Relative exposure to fine particulate matter and VOCs between transport microenvironments in Dublin: Personal exposure and uptake

Abstract

To compare the relative exposure to and uptake of air pollutants between modes of commuter transport, measurements of personal exposure to PM 2.5 and traffic-related VOCs were obtained over an 18-month period. In total, 468 samples were recorded comprising journeys equally divided between the four main modes of commuter transport in Dublin, Ireland: the private car, pedestrian, public bus and cyclist. Samples were recorded along two fixed routes approaching/exiting the city centre at fixed times of the day (morning and evening peak traffic flows, 08:00–09:00 and 17:00–18:00). Samples were measured using a high flow gravimetric personal sampler for PM 2.5 and a low flow vacuum operated bag sampler for VOCs. Sampling was always carried out simultaneously between two modes of transport to ensure a direct comparison regardless of meteorological and traffic conditions. Significant differences were found between the personal exposures recorded in the four modes investigated. The car commuter was found to have the highest exposure to VOCs, while the bus commuter was found to have the highest exposure to PM 2.5. The pedestrian was consistently found to have the lowest exposure. Significant differences were also found between the two fixed routes investigated. However, as there were differences in physiological states, exposure durations and exposure levels between the four modes of transport, it was deemed necessary to estimate the total uptake of pollutants by means of a numerical human respiratory tract model. The results showed the cyclist to have the highest deposition of PM 2.5 in the lungs followed by the bus, pedestrian and car. The car passenger had the highest absorption of VOCs followed by the cyclist, pedestrian and bus. Hence, the findings of the human respiratory tract model give a significantly different impression of relative uptake of pollutants to the relative exposure concentrations found initially.