Grantee Research Project Results
2010 Progress Report: Modeling Dietary Contributions to Arsenic Dose and Methylation: Elucidating Predictive Linkages
EPA Grant Number: R833992Title: Modeling Dietary Contributions to Arsenic Dose and Methylation: Elucidating Predictive Linkages
Investigators: Burgess, Jefferey L. , Harris, Robin B. , Martinez, M. Elena , O’Rourke, Mary Kay , Hsu, Paul
Institution: Mel and Enid Zuckerman College of Public Health
EPA Project Officer: Hahn, Intaek
Project Period: October 1, 2008 through September 30, 2010 (Extended to September 30, 2011)
Project Period Covered by this Report: October 1, 2009 through September 30,2010
Project Amount: $499,999
RFA: Development of Environmental Health Outcome Indicators (2007) RFA Text | Recipients Lists
Research Category: Human Health
Objective:
The objectives of this research are to utilize existing and archived population-based questionnaire and biological data that describe food and water consumption histories in order to construct predictive indicator models for urinary arsenic (uAs) biomarkers. For Aim 1, dietary recall data from three local population studies (NHEXAS-AZ, the Arizona Border Survey (ABS) and the Bi-national Arsenic Exposure Study (BAsES)) will be used to model total arsenic, the sum of inorganic arsenic and metabolites, and percent MMA in the urine collected (subsequently). Models will be tested with and without personal water consumption data and micronutrient data. Aim 2 will involve testing these models on a regional basis (NHEXAS-Region 5) and assessing the impact of differences in regional drinking water arsenic levels and differences in ethnicity. Aim 3 entails conducting an independent validation using a national database (NHANES 2003-04) of the predictive models constructed in Aim 1 based on the Arizona study populations.
Progress Summary:
Specific protocols were developed and followed assigning As and nutrient values to the food records, including approaches to assigning values to composite foods, missing information, and extreme over and under-reporting of kilocalories consumed.
Modeling of urinary total arsenic was completed in the ABS, NHEXAS-AZ and the two populations combined. Due to a high proportion of uAs values below the limit of detection (LOD) of 4.7 µg/L, uAs exposure was evaluated as a binary variable, above or below the LOD, and, for values above the LOD, as a continuous, log-transformed variable. A two-stage regression analysis approach was followed. First, generalized linear models were used to assess the relation between each of the five dietary As measures and uAs > LOD vs. ≤ LOD. In the 2nd stage, modeling was restricted to persons with uAs > LOD, and general linear and mixed models were run using bootstrap sampling with replacement (500 replications) from the entire population. Both crude models and models adjusted for sex, Hispanic ethnicity, current smoking, As in drinking wate, and As in water used in food preparation were run.
In the 1st stage models, total As measured from duplicate diet samples increased the odds of uAs > LOD by a factor of 4.55 (95% c.i., 1.18-17.55) in the ABS, but not in NHEXAS. None of the other estimates of dietary As were significant predictors in either ABS, NHEXAS or the combined population. In restricted models, all estimates of total dietary As were linearly related to uAs in NHEXAS and the combined population, but not in ABS. Exposure to As in drinking and cooking water were not significantly associated with uAs excretion. None of the additional covariates in the models were independent predictors of uAs.
Thus far, we have found that food is a significant source of exposure to total As, more important than tap water, and predictive of uAs in Arizona. Modeled dietary As consumption provides a correlative approach to estimating exposure that we were able to validate in this study.
Additional modeling was done to compare the effect of dietary As on uAs in subjects with tap water As concentration > 10 ppb vs. ≤ 10 ppb. Dietary As was significantly associated with urine As in both strata, but the coefficients were increased in subjects with tap water As >10ppb. Preliminary assessment of dietary data from the Binational Arsenic Exposure Study (BAsES) also has been completed. In unadjusted models, the dietary As estimates based on TDS and Schoof were significantly associated with uAs.
Future Activities:
BAsES and NHANES 2003-04
Adjusted models of the specific contribution of TDS and Schoof estimates of dietary total and inorganic As to total, inorganic, and %MMA in urine are planned. The effects of dietary micronutrients on uAs methylation will be evaluated in these models.
HISPANIC model
Using Arizona data only from the NHEXAS-AZ, ABS and BAsES studies, a stratified analysis of uAs will be modeled from food, beverage and water consumption data in U.S. Hispanics vs. U.S. non-Hispanics.
Journal Articles:
No journal articles submitted with this report: View all 8 publications for this projectSupplemental Keywords:
metalloid, modeling, exposure and risk assessment, metabolism, health effects, carcinogen, sensitive populations, public policyProgress 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.