The combined effect of persistent organic pollutants in the serum POP mixture in Greenlandic Inuit: xenoestrogenic, xenoandrogenic and dioxin-like transactivities

Diet, lifestyle and contaminants in three east Greenland Inuit municipalities

Persistent organic pollutants (POP) are environmental contaminants transported over long distances to the Arctic where they biomagnify in marine mammals subsistence hunted by Inuit and may therefore affect human health. Marine mammals in east Greenland are known to have the highest POP concentrations in the circumpolar Arctic area. Due to high intake of marine mammals, east Greenlandic Inuit likewise have the highest POP body burdens across the Arctic. This cross-sectional study aims to investigate the levels of POP and metals in Inuit with a high intake of top predatory species including killer whales and polar bears. Study participants include 37 men and 21 women from Kulusuk, Tasiilaq and Ittoqqortoormiit during year 2013-2015. Lipophilic POP (11 organochlorine-pesticides, 14 polychlorinated-biphenyls (PCB), 10 polybrominated diphenyl ethers), polyunsaturated fatty acids (PFUA) and cotinine were determined in plasma. Fifteen perfluoroalkylated substances (PFAS) were measured in serum and urine and the renal clearance was estimated. Finally the concentration of 10 metals were measured in whole blood. The median age was 38 years, Ittoqqortoormiit Inuit being the oldest. The smoking rate was around 70%, and Kulusuk participants had the lowest PFUA concentrations. Significant municipality differences were observed for lipophilic POP, serum PFAS, mercury, arsenic and selenium with highest concentrations in Ittoqqortoormiit Inuit. Males had higher blood concentrations of PFAS and lead. The estimated PFAS renal clearance and ratio of urine to serum were significantly higher for females, suggesting a sex difference in excretion via the kidney, maybe partly because men had higher serum PFAS concentrations. We observed that Inuit with intake of >200 g polar bear per week had significantly higher levels of PCB, PFAS, arsenic and selenium. In summary, the level of blood POP and heavy metals seems to relate to sex and the frequency intake of meat from marine mammals.

Maternal serum dioxin-like activity and gestational age at birth and indices of foetal growth: The Aarhus birth cohort

Human exposure to lipophilic persistent organic pollutants (lipPOP) is ubiquitous and life-long, beginning during foetal development. Exposure to lipPOP elicits a number of species and tissue specific responses including dioxin-like activity which involve the activation of aryl hydrocarbon receptor (AhR). This study aims i) to describe the combined dioxin-like activity in serum from Danish pregnant women collected during 2011-2013; ii) to assess the association between maternal serum dioxin-like activity, gestational age at birth and foetal growth indices. The serum lipPOP fraction was extracted using Solid Phase Extraction and cleaned-up on Supelco multi-layer silica and florisil columns. The combined dioxin-like activity of the extract was determined using the AhR reporter gene bioassay, expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalent (TEQ) [AhR-TEQ (pg/g lipid)]. The associations of AhR-TEQ and foetal growth indices (birth weight, birth length and head circumference) and gestational age were assessed by linear regression models. We detected AhR-TEQ in 93.9 % of maternal first trimester serum samples, with a median level of 185 pg/g lipid. Each ln-unit increase in AhR-TEQ was associated with an increase in birth weight of 36 g (95 % CI: 5; 68), birth length of 0.2 cm (95 % CI: 0.01; 0.3) and pregnancy duration of 1 day (95 % CI: 0; 1.5). In women who never smoked, higher AhR-TEQ values were associated with higher birth weight and longer duration of gestation, while in smokers the association was the opposite. Mediation analyses suggested that gestational age may mediate the association of AhR-TEQ with foetal growth indices. We conclude that AhR activating substances are present in the bloodstream of almost all pregnant women in Denmark and the AhR-TEQ level was around four times higher than previously reported. The AhR-TEQ was associated with slightly longer gestational duration and thereby higher birth weight and birth length.

