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An Analysis of Cumulative Risks Indicated by Biomonitoring Data of Six Phthalates Using the Maximum Cumulative Ratio
Reyes, J. AND P. Price. An Analysis of Cumulative Risks Indicated by Biomonitoring Data of Six Phthalates Using the Maximum Cumulative Ratio. 2017 Society of Toxicology Annual Meeting, Baltimore, MD, March 12 - 16, 2017.
This abstract presents the results of a new and novel analysis of phthalate biomonitoring data for phthalates that is based on the patterns of co-exposure for six phthalates. Phthalates are a group of chemicals that have been identified by the NAS as having a significant potential for causing combined effects when individuals are exposed to more then one of the compounds. The analysis suggests a modest impact of combined exposures for six phthalates in individuals ages six years and above.
The Maximum Cumulative Ratio (MCR) quantifies the degree to which a single component of a chemical mixture drives the cumulative risk of a receptor.1 This study used the MCR, the Hazard Index (HI) and Hazard Quotient (HQ) to evaluate co-exposures to six phthalates using biomonitoring data in 2454 individuals aged 6 years and older from the 2011-12 cycle of the National Health and Nutrition Examination Survey. The values of MCR, HI and phthalate-specific HQs were determined by calculating steady-state doses consistent with the concentrations of phthalate metabolites in urine and using Tolerable Daily Intake values.2 There were 22 individuals (0.9%) predicted to have at least one HQ value > 1 and an additional 17 (0.7%) with no HQ value > 1 but with an HI value > 1. The percent of individuals with HI values > 1 differed by age (0.9% for individuals between 6 – 17 y and 1.9% for individuals > 17 y). There is a statistically significant negative relationship between HI and MCR values in both age groups (p-values 1 and all HQs 1 were 1.1 (1.0-1.3) and 2.8 (1.1-13.7), respectively. The combined assessment found that 17/39 (43%) of the individuals with HI values > 1 are missed by chemical-by-chemical assessments of the phthalates. These findings suggest that determining combined exposures for the six phthalates has a modest impact on the predictions of the chemicals’ risks. Additional individuals with HI values >1 are identified, but HI values in these individuals are close to 1 (<1.3). Individuals with the largest HI values are identified by chemical-by-chemical assessments. The views expressed in this abstract are those of the authors and do not necessarily reflect the views or policies of the U.S. EPA.