title: Airborne particulates (PM10) and tracheal mucus: A case-control study at an American Thoroughbred racetrack.
abstract: BACKGROUND
  Particle mapping within stalls has demonstrated a relationship between particulate concentrations and visible accumulations of tracheal mucus. However, measurement of breathing zone particulate concentrations, which is the most accurate way to measure exposure, has not been performed to determine the relationship between exposures and accumulations of tracheal mucus sufficient to affect performance.
  
  
  OBJECTIVE
  To compare breathing zone particulate exposures between horses with tracheal mucus scores (MS) previously demonstrated to affect performance (MS≥2) and those without (MS = 0) visible tracheal mucus.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  We endoscopically examined 649 Thoroughbred racehorses over 7 months and selected 113 age-matched cases and controls based on the presence (MS≥2) or absence (MS = 0) of tracheal mucus, respectively. Inflammatory cell numbers in tracheal lavage were also determined. Breathing zone monitors recorded particulate exposure during 3 time periods (mid-day, evening and overnight). Total recording time averaged 17.5 h/horse.
  
  
  RESULTS
  The overall prevalence of MS≥2 in the observed stables was 23%. Breathing zone particular matter (PM10) concentrations were very similar to previously reported ambient concentrations. During the evening and overnight, cases had significantly higher breathing zone PM10 concentrations and neutrophil counts than controls. Inflammatory cell counts were associated with average PM10 concentrations throughout the day.
  
  
  CONCLUSIONS
  Breathing zone particulate concentrations are associated with MS≥2 and inflammatory cell numbers. If breathing zone particulate exposures are predominantly influenced by ambient PM concentrations, racing stable management practices to reduce particle exposures should greatly reduce the prevalence of tracheal mucus.
authors.affiliation: Department of Medicine, College of Human Medicine, Michigan State University, East Lansing, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Millerick-May
authors.affiliation: School of Public Health, University of Memphis, Tennessee, USA.
authors.forename: W
authors.initials: W
authors.lastname: Karmaus
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, USA.
authors.forename: F J
authors.initials: FJ
authors.lastname: Derksen
authors.affiliation: Cleveland Equine Clinics, Ravenna, Ohio, USA.
authors.forename: B
authors.initials: B
authors.lastname: Berthold
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, USA.
authors.forename: N E
authors.initials: NE
authors.lastname: Robinson
mesh_terms: D000375:Aging; D016902:Air Pollution, Indoor; D000818:Animals; D016022:Case-Control Studies; D006736:Horses; D006799:Housing, Animal; D009093:Mucus / Q000737:chemistry*; D010316:Particle Size; D052638:Particulate Matter / Q000737:chemistry*; D012420:Running; D013177:Sports; D014132:Trachea / Q000502:physiology*; D014481:United States
chemical_list: D052638:Particulate Matter
keywords: breathing zone; horse; mucus; neutrophils; particulate matter; personal monitoring