Exposure assessment methods for examining the role of non-chemical stressors in environmental health disparities

Increases in chronic diseases among children are cause for public health concern and action, particularly as children of color and low socioeconomic position are disproportionately impacted, with far-reaching consequences for health and well-being over the life-course. Environmental toxicants and non-chemical stressors have been linked with adverse health outcomes and disparities. Specifically, recent toxicological and epidemiological evidence suggests that chronic psychosocial stress may modify pollution effects on health. Thus, there is increasing interest in refined methods for assessing and incorporating non-chemical exposures, including social stressors, into environmental health research, towards identifying whether and how psychosocial stress interacts with chemical exposures to influence health and health disparities. The overall objective of this dissertation is to apply exposure science principles to develop and validate methods for non-chemical exposure assessment, toward examining differential susceptibility and disproportionate exposures in social-environmental epidemiology. To do so, I utilize a spatial approach to characterize intra-urban variation in and correlation among social stressors, socioeconomic position, and air pollution exposures across New York City. I present flexible GIS-based approaches for reformulating aggregate administrative indicators for global correlation analysis, accounting for spatial autocorrelation, and assessing perceived neighborhood geography. I assess multiple foci of the stress process paradigm using qualitative and quantitative methods, and evaluate the extent to which multiple components of social environment are implicated in psychosocial pathways, with specific attention to distinguishing socioeconomic and stress pathways. Complex interaction between air pollution and area-level deprivation effects on term birth weight suggested differential population susceptibility, and the need for mechanism-specific non-chemical exposure metrics. Spatially, ecologic indicators of social stressor exposures and air pollution were not consistently correlated with each other, or with indicators of socioeconomic position, and were not consistently associated with child asthma exacerbation rates. Community perceptions of important social stressors assessed through a qualitative process informed upon the design and implementation of a systematic survey to validate the resonance of ecologic stressor indicators against individual stress perception and mental health. Overall, these non-chemical exposure assessment methods enable characterization of complex confounding in urban environments, toward refining epidemiologic investigations of separate and combined effects of social and chemical exposures

Methods for Evaluating the Combined Effects of Chemical and Nonchemical Exposures for Cumulative Environmental Health Risk Assessment

Cumulative risk assessment (CRA) has been proposed as a means of evaluating possible additive and synergistic effects of multiple chemical, physical and social stressors on human health, with the goal of informing policy and decision-making, and protecting public health. Routine application of CRA to environmental regulatory and policy decision making, however, has been limited due to a perceived lack of appropriate quantitative approaches for assessing combined effects of chemical and nonchemical exposures. Seven research projects, which represented a variety of disciplines, including population health science, laboratory science, social sciences, geography, statistics and mathematics, were funded by the US Environmental Protection Agency (EPA) to help address this knowledge gap. We synthesize key insights from these unique studies to determine the implications for CRA practice and priorities for further research. Our analyses of these seven projects demonstrate that the necessary analytical methods to support CRA are available but are ultimately context-dependent. These projects collectively provided advancements for CRA in the areas of community engagement, characterization of exposures to nonchemical stressors, and assessment of health effects associated with joint exposures to chemical and psychosocial stressors