Exposure to persistent organic pollutants in Danish pregnant women: Hormone levels and fetal growth indices

This study examines possible associations of maternal Persistent Organic Pollutants (POP) exposure during pregnancy, maternal hormone levels and fetal growth indices (FGI). During 1st trimester, we measured maternal thyroids, androgens and estrogens, lipophilic POP and perfluorinated-alkyl-acid (PFAA) levels in serum from nulliparous women. Adjusted multivariate-linear regression models assessed associations between exposure and outcomes. Maternal characteristics and POP exposures associated with maternal hormone levels. Lipophilic POP elicited inverse association with androgen and estrogen levels but no strong association with thyroids. Higher level of PFAA was associated with higher thyroid and androgen levels. The PFAA did not associate with estrogens. Higher thyroid-peroxidase-antibody (TPO-Ab) and estradiol level associated with higher birth weight and length in sons. For daughters, the TPO-Ab associations were the opposite being inversely associated with birth weight and length, and higher TPO-Ab and estradiol associated with lower gestational age. Mediation analyses suggested that TPO-Ab mediates the association of PFAA with FGI.

Dioxin-like Activity in Pregnant Women and Indices of Fetal Growth: The ACCEPT Birth Cohort

Exposure to lipophilic persistent organic pollutants (lipPOPs) elicits a number of species- and tissue-specific toxic responses, many of which involve the aryl hydrocarbon receptor (AhR). This study aims to measure the combined serum dioxin-like activity of lipPOPs in Greenlandic Inuit pregnant women and the associations with fetal growth indices. The combined dioxin-like activity of serum lipPOPs extracts was determined using the AhR reporter gene bioassay and expressed as pico-gram (pg) TCDD equivalent (TEQ) per gram serum lipid [AhR-TEQ (pg/g lipid)]. Significant AhR-TEQ was found in >87% of serum samples with the median level of 86.2 pg TEQ/g lipid. The AhR-TEQ level positively correlated with the marine food intake biomarker n-3/n-6 polyunsaturated fatty acids ratio, while negatively correlated with body mass index and parity. Women giving birth to infants with low birth weight (<2500 g) and length (<50 cm) had higher AhR-TEQ level compared to those with normal weight and length infants. For previous smokers, we found significant inverse associations between maternal AhR-TEQ level and fetal growth indices. In conclusion, exposure of Greenlandic Inuit pregnant women to dioxin-like compounds through traditional marine food can adversely influence the fetal growth via induced AhR activity. Smoking might have modifying effects.

Prenatal exposure to persistent organic pollutants and metals and problematic child behavior at 3-5 years of age: a Greenlandic cohort study

High levels of persistent organic pollutants (POPs) and heavy metals are found in Arctic populations. POP and heavy metals are linked to impaired cognitive development. This study examined associations between prenatal POP and metals exposure and problematic child behavior using the Strength and Difficulties Questionnaire (SDQ). POPs and metals were measured in 102 pregnant Greenlandic women. During follow-up at 3–5 years, parents answered an assisted questionnaire including children’s SDQ scores. Associations were analyzed using linear and logistic regression analyses and adjusted for maternal plasma cotinine, educational level and age at delivery. In the adjusted analyses, the medium tertile of hexachlorobenzene (β = 3.06, p = 0.010), β-hexachlorocyclohexane (β = 3.58, p = 0.004) and trans-nonachlor (β = 2.06, p = 0.082) were positively associated with SDQ scores. The continuous cis-nonachlor (OR = 1.09, p = 0.079), dichloro-diphenyl-dichloroethylene (OR = 1.01, p = 0.077), trans-nonachlor (OR = 1.01, p = 0.091), and sum Organochlorine-Pesticides (OR = 1.00, p = 0.094) were positively associated with abnormal SDQ score and the continuous mirex (OR = 1.28, p = 0.096), oxychlordane (OR = 1.04, p = 0.066), and trans-nonachlor (OR = 1.02, p = 0.071) with abnormal hyperactivity score. We found no consistent evidence of associations between polychlorinated biphenyls, perfluoroalkylated substances and heavy metals and problematic behavior. Prenatal organochlorine pesticide exposure associated significantly with problematic behavior in 3–5 year old children.

