Pulmonary exposure to peat smoke extracts in rats decreases expiratory time and increases left heart end systolic volume

Abstract

Exposure to wildland fire-related particulate matter (PM) causes adverse health outcomes. However, the impacts of specific biomass sources remain unclear. The purpose of this study was to investigate cardiopulmonary responses in rats following exposure to PM extracts collected from peat fire smoke. We hypothesized that peat smoke PM would dose-dependently alter cardiopulmonary function. Male Sprague–Dawley rats (n = 8/group) were exposed to 35 µg (Lo PM) or 350 µg (Hi PM) of peat smoke PM extracts suspended in saline, or saline alone (Vehicle) via oropharyngeal aspiration (OA). Ventilatory expiration times, measured in whole-body plethysmographs immediately after OA, were the lowest in Hi PM exposed subjects at 6 min into recovery (p = .01 vs. Lo PM, p = .08 vs. Vehicle) and resolved shortly afterwards. The next day, we evaluated cardiovascular function in the same subjects via cardiac ultrasound under isoflurane anesthesia. Compared to Vehicle, Hi PM had 45% higher end systolic volume (p = .03) and 17% higher pulmonary artery blood flow acceleration/ejection time ratios, and both endpoints expressed significant increasing linear trends by dose (p = .01 and .02, respectively). In addition, linear trend analyses across doses detected an increase for end diastolic volume and decreases for ejection fraction and fractional shortening. These data suggest that exposure to peat smoke constituents modulates regulation of ventricular ejection and filling volumes, which could be related to altered blood flow in the pulmonary circulation. Moreover, early pulmonary responses to peat smoke PM point to irritant/autonomic mechanisms as potential drivers of later cardiovascular responses.

Keywords:

• Wildfire
• wildland fire
• smoke
• peat
• biomass
• particulate matter
• heart function
• ultrasound
• echocardiography
• pulmonary irritation

Acknowledgements

We would like to thank US EPA scientists Judy Richards for serum and lavage fluid analysis, and Drs. Colette Miller, Mike Narotsky and Steve Gavett for their thorough review of the manuscript.

Disclosure statement

The authors report no conflict of interest.

Disclaimer

The research presented in the article was reviewed and approved for publication by the National Health and Environmental Effects Research Laboratory at the U.S. Environmental Protection Agency. The contents of this manuscript do not necessarily reflect the views and policies of the agency nor does mention of trade names or commercial products signify endorsement or recommendation for use.