Characterizing populations of individuals using pooled samples

Current-use pesticide exposures in remote Inuit communities

The global use of pesticides is increasing; however, few studies have examined the exposure of current-use pesticide exposure in Inuit populations. Some current use pesticides are also capable of long-range transport, potentially increasing exposures to northern populations. The study aim was to analyse pesticide (chlorophenoxy, organophosphates, and pyrethroid pesticide) biomarker levels in pooled samples from an Inuit population in Nunavik, Quebec. Thirty pooled samples from the Qanuilirpitaa? 2017 survey (Q2017) from individuals aged 16-80 years were included. Creatinine-adjusted arithmetic (AM) were compared by sex, age, and region sub-groups, and geometric mean concentrations (GM) were compared to those in the Canadian Health Measures Survey (CHMS). Most analysed pesticide biomarkers were detected, and PNP (a metabolite of methyl and ethyl parathion), trans-DCCA (a metabolite of pyrethroids), and 3,5,6-TCP (a metabolite of chlorpyrifos) had the highest concentrations. Concentrations in Q2017 were largely similar to or less than CHMS concentrations. Although not significant, there was a general increase in 2,4-D (a chlorophenoxy biomarker), 3,5,6-TCP, 3-PBA (a metabolite of pyrethroids), and trans-DCCA with increasing age. Concentrations were also somewhat higher in females versus males, but these were not significant. Environmental exposures to current use pesticides were detected in Nunavik and concentrations were similar to or less than those in the general Canadian population. Regular monitoring of current use pesticide exposures is recommended given the increasing global use of pesticides.

Exposure to organophosphate esters among Inuit adults of Nunavik, Canada

Halogenated organophosphate esters (OPEs) are increasingly used as flame retardants to replace polybrominated diphenyl ethers (PBDEs), which have been phased out due to their confirmed persistence, toxicity, and ability to undergo long range atmospheric transport. Non-halogenated OPEs are primarily used as plasticizers. While human exposure to PBDEs in the Canadian Arctic is well documented, it is not the case for OPEs. To assess the exposure to OPEs in Inuit living in Nunavik (northern Québec, Canada), we measured 16 metabolites of halogenated and non-halogenated OPEs in pooled urine samples from the last population health survey conducted in Nunavik, the Qanuilirpitaa? 2017 Inuit Health Survey (Q2017). Urine samples (n = 1266) were pooled into 30 pools by sex (female; male), age groups (16-19; 20-29; 30-39; 40-59; 60+ years old) and regions (Hudson Bay; Hudson Strait; Ungava Bay). Q2017 geometric means and 95 % confidence intervals were compared with data from the Canadian Health Measures Survey Cycle 6 (2018-2019) (CHMS). Halogenated OPEs were systematically detected and generally found at higher concentrations than non-halogenated OPEs in both Q2017 and CHMS. Furthermore, urinary levels of BCIPP and BDCIPP (halogenated) were lower in Q2017 compared to CHMS while concentrations of DPhP, DpCP and DoCP (non-halogenated) were similar between Q2017 and CHMS. Across the 16 metabolites measured in Q2017, BCIPHIPP (halogenated) had the highest levels (geometric mean: 1.40 μg/g creatinine). This metabolite was not measured in CHMS and should be included in future surveys. Overall, our results show that Inuit in Nunavik are exposed to lower or similar OPEs levels than the rest of the general Canadian population suggesting that the main current exposure to OPEs may be from consumer goods containing flame retardants and imported from the south rather than long-range atmospheric transport to the Arctic.

Large-scale biomonitoring of bisphenol analogues and their metabolites in human urine from Guangzhou, China: Implications for health risk assessment

Bisphenol analogues (BPs) are ubiquitous in the environment and have gained significant attention regarding their associated health risks. However, there is a lack of comprehensive biomonitoring data on BPs and their metabolites in human urine. To address this, we conducted a study evaluate the exposure to BPs in the general population of Guangzhou, China. A total of 1440 urine samples were collected from volunteers and analyzed for the presence of BPs and their metabolites after being pooled into 36 groups based on age and gender. The findings revealed the common detection of ten free-form BPs, as well as the urinary metabolites of BPA and BPS, in the pooled urine samples. BPA was the predominant free-form compound, constituting 50% of the total BPs. The primary urinary metabolites of BPA and BPS are BPA-G and BPS-G, respectively, indicating glucuronidation as their primary metabolic pathway. The composition of urinary metabolites of BPA and BPS varied by age and sex, while the concentration of total BPs in urine was not significantly associated with age and sex. Enzymatic hydrolysis yielded a mean amplification of individual BPs concentrations in urine samples ranging from 1.8 times (BPA) to 4.6 times (BPS). Based on the outcomes, it was estimated that conjugated forms accounted for 96.9%, 96.2%, 94.7%, 94.1%, 92.6%, 89.1%, 87.3%, 87.2%, 87.1% and 85.8% of BPP, BPAF, BPZ, BPE, BPAP, BPF, BPA, BPC, BPS and BPF, respectively, in the pooled urine samples. Preliminary risk assessments indicated that the estimated daily intake of BPA was much higher than the latest proposed tolerable daily intake. Due to the unavailability of health-based guideline values for alternative BPs, some of them exhibit daily intakes comparable to BPA, implying that greater attention should be paid to health risks associated with exposure to BPs.

Exploration of urinary metabolite dynamicity for early detection of pregnancy in water buffaloes

Early and precise pregnancy diagnosis can reduce the calving interval by minimizing postpartum period. The present study explored the differential urinary metabolites between pregnant and non-pregnant Murrah buffaloes (Bubalus bubalis) during early gestation to identify potential pregnancy detection biomarkers. Urine samples were collected on day 0, 10, 18, 35 and 42 of gestation from the pregnant (n = 6) and on day 0, 10 and 18 post-insemination from the non-pregnant (n = 6) animals. ¹H-NMR-based untargeted metabolomics followed by multivariate analysis initially identified twenty-four differentially expressed metabolites, among them 3-Hydroxykynurenine, Anthranilate, Tyrosine and 5-Hydroxytryptophan depicted consistent trends and matched the selection criteria of potential biomarkers. Predictive ability of these individual biomarkers through ROC curve analyses yielded AUC values of 0.6–0.8. Subsequently, a logistic regression model was constructed using the most suitable metabolite combination to improve diagnostic accuracy. The combination of Anthranilate, 3-Hydroxykynurenine, and Tyrosine yielded the best AUC value of 0.804. Aromatic amino acid biosynthesis, Tryptophan metabolism, Phenylalanine and Tyrosine metabolism were identified as potential pathway modulations during early gestation. The identified biomarkers were either precursors or products of these metabolic pathways, thus justifying their relevance. The study facilitates precise non-invassive urinary metabolite-based pen-side early pregnancy diagnostics in buffaloes, eminently before 21 days post-insemination.

Soil pH, Calcium Content and Bacteria as Major Factors Responsible for the Distribution of the Known Fraction of the DNA Bacteriophage Populations in Soils of Luxembourg

Bacteriophages participate in soil life by influencing bacterial community structure and function, biogeochemical cycling and horizontal gene transfer. Despite their great abundance, diversity, and importance in microbial processes, they remain little explored in environmental studies. The influence of abiotic factors on the persistence of bacteriophages is now recognized; however, it has been mainly studied under experimental conditions. This study aimed to determine whether the abiotic factors well-known to influence bacteriophage persistence also control the natural distribution of the known DNA bacteriophage populations. To this end, soil from eight study sites including forests and grasslands located in the Attert River basin (Grand Duchy of Luxembourg) were sampled, covering different soil and land cover characteristics. Shotgun metagenomics, reference-based bioinformatics and statistical analyses allowed characterising the diversity of known DNA bacteriophage and bacterial communities. After combining soil properties with the identified DNA bacteriophage populations, our in-situ study highlighted the influence of pH and calcium cations on the diversity of the known fraction of the soil DNA bacteriophages. More interestingly, significant relationships were established between bacteriophage and bacterial populations. This study provides new insights into the importance of abiotic and biotic factors in the distribution of DNA bacteriophages and the natural ecology of terrestrial bacteriophages.

