title: Differential effects of air conditioning type on residential endotoxin levels in a semi-arid climate.
abstract: Residential endotoxin exposure is associated with protective and pathogenic health outcomes. Evaporative coolers, an energy-efficient type of air conditioner used in dry climates, are a potential source of indoor endotoxins; however, this association is largely unstudied. We collected settled dust biannually from four locations in homes with evaporative coolers (n=18) and central air conditioners (n=22) in Utah County, Utah (USA), during winter (Jan-Apr) and summer (Aug-Sept), 2014. Dust samples (n=281) were analyzed by the Limulus amebocyte lysate test. Housing factors were measured by survey, and indoor temperature and relative humidity measures were collected during both seasons. Endotoxin concentrations (EU/mg) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons. Endotoxin surface loads (EU/m2) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons and in upholstered furniture during winter. For the nine significant season-by-location comparisons, EU/mg and EU/m2were approximately three to six times greater in homes using evaporative coolers. A plausible explanation for these findings is that evaporative coolers serve as a reservoir and distribution system for Gram-negative bacteria or their cell wall components in homes.
authors.affiliation: Department of Health Science, Brigham Young University, Provo, Utah, USA.
authors.forename: J D
authors.identifier: 0000-0002-6009-7241
authors.initials: JD
authors.lastname: Johnston
authors.affiliation: Department of Health Science, Brigham Young University, Provo, Utah, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Kruman
authors.affiliation: Microbiology & Molecular Biology, Brigham Young University, Provo, Utah, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Nelson
authors.affiliation: Department of Health Science, Brigham Young University, Provo, Utah, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Merrill
authors.affiliation: Department of Health Science, Brigham Young University, Provo, Utah, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Graul
authors.affiliation: Microbiology & Molecular Biology, Brigham Young University, Provo, Utah, USA.
authors.forename: T G
authors.initials: TG
authors.lastname: Hoybjerg
authors.affiliation: Department of Health Science, Brigham Young University, Provo, Utah, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Tuttle
authors.affiliation: Microbiology & Molecular Biology, Brigham Young University, Provo, Utah, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Myers
authors.affiliation: Microbiology & Molecular Biology, Brigham Young University, Provo, Utah, USA.
authors.forename: R B
authors.initials: RB
authors.lastname: Cook
authors.affiliation: Microbiology & Molecular Biology, Brigham Young University, Provo, Utah, USA.
authors.forename: K S
authors.identifier: 0000-0003-3688-2191
authors.initials: KS
authors.lastname: Weber
mesh_terms: D000389:Air Conditioning / Q000379:methods*; D016902:Air Pollution, Indoor / Q000032:analysis*; D001512:Bedding and Linens; D002980:Climate; D003430:Cross-Sectional Studies; D004731:Endotoxins / Q000032:analysis*; D004784:Environmental Monitoring; D005430:Floors and Floorcoverings; D006798:Housing; D012621:Seasons; D014589:Utah
chemical_list: D004731:Endotoxins
keywords: air conditioning; asthma; endotoxin; evaporative cooling; hygiene hypothesis; indoor environmental quality