Receptor-based in vitro activities to assess human exposure to chemical mixtures and related health impacts

Humans are exposed to a large number of chemicals from sources such as the environment, food, and consumer products. There is growing concern that human exposure to chemical mixtures, especially during critical periods of development, increases the risk of adverse health effects in newborns or later in life. Historically, the one-chemical-at-a-time approach has been applied both for exposure assessment and hazard characterisation, leading to insufficient knowledge about human health effects caused by exposure to mixtures of chemicals that have the same target. To circumvent this challenge researchers can apply in vitro assays to analyse both exposure to and human health effects of chemical mixtures in biological samples. The advantages of using in vitro assays are: (i) that an integrated effect is measured, taking combined mixture effects into account and (ii) that in vitro assays can reduce complexity in identification of Chemicals of Emerging Concern (CECs) in human tissues. We have reviewed the state-of-the-art on the use of receptor-based in vitro assays to assess human exposure to chemical mixtures and related health impacts. A total of 43 studies were identified, in which endpoints for the arylhydrocarbon receptor (AhR), the estrogen receptor (ER), and the androgen receptor (AR) were used. The majority of studies reported biological activities that could be associated with breast cancer incidence, male reproductive health effects, developmental toxicities, human demographic characteristics or lifestyle factors such as dietary patterns. A few studies used the bioactivities to check the coverage of the chemical analyses of the human samples, whereas in vitro assays have so far not regularly been used for identifying CECs in human samples, but rather in environmental matrices or food packaging materials. A huge field of novel applications using receptor-based in vitro assays for mixture toxicity assessment on human samples and effect-directed analysis (EDA) using high resolution mass spectrometry (HRMS) for identification of toxic compounds waits for exploration. In the future this could lead to a paradigm shift in the way we unravel adverse human health effects caused by chemical mixtures.

Estrogenic activity of biological samples as a biomarker

Biological assays can evaluate the cumulative effect of a mixture, considering synergistic/antagonistic interactions and effects of unknown/unconsidered compounds. Therefore, their application could increase in the next years also to analyse biological samples. The aim of this review is to discuss the methodological approach and the application of estrogenic activity assays in human biological samples. 75 research articles were analysed and divided according to whether they used these assays: i) to quantify the level of estrogens and/or as a biomarker of estrogenic status ii) as a biomarker of exposure to endocrine disrupting chemicals (EDCs). For the first purpose, some authors extracted biological samples while others tested them directly without any treatment. The study of these methodologies outlined that the methodology applied influenced the specificity of analysis. The estrogenic activity biomarker was used to analyse physiological variations of estrogens, pediatric diseases, hormone-dependent diseases and estrogen suppression/enhancement after pharmaceutical treatments. For the second purpose, some authors extracted samples while others tested them directly, some authors divided endogenous estrogens from xenoestrogens while others tested samples without separation. The analysis of these methodologies outlined some limitations related to the efficiency of extraction and the incorrect separation of some compounds. The studies which applied this EDC biomarker showed that it was correlated with some EDCs, it varied according to the exposure of the population and it allowed the identification of some relationships between EDC exposure and breast cancer, type 1 diabetes and adverse health effects on children. In conclusion, the estrogenic activity of biological samples can be a useful tool: to quantify low levels of 17β-estradiol, to assess the combined effect of endogenous estrogens and xenoestrogens, to estimate the estrogenic status providing considerable insight into physiological or pathological conditions, to evaluate EDC presence implementing the existing knowledge about EDC exposure and adverse health effects.

Challenging the concept of de novo acute myeloid leukemia: Environmental and occupational leukemogens hiding in our midst

Myeloid neoplasms like acute myeloid leukemia (AML) originate from genomic disruption, usually in a multi-step fashion. Hematopoietic stem/progenitor cell acquisition of abnormalities in vital cellular processes, when coupled with intrinsic factors such as germline predisposition or extrinsic factors such as the marrow microenvironment or environmental agents, can lead to requisite pre-leukemic clonal selection, expansion and evolution. Several of these entities have been invoked as "leukemogens." The known leukemogens are numerous and are found in the therapeutic, occupational and ambient environments, however they are often difficult to implicate for individual patients. Patients treated with particular chemotherapeutic agents or radiotherapy accept a calculated risk of therapy-related AML. Occupational exposures to benzene, dioxins, formaldehyde, electromagnetic and particle radiation have been associated with an increased risk of AML. Although regulatory agencies have established acceptable exposure limits in the workplace, accidental exposures and even ambient exposures to leukemogens are possible. It is plausible that inescapable exposure to non-anthropogenic ambient leukemogens may be responsible for many cases of non-inherited de novo AML. In this review, we discuss the current understanding of leukemogens as they relate to AML, assess to what extent the term "de novo" leukemia is meaningful, and describe the potential to identify and characterize new leukemogens.