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.

Calcium homeostasis and stable fatty acid composition underpin heatwave tolerance of the keystone polychaete Hediste diversicolor

Extreme weather events, such as heatwaves, are becoming increasingly frequent, long-lasting and severe as global climate change continues, shaping marine biodiversity patterns worldwide. Increased risk of overheating and mortality across major taxa have been recurrently observed, jeopardizing the sustainability of ecosystem services. Molecular responses of species, which scale up to physiological and population responses, are determinant processes that modulate species sensitivity or tolerance to extreme weather events. Here, by integrating proteomic, fatty acid profiling and physiological approaches, we show that the tolerance of the intertidal ragworm Hediste diversicolor, a keystone species in estuarine ecosystems and an emergent blue bio-resource, to long-lasting heatwaves (24  vs 30 °C for 30 days) is shaped by calcium homeostasis, immune function and stability of fatty acid profiles. These features potentially enabled H. diversicolor to increase its thermal tolerance limit by 0.81 °C under the heatwave scenario and maintain survival. No growth trade-offs were detected, as wet weight remained stable across conditions. Biological variation of physiological parameters was lower when compared to molecular measures. Proteins showed an overall elevated coefficient of variation, although decreasing molecular variance under the heatwave scenario was observed for both proteins and fatty acids. This finding is consistent with the phenomenon of physiological canalization in extreme environments and contradicts the theory that novel conditions increase trait variation. Our results show that keystone highly valued marine polychaetes are tolerant to heatwaves, confirming the potential of H. diversicolor as a blue bio-resource and opening new avenues for sustainable marine aquaculture development.

Gastrointestinal parasites of a reintroduced semi-wild plains bison (Bison bison bison) herd: Examining effects of demographic variation, deworming treatments, and management strategy

Bison (Bison spp) are being reintroduced into semi-wild, spatially constrained herds across North America and Europe. Herd managers are concerned about gastrointestinal (GI) nematode parasites as they care for the health of their bison. We examine how demographics, grazing location, herd management, and anthelmintic treatments affect the fecal egg counts (FECs) of GI nematodes within a reintroduced Plains bison (Bison bison bison) herd in the Great Plains. Our results suggest that younger bison (<2 years of age) experience higher GI parasite eggs/oocysts per gram (epg/opg) and that some taxa are more prevalent throughout different periods of a bison's early years. Demographic findings suggest that calf and yearling (0–2 yrs age) bison have the highest FECs and that these decline until reaching a low in peak adulthood and thereafter (x > 6 yrs of age). FECs of both Trichuris spp. and particularly Nematodirus spp. were much more abundant, relatively, during the first year of a bison's life. This pattern was also true of Moniezia spp. and Eimeria spp., however, strongyle-type spp. FECs appeared to peak in relative abundance during the second year of life. Our data also indicate that FECs are influenced by differences in land-use histories of pastures previously grazed by cattle or by the proportion of frequent flooding in different pastures. Treatment results suggest that fenbendazole may more effective than moxidectin at lowering FECs of bison over the long-term, and lasting effects of at least one administered anthelmintic treatment. Multiplex PCR assays revealed that American bison share GI nematodes with cattle including: Ostertagia spp., Haemonchus placei, Cooperia onchophora, and Oesophagostomum spp, but did not detect the presence Trichostrongylus columbriformis. Our results may have wider conservation implications for reintroduction efforts of American bison, as well as the endangered European bison (Bison bonasus).

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Younger plains bison (<2 years of age) are more likely to have higher fecal egg counts of gastrointestinal nematodes.

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Eimeria spp., Trichuris spp., Moniezia spp., and Nematodirus spp. are more prevalent in plains bison between zero and 1 years of age, while strongyle-type nematodes are more prevalent in bison between 1 and 2 years of age.

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Both land-use histories and landscape features may influence higher fecal egg counts of gastrointestinal nematodes in plains bison.

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Plains bison share many of the same type of gastrointestinal parasites found in cattle.

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Fenbendazole anthelmintic was more effective than moxidectin treatments in reducing fecal egg counts of gastrointestinal parasites in plains bison.

The porcine respiratory microbiome: recent insights and future challenges

Understanding the structure of the respiratory microbiome and its complex interactions with opportunistic pathogenic bacteria has become a topic of great scientific and economic interest in livestock production, given the severe consequences of respiratory disease on animal health and welfare. The present review focuses on the microbial structures of the porcine upper and lower airways, and the factors that influence microbiome development and onset of respiratory disease. Following a literature search on PubMed and Scopus, 21 articles were selected based on defined exclusion criteria (20 studies performed by 16S rRNA gene sequencing and one by shotgun metagenomics). Analysis of the selected literature indicated that the microbial structure of the upper respiratory tract undergoes a remarkable evolution after birth and tends to stabilise around weaning. Antimicrobial treatment, gaseous ammonia concentration, diet and floor type are amongst the recognized environmental factors influencing microbiome structure. The predominant phyla of the upper respiratory tract are Proteobacteria and Firmicutes with significant differences at the genus level between the nasal and the oropharyngeal cavity. Only five studies investigated the lower respiratory tract and their results diverged in relation to the relative abundance of these two phyla and even more in the composition of the lung microbiome at the genus level, likely because of methodological differences. Reduced diversity and imbalanced microbial composition are associated with an increased risk of respiratory disease. However, most studies presented methodological pitfalls concerning specimen collection, sequencing target and depth, and lack of quality control. Standardization of sampling and sequencing procedures would contribute to a better understanding of the structure of the microbiota inhabiting the lower respiratory tract and its relationship with pig health and disease.

A comparison of individual-level vs. hypothetically pooled mercury biomonitoring data from the Maternal Organics Monitoring Study (MOMS), Alaska, 1999-2012

Biomonitoring for heavy metals is important to assess health risks, especially in Arctic communities where rural residents rely on locally harvested foods. However, laboratory testing for blood contaminants is expensive and might not be sustainable for long-term monitoring. We assessed whether pooled specimen biomonitoring could be a part of a plan for blood contaminant surveillance among pregnant women in rural Alaska using existing blood mercury level data from three cross sectional studies of pregnant women. We applied a hypothetical pooled specimen template stratified into 8 demographic groups based on age, coastal or inland residence, and pre-pregnancy weight. The hypothetical geometric mean blood mercury levels were similar to the individual-level geometric means. However, the 95% confidence intervals were much wider for the hypothetical geometric means compared to the true geometric means. Although the variability that resulted from pooling specimens using a small sample made it difficult to compare demographic groups to each other, pooled specimen results could be an accurate reflection of the population burden of mercury contamination in the Arctic in the context of large numbers of biomonitoring samples.

