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Carlo R. Bartoli,¹ Gregory A. Wellenius,^1,2 Edgar A. Diaz,¹ Joy Lawrence,¹ Brent A. Coull,³ Ichiro Akiyama,¹ Lani M. Lee,² Kazunori Okabe,⁴ Richard L. Verrier,² and John J. Godleski^1,5

¹Molecular and Integrative Physiological Sciences Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA; ²Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA; ³Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA; ⁴Sanyo National Hospital, Yamaguchi, Japan; ⁵Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts, USA

Abstract
Background: Epidemiologic studies suggest a positive association between fine particulate matter and arterial blood pressure, but the results have been inconsistent.

Objectives: We investigated the effect of ambient particles on systemic hemodynamics during a 5-hr exposure to concentrated ambient air particles (CAPs) or filtered air (FA) in conscious canines.

Methods: Thirteen dogs were repeatedly exposed via permanent tracheostomy to CAPs (358.1 ± 306.7 µg/m³, mean ± SD) or FA in a crossover protocol (55 CAPs days, 63 FA days) . Femoral artery blood pressure was monitored continuously via implanted telemetry devices. We measured baroreceptor reflex sensitivity before and after exposure in a subset of these experiments (n = 10 dogs, 19 CAPs days, 20 FA days) . In additional experiments, we administered α-adrenergic blockade before exposure (n = 8 dogs, 16 CAPs days, 15 FA days) . Blood pressure, heart rate, rate–pressure product, and baroreceptor reflex sensitivity responses were compared using linear mixed-effects models.

Results: CAPs exposure increased systolic blood pressure (2.7 ± 1.0 mmHg, p = 0.006) , diastolic blood pressure (4.1 ± 0.8 mmHg ; p < 0.001) , mean arterial pressure (3.7 ± 0.8 mmHg ; p < 0.001) , heart rate (1.6 ± 0.5 bpm ; p < 0.001) , and rate–pressure product (539 ± 110 bpm × mmHg ; p < 0.001) , and decreased pulse pressure (–1.7 ± 0.7 mmHg, p = 0.02) . These changes were accompanied by a 20 ± 6 msec/mmHg (p = 0.005) increase in baroreceptor reflex sensitivity after CAPs versus FA. After α-adrenergic blockade, responses to CAPs and FA no longer differed significantly.

Conclusions: Controlled exposure to ambient particles elevates arterial blood pressure. Increased peripheral vascular resistance may mediate these changes, whereas increased baroreceptor reflex sensitivity may compensate for particle-induced alterations in blood pressure.

Key words: α-adrenergic receptors, baroreceptors, blood pressure, hypertension, particulate air pollution. Environ Health Perspect 117:361–366 (2009) . doi:10.1289/ehp.11573 available via http://dx.doi.org/ [Online 6 October 2008]

Address correspondence to J.J. Godleski, Department of Environmental Health, Harvard School of Public Health, 665 Huntington Ave., II-227, Boston, MA 02115 USA. Telephone: (617) 432-1252. Fax: (617) 432-0014. E-mail: jgodlesk@hsph.harvard.edu

We thank S. Verrier, T. Katz, J. Pettit, M. Long, W. Bonafe, G. Funaro, and G. Calomeni for their assistance.

This study was supported by grants RD831917, R827353, and R832416 from the U.S. Environmental Protection Agency (EPA) and by grants ES012972 and ES00002 from the National Institute of Environmental Health Sciences (NIEHS) , National Institutes of Health (NIH) .

The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIH, or U.S. EPA.

The authors declare they have no competing financial interests.

Received 11 April 2008 ; accepted 6 October 2008.