Emissions from ships significantly contribute to global air pollution, especially in coastal regions. Marine engines emit high levels of particulate matter (PM), which may contain toxic heavy metals depending on the fuel used. Current regulations on fuel sulphur content (FSC) permit the use of heavy fuel oils (HFOs) only with wet sulphur scrubbers, but do not regulate the PM and heavy metal content directly. This study examines emission factors (EFs) of heavy metals bound to PM2.5 from a maritime research engine operating on various fuels: marine gas oil (MGO), hydrotreated vegetable oil (HVO), ultra-low sulphur heavy fuel oil (ULS-HFOar), and high-sulphur HFOs (HFO 0.5 and HFO 2.2). The impact of wet scrubbing technology and engine load variations (20 kW, 40 kW, 60 kW, 80 kW) was also assessed. Results show that HFO fuels, both with and without scrubbers, produce significantly higher emissions of PM2.5, particle number (PN), and heavy metals compared to MGO, HVO, and ULS-HFOar. While wet scrubbers effectively reduced sulphur emissions, they had limited or no impact on PM2.5, PN, or metal emissions associated with particles. At engine loads of 20 kW and 60 kW, switching from HFO 2.2 to HFO 0.5—following IMO 2020 sulphur regulations—reduced PM2.5 emissions by 23 % and 28 %, respectively, and PN by 30 % and 58 %. Heavy metal emissions decreased dramatically by 74 % and 81 %. The findings underscore the urgent need for particulate emission regulations in marine shipping, akin to those for road traffic, to protect public health from fine and ultrafine particles. Use of HFO in sulphur emission control areas should be reconsidered, even with wet scrubbers, to better address health and environmental risks.     «

Emissions from ships significantly contribute to global air pollution, especially in coastal regions. Marine engines emit high levels of particulate matter (PM), which may contain toxic heavy metals depending on the fuel used. Current regulations on fuel sulphur content (FSC) permit the use of heavy fuel oils (HFOs) only with wet sulphur scrubbers, but do not regulate the PM and heavy metal content directly. This study examines emission factors (EFs) of heavy metals bound to PM2.5 from a mariti...     »