Multicollector Inductively Coupled Plasma-Mass Spectrometry with 1013 Ω Faraday Cup Amplifiers for Ultrasensitive Mg Isotopic Analysis of Cerebrospinal Fluid Microsamples

Magnesium isotopic analysis of cerebrospinal fluid (CSF) is a potentially interesting approach for studies on neurodegeneration. However, this type of analysis is challenging because of the invasiveness of the sampling and small sample volume. In this work, a novel analytical method was developed for ultrasensitive Mg isotopic analysis of CSF microsamples via multicollector inductively coupled plasma-mass spectrometry (MC-ICP-MS) using high-gain 10¹³ Ω Faraday cup amplifiers. The intermediate and internal errors on the δ²⁶Mg value were improved up to fourfold using 10¹³ Ω resistors for the monitoring of both the ²⁴Mg and ²⁶Mg isotopes and up to twofold using a 10¹¹ Ω resistor for the most abundant ²⁴Mg isotope and a 10¹³ Ω resistor for the ²⁶Mg isotope. Magnesium isotope ratios measured at a concentration level of 7-10 μg L^-1 were in good agreement with those obtained using the conventional method at a concentration level of 150 μg L^-1. The expanded uncertainty for the quality control CSF material obtained at the ultratrace level was ±0.16‰. Ultrasensitive Mg isotopic analysis was carried out for CSF from hydrocephalus patients using only 5 μL of sample. δMg values thus obtained were not significantly different from those obtained using the conventional method using a sample volume of 400 μL instead (p ≤ 0.05). The Mg isotopic composition of the CSF from hydrocephalus patients ranged between -0.65 and 0.30‰, with a mean δ²⁶Mg value of -0.14 ± 0.27‰.

Urinary Concentrations of Bisphenols in the Australian Population and Their Association with the Per Capita Mass Loads in Wastewater

Health concerns and related regulation of bisphenol A (BPA) in some countries have led to an increase in the production and use of unregulated and poorly understood BPA analogues, including bisphenol S (BPS), bisphenol F (BPF), bisphenol B (BPB), and bisphenol AF (BPAF). To assess the temporal trends of human exposure to BPA analogues, urine and wastewater samples were collected from South East Queensland, Australia between 2012 and 2017 and analyzed for five bisphenols using validated isotope dilution liquid chromatography tandem mass spectrometry methods. BPA and BPS were the predominant bisphenols detected in both urine and wastewater samples, with median concentrations of 2.5 and 0.64 μg/L in urine and 0.94 and 1.1 μg/L in wastewater, respectively. BPB, BPF, and BPAF had low detection frequencies in both urine and wastewater samples. Concentrations of BPA in both urine and wastewater decreased over the sampling period, whereas concentrations of BPS increased, suggesting that BPS has become a BPA replacement. The contributions of urinary excretion to wastewater were calculated by the ratio of daily per capita urinary excretion to wastewater-based mass loads of bisphenols. Urinary BPA and BPS contributed to less than 1% of the load found in wastewater, indicating that much of the BPA and BPS originates from other sources.

ICP-MS characterization of seven North American snake venoms

Snake venoms are inherently complex. They are mixtures of multiple enzymes, peptides, lipids, carbohydrates, nucleosides, and metal ions. Metal ions make up a small portion of a snake's venom but play outsized roles in enzyme function and stability. Unlike enzyme primary structure, which is easily predicted from genomic sequences, a venom's metal ion content must be measured directly. We leveraged the high throughput and sensitivity of inductively coupled plasma mass spectrometry to analyze the metal ion content of seven North American snake venoms. All venoms were collected from snakes reared at one location, so we could discount variation from environmental or geographical factors. We profiled 71 metal isotopes. Selenium isotopes were consistently high across all venoms tested. When each venom's toxicity was graphed as a function of each different metal isotope, the only strong relationships between metal content and toxicity were for magnesium isotopes.

Concentrations of phthalate metabolites in Australian urine samples and their contribution to the per capita loads in wastewater

Exposure to phthalates is a public health concern. In this study, we collected both urine and wastewater samples from 2012 to 2017 and analysed for 14 phthalate metabolites to assess human exposure to phthalates in Southeast Queensland (SEQ), and for associations between phthalate metabolites in urine and wastewater samples. Twenty-four pooled urine samples were prepared from 2400 individual specimens every two years (stratified by age, gender and collection year). Wastewater samples were collected from the three major wastewater treatment plants (WWTPs) representing locations in the SEQ region including a regional city, part of the state capital city and a third major urban WWTP in the region. Over the period, decreases for most phthalate metabolites, i.e. mono-butyl phthalate (MBP), mono-isobutyl phthalate (MiBP), monobenzyl phthalate (MBzP), monocyclohexyl phthalate (MCHP), mono(3-carboxypropyl) phthalate (MCPP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and monomethyl phthalate (MMP), but an increase in monoethyl phthalate (MEP, particularly in young children) were observed in urine. In general, temporal changes were smaller in urine pools representing older age groups. We also found substantial variation in per capita mass loads of phthalate metabolites between samples from the three WWTPs with generally higher concentrations of most phthalates in the metropolitan areas. Per capita mass loads of most phthalate metabolites in wastewater were higher than would be expected from the per-capita excretion in urine, suggesting there are additional sources contributing to the majority of the observed phthalate metabolites in wastewater. For MEHHP and MEOHP we estimate that the urinary excretion accounts for a substantial fraction (average about 50%) of the mass load observed in the wastewater hence wastewater data may provide useful for monitoring trends in exposure.

Pesticide metabolite concentrations in Queensland pre-schoolers - Exposure trends related to age and sex using urinary biomarkers

This study aimed to assess pesticide concentration and composition trends associated with age and sex in Australian infants and toddlers. Individual urine samples (n = 400) were collected in 2014/5 from Queensland infants and toddlers aged 0-5 y and composited into 20 pools of 20 individual samples by age (of 5 strata) and sex. Nineteen biomarkers including organophosphate and pyrethroid pesticide metabolites, herbicides and metabolites, and an insect repellent, DEET, were measured. In total, seven organophosphate pesticide metabolites, three pyrethroid metabolites and one herbicide metabolite were detectable in >50% of the sample pools. A significant increase of concentrations of dimethyl phosphate, dimethyl dithiophosphate, diethyl thiophosphate (DETP), 3,5,6-trichloro-2-pyridinol (TCPY), 4-nitrophenol and 3-phenoxybenzoic acid with age was observed (with the p value of <0.0001 to 0.034). This suggested that exposure increases following weaning or as a result of increased dietary intake and mobility/activity. Significant age trends remained after adjustment for body weight and urine flow for DETP and TCPY (p = 0.029 and 0.016 respectively). The level of estimated "worst-case scenario" daily intake of chlorpyrifos from these pooled samples ranged from 0.40 to 1.8 μg/kg-day, which was below the Australian Acceptable Daily Intake guideline (3 μg/kg-day). This study presents the first dataset of age trends in concentrations of these pesticides for infants and toddlers and contributed to new understanding of exposure pathways and potential risks.

Polybrominated Diphenyl Ethers and Biphenyl in Serum: Time Trend Study from the National Health and Nutrition Examination Survey for Years 2005/06 through 2013/14

Eleven polybrominated diphenyl ether (tri- to deca-BDE) congeners and 2,2',4,4',5,5'-hexabromobiphenyl (BB153) have been measured in pooled serum samples from the National Health and Nutrition Examination Survey (NHANES) for one decade (from survey years 2005/06 through 2013/14). The pools, which are representative of the general noninstitutionalized population of the United States, encompassed thirty-two demographic groups defined by sex, race/ethnicity (Mexican American, non-Hispanic black, non-Hispanic white, and all other race/ethnicities), and age (12-19, >20-39, >40-59, and ≥60 years). The adjusted geometric means were determined in a multiple linear regression model for the six congeners (BDE28, BDE47, BDE99, BDE100, BDE153, and BB153) with detectable concentrations in at least 60% of pools in each of the thirty-two demographic groups; the level of significance for all statistical comparisons thereof were determined. BDE154 and BDE209 were detected in 60% of the NHANES 2011/12 and 2013/14 pools; only these two survey periods were evaluated for these congeners. The percent change in concentration by a 2-year survey period was calculated. All examined PBDEs reported in five survey periods decreased in concentration, except BDE153, for which concentrations increased by 12.0% (95% CI 7.1-16.4) and 8.4% (95% CI 2.9-14.1) for the age groups 40-59 and ≥60 years, respectively; no significant change was observed in younger age groups. Excluding BDE153, we observed larger percentage decreases by a 2-year survey period for the age groups 12-19, 20-39, and ≥60 years compared with the age group 40-59 years. The percentage decrease by a two-year survey period ranged between -19.6% (BDE99, 20-39 years old) and -4.5% (BDE100, 40-59 years old). Although five polybrominated diphenyl ether (PDBE) congeners and BB153 are still frequently detected in the U.S. general population, PBDE concentrations have decreased since 2005-2006, likely, because of changes in manufacturing practices that started in the mid-2000s.

