Cycling to work in London and inhaled dose of black carbon

Modelling studies suggest that urban cycling is associated with an increased inhaled dose of fossil fuel-derived black carbon (BC). Using the amount of black material in airway macrophages as a marker of long-term inhaled BC, we sought to compare inhaled BC dose in London (UK) cyclists and non-cyclists. Airway macrophage carbon was assessed in 28 (58%) out of 48 healthy adults (14 cyclists and 14 non-cyclists) who attended for induced sputum. Short-term (24 h) exposure to BC was assessed on a representative working day in 27 out of 28 subjects. Serum interleukin (IL)-1 beta, IL-2, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor and tumour necrosis factor (TNF)-alpha were assessed in 26 out of the 28 subjects. Cyclists were found to have increased airway macrophage carbon when compared with non-cyclists (mean +/- SE 1.81 +/- 0.21 versus 1.11 +/- 0.07 mu m(2); p < 0.01). Short-term monitoring showed no difference in 24 h BC exposure between the two groups. However, cyclists were exposed to higher concentrations of BC during commuting (p < 0.01). Airway macrophage carbon was associated with monitored commute BC (n = 28; r = 0.47, p < 0.05). TNF-alpha was found to be increased in cyclists (p < 0.05), but no other cytokines were increased. Commuting to work by bicycle in London is associated with increased long-term inhaled dose of BC. Whether cycling per se increases inhaled BC dose remains unclear.