Evaluation of biomonitoring data from the CDC National Exposure Report in a risk assessment context: perspectives across chemicals

Abstract

Background: Biomonitoring data reported in the National Report on Human Exposure to Environmental Chemicals [NER; Centers for Disease Control and Prevention (2012)] provide information on the presence and concentrations of > 400 chemicals in human blood and urine. Biomonitoring Equivalents (BEs) and other risk assessment-based values now allow interpretation of these biomonitoring data in a public health risk context.

Objectives: We compared the measured biomarker concentrations in the NER with BEs and similar risk assessment values to provide an across-chemical risk assessment perspective on the measured levels for approximately 130 analytes in the NER.

Methods: We identified available risk assessment-based biomarker screening values, including BEs and Human Biomonitoring-I (HBM-I) values from the German Human Biomonitoring Commission. Geometric mean and 95th percentile population biomarker concentrations from the NER were compared to the available screening values to generate chemical-specific hazard quotients (HQs) or cancer risk estimates.

Conclusions: Most analytes in the NER show HQ values of < 1; however, some (including acrylamide, dioxin-like chemicals, benzene, xylene, several metals, di-2(ethylhexyl)phthalate, and some legacy organochlorine pesticides) approach or exceed HQ values of 1 or cancer risks of > 1 × 10-4 at the geometric mean or 95th percentile, suggesting exposure levels may exceed published human health benchmarks. This analysis provides for the first time a means for examining population biomonitoring data for multiple environmental chemicals in the context of the risk assessments for those chemicals. The results of these comparisons can be used to focus more detailed chemical-specific examination of the data and inform priorities for chemical risk management and research.

Figure 1

HQs for NER analytes with available BEs or other biomarker-based screening values, excluding VOCs (see Figure 2 for VOCs); screening values and NHANES data reported in Table 1. Open symbols correspond to the HQ at the limit of detection (LOD) in cases where the analyte was not detected in the NHANES survey at the specified quantile. For dioxin toxic equvalency (TEQ) and PBDE-99, concentrations were not quantifiable at the GM, and variable LODs in the NHANES data set prevent selection of a single value to represent LOD. DDT, dioxin TEQ, and PCBs HQs are shown by age in years. ^aDeltamethrin and cyfluthrin were not detected at either the GM or the 95th percentile; the HQ associated with the LOD is indicated in the figure.

Figure 2

HQs for VOCs from the NHANES 2003–2004 cycle for those VOCs with available BE values (see Table 2). Open symbols correspond to the HQ at the limit of detection in cases where the analyte was not detected in the NHANES survey at the specified quantile.

Figure 3

Cancer risk estimates based on biomarker concentrations from the NER data set for those compounds with available cancer-based BE values. Open symbols correspond to the risk level at the limit of detection in cases where the analyte was not detected in the NHANES survey at the specified quantile. All risk estimates assume that biomarker concentrations represent lifetime exposure levels. DDT risk estimates are shown by age in years. [Cancer risk-based BE values are presented by Hays and Aylward 2008 (acrylamide); Aylward et al. 2010a (hexachlorobenzene); Kirman et al. 2011 (DDT); Hays et al. 2010 (arsenic), Hays et al. 2012 (benzene), and Aylward et al. 2008a (trihalomethanes)].

Figure 4

Analytes by NHANES subsample from 2003–2004 cycle. Subsamples A, B, and C represent approximately one-third samples of the full NHANES sample for a given cycle; the VOC subsample overlaps groups A, B, and C. Analytes were measured in blood or urine specimens from persons within the specified subsample and meeting the specified age cutoffs.

Figure 5

Box plots of HQs for individual THM compounds and the HI for the combined THM HQs calculated per Equation 2. Extreme values are omitted. The horizontal line indicates the median, boxes represent the interquartile range, and lower and upper whiskers extend to 1.5 times the interquartile range below the 25th and above the 75th percentiles, respectively.