Per- and polyfluoroalkyl substances (PFAS) in Australia: Current levels and estimated population reference values for selected compounds

BACKGROUND

Increased public awareness of PFAS contamination in Australia has resulted in serum biomonitoring efforts in individuals in potentially affected communities. However, population-based reference values for assessing whether individual results exceed the typical range in the Australian general population are not currently available.

OBJECTIVE

Estimate population upper bound reference values based on updated serum PFAS concentrations in pooled samples from southeast Queensland, Australia and population variation observed in the US National Health and Nutrition Examination Survey (NHANES) datasets.

METHODS

We calculated ratios of 95th percentile to arithmetic mean (P95:AM ratios) using data from the NHANES 2013-14 and 2015-16 cycle samples for frequently detected PFASs: PFOA, linear and branched PFOS, perfluorononanoate (PFNA), perfluorodecanoate (PFDA), and perfluorohexanesulfonate (PFHxS). We estimated Australian age-specific means for PFAS using pooled serum samples collected in 2014-15 and 2016-17. We used the P95:AM ratios to estimate 95th percentile concentrations in the Australian population based on the results of the 2016-17 pooled samples.

RESULTS AND CONCLUSIONS

P95:AM ratios for each PFAS were similar across NHANES cycle and age group, so overall compound-specific ratios were estimated for PFOA (2.1), PFNA (2.4), PFDA (2.7), PFHxS (2.7), and linear (2.4) and summed PFOS (2.3). Australian mean PFAS concentrations continued previously reported declining trends. The estimated P95 values can be used as preliminary substitutes for more rigorous population reference values to identify samples with clearly elevated serum PFAS concentrations in Australian biomonitoring efforts. Given uncertainties and variability inherent in this evaluation, the estimated P95 values should be interpreted with caution. Mean and estimated P95 serum PFAS concentrations in Australia should continue to be monitored to document declining trends in population serum concentrations.

Urinary metabolites of organophosphate esters: Concentrations and age trends in Australian children

There is growing concern around the use of organophosphate esters (OPEs) due to their suspected reproductive toxicity, carcinogenicity, and neurotoxicity. OPEs are used as flame retardants and plasticizers, and due to their extensive application in consumer products, are found globally in the indoor environment. Early life exposure to OPEs is an important risk factor for children's health, but poorly understood. To study age and sex trends of OPE exposures in infants and young children, we collected, pooled, and analysed urine samples from children aged 0-5years from Queensland, Australia for 9 parent OPEs and 11 metabolites. Individual urine samples (n=400) were stratified by age and sex, and combined into 20 pools. Three individual breast milk samples were also analysed to provide a preliminary estimate on the contribution of breast milk to the intake of OPEs. Bis(1-chloroisopropyl) phosphate (BCIPP), 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP), bis(1,3-dichloroisopropyl) phosphate (BDCIPP), dibutyl phosphate (DBP), diphenyl phosphate (DPHP), bis(2-butoxyethyl) phosphate (BBOEP), bis(2-butoxyethyl) 3-hydroxyl-2-butoxyethyl phosphate (3OH-TBOEP), and bis(2-butoxyethyl) hydroxyethyl phosphate (BBOEHEP) were detected in all urine samples, followed by bis(methylphenyl) phosphate (80%), and bis(2-ethylhexyl) phosphate (BEHP, 20%), and bis(2-chloroethyl) phosphate (BCEP, 15%). Concentrations of tris(2-chloroethyl) phosphate (TCEP), BCEP, tris(2-ethylhexyl) phosphate (TEHP), and DBP decreased with age, while bis(methylphenyl) phosphate (BMPP) increased with age. Significantly higher concentrations of DPHP (p=0.039), and significantly lower concentrations of TEHP (p=0.006) were found in female samples compared to males. The estimated daily intakes (EDIs) via breastfeeding, were 4.6, 26 and 76ng/kg/day for TCEP, TBP and TEHP, respectively, and were higher than that via air and dust, suggesting higher exposure through consumption of breast milk.

Combined proteomic and metallomic analyses in Scrobicularia plana clams to assess environmental pollution of estuarine ecosystems

Estuaries are very important ecosystems with great ecological and economic value, but usually highly impacted by anthropogenic pressure. Thus, the assessment of pollution levels in these habitats is critical in order to evaluate their environmental quality. In this work, we combined complementary metallomic and proteomic approaches with the aim to monitor the effects of environmental pollution on Scrobicularia plana clams captured in three estuarine systems from the south coast of Portugal; Arade estuary, Ria Formosa and Guadiana estuary. Multi-elemental profiling of digestive glands was carried out to evaluate the differential pollution levels in the three study areas. Then, proteomic analysis by means of two-dimensional gel electrophoresis and mass spectrometry revealed twenty-one differential proteins, which could be associated with multiple toxicological mechanisms induced in environmentally stressed organisms. Accordingly, it could be concluded that the combination of different omic approaches presents a great potential in environmental research.

Cross-sectional biomonitoring study of pesticide exposures in Queensland, Australia, using pooled urine samples

A range of pesticides are available in Australia for use in agricultural and domestic settings to control pests, including organophosphate and pyrethroid insecticides, herbicides, and insect repellents, such as N,N-diethyl-meta-toluamide (DEET). The aim of this study was to provide a cost-effective preliminary assessment of background exposure to a range of pesticides among a convenience sample of Australian residents. De-identified urine specimens stratified by age and sex were obtained from a community-based pathology laboratory and pooled (n = 24 pools of 100 specimens). Concentrations of urinary pesticide biomarkers were quantified using solid-phase extraction coupled with isotope dilution high-performance liquid chromatography-tandem mass spectrometry. Geometric mean biomarker concentrations ranged from <0.1 to 36.8 ng/mL for organophosphate insecticides, <0.1 to 5.5 ng/mL for pyrethroid insecticides, and <0.1 to 8.51 ng/mL for all other biomarkers with the exception of the DEET metabolite 3-diethylcarbamoyl benzoic acid (4.23 to 850 ng/mL). We observed no association between age and concentration for most biomarkers measured but noted a "U-shaped" trend for five organophosphate metabolites, with the highest concentrations observed in the youngest and oldest age strata, perhaps related to age-specific differences in behavior or physiology. The fact that concentrations of specific and non-specific metabolites of the organophosphate insecticide chlorpyrifos were higher than reported in USA and Canada may relate to differences in registered applications among countries. Additional biomonitoring programs of the general population and focusing on vulnerable populations would improve the exposure assessment and the monitoring of temporal exposure trends as usage patterns of pesticide products in Australia change over time.