Associations of Fetal Growth Outcomes with Measures of the Combined Xenoestrogenic Activity of Maternal Serum Perfluorinated Alkyl Acids in Danish Pregnant Women

BACKGROUND

Higher concentrations of single perfluorinated alkyl acids (PFAAs) have been associated with lower birth weight (BW), but few studies have examined the combined effects of PFAA mixtures. PFAAs have been reported to induce estrogen receptor (ER) transactivity, and estrogens may influence human fetal growth. We hypothesize that mixtures of PFAAs may affect human fetal growth by disrupting the ER.

OBJECTIVES

We aimed to study the associations between the combined xenoestrogenic activity of PFAAs in pregnant women's serum and offspring BW, length, and head circumference.

METHODS

We extracted the actual mixture of PFAAs from the serum of 702 Danish pregnant women (gestational wk 11–13) enrolled in the Aarhus Birth Cohort (ABC) using solid phase extraction, high-performance liquid chromatography (HPLC), and weak anion exchange. PFAA-induced xenoestrogenic receptor transactivation (XER) was determined using the stable transfected MVLN cell line. Associations between XER and measures of fetal growth were estimated using multivariable linear regression with primary adjustment for maternal age, body mass index (BMI), educational level, smoking, and alcohol intake, and sensitivity analyses with additional adjustment for gestational age (GA) (linear and quadratic).

RESULTS

On average, an interquartile range (IQR) increase in XER was associated with a [Formula: see text] [95% confidence interval (CI): [Formula: see text], [Formula: see text]] decrease in BW and a [Formula: see text] (95% CI: 0.1, 0.5) decrease in birth length. Upon additional adjustment for GA, the estimated mean differences were [Formula: see text] (95% CI: [Formula: see text], 4) and [Formula: see text] (95% CI: [Formula: see text], 0.0), respectively.

CONCLUSION

Higher-serum PFAA-induced xenoestrogenic activities were associated with lower BW and length in offspring, suggesting that PFAA mixtures may affect fetal growth by disrupting ER function. https://doi.org/10.1289/EHP1884.

Polychlorinated biphenyls (PCBs) as sentinels for the elucidation of Arctic environmental change processes: a comprehensive review combined with ArcRisk project results

Polychlorinated biphenyls (PCBs) can be used as chemical sentinels for the assessment of anthropogenic influences on Arctic environmental change. We present an overview of studies on PCBs in the Arctic and combine these with the findings from ArcRisk-a major European Union-funded project aimed at examining the effects of climate change on the transport of contaminants to and their behaviour of in the Arctic-to provide a case study on the behaviour and impact of PCBs over time in the Arctic. PCBs in the Arctic have shown declining trends in the environment over the last few decades. Atmospheric long-range transport from secondary and primary sources is the major input of PCBs to the Arctic region. Modelling of the atmospheric PCB composition and behaviour showed some increases in environmental concentrations in a warmer Arctic, but the general decline in PCB levels is still the most prominent feature. 'Within-Arctic' processing of PCBs will be affected by climate change-related processes such as changing wet deposition. These in turn will influence biological exposure and uptake of PCBs. The pan-Arctic rivers draining large Arctic/sub-Arctic catchments provide a significant source of PCBs to the Arctic Ocean, although changes in hydrology/sediment transport combined with a changing marine environment remain areas of uncertainty with regard to PCB fate. Indirect effects of climate change on human exposure, such as a changing diet will influence and possibly reduce PCB exposure for indigenous peoples. Body burdens of PCBs have declined since the 1980s and are predicted to decline further.

Detection of aryl hydrocarbon receptor agonists in human samples

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor with important functions in the immune response and cancer. AHR agonists are provided by the environment, the commensal flora and the metabolism. Considering AHR physiological functions, AHR agonists may have important effects on health and disease. Thus, the quantification of AHR agonists in biological samples is of scientific and clinical relevance. We compared different reporter systems for the detection of AHR agonists in serum samples of Multiple Sclerosis (MS) patients, and assessed the influence of transfection methods and cell lines in a reporter-based in vitro assay. While the use of stable or transient reporters did not influence the measurement of AHR agonistic activity, the species of the cell lines used in these reporter assays had important effects on the reporter readings. These observations suggest that cell-specific factors influence AHR activation and signaling. Thus, based on the reported species selectivity of AHR ligands and the cell species-of-origin effects that we describe in this manuscript, the use of human cell lines is encouraged for the analysis of AHR agonistic activity in human samples. These findings may be relevant for the analysis of AHR agonists in human samples in the context of inflammatory and neoplastic disorders.

