Effect of inhaled carbon ultrafine particles on reactive hyperemia in healthy human subjects.
BACKGROUND
Ultrafine particles (UFP) may contribute to the cardiovascular effects of exposure to particulate air pollution, partly because of their relatively efficient alveolar deposition and potential to enter the pulmonary vascular space.


OBJECTIVE
This study tested the hypothesis that inhalation of elemental carbon UFP alters systemic vascular function.


METHODS
Sixteen healthy subjects (mean age, 26.9 +/- 6.5 years) inhaled air or 50 microg/m3 elemental carbon UFP by mouthpiece for 2 hr, while exercising intermittently. Measurements at preexposure baseline, 0 hr (immediately after exposure), 3.5 hr, 21 hr, and 45 hr included vital signs, venous occlusion plethysmography and reactive hyperemia of the forearm, and venous plasma nitrate and nitrite levels.


RESULTS
Peak forearm blood flow after ischemia increased 3.5 hr after exposure to air but not UFP (change from preexposure baseline, air: 9.31 +/- 3.41; UFP: 1.09 +/- 2.55 mL/min/100 mL; t-test, p = 0.03). Blood pressure did not change, so minimal resistance after ischemia (mean blood pressure divided by forearm blood flow) decreased with air, but not UFP [change from preexposure baseline, air: -0.48 +/- 0.21; UFP: 0.07 +/- 0.19 mmHg/mL/min; analysis of variance (ANOVA), p = 0.024]. There was no UFP effect on pre-ischemia forearm blood flow or resistance, or on total forearm blood flow after ischemia. Venous nitrate levels were significantly lower after exposure to carbon UFP compared with air (ANOVA, p = 0.038). There were no differences in venous nitrite levels.


CONCLUSIONS
Inhalation of 50 microg/m3 carbon UFP during intermittent exercise impairs peak forearm blood flow during reactive hyperemia in healthy human subjects.
Shah
Alpa P
AP
Department of Medicine, University of Rochester Medical Center, Rochester, New York, USA.
Pietropaoli
Anthony P
AP
Frasier
Lauren M
LM
Speers
Donna M
DM
Chalupa
David C
DC
Delehanty
Joseph M
JM
Huang
Li-Shan
LS
Utell
Mark J
MJ
Frampton
Mark W
MW
D000293:Adolescent; D000328:Adult; D000393:Air Pollutants / Q000633:toxicity*; D002244:Carbon / Q000633:toxicity*; D015444:Exercise; D005260:Female; D005542:Forearm / Q000098:blood supply; D006439:Hemodynamics; D006801:Humans; D006940:Hyperemia / Q000139:chemically induced*; D019570:Inhalation Exposure / Q000009:adverse effects*; D008297:Male; D052638:Particulate Matter / Q000633:toxicity*; D013997:Time Factors
D000393:Air Pollutants; D052638:Particulate Matter; D002244:Carbon