Modulation of the acute respiratory effects of winter air pollution by serum and dietary antioxidants: a panel study.

This study investigated whether a high dietary intake or serum concentration of antioxidant (pro-) vitamins could attenuate the acute respiratory effects of air pollution in panels of adults (n = 227) aged 50-70 yrs with chronic respiratory symptoms in two winters starting in 1993/1994. Subjects performed daily peak expiratory flow (PEF) measurements in the morning and evening and reported the occurrence of respiratory symptoms in two regions (urban and nonurban) each winter. Logistic regression analysis was used with the prevalences of large PEF decrements as dependent variables and air pollution levels as independent variables. Analyses were performed separately for subjects below and above the median levels of serum beta-carotene and the intake of dietary vitamin C and beta-carotene. Subjects with low levels of serum beta-carotene more often had large PEF decrements when particles <10 microm in diameter or black smoke levels which were higher compared to subjects with high levels of serum beta-carotene. The same results tended to be observed for dietary vitamin C or beta-carotene, but there were less significant air pollution effects in the low dietary antioxidant group. The results suggest that serum beta-carotene and to a lesser extent dietary vitamin C and beta-carotene may attenuate peak expiratory flow decrements due to air pollution in subjects with chronic respiratory symptoms.