Pulmonary health effects of wintertime particulate matter from California and China following repeated exposure and cessation.

Epidemiological studies show strong associations between fine particulate matter (PM _2.5 ) air pollution and adverse pulmonary effects. In the present study, wintertime PM _2.5 samples were collected from three geographically similar regions-Sacramento, California, USA; Jinan, Shandong, China; and Taiyuan, Shanxi, China-and extracted to form PM _CA , PM _SD , and PM _SX , respectively, for comparison in a BALB/c mouse model. Each of four groups was oropharyngeally administered Milli-Q water vehicle control (50 μL) or one type of PM extract (20 μg/50 μL) five times over two weeks. Mice were necropsied on post-exposure days 1, 2, and 4 and examined using bronchoalveolar lavage (BAL), histopathology, and assessments of cytokine/chemokine mRNA and protein expression. Chemical analysis demonstrated all three extracts contained black carbon, but PM _SX contained more sulfates and polycyclic aromatic hydrocarbons (PAHs) associated with significantly greater neutrophil numbers and greater alveolar/bronchiolar inflammation on post-exposure days 1 and 4. On day 4, PM _SX -exposed mice also exhibited significant increases in interleukin-1 beta, tumor necrosis factor-alpha, and chemokine C-X-C motif ligands-3 and -5 mRNA, and monocyte chemoattractant protein-1 protein. These combined findings suggest greater sulfate and PAH content contributed to a more intense and progressive inflammatory response with repeated PM _SX compared to PM _CA or PM _SD exposure.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)