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Background: Long-term exposure to high concentrations of PM2.5 may cause immune system dysfunction and damage to the respiratory and cardiovascular systems. PM2.5 may cause CD4 + T helper cells to polarize toward TH1 or TH2 cell types, which may be associated with the onset and progression of many human diseases. Recent studies have shown that omega-3 fatty acids can regulate human immune function and reduce physiological damage caused by air pollution; however, only limited research has examined the therapeutic effects of omega-3 fatty acids on subjects with high exposure to PM2.5 in mass transit systems such as subways.Methods: This study was designed as a prospective, randomized, double-blinded (to participants and researchers), placebo-controlled clinical trial. The research plan is to randomly select 120 eligible adults based on the difference in PM2.5 exposure in the Chengdu subway station. They should be aged 20-65 years old and work in the subway station more than or equal to 3 times a week, each time greater than or equal to 8 h, and had worked continuously in the subway station for more than 2 years. All participants will receive omega-3 fatty acids or placebo for 8 weeks. The primary outcomes will be changes in the TH1/TH2 cell polarization index and changes in serum cytokine concentrations. Secondary outcomes will be changes in early indicators of atherosclerosis, pulmonary function, COOP/WONCA charts, and scores on the Short-Form 36 Health Survey for quality of life. Results will be analyzed to evaluate differences in clinical efficacy between the two groups. A 6-month follow-up period will be used to assess the long-term value of omega-3 fatty acids for respiratory and cardiovascular disease endpoints.Discussion: We will explore the characteristics of the TH1/TH2 cell polarization index in a population with high exposure to PM2.5. Omega-3 fatty acids and placebo will be compared in many ways to test the effect on people exposed to PM2.5 subway stations. This study is expected to provide reliable evidence to support the promotion of omega-3 fatty acids in clinical practice to protect individuals who are highly exposed to PM2.5.Trial Registration: Chinese Clinical Trial Registry ChiCTR2000038065 . Registered on September 9, 2020. [ABSTRACT FROM AUTHOR]

Background: Extended exposure to high concentrations of PM2.5 changes the human microbiota profile, which in turn may increase morbidity and mortality due to respiratory system damage. A balanced microecosystem is crucial to human health, and certain health-related problems may be addressed by effective microecosystem regulation. Recent studies have confirmed that probiotics may reduce the incidence of respiratory diseases. However, few studies have investigated probiotic treatment outcomes in subjects exposed to high concentrations of PM2.5.Methods: This study is designed as a prospective, randomized, participants- and assessor-blinded, placebo-controlled trial. One hundred and twenty eligible volunteers recruited from October 2019 to July 2020 in downtown Chengdu, China, will be treated with either probiotics or placebo over 4 consecutive weeks. The primary outcome will be 16SrRNA sequencing assay data from nasal and intestinal secretions. Secondary outcomes will be pulmonary function, score on a gastrointestinal symptom rating scale, COOP/WONCA charts, and the Short-Form Health Survey 36 for quality of life. Results will be analyzed to assess differences in clinical efficacy between groups. Six-month follow-up examinations will evaluate the long-term value of probiotics on cardiovascular and respiratory disease end-point events.Discussion: We will explore the characteristics of nasal and intestinal microbiota in a population with high exposure to PM2.5. Probiotics and placebo interventions will be tested for efficacy in microbial balance regulation, effects on lung and physical functions, and quality of life improvement. This study is expected to provide reliable evidence to support the widespread promotion of probiotics in clinical practice for the protection of individuals with high exposure to PM2.5.Trial Registration: Chinese Clinical Trial Registry ChiCTR1900025469 . Registered on 27 August 2019. [ABSTRACT FROM AUTHOR]