['People near major transportation emissions sources experience higher exposure to hazardous pollutants. We present population size and demographic composition estimates for exposure to diesel particulate matter (DPM) exhaust from US harbor activities.', 'We examined 43 US marine harbor areas to determine outdoor, ambient concentrations from port-related DPM emissions and then determined intake fractions of those emissions in each harbor area. We estimated the distribution of health risk by combining ambient concentrations with exposure and carcinogenic risk factors. We assessed demographic differences by stratifying the health risks by race/ethnicity and income.', 'Intake fractions for 42 of the harbor areas ranged from 0.02 × 10(-6) to 3.66 × 10(-6). A DPM-affected population of more than 4 million has a risk level greater than 100 per million; a population of 41 million, a risk level greater than 10 per million. Most exposures occur in a small number of marine harbor areas. Low-income households and both Hispanics and non-Hispanic Blacks are overrepresented in the affected populations.'] Do analysis of diesel particulate matter health risk disparities in selected US harbor areas?