Receptor activities of persistent pollutant serum mixtures and breast cancer risk

Studies on associations between persistent organic pollutants (POPs) and breast cancer risk are inconclusive. The majority of studies have evaluated the effect of single compounds, without considering multiple exposures to and interactions between different POPs. The present study aimed at evaluating breast cancer risk related to combined effects of serum POP mixtures on cellular receptor functions. Data on breast cancer cases (n = 77) and controls (n = 84) were collected among Greenlandic Inuit women. Serum mixtures of lipophilic POPs (lipPOPs), perfluoroalkyl acids (PFAAs) and dioxin-like POPs were extracted. The effect of the mixture extracts on the estrogen receptor (ER), androgen receptor (AR) and aryl hydrocarbon receptor (AhR) was determined using cell culture reporter gene assays. The serum mixtures were analyzed alone and upon co-exposure with natural receptor ligands to determine agonistic and antagonistic/competitive activity. We found that the frequency of lipPOP mixtures eliciting no, decreasing, or agonizing xenoandrogenic effect differed by breast cancer status. Using lipPOP mixtures with no effect on AR as reference, the mixtures with decreasing effects reduced breast cancer risk (OR: 0.30 (0.12; 0.76)). The AhR-toxic equivalent of serum mixtures was significantly lower in cases than in controls, and a reduced breast cancer risk was found when comparing the third tertile to the first (OR: 0.34 (0.14; 0.83)). We found no association between the xenoestrogenic activities of lipPOPs or PFAAs and breast cancer risk. Serum lipPOP mixtures are hormone disruptive and may influence breast cancer risk, whereas PFAAs seem to influence breast cancer risk through other pathways.

Health effects associated with measured levels of contaminants in the Arctic

The Human Health Assessment Group has over the past decade recommended that effect studies be conducted in the circumpolar area. Such studies examine the association between contaminant exposure in the Arctic populations and health effects. Because foetuses and young children are the most vulnerable, effect studies are often prospective child cohort studies. The emphasis in this article is on a description of the effects associated with contaminant exposure in the Arctic. The main topics addressed are neurobehavioural, immunological, reproductive, cardiovascular, endocrine and carcinogenic effect. For each topic, the association between exposure and effects is described, and some results are reported for similar studies outside the Arctic.

Estrone sulfate and dehydroepiandrosterone sulfate: Transactivation of the estrogen and androgen receptor

Dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E1S) are two of the most abundant steroids in the human circulation. The enzyme steroid sulfatase (STS) cleaves the sulfate group of DHEAS and E1S leading to biosynthesis of endogenous hormones such as testosterone and estrone. In the current study we aimed at determining the effect of E1S and DHEAS on estrogen receptor (ER) and androgen receptor (AR) transactivation. Using luciferase reporter gene assays, the ER and AR transactivities of E1S and DHEAS were determined by direct cell exposure; as well as upon extraction from human serum using a method to extract perfluorinated alkyl acids (PFAAs). By direct cell exposure, both E1S and DHEAS transactivated the ER and the AR in dose-dependent manners. The DHEAS-induced AR transactivity could be abolished by the STS inhibitor STX64. Immunoassay analysis confirmed the presence of E1S and DHEAS in the serum PFAA extracts with mean recoveries below 2.5%. For the PFAA extracts of human male and female serum, only the AR was significantly transactivated. The AR transactivity of the sulfated steroids in the extracts was abolished by STX64 to obtain the net PFAA induced xenohormone transactivity, but further cleanup might be needed at high concentrations of E1S.