Monitoring exposure to polycyclic aromatic hydrocarbons in an Australian population using pooled urine samples

Integrated exposure to polycyclic aromatic hydrocarbons (PAHs) can be assessed through monitoring of urinary mono-hydroxylated PAHs (OH-PAHs). The aim of this study was to provide the first assessment of exposure to PAHs in a large sample of the population in Queensland, Australia including exposure to infant (0-4years). De-identified urine specimens, obtained from a pathology laboratory, were stratified by age and sex, and pooled (n=24 pools of 100) and OH-PAHs were measured by gas chromatography-isotope dilution-tandem mass spectrometry. Geometric mean (GM) concentrations ranged from 30ng/L (4-hydroxyphenanthrene) to 9221ng/L (1-naphthol). GM of 1-hydroxypyrene, the most commonly used PAH exposure biomarker, was 142ng/L. The concentrations of OH-PAHs found in this study are consistent with those in developed countries and lower than those in developing countries. We observed no association between sex and OH-PAH concentrations. However, we observed lower urinary concentrations of all OH-PAHs in samples from infants (0-4years), children (5-14years) and the elderly (>60year old) compared with samples from other age groups (15-29, 30-44 and 45-59years) which may be attributed to age-dependent behaviour-specific exposure sources.

Global gene expression profiling using heterologous DNA microarrays to analyze alterations in the transcriptome of Mus spretus mice living in a heavily polluted environment

Microarray platforms are a good approach for assessing biological responses to pollution as they enable the simultaneous analyses of changes in the expression of thousands of genes. As an omic and non-targeted methodology, this technique is open to unforeseen responses under particular environmental conditions. In this study, we successfully apply a commercial oligonucleotide microarray containing Mus musculus whole-genome probes to compare and assess the biological effects of living in a heavily polluted settlement, the Domingo Rubio stream (DRS), at the Huelva Estuary (SW Spain), on inhabitant free-living Mus spretus mice. Our microarray results show that mice living in DRS suffer dramatic changes in gene and protein expression compared with reference specimens. DRS mice showed alteration in the oxidative status of hepatocytes, with activation of both the innate and the acquired immune responses and the induction of chronic inflammation, accompanied by metabolic alterations that imply the accumulation of lipids in the liver (hepatic steatosis). The identified deregulated genes may be useful as biomarkers of environmental pollution.

Concentrations of phthalates and DINCH metabolites in pooled urine from Queensland, Australia

Dialkyl phthalate esters (phthalates) are ubiquitous chemicals used extensively as plasticizers, solvents and adhesives in a range of industrial and consumer products. 1,2-Cyclohexane dicarboxylic acid, diisononyl ester (DINCH) is a phthalate alternative introduced due to a more favourable toxicological profile, but exposure is largely uncharacterised. The aim of this study was to provide the first assessment of exposure to phthalates and DINCH in the general Australian population. De-identified urine specimens stratified by age and sex were obtained from a community-based pathology laboratory and pooled (n=24 pools of 100). Concentrations of free and total species were measured using online solid phase extraction isotope dilution high performance liquid chromatography tandem mass spectrometry. Concentrations ranged from 2.4 to 71.9ng/mL for metabolites of di(2-ethylhexyl)phthalate, and from <0.5 to 775ng/mL for all other metabolites. Our data suggest that phthalate metabolites concentrations in Australia were at least two times higher than in the United States and Germany; and may be related to legislative differences among countries. DINCH metabolite concentrations were comparatively low and consistent with the limited data available. Ongoing biomonitoring among the general Australian population may help assess temporal trends in exposure and assess the effectiveness of actions aimed at reducing exposures.

Use of pooled samples to assess human exposure to parabens, benzophenone-3 and triclosan in Queensland, Australia

Parabens, benzophenone-3 and triclosan are common ingredients used as preservatives, ultraviolet radiation filters and antimicrobial agents, respectively. Human exposure occurs through consumption of processed food and use of cosmetics and consumer products. The aim of this study was to provide a preliminary characterisation of exposure to selected personal care product chemicals in the general Australian population. De-identified urine specimens stratified by age and sex were obtained from a community-based pathology laboratory and pooled (n=24 pools of 100). Concentrations of free and total (sum of free plus conjugated) species of methyl, ethyl, propyl and butyl paraben, benzophenone-3 and triclosan were quantified using isotope dilution tandem mass spectrometry; with geometric means 232, 33.5, 60.6, 4.32, 61.5 and 87.7ng/mL, respectively. Age was inversely associated with paraben concentration, and females had concentrations approximately two times higher than males. Total paraben and benzophenone-3 concentrations are significantly higher than reported worldwide, and the average triclosan concentration was more than one order of magnitude higher than in many other populations. This study provides the first data on exposure of the general Australian population to a range of common personal care product chemical ingredients, which appears to be prevalent and warrants further investigation.

Confidence interval estimation for pooled-sample biomonitoring from a complex survey design

The National Centers for Disease Control and Prevention (CDC) is using a weighted pooled-sample design to characterize concentrations of persistent organic pollutants (POPs) in the U.S.

POPULATION

Historically, this characterization has been based on individual measurements of these compounds in body fluid or tissue from representative samples of the population using stratified multistage selection. Pooling samples before making analytical measurements reduces the costs of biomonitoring by reducing the number of analyses. Pooling samples also allows for larger sample volumes which can result in fewer left censored results. But because samples are pooled across the sampling design cells of the original survey, direct calculation of the design effects needed for accurate standard error and confidence interval (CI) estimation is not possible. So in this paper I describe a multiple imputation (MI) method for calculating design effects associated with pooled-sample estimates. I also evaluate the method presented, by simulating NHANES individual sample data from which artificial pools are created for use in a comparison of pooled-sample estimates with estimates based on individual samples. To further illustrate and evaluate the method proposed in this paper I present geometric mean and various percentile estimates along with their 95% CIs for two chemical compounds from NHANES 2005-2006 pooled samples and compare them to individual-sample based estimates from NHANES 1999-2004.

Pooling Bio-Specimens in the Presence of Measurement Error and Non-Linearity in Dose-Response: Simulation Study in the Context of a Birth Cohort Investigating Risk Factors for Autism Spectrum Disorders

We sought to determine the potential effects of pooling on power, false positive rate (FPR), and bias of the estimated associations between hypothetical environmental exposures and dichotomous autism spectrum disorders (ASD) status. Simulated birth cohorts in which ASD outcome was assumed to have been ascertained with uncertainty were created. We investigated the impact on the power of the analysis (using logistic regression) to detect true associations with exposure (X₁) and the FPR for a non-causal correlate of exposure (X₂, r = 0.7) for a dichotomized ASD measure when the pool size, sample size, degree of measurement error variance in exposure, strength of the true association, and shape of the exposure-response curve varied. We found that there was minimal change (bias) in the measures of association for the main effect (X₁). There is some loss of power but there is less chance of detecting a false positive result for pooled compared to individual level models. The number of pools had more effect on the power and FPR than the overall sample size. This study supports the use of pooling to reduce laboratory costs while maintaining statistical efficiency in scenarios similar to the simulated prospective risk-enriched ASD cohort.

iTRAQ analysis of hepatic proteins in free-living Mus spretus mice to assess the contamination status of areas surrounding Doñana National Park (SW Spain)

This work aims to develop and integrate new -omics tools that would be applicable to different ecosystem types for a technological updating of environmental evaluations. We used a 2nd-generation (iTRAQ-8plex) proteomic approach to identify/quantify proteins differentially expressed in the liver of free-living Mus spretus mice from Doñana National Park or its proximities. Mass spectrometry was performed in an LTQ Orbitrap system for iTRAQ reporter ion quantitation and protein identification using a Mus musculus database as reference. A prior IEF step improved the separation of the complex peptide mixture. Over 2000 identified proteins were altered, of which 118 changed by ≥2.5-fold in mice from at least two problem sites. Part of the results obtained with the iTRAQ analysis was confirmed by Western blot. Over 75% of the 118 proteins were upregulated in animals captured at polluted sites and only 16 proteins were downregulated. Upregulated proteins were involved in stress response; cell proliferation and apoptosis; signal transduction; metastasis or tumour suppression; xenobiotic export or vesicular trafficking; and metabolism. The downregulated proteins, all potentially harmful, were classified as oncoproteins and proteins favouring genome instability. The iTRAQ results presented here demonstrated that the survival of hepatic cells is compromised in animals living at polluted sites, which showed deep alterations in metabolism and the signalling pathways. The identified proteins may be useful as biomarkers of environmental pollution and provide insight about the metabolic pathways and/or physiological processes affected by pollutants in DNP and its surrounding areas.

