Polycyclic aromatic hydrocarbon exposure, obesity and childhood asthma in an urban cohort

Abstract

Background: Exposure to traffic-related air pollutants, including polycyclic aromatic hydrocarbons (PAHs) from traffic emissions and other combustion sources, and childhood obesity, have been implicated as risk factors for developing asthma. However, the interaction between these two on asthma among young urban children has not been studied previously.

Methods: Exposure to early childhood PAHs was measured by two week residential indoor monitoring at age 5-6 years in the Columbia Center for Children's Environmental Health birth cohort (n=311). Semivolatile [e.g., methylphenanthrenes] and nonvolatile [e.g., benzo(a)pyrene] PAHs were monitored. Obesity at age 5 was defined as a body mass index (BMI) greater than or equal to the 95th percentile of the year 2000 age- and sex-specific growth charts (Center for Disease Control). Current asthma and recent wheeze at ages 5 and 7 were determined by validated questionnaires. Data were analyzed using a modified Poisson regression in generalized estimating equations (GEE) to estimate relative risks (RR), after adjusting for potential covariates.

Results: Neither PAH concentrations or obesity had a main effect on asthma or recent wheeze. In models stratified by presence/absence of obesity, a significant positive association was observed between an interquartile range (IQR) increase in natural log-transformed 1-methylphenanthrene (RR [95% CI]: 2.62 [1.17-5.88] with IQRln=0.76), and 9-methylphenanthrene (2.92 [1.09-7.82] with IQRln=0.73) concentrations and asthma in obese children (n=63). No association in non-obese (n=248) children was observed at age 5 (Pinteraction<0.03). Similar associations were observed for 3-methylphenanthrene, 9-methylphenanthrene, and 3,6-dimethylphenanthrene at age 7.

Conclusions: Obese young children may be more likely to develop asthma in association with greater exposure to PAHs, and methylphenanthrenes in particular, than non-obese children.

Keywords: 2-methylphenanthrene (2Meph); 3-methylphenanthrene (3Meph), 9-methylphenanthrene (9Meph), 1,7-dimethylphenanthrene (1,7DMeph), 3,6-dimethylphenanthrene (3,6DMeph), and pyrene; ACQ; Asthma; Asthma Control Questionnaire; BC; BMI; BRQ; Brief Respiratory Questionnaire; CCCEH; Childhood obesity; Columbia Center for Children's Environmental Health; DEP; Diesel Exhaust Particle; EC; ER; ETS; Emergency Room; FEV(1); ICS; IQR; ISAAC; International Study of Asthma and Allergies in Childhood; Methylphenanthrenes; NO(2); NYC; New York City; Nonatopic children; PAH; PM; PUF; Polycyclic aromatic hydrocarbons; Polyurethane Foam; RR; benzo[b]fluoranthene (BbFA); benzo[k]fluoranthene (BkFA), benzo[a]pyrene (BaP), indeno[1,2,3-c,d]pyrene (IP), dibenz[a,h]anthracene (DahA), and benzo[g,h,i]perylene (BghiP); black carbon; body mass index; elemental carbon; environmental tobacco smoke; forced expiratory volume in 1s; inhaled corticosteroids; interquartile range; nitrogen dioxide; particulate matter; polycyclic aromatic hydrocarbons; relative risk; sum of 8 high molecular-weight-PAH≥228, including benz[a]anthracene (BaA), chrysene/iso-chrysene (Chry); sum of 8 low molecular-weight-PAH≤206, including phenanthrene (Phe), 1-methylphenanthrene (1Meph); ∑(8)PAH(nonvolatile); ∑(8)PAH(semivolatile).