In this peer-reviewed article, published in the American Journal of Public Health, ICF experts found that the most important factor for predicting diesel particulate matter (DPM) intake fractions for harbor activities is the proximate population density. Evidence has shown that people living in close proximity to major transportation sources, such as roads, experience higher exposure to pollutants directly emitted by motor vehicles. At least one study has suggested that residents nearby marine harbor areas are exposed to significantly higher concentrations of pollution, including particulate matter. Our twofold purpose was (1) to compare harbor areas across the United States with respect to the DPM inhalation intake fraction, that is, the intake-to-emissions ratio; and (2) to estimate the size and demographic composition of populations experiencing enhanced carcinogenic health risks as a result of exposure to DPM emitted from activities in U.S. harbor areas.