In-home particle concentrations and childhood asthma morbidity

Abstract

Background: Although outdoor particulate matter (PM) has been linked to mortality and asthma morbidity, the impact of indoor PM on asthma has not been well established.

Objective: This study was designed to investigate the effect of in-home PM on asthma morbidity.

Methods: For a cohort of 150 asthmatic children (2-6 years of age) from Baltimore, Maryland, a technician deployed environmental monitoring equipment in the children's bedrooms for 3-day intervals at baseline and at 3 and 6 months. Caregivers completed questionnaires and daily diaries during air sampling. Longitudinal data analyses included regression models with generalized estimating equations.

Results: Children were primarily African Americans (91%) from lower socioeconomic backgrounds and spent most of their time in the home. Mean (+/- SD) indoor PM(2.5-10) (PM with aerodynamic diameter 2.5-10 microm) and PM(2.5) (aerodynamic diameter < 2.5 microm) concentrations were 17.4 +/- 21.0 and 40.3 +/- 35.4 microg/m(3). In adjusted models, 10-microg/m(3) increases in indoor PM(2.5-10) and PM(2.5) were associated with increased incidences of asthma symptoms: 6% [95% confidence interval (CI), 1 to 12%] and 3% (95% CI, -1 to 7%), respectively; symptoms causing children to slow down: 8% (95% CI, 2 to 14%) and 4% (95% CI, 0 to 9%), respectively; nocturnal symptoms: 8% (95% CI, 1 to 14%) and 6% (95% CI, 1 to 10%), respectively; wheezing that limited speech: 11% (95% CI, 3 to 19%) and 7% (95% CI, 0 to 14%), respectively; and use of rescue medication: 6% (95% CI, 1 to 10%) and 4% (95% CI, 1 to 8%), respectively. Increases of 10 microg/m(3) in indoor and ambient PM(2.5) were associated with 7% (95% CI, 2 to 11%) and 26% (95% CI, 1 to 52%) increases in exercise-related symptoms, respectively.

Conclusions: Among preschool asthmatic children in Baltimore, increases in in-home PM(2.5-10) and PM(2.5) were associated with respiratory symptoms and rescue medication use. Increases in in-home and ambient PM(2.5) were associated with exercise-related symptoms. Although reducing PM outdoors may decrease asthma morbidity, reducing PM indoors, especially in homes of inner-city children, may lead to improved asthma health.

Keywords: air pollution; asthma; indoor; particulate matter; pediatric; urban.

Figure 1

Indoor and ambient concentrations of PM_2.5–10 (A) and PM_2.5 (B). Boxes show the interquartile range (IQR), and the heavy dark lines are the median values. Whiskers represent the closest value within 1.5 times the IQR. Indoor PM concentrations were significantly higher than simultaneously measured ambient concentrations. The dashed line (B) indicates the U.S. EPA annual limit for ambient PM_2.5. Eighty-five percent of homes had indoor PM_2.5 concentrations that exceeded this ambient limit. There are currently no standards for ambient coarse PM. Asterisks indicate positive outliers, with values up to 288 μg/m³ for indoor PM_2.5–10 (A; n = 24) and up to 216 μg/m³ for indoor PM_2.5 (B; n = 27).