Feasibility and informative value of environmental sample collection in the National Children's Vanguard Study

BACKGROUND

Birth cohort studies provide the opportunity to advance understanding of the impact of environmental factors on childhood health and development through prospective collection of environmental samples.

METHODS

We evaluated the feasibility and informative value of the environmental sample collection methodology in the initial pilot phase of the National Children's Study, a planned U.S. environmental birth cohort study. Environmental samples were collected from January 2009-September 2010 at up to three home visits: pre-pregnancy (n=306), pregnancy (n=807), and 6-months postnatal (n=117). Collections included air for particulate matter ≤2.5 µm (PM2.5), nitrogen dioxide, ozone, volatile organic compounds (VOCs), and carbonyls; vacuum dust for allergens/endotoxin; water for VOCs, trihalomethanes (THMs), and haloacetic acids (HAAs); and wipe samples for pesticides, semi-volatile organics, and metals. We characterized feasibility using sample collection rates and times and informative value using analyte detection frequencies (DF).

RESULTS

Among the 1230 home visits, environmental sample collection rates were high across all sample types (mean=89%); all samples except the air PM2.5 samples had collection times <30 min. Informative value was low for water VOCs (median DF=0%) and pesticide floor wipes (median DF=5%). Informative value was moderate for air samples (median DF=35%) and high for water THMs and HAAs (median DF=91% and 75%, respectively).

CONCLUSIONS

Though collection of environmental samples was feasible, some samples (e.g., wipe pesticides and water VOCs) yielded limited information. These results can be used in conjunction with other study design considerations, such as target population size and hypotheses of interest, to inform the method selection of future environmental health birth cohort studies.

Spatial and temporal trends of the Stockholm Convention POPs in mothers' milk -- a global review

Persistent organic pollutants (POPs) have been of environmental and health concern for more than half a century and have their own intergovernmental regulation through the Stockholm Convention, from 2001. One major concern is the nursing child's exposure to POPs, a concern that has led to a very large number of scientific studies on POPs in mothers' milk. The present review is a report on the assessment on worldwide spatial distributions of POPs and of their temporal trends. The data presented herein is a compilation based on scientific publications between 1995 and 2011. It is evident that the concentrations in mothers' milk depend on the use of pesticides and industrial chemicals defined as POPs. Polychlorinated biphenyls (PCBs) and "dioxins" are higher in the more industrialized areas, Europe and Northern America, whereas pesticides are higher in Africa and Asia and polybrominated diphenyl ethers (PBDEs) are reported in higher concentrations in the USA. POPs are consequently distributed to women in all parts of the world and are thus delivered to the nursing child. The review points out several major problems in the reporting of data, which are crucial to enable high quality comparisons. Even though the data set is large, the comparability is hampered by differences in reporting. In conclusion, much more detailed instructions are needed for reporting POPs in mothers' milk. Temporal trend data for POPs in mothers' milk is scarce and is of interest when studying longer time series. The only two countries with long temporal trend studies are Japan and Sweden. In most cases, the trends show decreasing concentrations of POPs in mothers' milk. However, hexabromocyclododecane is showing increasing temporal concentration trends in both Japan and Sweden.

Positing, fitting, and selecting regression models for pooled biomarker data

Pooling biospecimens prior to performing lab assays can help reduce lab costs, preserve specimens, and reduce information loss when subject to a limit of detection. Because many biomarkers measured in epidemiological studies are positive and right-skewed, proper analysis of pooled specimens requires special methods. In this paper, we develop and compare parametric regression models for skewed outcome data subject to pooling, including a novel parameterization of the gamma distribution that takes full advantage of the gamma summation property. We also develop a Monte Carlo approximation of Akaike's Information Criterion applied to pooled data in order to guide model selection. Simulation studies and analysis of motivating data from the Collaborative Perinatal Project suggest that using Akaike's Information Criterion to select the best parametric model can help ensure valid inference and promote estimate precision.

Population variation in biomonitoring data for persistent organic pollutants (POPs): an examination of multiple population-based datasets for application to Australian pooled biomonitoring data

BACKGROUND

Australian national biomonitoring for persistent organic pollutants (POPs) relies upon age-specific pooled serum samples to characterize central tendencies of concentrations but does not provide estimates of upper bound concentrations. This analysis compares population variation from biomonitoring datasets from the US, Canada, Germany, Spain, and Belgium to identify and test patterns potentially useful for estimating population upper bound reference values for the Australian population.

METHODS

Arithmetic means and the ratio of the 95th percentile to the arithmetic mean (P95:mean) were assessed by survey for defined age subgroups for three polychlorinated biphenyls (PCBs 138, 153, and 180), hexachlorobenzene (HCB), p,p-dichlorodiphenyldichloroethylene (DDE), 2,2',4,4' tetrabrominated diphenylether (PBDE 47), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS).

RESULTS

Arithmetic mean concentrations of each analyte varied widely across surveys and age groups. However, P95:mean ratios differed to a limited extent, with no systematic variation across ages. The average P95:mean ratios were 2.2 for the three PCBs and HCB; 3.0 for DDE; 2.0 and 2.3 for PFOA and PFOS, respectively. The P95:mean ratio for PBDE 47 was more variable among age groups, ranging from 2.7 to 4.8. The average P95:mean ratios accurately estimated age group-specific P95s in the Flemish Environmental Health Survey II and were used to estimate the P95s for the Australian population by age group from the pooled biomonitoring data.

CONCLUSIONS

Similar population variation patterns for POPs were observed across multiple surveys, even when absolute concentrations differed widely. These patterns can be used to estimate population upper bounds when only pooled sampling data are available.

Short term variability in urinary bisphenol A in Australian children

Used frequently in food contact materials, bisphenol A (BPA) has been studied extensively in recent years, and ubiquitous exposure in the general population has been demonstrated worldwide. Characterizing within- and between-individual variability of BPA concentrations is important for characterizing exposure in biomonitoring studies, and this has been investigated previously in adults, but not in children. The aim of this study was to characterize the short-term variability of BPA in spot urine samples in young children. Children aged ≥2-<4 years (n=25) were recruited from an existing cohort in Queensland, Australia, and donated four spot urine samples each over a two day period. Samples were analysed for total BPA using isotope dilution online solid phase extraction-liquid chromatography-tandem mass spectrometry, and concentrations ranged from 0.53 to 74.5 ng/ml, with geometric mean and standard deviation of 2.70 ng/ml and 2.94 ng/ml, respectively. Sex and time of sample collection were not significant predictors of BPA concentration. The between-individual variability was approximately equal to the within-individual variability (ICC=0.51), and this ICC is somewhat higher than previously reported literature values. This may be the result of physiological or behavioural differences between children and adults or of the relatively short exposure window assessed. Using a bootstrapping methodology, a single sample resulted in correct tertile classification approximately 70% of the time. This study suggests that single spot samples obtained from young children provide a reliable characterization of absolute and relative exposure over the short time window studied, but this may not hold true over longer timeframes.

