This paper presents measurements and analyses of the concentrations of black carbon (BC), particle number concentration (PNC), and PM 2.5 (≤2.5 µm) while commuting by ferries in Istanbul. In this context, exposures to the mentioned pollutants were estimated for car ferry, fast ferry, and at the piers, and for two travel routes, for a total of 89 trips. BC, PNC, and PM 2.5 measurements were simultaneously performed in a ferry and at the piers, and the correlation between pollutant concentrations, meteorological parameters, and environmental factors were analyzed. The mean concentrations for all pollutants in car ferry were lower than the average concentrations in fast ferry. The concentration ratios of fast ferry to car ferry for BC, PNC, and PM 2.5 were 6.4, 1.2, and 1.3, respectively. High variability in the concentrations was observed at the piers and in ferry during berthing. The highest mean concentrations (±standard deviation) of BC (14.3 ± 10.1 µg m −3 ) and PNC (42,005 ± 30,899 pt cm −3 ) were measured at Yalova pier. The highest mean concentration (±standard deviation) of PM 2.5 (26.1 ± 11.5) was measured at Bostancı pier. It was observed that the main external sources of BC, PNC, and PM 2.5 at the piers were road transport, residential heating, and shipping activity. There were no significant correlations between BC, PNC, and PM 2.5 in fast ferry, while BC was positively correlated with PNC (r = 0.61, p < 0.01) and PM 2.5 (r = 0.76, p < 0.01) in car ferry. At the piers, significant relations between pollutants and meteorological variables were observed. It was noticed that there was no significant difference between summer and winter in ferry and at the pier concentrations of BC, PNC, and PM 2.5 except for Yenikapı pier and Bakırköy pier. The highest total exposure to PNC and PM 2.5 was in car ferry mode, while the highest total exposure to BC was in fast ferry mode.Atmosphere 2019, 10, 439 2 of 16 no sufficient data nor detailed information available on commuter exposure in ferry and at the piers. Most of marine air quality studies are about the determination of emissions from ships. Only a few studies were conducted in ferry. Lau and Chan [4] investigated the volatile organic compound VOC levels in ferry, road transport, and railway, and they revealed that the exposure levels in ferry were the lowest. Chan et al. [5] collected PM 10 samples in ferry in Hong Kong, they found PM 10 levels in ferries were higher than the air-conditioned roadway transport.Particles with an aerodynamic diameter smaller than 0.1 µm are defined as ultrafine particles (UFP) [6]. UFP contribute to 90% of particle number concentration (PNC) in urban areas and the major source of UFP is combustion engines [7,8]. Due to the small size of the UFP, it easily causes adverse effects on respiratory and cardiovascular systems [9]. Black carbon (BC), a component of fine particle (PM 2.5 ) [10], causes respiratory diseases including lung cancer [11], and is also considered as the second most major pollutant affecting climate change after ...