In-home particle concentrations and childhood asthma morbidity

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.