Pooled biological specimens for human biomonitoring of environmental chemicals: opportunities and limitations

Biomonitoring has become the "gold standard" in assessing chemical exposures, and has an important role in risk assessment. The pooling of biological specimens-combining multiple individual specimens into a single sample-can be used in biomonitoring studies to monitor levels of exposure and identify exposure trends or to identify susceptible populations in a cost-effective manner. Pooled samples provide an estimate of central tendency and may also reveal information about variation within the population. The development of a pooling strategy requires careful consideration of the type and number of samples collected, the number of pools required and the number of specimens to combine per pool in order to maximise the type and robustness of the data. Creative pooling strategies can be used to explore exposure-outcome associations, and extrapolation from other larger studies can be useful in identifying elevated exposures in specific individuals. The use of pooled specimens is advantageous as it saves significantly on analytical costs, may reduce the time and resources required for recruitment and, in certain circumstances, allows quantification of samples approaching the limit of detection. In addition, the use of pooled samples can provide population estimates while avoiding ethical difficulties that may be associated with reporting individual results.

Heterologous microarray analysis of transcriptome alterations in Mus spretus mice living in an industrial settlement

This work demonstrates the successful application of a commercial oligonucleotide microarray containing Mus musculus whole-genome probes to assess the biological effects of an industrial settlement on inhabitant Mus spretus mice. The transcriptomes of animals in the industrial settlement contrasted with those of specimens collected from a nearby protected ecosystem. Proteins encoded by the differentially expressed genes were broadly categorized into six main functional classes. Immune-associated genes were mostly induced and related to innate and acquired immunity and inflammation. Genes sorted into the stress-response category were mainly related to oxidative-stress tolerance and biotransformation. Metabolism-associated genes were mostly repressed and related to lipid metabolic pathways; these included genes that encoded 11 of the 20 cholesterol biosynthetic pathway enzymes. Crosstalk between members of different functional categories was also revealed, including the repression of serine-protease genes and the induction of protease-inhibitor genes to control the inflammatory response. Absolute quantification of selected transcripts was performed via RT-PCR to verify the microarray results and assess interindividual variability. Microarray data were further validated by immunoblotting and by cholesterol and protein-thiol oxidation level determinations. Reported data provide a broad impression of the biological consequences of residing in an industrial area.

Pooling samples for "top-down" molecular exposomics research: the methodology

BACKGROUND

Exposomics is the cutting-edge concept of screening the environmental risk factors for disease. In the novel "top-down" approach, we estimate the molecular exposome by measuring all body fluid analytes in a case-controlled study. However, to detect diverse pollutants, a sufficient sample size and multiple analytical methods are required. This may lead to dramatically increased costs and research workload.

METHODS

To help reduce complexity, we suggest a sample pooling strategy along with a scheme for combining both general unknown or multi-targeted screening with targeted analysis. The sample pooling method was tested using computer simulations.

RESULTS

By comprehensively analysis of pooled samples, it is possible to identify environmental risk factors. Factors are initially screened in the pooled case and control population samples, then in the randomized grouped and pooled case and control subpopulation samples. In the sample grouping, five or more pools were suggested for groups having 30 individuals per pool.

CONCLUSIONS

This study suggests that sample pooling is a useful strategy for exposomics research, which provides a hypothesis-free method for pollutant risk screening.

Polybrominated diphenyl ethers, polychlorinated biphenyls, and persistent pesticides in serum from the national health and nutrition examination survey: 2003-2008

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and persistent pesticides have been measured in pooled samples representative of the general noninstitutionalized population of the United States. The pools were made from individual sera from the National Health and Nutrition Examination Survey (NHANES) during 2005/06 and 2007/08. The pooled concentrations have been contrasted to NHANES 2003/04 individual measurements to evaluate changes in concentration over time and within survey period differences among age groups, race/ethnicity groups (Mexican American, non-Hispanic Black, non-Hispanic White), and sex. The arithmetic mean serum concentrations of several PCB congeners decreased from NHANES 2003/04 through 2007/08. Larger percentage reductions were seen for younger subjects (12-19 years) compared with older subjects (≥60 years). For example, the arithmetic mean concentration of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153) was 36% lower in 12-19 year old adolescents when comparing NHANES 2007/08 with 2003/04; while for subjects over the age of 60 a 14% lower concentration was seen, although, the 95% confidence intervals overlapped. Similarly, the arithmetic mean serum concentrations of tri- to hexaBDEs were lower in NHANES 2007/08 than in 2003/04; however, most confidence intervals of the arithmetic means overlapped. These findings suggest that a reduction in PBDE serum concentrations cannot yet be detected following the discontinuation of pentaBDE in 2004.

Bisphenol A exposure is not associated with area-level socioeconomic index in Australian children using pooled urine samples

Bisphenol A (BPA) is used extensively in food-contact materials and has been detected routinely in populations worldwide; this exposure has been linked to a range of negative health outcomes in humans. There is some evidence of an association between BPA and different socioeconomic variables which may be the result of different dietary patterns. The aim of this study was to conduct a preliminary investigation of the association between BPA and socioeconomic status in Australian children using pooled urine specimens and an area-level socioeconomic index. Surplus pathology urine specimens collected from children aged 0-15 years in Queensland, Australia, as samples of convenience (n=469), were pooled by age, sex and area-level socioeconomic index (n=67 pools) and analysed for total BPA using online solid-phase extraction LC-MS/MS. Concentration ranged from 1.08 to 27.4 ng/ml with geometric mean 2.57 ng/ml, and geometric mean exposure was estimated as 70.3 ng/kg d(-1). Neither BPA concentration nor excretion was associated with age or sex, and the authors found no evidence of an association with socioeconomic status. These results suggest that BPA exposure is not associated with socioeconomic status in the Australian population due to relatively homogenous exposures in Australia, or that the socioeconomic gradient is relatively slight in Australia compared with other OECD countries.

Maternal exposure to bisphenol-A and fetal growth restriction: a case-referent study

We conducted a case-referent study of the effect of exposure to bisphenol-A on fetal growth in utero in full-term, live-born singletons in Alberta, Canada. Newborns <10 percentile of expected weight for gestational age and sex were individually matched on sex, maternal smoking and maternal age to referents with weight appropriate to gestational age. Exposure of the fetus to bisphenol-A was estimated from maternal serum collected at 15-16 weeks of gestation. We pooled sera across subjects for exposure assessment, stratified on case-referent status and sex. Individual 1:1 matching was maintained in assembling 69 case and 69 referent pools created from 550 case-referent pairs. Matched pools had an equal number of aliquots from individual women. We used an analytical strategy conditioning on matched set and total pool-level values of covariates to estimate individual-level effects. Pools of cases and referents had identical geometric mean bisphenol-A concentrations (0.5 ng/mL) and similar geometric standard deviations (2.3-2.5). Mean difference in concentration between matched pools was 0 ng/mL, standard deviation: 1 ng/mL. Stratification by sex and control for confounding did not suggest bisphenol-A increased fetal growth restriction. Our analysis does not provide evidence to support the hypothesis that bisphenol-A contributes to fetal growth restriction in full-term singletons.

Incorporating new technologies into toxicity testing and risk assessment: moving from 21st century vision to a data-driven framework

Based on existing data and previous work, a series of studies is proposed as a basis toward a pragmatic early step in transforming toxicity testing. These studies were assembled into a data-driven framework that invokes successive tiers of testing with margin of exposure (MOE) as the primary metric. The first tier of the framework integrates data from high-throughput in vitro assays, in vitro-to-in vivo extrapolation (IVIVE) pharmacokinetic modeling, and exposure modeling. The in vitro assays are used to separate chemicals based on their relative selectivity in interacting with biological targets and identify the concentration at which these interactions occur. The IVIVE modeling converts in vitro concentrations into external dose for calculation of the point of departure (POD) and comparisons to human exposure estimates to yield a MOE. The second tier involves short-term in vivo studies, expanded pharmacokinetic evaluations, and refined human exposure estimates. The results from the second tier studies provide more accurate estimates of the POD and the MOE. The third tier contains the traditional animal studies currently used to assess chemical safety. In each tier, the POD for selective chemicals is based primarily on endpoints associated with a proposed mode of action, whereas the POD for nonselective chemicals is based on potential biological perturbation. Based on the MOE, a significant percentage of chemicals evaluated in the first 2 tiers could be eliminated from further testing. The framework provides a risk-based and animal-sparing approach to evaluate chemical safety, drawing broadly from previous experience but incorporating technological advances to increase efficiency.

