure HRV indices, including standard deviation of normal-to-normal intervals (SDNN) and square root of the mean squared differences of successive intervals (r-MSSD) by ambulatory electrocardiographic (ECG). Personal exposure to particulate matter less than or equal to 2.5 μm in diameter (PM2.5) was measured by a dust monitor. The association between 5-minute mean PM2.5 and log10-transformed HRV indices was analyzed by mixed-effects models. We found 5-minute mean PM2.5 was associated with 8.9% and 10.3% decreases in SDNN and r-MSSD. Effect of PM2.5 on HRV indices was greatest among workers without respirator {SDNN: 12.4% (95% confidence interval = -18.8--6.9); r-MSSD: 14.7% (95% confidence interval = -20.8--8.6)}. Workers with respirator showed slight decreases in HRV indices {SDNN: 2.2% (95% confidence interval = -6.3--1.9); r-MSSD: 4.0% (95% confidence interval = -6.4--1.6)}. We conclude that respirator use reduces the effect of PM2.5 exposure on HRV among workers performing welding in a shipyard.