Biomonitoring Equivalents for 2,2′,4,4′,5-pentabromodiphenylether (PBDE-99)

Explore the Dosimetric Relationship between the Intake of Chemical Contaminants and Their Occurrence in Blood and Urine

The dosimetric relationship between the human intake dose of a chemical contaminant (an "external dose") and its concentrations in bodily fluids such as blood and urine (related to an "internal dose"), often characterized by a dose-to-concentration ratio, has critical applications in exposure science, toxicology, and risk assessment, especially in the "new approach methods" era. However, there is a lack of a mechanistic, systematic understanding of how such a dosimetric relationship depends on fundamental chemical properties, such as partition coefficients and biotransformation half-lives. Here, we investigate this issue using a well-evaluated toxicokinetic model, which links external and internal doses by quantifying the absorption and elimination of chemicals. Results are visualized in a series of chemical partitioning space plots, whereby a chemical's dose-to-concentration ratio can be approximately predicted based on its partitioning between air, water, and octanol phases. Our results indicate that when taken in equal doses, chemicals with low volatility and moderate to high hydrophobicity exhibit the highest concentrations in the blood, and chemicals undergoing significant biotransformation tend to exhibit lower concentrations in comparison to their counterparts undergoing negligible biotransformation but possessing similar partitioning properties. Chemicals with high hydrophilicity have the highest concentrations in urine. Such revealed property dependence is similar for both adults and children and for individuals with normal body weights and with obesity. Overall, insights gained from this study are important in predicting blood and urinary concentrations from exposure information and in determining the exposure rate that produces the blood or urinary concentrations observed in biomonitoring studies.

Exposure of Swedish adolescents to elements, persistent organic pollutants (POPs), and rapidly excreted substances - The Riksmaten adolescents 2016-17 national survey

Adolescence is a period of significant physiological changes, and likely a sensitive window to chemical exposure. Few nation-wide population-based studies of chemical body burdens in adolescents have been published. In the national dietary survey Riksmaten Adolescents (RMA) 2016-17, over 13 chemical substance groups, including elements, chlorinated/brominated/fluorinated persistent organic pollutants (POPs) were analysed in blood, and in urine metabolites of phthalates/phthalate alternatives, phosphorous flame retardants, polycyclic aromatic hydrocarbons (PAHs), and pesticides, along with bisphenols and biocide/preservative/antioxidant/UV filter substances (N = 1082, ages 11-21). The aim was to characterize the body burdens in a representative population of adolescents in Sweden, and to compare results with human biomonitoring guidance values (HBM-GVs). Cluster analyses and Spearman's rank order correlations suggested that concentrations of substances with known common exposure sources and similar toxicokinetics formed obvious clusters and showed moderate to very strong correlations (r ≥ 0.4). No clusters were formed between substances from different matrices. Geometric mean (GM) concentrations of the substances were generally less than 3-fold different from those observed among adolescents in NHANES (USA 2015-16) and GerES V (Germany 2014-17). Notable exceptions were brominated diphenyl ethers (PBDEs) with >20-fold lower GM concentrations, and the biocide triclosan and ultraviolet (UV) filter benzophenone-3 with >15-fold lower mean concentrations in RMA compared to NHANES. Exceedance of the most conservative HBM-GVs were observed for aluminium (Al, 26% of subjects), perfluorooctanesulfonic acid (PFOS, 19%), perfluorooctanoic acid (PFOA, 12%), lead (Pb, 12%), MBP (dibutyl phthalate metabolite, 4.8%), hexachlorobenzene (HCB, 3.1%) and 3-phenoxybenzoic acid (PBA, pyrethroid metabolite, 2.2%). Males showed a higher proportion of exceedances than females for Pb, HCB and PFOS; otherwise no gender-related differences in exceedances were observed. A higher proportion of males than females had a Hazard Index (HI) of substances with liver and kidney toxicity and neurotoxicity >1. Industrialized countries with similarly high standards of living, with some exceptions, show comparable average body burdens of a variety of toxic chemicals among adolescents from the general population. The exceedances of HBM-GVs and HIs strongly suggests that further efforts to limit chemical exposure are warranted.

