Indoor black carbon of outdoor origin and oxidative stress biomarkers in patients with chronic obstructive pulmonary disease

Abstract

ObjectivesWe assessed relationships between indoor black carbon (BC) exposure and urinary oxidative stress biomarkers, 8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA), in participants with chronic obstructive pulmonary disease (COPD). MethodsEighty-two participants completed in-home air sampling for one week prior to providing urine samples up to four times in a year. Weekly indoor and daily outdoor concentrations were used to estimate indoor daily lags and moving averages. There were no reported in-home BC sources, thus indoor levels closely represented outdoor BC infiltration. Mixed effects regression models with a random intercept for each participant were used to assess relationships between indoor BC and 8-OHdG and MDA, adjusting for age, race, BMI, diabetes, heart disease, season, time of urine collection, urine creatinine, and outdoor humidity and temperature. ResultsThere were positive effects of BC on 8-OHdG and MDA, with the greatest effect the day before urine collection (6.9% increase; 95% CI 0.9–13.3%, per interquartile range: 0.22 μg/m3) for 8-OHdG and 1 to 4 days before collection (8.3% increase; 95% CI 0.03–17.3% per IQR) for MDA. Results were similar in models adjusting for PM2.5 not associated with BC and NO2 (10.4% increase, 95% CI: 3.5–17.9 for 8-OHdG; 8.1% increase, 95% CI: −1.1–18.1 for MDA). Effects on 8-OHdG were greater in obese participants. ConclusionsWe found positive associations between BC exposure and 8-OHdG and MDA, in which associations with 8-OHdG were stronger in obese participants. These results suggest that exposure to low levels of traffic-related pollution results in lipid peroxidation and oxidative DNA damage in individuals with COPD.