Friday, February 27, 2009

Some Evidence That Ultrafine Carbon Particles Cause autonomic modulation of the heart and repolarization of the ventricular myocardium.

ECG Parameters and Exposure to Carbon Ultrafine Particles in Young Healthy Subjects.
Zareba, Wojciech1Couderc, Jean Philippe1Oberdörster, Gunter2Chalupa, David1Cox, Christopher3Li-Shan Huang4Peters, Annette5Utell, Mark J.1Frampton, Mark W.1 mark•
Inhalation Toxicology; Mar2009, Vol. 21 Issue 3, p223-233, 11p
The mechanisms underlying the association between air pollution and cardiovascular morbidity and mortality are unknown. This study aimed to determine whether controlled exposure to elemental carbon ultrafine particles (UFP) affects electrocardiogram (ECG) parameters describing heart rate variability; repolarization duration, morphology, and variability; and changes in the ST segment. Two separate controlled studies (12 subjects each) were performed using a crossover design, in which each subject was exposed to filtered air and carbon UFP for 2 hours. The first protocol involved 2 exposures to air and 10 μg/m3 (∼ 2× 106 particles/cm3, count median diameter ∼25 nm, geometric standard deviation ∼1.6), at rest. The second protocol included 3 exposures to air, 10, and 25 μg/m3 UFP (∼ 7× 106 particles/cm3), with repeated exercise. Each subject underwent a continuous digital 12-lead ECG Holter recording to analyze the above ECG parameters. Repeated measures analysis of variance (ANOVA) was used to compare tested parameters between exposures. The observed responses to UFP exposure were small and generally not significant, although there were trends indicating an increase in parasympathetic tone, which is most likely also responsible for trends toward ST elevation, blunted QTc shortening, and increased variability of T-wave complexity after exposure to UFP. Recovery from exercise showed a blunted response of the parasympathetic system after exposure to UFP in comparison to air exposure. In conclusion, transient exposure to 10-25 μ g/m3 ultrafine carbon particles does not cause marked changes in ECG-derived parameters in young healthy subjects. However, trends are observed indicating that some subjects might be susceptible to air pollution, with a response involving autonomic modulation of the heart and repolarization of the ventricular myocardium.
BrooklynDodger(s) Comment: Oberdorster is a leading authority on health effects of inhalation of small particles. Remember that carbon used to be considered inert, but now is a 2B carcinogen, among other respiratory effects. The text of the abstract gives indication of negotiation with the reviewers; whether the conclusion was bargained down or bargained up can't be told. So maybe this is equivocal evidence rather than some evidence for an effect on the heart after 2 hours at 25 ug/M3 in a small sample size of healthy volunteers. ?graduate students?

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