Maternal and child biomonitoring strategies and levels of exposure in western Canada during the past seventeen years: The Alberta Biomonitoring Program: 2005-2021

The Alberta Biomonitoring Program (ABP) was created in 2005 with the initial goal of establishing baseline levels of exposure to environmental chemicals in specific populations in the province of Alberta, Canada, and was later expanded to include multiple phases. The first two phases focused on evaluating exposure in pregnant women (Phase One, 2005) and children (Phase Two, 2004-2006) by analyzing residual serum specimens. Phase Three (2013-2016) employed active recruitment techniques to evaluate environmental exposures using a revised list of chemicals in paired serum pools from pregnant women and umbilical cord blood. These three phases of the program monitored a total of 226 chemicals in 285 pooled serum samples representing 31,529 individuals. Phase Four (2017-2020) of the ABP has taken a more targeted approach, focusing on the impact of the federal legalization of cannabis on the exposure of pregnant women in Alberta to cannabis, as well as tobacco and alcohol using residual prenatal screening serum specimens. Chemicals monitored in the first three phases include herbicides, neutral pesticides, metals, metalloids, and micronutrients, methylmercury, organochlorine pesticides, organophosphate pesticides, parabens, phthalate metabolites, perfluoroalkyl substances (PFAS), phenols, phytoestrogens, polybrominated compounds, polychlorinated biphenyls (PCBs), dioxins and furans, polycyclic aromatic hydrocarbons (PAHs), and tobacco biomarkers. Phase Four monitored six biomarkers of tobacco, alcohol, and cannabis. All serum samples were pooled. Mean concentrations and 95% confidence intervals (CIs) were calculated for the chemicals detected in ≥25% of the sample pools. cross the first three phases, the data from the ABP has provided baseline exposure levels for the chemicals in pregnant women, children, and newborns across the province. Comparison within and among the phases has highlighted differences in exposure levels with age, geography, seasonality, sample type, and time. The strategies employed throughout the program phases have been demonstrated to provide effective models for population biomonitoring.

Chemical Mixtures in the EU Population: Composition and Potential Risks

Regulating chemical mixtures is a complex scientific and policy task. The aim of this study was to investigate typical mixtures and their potential risks based on internal exposure levels in the European population. Based on human biomonitoring (HBM) data made available via the HBM4EU project, we derived generic mixtures representative of a median (P50) and a worst-case scenario (P95) for adults and children. We performed a mixture risk assessment based on HBM concentrations, health-based guidance values (HBGVs) as internal thresholds of concern, and the conservative assumption of concentration addition applied across different toxicological endpoints. Maximum cumulative ratios (MCRs) were calculated to characterize the mixture risk. The mixtures comprise 136 biomarkers for adults and 84 for children, although concentration levels could be quantified only for a fraction of these. Due to limited availability of HBGVs, the mixture risk was assessed for a subset of 20 substance-biomarker pairs for adults and 17 for children. The mixture hazard index ranged from 2.8 (P50, children) to 9.2 (P95, adults). Six to seven substances contributed to over 95% of the total risk. MCR values ranged between 2.6 and 5.5, which is in a similar range as in previous studies based on human external exposures assessments. The limited coverage of substances included in the calculations and the application of a hazard index across toxicological endpoints argue for caution in the interpretation of the results. Nonetheless the analyses of MCR and MAF_ceiling can help inform a possible mixture assessment factor (MAF) applicable to single substance risk assessment to account for exposure to unintentional mixtures.

Biomonitoring in firefighters for volatile organic compounds, semivolatile organic compounds, persistent organic pollutants, and metals: A systematic review

Firefighters are exposed to a wide range of toxic chemicals due to combustion, with numerous biomonitoring studies completed that have assessed exposure. Many of these studies focus on individual classes of chemicals, with a few considering a broad range of systemic exposures. As yet, no review process has been undertaken to comprehensively examine these studies. The aims of this review are to: (1) ascertain whether biomonitoring studies pertaining to firefighters demonstrate occupational exposure to volatile organic compounds, semivolatile organic compounds, and metals; (2) determine and present results of biomonitoring studies; (3) provide any recommendations presented from the literature that may support exposure mitigation; and (4) suggest future study parameters that may assist in providing a greater understanding surrounding the occupational exposure of firefighters. A systematic review was undertaken with regards to firefighters and biomonitoring studies utilising the matrices of blood, urine, semen and breast milk. This yielded 5690 results. Following duplicate removal, inclusion and exclusion criteria screening and full text screening, 34 studies remained for review. Results of over 80% of studies analysed determined firefighters to experience occupational exposure. Results also show firefighters to be exposed to a wide range of toxic chemicals due to fire smoke; potentially exceeding the range of exposure of other occupations. As firefighters may face increased risk of health effects due to the additive, synergistic, and/or antagonistic effects of chemical exposure, all care must be taken to reduce exposure. This may be achieved by considering tactical decisions, increased personal hygiene, and thorough decontamination procedures. Future biomonitoring studies recognising and assessing the range of chemical exposure firefighters face would be beneficial.

