This study analysed national data and city case studies to understand why cycling is more popular in the Netherlands, Denmark and Germany than in the UK or the USA.
2. Exposure to particulate matter in traffic: A comparison of cyclists and car passengers.
Int Panis, L., de Geus, B., Vandenbulcke, G. et al. (2010). Exposure to particulate matter in traffic: A comparison of cyclists and car passengers. Atmospheric Environment. 44:2263-2270.
summary of findings:
In this study, researchers in Belgium compared the exposure to traffic emissions for cyclists and car passengers. 55 healthy, non-smoking participants were driven by motor car along a test route with the windows closed, air conditioning off and fan mode set at '1'. Air in the breathing zone (about 30cm from the mouth) was sampled for each trip to measure PM concentrations. Each person then cycled the same route immediately afterwards.
Three test routes were selected in different regions of Belgium: one in Brussels, one in Louvain-la-Neuve, a new town, and one in Mol, a small rural town. During each trip, the breathing frequency, depth, oxygen uptake and heart rate were measured. These measurements were used to calculate the volume of air breathed in and out per minute, the amount of PM inhaled and the estimated amount of PM that would be deposited in the lungs for each participant.
Compared with more stable concentrations inside cars, particle number concentrations (PNCs) fluctuated more for cyclists in traffic, reaching peaks of 100,000 particles per cubic centimetre. PNC values were about three times higher in Brussels than the other two sites.
Cyclists breathed more frequently and took more deep breaths than car passengers. They breathed in and out about 4.3 times more air per minute than car passengers. In addition, cyclists inhaled 400 to 900 per cent more emission particles than car passengers on the same route. The fraction of particles that remain deposited in the lungs after being inhaled was significantly higher for cyclists than car passengers.