title: In-car particles and cardiovascular health: an air conditioning-based intervention study.
abstract: Exposure to traffic-related particulate matter (PM) is considered a potential risk for cardiovascular events. Little is known about whether improving air quality in car can modify cardiovascular effects among human subjects during commuting. We recruited a panel of 60 healthy subjects to commute for 2 h by a car equipped with an air conditioning (AC) system during the morning rush hour in Taipei. Operation modes of AC system using outside air (OA-mode), circulating inside air (IA-mode) and turning off (Off-mode) were examined. Repeated measurements of heart rate variability (HRV) indices, PM≤2.5 μm in aerodynamic diameter (PM2.5) and noise level were conducted for each participant in different modes during the commute. We used linear mixed-effects models to associate HRV indices with in-car PM2.5. We found that decreases in HRV indices were associated with increased levels of in-car PM2.5. For Off-mode, an interquartile range (IQR) increase in in-car PM2.5 with 15-min moving average was associated with 2.7% and 4.1% decreases in standard deviation of NN intervals (SDNN) and the square root of the mean of the sum of the squares of differences between adjacent NN intervals (r-MSSD), respectively. During OA and IA modes, participants showed slight decreases in SDNN (OA mode: 0.1%; IA mode: 1.3%) and r-MSSD (OA mode: 1.1%; IA mode: 1.8%) by an IQR increase in in-car PM2.5 with 15-min moving average. We concluded that in-car PM2.5 is associated with autonomic alteration. Utilization of the car's AC system can improve air quality and modify the effects of in-car PM2.5 on HRV indices among human subjects during the commute.
authors.affiliation: Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Hsiao-Chi
authors.initials: HC
authors.lastname: Chuang
authors.forename: Lian-Yu
authors.initials: LY
authors.lastname: Lin
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Hsu
authors.forename: Chih-Ming
authors.initials: CM
authors.lastname: Ma
authors.forename: Kai-Jen
authors.initials: KJ
authors.lastname: Chuang
mesh_terms: D000328:Adult; D000389:Air Conditioning; D016902:Air Pollution, Indoor; D001336:Automobiles; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D009622:Noise / Q000009:adverse effects*; D033281:Nontherapeutic Human Experimentation; D010316:Particle Size; D052638:Particulate Matter / Q000009:adverse effects* / Q000032:analysis; D013624:Taiwan; D055815:Young Adult
chemical_list: D052638:Particulate Matter