Research report (Health Effects Institute)
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Res Rep Health Eff Inst · May 2016
Ambient and Controlled Particle Exposures as Triggers for Acute ECG Changes.
Previous studies have examined changes in heart rate variability (HRV*) and repolarization associated with increased particulate matter (PM) concentrations on the same and previous few days. However, few studies have examined whether these health responses to PM occur within a few hours or even less. Moreover, it is not clear whether exposure of subjects to ambient or-controlled PM concentrations both lead to similar health effects or whether any of the subjects' individual characteristics modify any of their responses to PM. The aims of the cur- rent study were to investigate whether exposure to PM was associated with rapid changes (< 60 minutes or con- current hour up to a delay of 6 hours) in markers of car- diac rhythni or changes in total antioxidant capacity (a marker of protection against oxidative stress) and whether any PM effects on cardiac rhythm markers were modified by total antioxidant capacity, age, obesity, smoking, hypertension, exertion, prior myocardial infarction (MI), or medication. ⋯ Increased UFP concentrations were associated with decreased SDNN in both of the panel studies and one of the two controlled-exposure studies. We also found that decreased SDNN was associated with both increased PM2.5 and AMP concentrations in the previous 6 hours in the panel studies and that decreased RMSSD was associ- ated with increased PM2.5 concentrations in the previous 6 hours in the panel studies. We therefore concluded that the research questions were replicated. Our findings suggest that both UFPs and PM2.5 are associated with autonomic dysfunction within hours of exposure, which may in part. explain the previously reported risk of acute cardiovascular events associated with increased PM in the previous few hours. Despite the heterogeneity of the study populations,and protocols, our findings provided consistent evidence for the induction of rapid pathophysiological responses by UFPs and PM2.5- The absence of consistent associations between UFPs, PM2.5, and these outcomes when examining shorter time intervals indicates that the 5- to 60-minute responses may be less pronounced than the responses occurring within hours. However, the findings from the 5-minute intervals may have been affected by the variety of proto- cols and conditions from study to study as well as by the potential effects of underlying diseases (e.g., healthy indi- viduals versus individuals with diabetes or a recent cor- onary artery. event), physical activity, circadian rhythms, stress, and/or medications.