title: Short-term dynamics of indoor and outdoor endotoxin exposure: Case of Santiago, Chile, 2012.
abstract: Indoor and outdoor endotoxin in PM2.5 was measured for the very first time in Santiago, Chile, in spring 2012. Average endotoxin concentrations were 0.099 and 0.094 [EU/m(3)] for indoor (N=44) and outdoor (N=41) samples, respectively; the indoor-outdoor correlation (log-transformed concentrations) was low: R=-0.06, 95% CI: (-0.35 to 0.24), likely owing to outdoor spatial variability. A linear regression model explained 68% of variability in outdoor endotoxins, using as predictors elemental carbon (a proxy of traffic emissions), chlorine (a tracer of marine air masses reaching the city) and relative humidity (a modulator of surface emissions of dust, vegetation and garbage debris). In this study, for the first time a potential source contribution function (PSCF) was applied to outdoor endotoxin measurements. Wind trajectory analysis identified upwind agricultural sources as contributors to the short-term, outdoor endotoxin variability. Our results confirm an association between combustion particles from traffic and outdoor endotoxin concentrations. For indoor endotoxins, a predictive model was developed but it only explained 44% of endotoxin variability; the significant predictors were tracers of indoor PM2.5 dust (Si, Ca), number of external windows and number of hours with internal doors open. Results suggest that short-term indoor endotoxin variability may be driven by household dust/garbage production and handling. This would explain the modest predictive performance of published models that use answers to household surveys as predictors. One feasible alternative is to increase the sampling period so that household features would arise as significant predictors of long-term airborne endotoxin levels.
authors.affiliation: Departmento de Ingeniería Química y Bioprocesos, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago 7820436, Chile.
authors.forename: Francisco
authors.initials: F
authors.lastname: Barraza
authors.affiliation: Departmento de Ingeniería Química y Bioprocesos, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago 7820436, Chile; Centro de Investigación en Nanotecnología y Materiales Avanzados, CIEN-UC, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago 7820436, Chile. Electronic address: jorquera@ing.puc.cl.
authors.forename: Héctor
authors.initials: H
authors.lastname: Jorquera
authors.affiliation: Departmento de Ingeniería Química y Bioprocesos, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago 7820436, Chile.
authors.forename: Johanna
authors.initials: J
authors.lastname: Heyer
authors.affiliation: Departamento de Estadística, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Santiago 7820436, Chile.
authors.forename: Wilfredo
authors.initials: W
authors.lastname: Palma
authors.affiliation: Facultad de Química, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago 7820436, Chile.
authors.forename: Ana María
authors.initials: AM
authors.lastname: Edwards
authors.affiliation: Facultad de Química, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago 7820436, Chile.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Muñoz
authors.affiliation: Departamento de Salud Pública, Pontificia Universidad Católica de Chile, Marcoleta 340, Santiago 8330033, Chile.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Valdivia
authors.affiliation: Civil, Environmental and Architectural Engineering Department, University of Colorado Boulder, UCB 428, Boulder, Colorado, United States.
authors.forename: Lupita D
authors.initials: LD
authors.lastname: Montoya
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D016902:Air Pollution, Indoor / Q000032:analysis*; D002677:Chile; D002947:Cities; D004391:Dust / Q000032:analysis; D004731:Endotoxins / Q000008:administration & dosage* / Q000737:chemistry*; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D006801:Humans; D012621:Seasons
chemical_list: D000393:Air Pollutants; D004391:Dust; D004731:Endotoxins
keywords: Endotoxin exposure; Endotoxins and combustion particles; Household features; Indoor and outdoor air quality; PSCF; Wind trajectory analysis