The community assessment of freeway exposure and health study: modeling personal exposures to ultrafine particles and effects on biomarkers of cardiovascular health

Abstract

Approximately 45 million people in the United States live, work, or attend schools within 300 feet of a major road, airport or railroad, and approximately 11% of US households reside within lOOm of highways making exposure to TRAPs a major public health concern (EPA, 2014; Brugge et al., 2007). Vehicle emissions are the primary source by which people are exposed to ultrafine particles (particles <100 nm in aerodynamic diameter, UFP), but there are substantial limitations that impede the Environmental Protection Agency's (EPA) ability to adequately monitor and develop a UFP standard. UFPs constitute a developing area of exposure and epidemiological research that requires novel modeling approaches to deal with bias stemming from the high spatial and temporal variability of this pollutant. This dissertation aids in filling the UFP research gap through an examination of the association between UFP and biomarkers of cardiovascular health. During the dissertation I have designed, validated and tested a novel geocoding methodology and implemented a time-activity exposure assignment model as a way to deal with error from various sources that lead to exposure misclassification. This dissertation demonstrates: 1) that epidemiological studies focusing on proximity to major roadways could have reduced ability to detect true association with adverse health effects due to inaccurate geocoding and the effects of population mobility; 2) that inclusion of time-activity in the assignment of personal exposure to UFPs produce more accurate beta estimates during health analysis; 3) positive associations between UFP measured as particle number concentration (PNC) and hsCRP, IL-6 and TNFRll that were evident after adjusting for other cardiovascular disease risk factors. To our knowledge, this is the first study to examine the association between chronic exposure to UFP and biomarkers of systemic inflammation and coagulation.