Development of Biomonitoring Equivalents for chlordane and toxaphene with application to the general Canadian population

Biomonitoring Equivalents (BEs) were developed for chlordane and toxaphene using one-compartment pharmacokinetic models and compared with biomonitoring data from the Canadian Health Measures Survey, Cycle 1 (2007-2009). A secondary objective was to examine the toxicities of the components of technical chlordane in a HEPG2 cell culture experiment. Oral reference doses were identified from national and international regulatory agencies and sources. Pharmacokinetic parameters were obtained from experimental data in rodent models. A set of BEs have been derived for the main chlordane isomers, cis-chlordane, trans-chlordane, cis-nonachlor, and trans-nonachlor, and the chlordane metabolite, oxychlordane. BEs were also derived for the main toxaphene isomers found in biota, Parlar No. 26, 50 and 62. Among the general Canadian population, no exceedances of chlordane or toxaphene BEs were observed. Based on the LC50 from the in vitro study, trans-nonachlor was the most toxic, and the trans-isomers were more toxic than the cis-isomers. The derived BE values can be used as screening guidelines to assess the risk of biomonitoring data in human populations. The results of an in vitro experiment suggest that trans-nonachlor is more toxic than technical chlordane and, therefore, the BE for this compound may need to be further lowered.

Exposure to polybrominated diphenyl ethers (PBDEs) in American and Canadian workers: Biomonitoring data from two national surveys

Polybrominated diphenyl ethers (PBDEs) are flame retardants commonly found in many household and industrial products. They can be detected in the serum of the general population, and in even higher concentrations in workers of certain industries, due to an additional occupational exposure. The purpose of this analysis is to determine background exposure levels of PBDEs in the general working population, using national surveys where working status was self-reported. Participants aged 20-65 were selected from the 2003-2004 U.S. National Health and Nutrition Examination Survey (n=1141) and the 2007-2009 Canadian Health Measures Survey (n=1337). Only four congeners were detected in at least 25% of samples for both surveys: BDE47, 99, 100 and 153. NHANES workers had a geometric mean (GM [95% C.I.]) BDE47 concentration of 20.9ng/g lipids [19.3, 22.7], and CHMS workers, 11.4ng/g lipids [10.8, 12.1]. PBDE levels were not statistically significantly different between workers and non-workers, except for BDE153 in CHMS. Among workers, women had a significantly lower concentration of BDE153 than men in both surveys (% change [95% C.I.] with 1ng/g lipid increase: -33.4% [-49.0, -12.9] in NHANES, -18.8% [-27.5, - 8.9] in CHMS), in regressions adjusted for age, body mass index, smoking status, ethnicity and education. CHMS workers in the Information, finance, real-estate, and education industry group had significantly higher BDE47 concentrations than non-workers. These results indicate a high exposure to PBDEs in two North American countries, compared to data from other national surveys. The heterogeneity of the data did not permit a clear-cut distinction between workers and non-workers. Sex differences noted with BDE153 are consistent with those reported in other human exposure assessments and animal studies. Overall, industry-specific concentrations showed no particular pattern across both surveys. Despite some limitations, these data provide a useful estimate of the background exposure to PBDEs in American and Canadian workers.

Biomarkers of exposure in environment-wide association studies - Opportunities to decode the exposome using human biomonitoring data

BACKGROUND

The European Union's 7th Framework Programme (EU's FP7) project HEALS - Health and Environment-wide Associations based on Large Population Surveys - aims a refinement of the methodology to elucidate the human exposome. Human biomonitoring (HBM) provides a valuable tool for understanding the magnitude of human exposure from all pathways and sources. However, availability of specific biomarkers of exposure (BoE) is limited.

OBJECTIVES

The objective was to summarize the availability of BoEs for a broad range of environmental stressors and exposure determinants and corresponding reference and exposure limit values and biomonitoring equivalents useful for unraveling the exposome using the framework of environment-wide association studies (EWAS).

METHODS

In a face-to-face group discussion, scope, content, and structure of the HEALS deliverable "Guidelines for appropriate BoE selection for EWAS studies" were determined. An expert-driven, distributed, narrative review process involving around 30 individuals of the HEALS consortium made it possible to include extensive information targeted towards the specific characteristics of various environmental stressors and exposure determinants. From the resulting 265 page report, targeted information about BoE, corresponding reference values (e.g., 95th percentile or measures of central tendency), exposure limit values (e.g., the German HBM I and II values) and biomonitoring equivalents (BEs) were summarized and updated.

