Measurements of diesel particulate emissions from maritime sources are rare, although this form of transportation causes significant air pollution. However, unlike the land environment, the nautical environment is free of interference from other combustion sources. Continuous measurements of diesel particulate matter (DPM) were recently conducted in conventional diesel-electric submarines. The average DPM concentration in the engine room was 150 mu g m(-3), with particle size distributions in the range of 0.5-2 mu m. Chemical speciation of elemental carbon (EC), organic carbon (OC) and total carbon (TC) were determined. Both the National Institute of Occupational Safety and Health (NIOSH) Method 5040 and the Interagency Monitoring of Protected Visual Environment (IMPROVE) method showed EC as being composed of 45% TC. Soluble inorganic components of DPM were characterised. After correction for salt contribution, TC was found to be of 80% DPM. EC, TC and DPM were found to conform to the characteristics defined for exposure and risk assessments by government authorities. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.