Age-related trends in urinary excretion of bisphenol A in Australian children and adults: evidence from a pooled sample study using samples of convenience

Bisphenol A (BPA or 4,4'-(propane-2,2-diyl)diphenol) is a chemical intermediate in the production of polycarbonate and epoxy resins, and is used in a wide range of applications. BPA has attracted significant attention in the past decade due to its frequency of detection in human populations worldwide, and has demonstrated animal toxicity and potential impact on human health, particularly during critical periods of development. The aim of this study was to perform a preliminary assessment of age-related trends in urinary concentration and to estimate daily excretion of BPA in Australian children (aged >0 to <5 yr) and adults (≥15 to <75 yr). This was achieved using 79 samples pooled by age and gender, created from 868 individual samples of convenience collected as part of routine, community-based pathology testing. Total BPA was analyzed using online solid phase extraction (SPE)-liquid chromatography tandem mass spectrometry (LC-MS/MS) and detected in all samples with a range of 0.65-265 ng/ml. No significant differences were observed between males and females. A urine flow model was constructed from published values and was used to provide an estimate of daily excretion per unit body weight for each pooled sample. The daily excretion estimates ranged from 26.2 to 18,200 ng/kg-d for children, and from 20.1 to 165 ng/kg-d for adults. Urinary concentrations and estimated excretion rates were inversely associated with age, and estimated daily excretion in infants and young children was significantly higher than in adults (geometric mean: 107 and 47.0 ng/kg-d, respectively). Higher excretion of BPA in children may be explained by their higher food consumption relative to body weight compared to adults and adolescents, and may also reflect alternative exposure pathways and sources.

Use of pooled samples from the National Health and Nutrition Examination Survey

The National Centers for Disease Control and Prevention (CDC) provides an ongoing assessment of the US population's exposure to environmental chemicals by using biomonitoring in conjunction with CDC's National Health and Nutrition Examination Survey (NHANES). Characterizing the distributions of concentrations of environmental compounds or their metabolites in the US population is a primary objective of CDC's biomonitoring program. Historically, this characterization has been based on individual measurements of these compounds in body fluid or tissue from representative samples of the population. Pooling samples before making analytical measurements can reduce the costs of biomonitoring by reducing the number of analyses. For the first time in NHANES 2005-2006, a weighted pooled-sample design was implemented to facilitate pooling samples before making analytical measurements. This paper describes this design and the estimation method being developed in the National Center for Environmental Health, Division of Laboratory Sciences (NCEH/DLS) to characterize concentrations of polychlorinated and polybrominated compounds. We present percentile estimates for 2,2 ( ' ) ,4,4 ( ' ) ,5,5 ( ' ) -hexachlorobiphenyl (PCB153) in specific subpopulations of the US based on the NHANES 2005-2006 pooled-sample design. We also compare estimates based on individual samples from NHANES 2003-2004 with estimates based on artificially created pools from NHANES 2003-2004 using a pooled-sample design similar to the one used for NHANES 2005-2006. For NHANES 2005-2006 the number of analyses required to characterize the levels of 61 polychlorinated and 13 polybrominated compounds in the US population was reduced from 2201 to 228. At a cost of $1400 per analytical measurement, this represents a savings of approximately $2.78 million. Published 2012. This article is a US Government work and is in the public domain in the USA.

Concentrations of bisphenol A and seven other phenols in pooled sera from 3-11 year old children: 2001-2002 National Health and Nutrition Examination Survey

Concerns exist regarding children's exposure to bisphenol A (BPA) and other phenols because of the higher sensitivity, compared to adults, of children's developing organs to endocrine disruptors. Several studies reported the urinary concentrations of these phenols in children, but data on levels of these compounds in children's serum are limited. We present here the total (free plus conjugated) and free concentrations of BPA and seven other phenols in 24 pooled serum samples prepared from individual specimens collected from 936 children 3-11 years old who participated in the 2001-2002 National Health and Nutrition Examination Survey. We detected benzophenone-3, triclosan, 2,4-dichlorophenol, 2,5- dichlorophenol, and three parabens in at least 60% of the pools suggesting children's exposure to these compounds or their precursors. Conjugated phenols were the major species. However, although many previous studies have shown widespread detection of BPA in children's urine, we only detected total or free BPA in 3 and 2 pooled serum samples, respectively, at concentrations of 0.1-0.2 μg/L. The nonpersistent nature of BPA and the phenols examined and the likely episodic nature of the exposures to these compounds (or their precursors) suggest that for general population biomonitoring of these nonpersistent phenols, urine, not serum or plasma, is the preferred matrix.

Polybrominated diphenyl ethers (PBDEs) in marine mammals from Arctic and North Atlantic regions, 1986-2009

A selection of PBDE congeners was analyzed in pooled blubber samples of pilot whale (Globicephala melas), ringed seal (Phoca hispida), minke whale (Balaenoptera acutorostrata), fin whale (Balaenoptera physalus), harbor porpoise (Phocoena phocoena), hooded seal (Cystophora cristata) and Atlantic white-sided dolphin (Lagenorhynchus acutus), covering a time period of more than 20 years (1986-2009). The analytes were extracted and cleaned-up using open column extraction and multi-layer silica gel column chromatography, and the analysis was performed on a GC-MS system operating in the NCI mode. The highest PBDE levels were found in the toothed whale species pilot whale and white-sided dolphin, and the lowest levels in fin whales and ringed seals. One-sided analyses of variance (ANOVA) followed by Tukey comparisons of means were applied to test for differences between years and sampling areas. Due to inter-year sampling variability, only general comparisons of PBDE concentrations between different sampling areas could be made. Differences in PBDE concentrations between three sampling periods, from 1986 to 2007, were evaluated in samples of pilot whales, ringed seals, white-sided dolphins and hooded seals. The highest PBDE levels were found in samples from the late 1990s or beginning of 2000, possibly reflecting the increase in the global production of technical PBDE mixtures in the 1990s. The levels of BDE #153 and #154 increased relative to the total PBDE concentration in some of the species in recent years, which may indicate an increased relative exposure to higher brominated congeners. In order to assess the effect of measures taken in legally binding international agreements, it is important to continuously monitor POPs such as PBDEs in sub-Arctic and Arctic environments.

Pooled exposure assessment for matched case-control studies

Exposure assessment using biologic specimens is important for epidemiology but may become impracticable if assays are expensive, specimen volumes are marginally adequate, or analyte levels fall below the limit of detection. Pooled exposure assessment can provide an effective remedy for these problems in unmatched case-control studies. We extend pooled exposure strategies to handle specimens collected in a matched case-control study. We show that if a logistic model applies to individuals, then a logistic model also applies to an analysis using pooled exposures. Consequently, the individual-level odds ratio can be estimated while conserving both cost and specimen. We discuss appropriate pooling strategies for a single exposure, with adjustment for multiple, possibly continuous, covariates (confounders) and assessment of effect modification by a categorical variable. We assess the performance of the approach via simulations and conclude that pooled strategies can markedly improve efficiency for matched as well as unmatched case-control studies.