Abstract
BackgroundIn occupational settings, boilermakers are exposed to high levels of metallic fine particulate matter (PM2.5) generated during the welding process. The effect of welding PM2.5 on heart rate variability (HRV) has been described, but the relationship between PM2.5, DNA methylation, and HRV is not known.MethodsIn this repeated-measures panel study, we recorded resting HRV and measured DNA methylation levels in transposable elements Alu and long interspersed nuclear element-1 (LINE-1) in peripheral blood leukocytes under ambient conditions (pre-shift) and right after a welding task (post-shift) among 66 welders. We also monitored personal PM2.5 level in the ambient environment and during the welding procedure.ResultsThe concentration of welding PM2.5 was significantly higher than background levels in the union hall (0.43 mg/m3 vs. 0.11 mg/m3, p < 0.0001). The natural log of transformed power in the high frequency range (ln HF) had a significantly negative association with PM2.5 exposure (β = -0.76, p = 0.035). pNN10 and pNN20 also had a negative association with PM2.5 exposure (β = -0.16%, p = 0.006 and β = -0.13%, p = 0.030, respectively). PM2.5 was positively associated with LINE-1 methylation [β = 0.79%, 5-methylcytosince (%mC), p = 0.013]; adjusted for covariates. LINE-1 methylation did not show an independent association with HRV.ConclusionsAcute decline of HRV was observed following exposure to welding PM2.5 and evidence for an epigenetic response of transposable elements to short-term exposure to high-level metal-rich particulates was reported.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2458-14-1279) contains supplementary material, which is available to authorized users.
Highlights
In occupational settings, boilermakers are exposed to high levels of metallic fine particulate matter (PM2.5) generated during the welding process
Studies have shown an association between increased circulating levels of C-reactive protein (CRP) and decreased heart rate variability (HRV) in middle-aged men free of coronary artery disease (CAD), which suggests a relationship between ANS dysfunction induced and systemic inflammation [11]
In the crude analysis adjusting only for PM2.5, the results showed a positive association between long interspersed nuclear element-1 (LINE-1) and ln rMSSD, ln Power spectral density in the low frequency (LF), and ln Power spectral density in the high frequency (HF) (β = 0.05, p = 0.020; β = 0.09, p = 0.026 and β = 0.10, p = 0.043, respectively)
Summary
Boilermakers are exposed to high levels of metallic fine particulate matter (PM2.5) generated during the welding process. Numerous air pollution studies have shown that both acute and cumulative exposures to fine particulate matter (PM2.5) are associated with increased risk of adverse cardiovascular events, such as the onset of atrial fibrillation (AF), incidence and recurrences of myocardial infarction, heart failure and stroke, and mortality from cardiovascular disease [1,2,3,4]. Welders are exposed to high levels of PM2.5 generated during the welding process. Studies have shown an association between increased circulating levels of CRP and decreased HRV in middle-aged men free of CAD, which suggests a relationship between ANS dysfunction induced and systemic inflammation [11].
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