Effects of ambient benzene and toluene on emergency COPD hospitalizations: A time series study in Hong Kong

Background: Although numerous studies have demonstrated that the criteria air pollutants increased the risk of exacerbation of chronic obstructive pulmonary disease (COPD), few have explored the effects of ambient benzene and toluene on COPD. Objective: This study aimed to evaluate the short-term effects of ambient benzene and toluene on emergency COPD (eCOPD) hospitalizations. Methods: We obtained daily mean and maximum concentrations of benzene and toluene during April 1, 2011 - December 31, 2014 from the Hong Kong Environmental Protection Department, and daily counts of eCOPD hospitalizations from the Hospital Authority. Generalized additive distributed lag models were used to estimate the percentage excess risk (ER%) of eCOPD hospitalizations per interquartile range (IQR) increase in ambient benzene and toluene. Results: The ER% estimates of eCOPD hospitalizations post cumulative exposure of up to two days were 2.62% (95%CI: 0.17% to 5.13%) and 1.42% (0.16% to 2.69%), for per IQR increase of daily mean benzene (1.4 μg/m³) and toluene (4.6 μg/m³), respectively. People below the age of 65 had a significantly higher risk of eCOPD hospitalizations associated with daily maximum toluene than the elderly. Conclusions: Ambient benzene and toluene might be environmental stressors for acute exacerbations of COPD in the Hong Kong population.