Indoor particulate matter increases asthma morbidity in children with non-atopic and atopic asthma

Abstract

Background: Compared with atopic asthma, fewer environmental modifications are recommended for non-atopic asthma in children.

Objective: To better understand the role of indoor pollutants in provoking non-atopic asthma, we investigated the effect of in-home particulate matter on asthma symptoms among non-atopic and atopic children living in inner-city Baltimore.

Methods: A cohort of 150 children ages 2 to 6 years with asthma underwent home environmental monitoring for 3-day intervals at baseline, 3, and 6 months. Children were classified as non-atopic if they were skin test negative to a panel of 14 aeroallergens. Caregivers completed questionnaires assessing symptoms and rescue medication use. Longitudinal data analysis included regression models with generalized estimating equations.

Results: Children were primarily African American from lower socioeconomic backgrounds and spent most of their time in the home. Thirty-one percent were non-atopic, and 69% were atopic. Among non-atopic and atopic children, increased in-home fine (PM2.5) and coarse (PM2.5-10) particle concentrations were associated with significant increases in asthma symptoms and rescue medication use ranging from 7% (95% confidence interval [CI], 0-15) to 14% (95% CI, 1-27) per 10 μg/m(3) increase in particle concentration after adjustment for confounders.

Conclusions: In-home particles similarly cause increased symptoms of asthma in non-atopic and atopic children. Environmental control strategies that reduce particle concentrations may prove to be an effective means of improving asthma outcomes, especially for non-atopic asthma, for which there are few environmental control practice recommendations.

Figure 1

Indoor coarse PM concentrations in the homes of non-atopic and atopic children. 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 concentrations of coarse PM did not significantly differ between non-atopic and atopic children.

Figure 2

Indoor fine PM concentrations in the homes of non-atopic and atopic children. Over 75% of homes had indoor fine PM concentrations that exceeded the EPA annual outdoor limit, demonstrated by the dashed red line. Indoor concentrations of fine PM were greater in the homes of non-atopic children compared with atopic children.

Figure 3

Multivariate analysis of the effect of indoor coarse PM on asthma morbidity. Incidence rate ratios are displayed as point estimates and 95% confidence intervals for the effect of indoor coarse PM_2.5–10 on asthma symptom outcomes and rescue medication use. Models were adjusted for age, race, gender, parent education, season, indoor PM_2.5, outdoor PM_2.5, and outdoor PM_2.5–10. With the exception of symptoms with exercise, there was an increase in the incidence of asthma morbidity outcomes for every 10μg/m³ increase in PM_2.5–10 among both the non-atopic and atopic children with narrower confidence intervals for non-atopic asthma.

Figure 4

Multivariate analysis of the effect of indoor fine PM on asthma morbidity. Incidence rate ratios are displayed as point estimates and 95% confidence intervals for the effect of indoor PM_2.5 on asthma symptom outcomes and rescue medication use. Models were adjusted for age, race, gender, parent education, season, indoor PM_2.5–10, outdoor PM_2.5, and outdoor PM_2.5–10. There was an increase in the incidence of asthma morbidity outcomes for every 10μg/m³ increase in PM_2.5 for most symptom outcomes and for rescue medication use among both non-atopic and atopic children.