Pulmonary effects of indoor- and outdoor-generated particles in children with asthma

Environ Health Perspect. 2005 Apr;113(4):499-503. doi: 10.1289/ehp.7511.


Most particulate matter (PM) health effects studies use outdoor (ambient) PM as a surrogate for personal exposure. However, people spend most of their time indoors exposed to a combination of indoor-generated particles and ambient particles that have infiltrated. Thus, it is important to investigate the differential health effects of indoor- and ambient-generated particles. We combined our recently adapted recursive model and a predictive model for estimating infiltration efficiency to separate personal exposure (E) to PM2.5 (PM with aerodynamic diameter < or = 2.5 microm) into its indoor-generated (Eig) and ambient-generated (Eag) components for 19 children with asthma. We then compared Eig and Eag to changes in exhaled nitric oxide (eNO), a marker of airway inflammation. Based on the recursive model with a sample size of eight children, Eag was marginally associated with increases in eNO [5.6 ppb per 10-microg/m3 increase in PM2.5; 95% confidence interval (CI), -0.6 to 11.9; p = 0.08]. Eig was not associated with eNO (-0.19 ppb change per 10 microg/m3). Our predictive model allowed us to estimate Eag and Eig for all 19 children. For those combined estimates, only Eag was significantly associated with an increase in eNO (Eag: 5.0 ppb per 10-microg/m3 increase in PM2.5; 95% CI, 0.3 to 9.7; p = 0.04; Eig: 3.3 ppb per 10-microg/m3 increase in PM2.5; 95% CI, -1.1 to 7.7; p = 0.15). Effects were seen only in children who were not using corticosteroid therapy. We conclude that the ambient-generated component of PM2.5 exposure is consistently associated with increases in eNO and the indoor-generated component is less strongly associated with eNO.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adrenal Cortex Hormones
  • Air Pollutants / adverse effects*
  • Air Pollutants / analysis
  • Air Pollution, Indoor / adverse effects*
  • Air Pollution, Indoor / analysis
  • Asthma / epidemiology*
  • Child
  • Cohort Studies
  • Dust / analysis
  • Housing
  • Humans
  • Inhalation Exposure*
  • Models, Theoretical*
  • Nitric Oxide / analysis*
  • Particle Size
  • Spirometry
  • Washington / epidemiology


  • Adrenal Cortex Hormones
  • Air Pollutants
  • Dust
  • Nitric Oxide