title: Does ambient temperature interact with air pollution to alter blood pressure? A repeated-measure study in healthy adults.
abstract: OBJECTIVE
  Both low temperature and high air pollution have been associated with an increased risk of cardiovascular events, which could be predicted by increased arterial blood pressure (BP) within short periods. However, whether exposures to temperature and air pollution simultaneously may have interactive effects on BP has been unknown. We investigated this potential interaction during 460 repeated visits in 39 healthy university students in the context of traffic-related air pollution.
  
  
  METHODS
  Study participants in the Healthy Volunteer Natural Relocation study underwent repeated BP measurements for 12 occasions under three exposure scenarios in Beijing, China, in 2010-2011. We used generalized linear mixed-effects models to estimate exposure effects.
  
  
  RESULTS
  Decreasing temperature was associated with significant increases in BP. There were significant interactions between temperature and traffic-related air pollutants (particulate matter with an aerodynamic diameter ≤2.5 μm, organic carbon, elemental carbon and nitrogen dioxide) on BP (P < 0.05 for all interaction tests). The estimated increases in SBP and DBP were 4.9 mmHg [95% confidence interval (CI) 2.9-6.8] and 3.7 mmHg (95% CI 2.3-5.1) at high elemental carbon level (≥median), and were -1.3 mmHg (95% CI -6.3 to 3.6) and 0.7 mmHg (95% CI -2.8 to 4.2) at low elemental carbon level (<median) per 10°C decrease in daily minimum temperature. We also found stronger air pollution effects on BP at low temperature levels (<median) than at high temperature levels (≥median).
  
  
  CONCLUSIONS
  Low temperature and high air pollution may act synergistically to increase BP in healthy adults. Our findings may have potential implications for prevention of cardiovascular events associated with increased BP among high-risk individuals.
authors.affiliation: aDepartment of Occupational and Environmental Health Sciences, Peking University School of Public Health, Beijing, China bDepartment of Public Health, Hyogo College of Medicine, Hyogo, Japan.
authors.forename: Shaowei
authors.initials: S
authors.lastname: Wu
authors.forename: Furong
authors.initials: F
authors.lastname: Deng
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Qin
authors.forename: Chanjuan
authors.initials: C
authors.lastname: Zheng
authors.forename: Hongying
authors.initials: H
authors.lastname: Wei
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shima
authors.forename: Xinbiao
authors.initials: X
authors.lastname: Guo
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000737:chemistry / Q000633:toxicity*; D000397:Air Pollution / Q000009:adverse effects; D000068476:Beijing; D001794:Blood Pressure / Q000187:drug effects*; D002244:Carbon / Q000633:toxicity; D004781:Environmental Exposure / Q000009:adverse effects*; D064368:Healthy Volunteers; D006801:Humans; D006973:Hypertension / Q000209:etiology*; D016014:Linear Models; D008297:Male; D009585:Nitrogen Dioxide / Q000633:toxicity; D052638:Particulate Matter / Q000737:chemistry / Q000633:toxicity*; D013696:Temperature; D001335:Vehicle Emissions / Q000633:toxicity
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions; D002244:Carbon; D009585:Nitrogen Dioxide