Low levels of fine particulate matter increase vascular damage and reduce pulmonary function in young healthy adults

Abstract

Background: Fine particulate matter (PM_2.5) related mild inflammation, altered autonomic control of cardiovascular function, and changes to cell function have been observed in controlled human exposure studies.

Methods: To measure the systemic and cardiopulmonary impacts of low-level PM exposure, we exposed 20 healthy, young volunteers to PM_2.5, in the form of concentrated ambient particles (mean: 37.8 μg/m³, SD 6.5), and filtered air (mean: 2.1 μg/m³, SD 2.6). In this double-blind, crossover study the exposure order was randomized. During the 4 h exposure, volunteers (7 females and 13 males) underwent light intensity exercise to regulate ventilation rate. We measured pulmonary, cardiac, and hematologic end points before exposure, 1 h after exposure, and again 20 h after exposure.

Results: Low-level PM_2.5 resulted in both pulmonary and extra-pulmonary changes characterized by alterations in systematic inflammation markers, cardiac repolarization, and decreased pulmonary function. A mean increase in PM_2.5 concentration (37.8 μg/m³) significantly increased serum amyloid A (SAA), C-reactive protein (CRP), soluble intercellular adhesion molecule-1 (sICAM-1), and soluble vascular cell adhesion molecule-1 (sVCAM-1), 1 h after exposure by 8.7, 9.1, 10.7, and 6.6%, respectively, relative to the filtered air control. SAA remained significantly elevated (34.6%) 20 h after PM_2.5 exposure which was accompanied by a 5.7% decrease in percent neutrophils. Decreased pulmonary function was observed 1 h after exposure through a 0.8 and 1.2% decrease in forced expiratory volume in 1 s (FEV₁) and FEV₁/ forced vital capacity (FEV₁/FVC) respectively. Additionally, sex specific changes were observed in repolarization outcomes following PM_2.5 exposure. In males, P-wave and QRS complex were increased by 15.4 and 5.4% 1 h after exposure.

Conclusions: This study is the first controlled human exposure study to demonstrate biological effects in response to exposure to concentrated ambient air PM_2.5 particles at levels near the PM_2.5 US NAAQS standard.

Clinical trial registration information: clinicaltrials.gov ; Identifier: NCT03232086 . The study was registered retrospectively on July 25, 2017, prior to final data collection on October 25, 2017 and data analysis.

Keywords: Controlled exposure; Healthy human volunteers; Particulate matter air pollution; Systemic inflammatory effect.