RESULTS

64 individual biological, chemical, physical, psychological and social environmental stressors or exposure determinants were included to fulfil the requirements of EWAS. The list of available BoEs is extensive with a number of 135; however, 12 of the stressors and exposure determinants considered do not leave any measurable specific substance in accessible body specimens. Opportunities to estimate the internal exposure stressors not (yet) detectable in human specimens were discussed.

CONCLUSIONS

Data about internal exposures are useful to decode the exposome. The paper provides extensive information for EWAS. Information included serves as a guideline - snapshot in time without any claim to comprehensiveness - to interpret HBM data and offers opportunities to collect information about the internal exposure of stressors if no specific BoE is available.

Toxicokinetics of short-chain chlorinated paraffins in Sprague-Dawley rats following single oral administration

Short-chain chlorinated paraffins (SCCPs) have attracted considerable attention for their characteristic of persistent organic pollutants. However, very limited information is available for their toxicokinetic characteristics, limiting the evaluation of their health risks. In this study, we performed a toxicokinetics study to explore the absorption and excretion processes of SCCPs (a mixture of C10-, C11-, C12- and C13-CPs) after a single oral administration to the Sprague-Dawley rats. The toxicokinetic results showed that peak blood concentration of total SCCPs was attained at 2.8 day with Cmax value of 2.3 mg L(-1). The half-lives of total SCCPs in blood for the absorption t1/2 (ka), distribution t1/2 (α) and elimination phases t1/2 (β) were calculated to be 1.0, 1.7 and 6.6 days, respectively. During the 28 days post-dosing, about 27.9% and 3.5% of orally administrated SCCPs were excreted through feces and urine without metabolism, respectively. Congener group abundance profiles indicate a relative increase of Cl5-SCCPs in blood and urine in the elimination stage, and a higher accumulation of Cl8-10-SCCPs in feces. The distribution discrepancies of SCCPs congener groups in blood and excreta were more dependent on chlorine contents than on carbon chain lengths.

California biomonitoring data: Comparison to NHANES and interpretation in a risk assessment context

The California Environmental Biomonitoring Program (also known as Biomonitoring California) has been generating human biomonitoring data and releasing it via their website. The current Biomonitoring California program is a collection of smaller studies, targeting specific populations (e.g., fire fighters, breast cancer patients and controls, etc.). In this paper we compare the results from Biomonitoring California with those from the US National Health and Nutrition Examination Survey (NHANES). We also compare California's results with Biomonitoring Equivalents (BEs) for those compounds for which BEs exist. In general, the results from California are consistent with the biomonitoring levels found across the US via NHANES. A few notable exceptions are levels of flame retardants amongst fire fighters in California, which are higher than observed in NHANES and some persistent organic chemicals amongst a study of breast cancer patients and controls in California which are higher than in the overall adult population in NHANES. The higher levels amongst fire fighters may be a result of fire fighters being exposed to higher levels of flame retardants while fighting fires. The higher levels of the persistent organics amongst breast cancer patients is likely due to this population being older than the mean age in NHANES. Comparisons to BEs indicate that biomonitoring levels in California are all consistently below levels of concern as established by regulatory agencies.

Screening of population level biomonitoring data from the Canadian Health Measures Survey in a risk-based context

Since 2007, the Canadian Health Measures Survey (CHMS) has been collecting biomonitoring data from the general Canadian population and has provided, to date, nationally representative concentrations for hundreds of environmental biomarkers in blood or urine. Biomonitoring Equivalents (BEs) have been developed as tools to help interpret biomonitoring data in a health risk context at a population level. In this paper, BEs are used to relate biomonitoring data from the CHMS (2007-2011) to existing exposure guidance values developed by Health Canada and other government agencies. Chemical-specific hazard quotients (HQs) and/or cancer risk estimates are calculated using existing BEs corresponding to environmental chemicals analyzed in the CHMS. For the majority of environmental chemicals, calculated HQ values are less than 1 indicating exposure is below published exposure guidance values. Individual biomonitoring data for two biomarkers of metal exposure (inorganic arsenic and cadmium) resulted in HQ values exceeding 1 suggesting that exposure may be above existing guidance values for a portion of the population, at least intermittently. This type of analysis may be used by researchers, risk assessors, and risk managers in prioritization efforts.

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

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.