The contribution of moped emissions to ultrafine and fine particle concentrations on bike lanes.

Although not emitting air pollution themselves, cyclists are exposed to air pollution from motorised traffic. Because of the close proximity of mopeds to cyclists, moped emissions may affect cyclist exposure. However, the quantitative contribution of mopeds to cyclists' air pollution exposures is uncertain. The aim of the research was to quantify the contribution of moped emissions to air pollution concentrations on bike lanes. Measurements of Particle Number Concentrations (PNC), Particulate Matter (PM) and Black Carbon (BC) on bike lanes were performed in September 2016 in four Dutch cities. Passing two- and four-stroke mopeds and other traffic were recorded and distinguished by sound by the trained field worker. One-second PNC, PM and one-minute BC concentrations were measured. Using regression analyses the contribution of passing mopeds to air pollution exposure was analysed. At 18 non-tunnel locations, two-stroke and four-stroke mopeds contributed at average 12,000 and 3000 pt./cm PNC per second when passing by, respectively. In a tunnel, this was 92,000 and 12,000 pt./cm. Two- and four-strokes added 3 to 19% to total PNC at non-tunnel sites and 58% in a tunnel. Four-strokes caused at average 54% of the contribution of moped emissions to total PNC. At non-tunnel sites, the contribution of mopeds to PM was 1.2 and 0.2 μg/m for two- and four-strokes, respectively. In a tunnel this was 3.9 and 2.3 μg/m. Minute-measurements of BC did not show a relation between mopeds passing by and BC. Mopeds caused substantial short-term increases in air pollution levels on bike lanes, especially in a tunnel. Two-stroke mopeds caused higher concentration peaks than four-stroke mopeds. The contribution to total air pollution concentrations of four-stroke mopeds was larger, because of the higher share of four-strokes. Because of the close proximity of mopeds to cyclists, cyclists air pollution exposure can be largely influenced by moped emissions.