Grantee Research Project Results
2013 Progress Report: Analytical Strategies for Assessing Cumulative Effects of Chemical and Nonchemical Stressors
EPA Grant Number: R834580Title: Analytical Strategies for Assessing Cumulative Effects of Chemical and Nonchemical Stressors
Investigators: Lai, Dejian , Linder, Stephen H. , Sexton, Ken , Peek, M. Kristin , Cutchin, Malcolm , Stowe, Raymond
Institution: The University of Texas at Houston , The University of Texas at Austin , Microgen LLC , University of Minnesota , University of North Carolina at Chapel Hill , The University of Texas Medical Branch - Galveston
Current Institution: The University of Texas at Houston , Microgen LLC , The University of Texas Medical Branch - Galveston , The University of Texas at Austin , University of Minnesota , University of North Carolina at Chapel Hill
EPA Project Officer: Hahn, Intaek
Project Period: June 1, 2010 through May 31, 2014 (Extended to May 31, 2015)
Project Period Covered by this Report: January 1, 2013 through December 31,2013
Project Amount: $555,923
RFA: Understanding the Role of Nonchemical Stressors and Developing Analytic Methods for Cumulative Risk Assessments (2009) RFA Text | Recipients Lists
Research Category: Human Health
Objective:
The study’s purpose is to develop and test empirically-valid models for understanding cumulative risks in community settings. We are modeling population data drawn from Texas City in 2004-2006, using generalized linear latent and mixed models, to understand how ambient chemical exposures interact with nonchemical stressors (at both the neighborhood and individual levels) and result in adverse health effects. The key health effect of interest is allostatic load, as measured by a suite of biological markers.
Progress Summary:
Accomplishments for this period built on the indicator work from 2012. Again, the emphasis was on solving technical problems antecedent to completing the model specification and getting to document the risk drivers.
- Each latent factor (the model currently contains five) requires a measurement model based on grouping the indicators properly. We accomplished several rounds of measurement modelling, moving between quantitative estimation via factor analysis and iterative adjustment of indicator sets for each latent factor.
- With provisional measurement models in place, we were able to begin path specification and estimation, linking the latent factors to allostatic load. Each time the paths or linkages across factors are estimated and refined, the measurement relations can change and require iterative adjustment. This step was repeated a number of times.
- The GLLAMM software performed multi-level analyses but permitted fewer parameters for stable estimation and convergence to a solution. We changed our modeling strategy to build from rudimentary to complex linkages. The threshold to achieve a stable solution was too low to accommodate our theoretical claims and empirical hypotheses.
With success and experience in our measurement models, we decided to adopt an alternative estimation approach and move to software that would estimate structural equations. After some evaluation, we adopted MPlus and repeated the measurement procedures from steps 1 and 2 above.
Future Activities:
We will continue the migration of our measurement models and our theoretical expectations from GLLAMM to MPlus. The next phase will concentrate on model fitting: testing alternative model specifications, monitoring measures of fit and making iterative adjustments in linkages and measurement models.
Journal Articles on this Report : 4 Displayed | Download in RIS Format
| Other project views: | All 17 publications | 17 publications in selected types | All 17 journal articles |
|---|
| Type | Citation | ||
|---|---|---|---|
|
|
Linder SH, Sexton K. Conceptual models for cumulative risk assessment. American Journal of Public Health 2011;101(Suppl 1):S74-S81. |
R834580 (2010) R834580 (2011) R834580 (2012) R834580 (2013) |
Exit Exit Exit |
|
|
Salinas JJ, Shah M, Abdelbary B, Gay JL, Sexton K. Application of a novel method for assessing cumulative risk burden by county. International Journal of Environmental Research and Public Health 2012;9(5):1820-1835. |
R834580 (2012) R834580 (2013) |
Exit Exit Exit |
|
|
Sexton K, Linder SH. Cumulative risk assessment for combined health effects from chemical and nonchemical stressors. American Journal of Public Health 2011;101(Suppl 1):S81-S88. |
R834580 (2010) R834580 (2011) R834580 (2012) R834580 (2013) |
Exit Exit Exit |
|
|
Sexton K. Cumulative risk assessment: an overview of methodological approaches for evaluating combined health effects from exposure to multiple environmental stressors. International Journal of Environmental Research and Public Health 2012;9(2):370-390. |
R834580 (2010) R834580 (2012) R834580 (2013) |
Exit Exit Exit |
Supplemental Keywords:
cumulative environmental stressors, MPlus, allostatic load, NATA 2005Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.