title: A field application of a personal sensor for ultrafine particle exposure in children.
abstract: BACKGROUND
  Ultrafine particles (UFPs) have been associated with adverse health outcomes in children, but studies are often limited by surrogate estimates of exposure. Accurately characterizing children's personal exposure to UFP is difficult due to the high spatiotemporal variability of UFP and children's time-activity patterns.
  
  
  OBJECTIVE
  The objectives of this study were to conduct a field test of a personal sensor for UFP (PUFP) by measuring UFP exposure among children and assess the sensor's capabilities and limitations.
  
  
  METHODS
  Children wore the sensor at school, during transit periods between school and home, and in their home for 2-4h on 2 consecutive days and provided feedback regarding their experience with the sensor. The PUFP sensor recorded UFP number concentration at one second intervals and recorded GPS location allowing for comparisons of UFP exposure at homes, schools, and during transit. A mixed-effects linear model was used to compare the effect of microenvironment on personal UFP measurements.
  
  
  RESULTS
  The overall total median personal exposure to UFP was 12,900 particles/cm(3) (p/cm(3)). Median UFP exposure at homes, schools and during transit was 17,800, 11,900, and 13,600 p/cm(3), respectively. Results of the mixed-effects model found that riding in a car and walking were significantly associated with 1.36 (95% CI 1.33-1.39) and 2.51 (95% CI 2.44-2.57) times higher UFP concentrations compared to the home.
  
  
  CONCLUSIONS
  The PUFP sensor can measure near real-time exposure to UFP with high spatiotemporal resolution. Children's exposure to UFP varies by location, with increased exposure during transit to and from school.
authors.affiliation: Cincinnati Children's Hospital Medical Center, Division of Biostatistics and Epidemiology, Cincinnati, OH, USA; University of Cincinnati, Department of Environmental Health, Division of Epidemiology and Biostatistics, Cincinnati, OH, USA. Electronic address: patrick.ryan@cchmc.org.
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Ryan
authors.affiliation: University of Cincinnati, Department of Mechanical and Materials Engineering, Cincinnati, OH, USA.
authors.forename: Sang Young
authors.initials: SY
authors.lastname: Son
authors.affiliation: University of Cincinnati, Department of Environmental Health, Division of Epidemiology and Biostatistics, Cincinnati, OH, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Wolfe
authors.affiliation: University of Cincinnati, Department of Environmental Health, Cincinnati, OH, USA; University of Cincinnati, Department of Internal Medicine, Cincinnati, OH, USA.
authors.forename: James
authors.initials: J
authors.lastname: Lockey
authors.affiliation: University of Cincinnati, Department of Environmental Health, Division of Epidemiology and Biostatistics, Cincinnati, OH, USA.
authors.forename: Cole
authors.initials: C
authors.lastname: Brokamp
authors.affiliation: University of Cincinnati, Department of Environmental Health, Division of Epidemiology and Biostatistics, Cincinnati, OH, USA; Cincinnati Children's Hospital Medical Center, Division of Asthma Research, Cincinnati, OH, USA.
authors.forename: Grace
authors.initials: G
authors.lastname: LeMasters
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002648:Child; D004781:Environmental Exposure / Q000032:analysis* / Q000706:statistics & numerical data; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D052638:Particulate Matter / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Children; Personal monitoring; Ultrafine particles