Assessing Exposure Factors of Asthmatic Children

Abstract

TAB3-PD-08 Since 1980, there has been a 75% increase in the prevalence of asthma in children in the United States. A pilot study was conducted in a southeastern U.S. city to develop and to evaluate methods and factors associated with asthmatic children's (<6 years) exposures to air pollutants. Nine asthmatic children who did not attend preschool or daycare programs were recruited for personal, residential indoor and outdoor, and central site monitoring. The concentrations of combustion related products, PM, and air toxics were monitored over a 4-day period, including weekdays and weekends. Residence, participant, and follow-up survey information was collected, and the children's daily activities (including their locations) were recorded every 15 minutes by the parents in a time activity diary (TAD). The children wore an accelerometer on one ankle to obtain an objective and direct measure of exertion (eg, sedentary, light, moderate, and vigorous). Data from the diaries were also used to estimate the activity exertion levels of the child. The concentrations of the monitored pollutants were within the acceptable limits for the National Ambient Air Quality Standards (NAAQS). Variations in PM and peak concentrations measured with continuous nephelometers were consistent with information collected from the TADs, residence surveys, participant surveys, and follow-up questionnaires. Digital accelerometer exertion data and TAD information were highly correlated (r = 0.9). On average, the children participated in sedentary activities 45% of the time and spent 81% of their time indoors at home. Their estimated ventilation rates averaged 39% less than the predicted rates for children without asthma for the same age, gender, and body mass class, as determined using the Child Specific Exposure Factors Handbook. The information collected from the surveys and questionnaires was useful for identifying sources and activities that may impact asthmatic children's exposures to air pollutants. The lower estimated ventilation rates likely resulted in lower potential intake doses for the asthmatic children, as compared with nonasthmatic children. However, lifestyle factors such as obesity, sedentary activities, housing factors, and the amount of time spent indoors may have a greater influence on the disease state. The observations support the need to collect data on activities and lifestyle factors in large-scale asthma studies to model asthmatic children's exposures and intake dose rates.