Physical activity, black carbon exposure and airway inflammation in an urban adolescent cohort

Abstract

Objective: Regular physical activity can improve cardiopulmonary health; however, increased respiratory rates and tidal volumes during activity may increase the effective internal dose of air pollution exposure. Our objective was to investigate the impact of black carbon (BC) measured by personal sampler on the relationship between physical activity and fractional exhaled nitric oxide (FeNO), a marker of airway inflammation. We hypothesized that higher personal BC would attenuate the protective effect of physical activity on airway inflammation.

Methods: We performed a cross-sectional study nested in a birth cohort of African American and Dominican children living in the Bronx and Northern Manhattan, New York City. Children were recruited based on age (target 9-14 year olds) and presence (n=70) or absence (n=59) of current asthma. Children wore wrist mounted accelerometers for 6 days and were classified as 'active' if they had ≥60min of moderate-to-vigorous activity (MVA) each day and 'non-active' if they had <60min of MVA on any given day, based on CDC guidelines. Personal BC measured using a MicroAeth, was assessed during two 24-h periods, at the beginning and end of physical activity assessment. High BC was defined as the upper tertile of BC measured with personal sampler. FeNO measurements were sampled at the beginning and end of the of physical activity assessment.

Results: In multivariable linear regression models, 'active' children had 25% higher personal BC concentrations (p=0.02) and 20% lower FeNO (p=0.04) compared to 'non-active' children. Among children with high personal BC (n=33), there was no relationship between activity and FeNO (p=1.00). The significant protective relationship between activity and airway inflammation was largely driven by children with lower personal BC (n=96, p=0.04).

Conclusions: Children that live in an urban environment and are physically active on a daily basis have higher personal exposure to BC. High BC offsets the protective relationship between physical activity and airway inflammation.

Keywords: Air pollution; Asthma; Exercise; FeNO; Urban environment.

Figure 1. Schematic representation of sample size

Of the 163 children enrolled in the parent study, 23 children had incomplete physical activity data, 4 children did not meet compliance standards for wearing personal BC exposure equipment, 3 children had missing FeNO measurements on both sampling days and 4 children did not have specific IgE data yielding a final sample size of 129 children for the current analysis. BC: black carbon, FeNO: fractional exhaled nitric oxide, IgE: Immunoglobulin E

Figure 2. Sampling scheme for actical, BC, and FeNO collection

BC: black carbon, FeNO: fractional exhaled nitric oxide

Figure 3. Personal BC exposure stratified by CDC recommended physical activity levels

24-hour BC exposure was averaged across 2 days of measurement and plotted on a logarithmic scale. N=57 with no daily physical activity, n=52 with ≥ 60 min of MVA daily, n= 20 with ≥ 60 min MVA daily and ≥ 10 min VA, 3 days/week. The small lines indicate individual observations, while the white, grey, and black areas demonstrate the distribution. The dotted line indicates the overall geometric mean and the thicker solid lines represent the geometric mean concentration for each group of activity. BC: black carbon, MVA: moderate to vigorous activity, VA: vigorous activity.