title: A cross-sectional study of determinants of indoor environmental exposures in households with and without chronic exposure to biomass fuel smoke.
abstract: BACKGROUND
  Burning biomass fuels indoors for cooking is associated with high concentrations of particulate matter (PM) and carbon monoxide (CO). More efficient biomass-burning stoves and chimneys for ventilation have been proposed as solutions to reduce indoor pollution. We sought to quantify indoor PM and CO exposures in urban and rural households and determine factors associated with higher exposures. A secondary objective was to identify chronic vs. acute changes in cardiopulmonary biomarkers associated with exposure to biomass smoke.
  
  
  METHODS
  We conducted a census survey followed by a cross-sectional study of indoor environmental exposures and cardiopulmonary biomarkers in the main household cook in Puno, Peru. We measured 24-hour indoor PM and CO concentrations in 86 households. We also measured PM2.5 and PM10 concentrations gravimetrically for 24 hours in urban households and during cook times in rural households, and generated a calibration equation using PM2.5 measurements.
  
  
  RESULTS
  In a census of 4903 households, 93% vs. 16% of rural vs. urban households used an open-fire stove; 22% of rural households had a homemade chimney; and <3% of rural households participated in a national program encouraging installation of a chimney. Median 24-hour indoor PM2.5 and CO concentrations were 130 vs. 22 μg/m3 and 5.8 vs. 0.4 ppm (all p<0.001) in rural vs. urban households. Having a chimney did not significantly reduce median concentrations in 24-hour indoor PM2.5 (119 vs. 137 μg/m3; p=0.40) or CO (4.6 vs. 7.2 ppm; p=0.23) among rural households with and without chimneys. Having a chimney did not significantly reduce median cook-time PM2.5 (360 vs. 298 μg/m3, p=0.45) or cook-time CO concentrations (15.2 vs. 9.4 ppm, p=0.23). Having a thatched roof (p=0.007) and hours spent cooking (p=0.02) were associated with higher 24-hour average PM concentrations. Rural participants had higher median exhaled CO (10 vs. 6 ppm; p=0.01) and exhaled carboxyhemoglobin (1.6% vs. 1.0%; p=0.04) than urban participants.
  
  
  CONCLUSIONS
  Indoor air concentrations associated with biomass smoke were six-fold greater in rural vs. urban households. Having a homemade chimney did not reduce environmental exposures significantly. Measures of exhaled CO provide useful cardiopulmonary biomarkers for chronic exposure to biomass smoke.
authors.forename: Suzanne L
authors.initials: SL
authors.lastname: Pollard
authors.forename: D'Ann L
authors.initials: DL
authors.lastname: Williams
authors.forename: Patrick N
authors.initials: PN
authors.lastname: Breysse
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Baron
authors.forename: Laura M
authors.initials: LM
authors.lastname: Grajeda
authors.forename: Robert H
authors.initials: RH
authors.lastname: Gilman
authors.forename: J Jaime
authors.initials: JJ
authors.lastname: Miranda
authors.affiliation: Division of Pulmonary and Critical Care, School of Medicine, Johns Hopkins University, 1800 Orleans Ave, Suite 9121, Baltimore, MD, USA. wcheckl1@jhmi.edu.
authors.forename: William
authors.initials: W
authors.lastname: Checkley
mesh_terms: D000328:Adult; D016902:Air Pollution, Indoor / Q000032:analysis*; D018533:Biomass; D001944:Breath Tests; D002248:Carbon Monoxide / Q000032:analysis / Q000378:metabolism; D003296:Cooking; D003430:Cross-Sectional Studies; D004784:Environmental Monitoring; D005191:Family Characteristics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000032:analysis; D010568:Peru; D012424:Rural Population; D012906:Smoke; D014505:Urban Population; D014691:Ventilation
chemical_list: D052638:Particulate Matter; D012906:Smoke; D002248:Carbon Monoxide