Exposure to black carbon and PM2.5 was found to be associated with lower measures of desirable HDL cholesterol in a paper based on the Multi-ethnic Study of Atherosclerosis (MESA) cohort. As a part of the MESA Air study led by the University of Washington, investigators examined the association of PM2.5 and black carbon exposures with two measures of HDL cholesterol in a cross-sectional analysis for the year 2000 involving 6,654 adults. Exposure to black carbon over the previous 1 year was associated with significantly lower HDL cholesterol. Exposure to PM2.5 over the previous 3 months was also associated with lower HDL particle number (but not lower HDL cholesterol). These results are consistent with the hypothesis that exposure to air pollution is adversely associated with measures of HDL, which may contribute to cardiovascular disease development.