Commuters’ Exposure to Particulate Matter Air Pollution Is Affected by Mode of Transport, Fuel Type, and Route

TLDR

Commuters are exposed to high concentrations of traffic‑related air pollutants, yet quantitative data on how exposure varies by transport mode, route, and fuel type are scarce. The study aimed to quantify how commuters’ exposure to traffic‑related air pollution differs by transport mode, route, and fuel type. Researchers measured particle number counts and PM2.5, PM10, and soot concentrations during rush‑hour commutes across diesel and electric buses, gasoline‑ and diesel‑fueled cars, and two bicycle routes with differing traffic intensities, plus an urban background site, over 47 weekdays between June 2007 and June 2008. Cyclists on the high‑traffic route and diesel‑bus passengers had the highest particle number counts, diesel buses had the highest PM10 and soot levels, and overall inhaled doses were greatest for cyclists and lowest for electric‑bus passengers.

Abstract

Commuters are exposed to high concentrations of air pollutants, but little quantitative information is currently available on differences in exposure between different modes of transport, routes, and fuel types.The aim of our study was to assess differences in commuters' exposure to traffic-related air pollution related to transport mode, route, and fuel type.We measured particle number counts (PNCs) and concentrations of PM2.5 (particulate matter <or= 2.5 microm in aerodynamic diameter), PM10, and soot between June 2007 and June 2008 on 47 weekdays, from 0800 to 1000 hours, in diesel and electric buses, gasoline- and diesel-fueled cars, and along two bicycle routes with different traffic intensities in Arnhem, the Netherlands. In addition, each-day measurements were taken at an urban background location.We found that median PNC exposures were highest in diesel buses (38,500 particles/cm3) and for cyclists along the high-traffic intensity route (46,600 particles/cm3) and lowest in electric buses (29,200 particles/cm3). Median PM10 exposure was highest from diesel buses (47 microg/m3) and lowest along the high- and low-traffic bicycle routes (39 and 37 microg/m3). The median soot exposure was highest in gasoline-fueled cars (9.0 x 10-5/m), diesel cars (7.9 x 10-5/m), and diesel buses (7.4 x 10-5/m) and lowest along the low-traffic bicycle route (4.9 x 10-5/m). Because the minute ventilation (volume of air per minute) of cyclists, which we estimated from measured heart rates, was twice the minute ventilation of car and bus passengers, we calculated that the inhaled air pollution doses were highest for cyclists. With the exception of PM10, we found that inhaled air pollution doses were lowest for electric bus passengers.Commuters' rush hour exposures were significantly influenced by mode of transport, route, and fuel type.