In the general public, certain sub-populations are at higher risk for adverse health effects due to air pollution exposure. Asthmatics have been identified as one such susceptible population due to the observed association of elevated air pollution levels and increased incidences of acute asthma exacerbations as evidenced by decreased lung function values and respiratory symptoms, shortness of breath, emergency department (ED) visits, and hospitalizations (6-13). A study conducted by Mar et al (2004) reported that health outcomes associated with coarse particulate matter (PM2.5-10) were more notable in children with asthma than in adults with asthma (14) and a large epidemiological study of asthmatic children in the Northeastern US showed that asthma morbidity on high ozone days was consistently highest among children age 6 to 18 years (15). Furthermore, children with persistent asthma (requiring daily maintenance medication) were shown to be at increased risk of respiratory symptoms and rescue medication use after ambient ozone exposure compared to children with mild intermittent asthma (16). Together, these studies demonstrate an additional level of susceptibility to air pollution in children compared with adults and in children with persistent asthma compared with mild intermittent asthma.
African-American patients appear to be particularly susceptible to asthma-related complications, with rates of asthma-related emergency department visits, hospitalizations, and death approximately 2 to 3 times the rates found in Caucasian subjects (17) . Furthermore, a higher proportion of African-American asthmatics have poorly-controlled asthma compared to non-African-American asthmatics (18). In a recent pediatric study, very poorly controlled asthmatics had an increased risk of asthma-related hospitalization, emergency department visits, or corticosteroid burst (OR, 6.4; 95% CI, 1.2-34.5) compared with those whose asthma was under better control over a 2-year period (19).
The goal of this panel study is to determine if African-American children with poorly-controlled moderate-to-severe persistent asthma are at increased risk for cardiopulmonary effects as a result of ambient air pollution exposure compared to age- and race-matched well-controlled moderate-to-severe asthmatic children. The primary cohort for this panel study will be African-American children between the ages of 12-17 years with moderate-to-severe asthma (divided between the study populations of poorly-controlled asthma and well-controlled asthma). Since this study is exclusively focused on an African-American population, it is not designed to address the effect of race/ethnicity on baseline asthma control. Volunteers will be recruited primarily from the UNC Pediatric Pulmonary clinic and the UNC Allergy/Immunology clinic located at Rex Hospital in Raleigh, NC in which Dr. Hernandez is an attending physician. These volunteers are well-characterized asthmatics followed regularly by a pediatric pulmonologist (Dr. Ceila Loughlin) and by a pediatric allergist (Dr. Michelle Hernandez) at the Rex location. In order to ensure that the two cohorts experience equivalent daily exposures to ambient air pollutants, the study population will be recruited from a defined geographical region within a reasonable driving distance of the Rex Hospital and in relative proximity to the state-operated monitoring station for ambient air pollutants.
Establishing a relationship between asthma control and adverse health outcomes in response to air pollution exposure will provide health care providers and parents of children with moderate-to-severe asthma the information necessary to take proactive action on high air pollution days as they are communicated to the public through color-coded days based on the National Ambient Air Quality Standards (NAAQS) established by the EPA. If asthma control is determined in this study to be a risk factor for susceptibility, future work will be directed toward establishing the mechanism underlying the susceptibility which may then lead to the potential design of new therapies or intervention strategies.