Serum and adipose tissue as matrices for assessment of exposure to persistent organic pollutants in breast cancer patients

The aim of this study was to assess differences between two biological matrices (serum and breast adipose tissue) in the evaluation of persistent organic pollutant (POP) exposure in breast cancer patients. The study population consisted of 103 women undergoing surgery for newly diagnosed breast carcinoma in a public hospital in Granada, Southern Spain. Independent variables were gathered from questionnaires and clinical records. POP concentrations were quantified in breast adipose tissue and serum samples. Spearman correlation tests were performed between pairs of POP concentrations and stepwise multivariable linear regression analyses were conducted to assess predictors of concentrations in the two matrices. p,p'- Dichlorodiphenyldichloroethylene (p,p'-DDE) showed the the highest median concentration in both matrices (194.34 and 173.84 ng/g lipid in adipose tissue and serum, respectively). Median wet-basis adipose tissue:serum ratios ranged from 109.34 to 651.62, while lipid-basis ratios ranged from 0.88 to 4.34. In general, we found significant positive correlation coefficients between pairs of POPs in adipose tissue and in serum, which were always higher in adipose tissue. We found positive and statistically significant correlations between serum and adipose tissue concentrations of p,p'-DDE and hexachlorobenzene (HCB) but not of polychlorinated biphenyls (PCBs). Age was positively associated with most POPs in adipose tissue and serum, while the body mass index was positively associated with adipose tissue HCB concentrations and negatively associated with serum PCB-153 and PCB-138 concentrations. Recent weight loss was inversely associated with POP residues in adipose tissue and positively associated with POP residues in serum. Serum HCB and PCB-180 concentrations were lower in patients who had received preoperative chemotherapy. According to our results, serum and adipose tissue POP concentrations in breast cancer patients may be differentially affected by external predictors. Taken together, these findings indicate the need to take account of the individual POP(s) under study and the biological matrix used when relating internal POP exposure to breast cancer disease and to make a careful selection of covariates for adjusting the model.

Extraction of perfluorinated alkyl acids from human serum for determination of the combined xenoestrogenic transactivity: a method development

Humans are exposed to perfluorinated alkyl acids (PFAAs) through food, drinking water, consumer products, dust, etc. The human metabolism and excretion of the long-chain PFAAs is slow with half-lives up to 8.8years. Studies suggest that the PFAAs are potential endocrine-disrupting compounds that might affect human health. We developed a method for extraction of PFAAs from human serum with simultaneous removal of endogenous sex hormones. The developed method includes solid phase extraction, liquid/liquid extraction, HPLC fractionation and weak anion exchange. The method was validated by extraction of seven persistent PFAAs spiked to human male serum obtaining mean recoveries between 49.6% and 78.6%. Using an estrogen receptor (ER) transactivation luciferase reporter gene assay, analysis of the extracted PFAA serum fraction from three pregnant women showed the ER-active endogenous hormones were removed. The developed method was further documented by extraction of the PFAAs from the serum of 18 Danish pregnant women. The PFAA fraction from three of the 18 samples significantly induced the ER-transactivity. Upon co-exposure with the natural ER-ligand 17β-estradiol (E2), 17 of the 18 PFAA fractions caused a significant further increase of the E2 induced ER-transactivity. In conclusion, we developed a method to extract PFAAs from human serum, and the method documentation suggested that PFAAs at the levels found in human serum can transactivate the ER.

Association between environmental contaminants and health outcomes in indigenous populations of the Circumpolar North

Background

Since the 1990s, research has been carried out to monitor environmental contaminants and their effects on human health in the Arctic. Although evidence shows that Arctic indigenous peoples are exposed to higher levels of contaminants and do worse on several dimensions of health compared with other populations, the contribution of such exposures on adverse outcomes is unclear.

Objective

The purpose of this review is to provide a synopsis of the published epidemiological literature that has examined association between environmental contaminants and health outcomes in Arctic indigenous populations.

Design

A literature search was conducted in OVID Medline (1946-January 2014) using search terms that combined concepts of contaminant and indigenous populations in the Arctic. No language or date restrictions were applied. The reference lists of review articles were hand-searched.

Results

Of 559 citations, 60 studies were relevant. The studies fell under the following categories: paediatric (n=18), reproductive health (n=18), obstetrics and gynaecology (n=9), cardiology (n=7), bone health (n=2), oncology (n=2), endocrinology (n=2) and other (n=2). All studies, except one from Arctic Finland, were either from Nunavik or Greenland. Most studies assessed polychlorinated biphenyls (n=43) and organochlorine pesticides (n=29). Fewer studies examined heavy metals, perfluorinated compounds, or polybrominated diphenyl ethers. Details of study results for each health category are provided.

Conclusions

It is difficult to make conclusive statements about the effects of environmental contaminants on health due to mixed results, small number of studies and studies being restricted to a small number of regions. Meta-analytical synthesis of the evidence should be considered for priority contaminants and health outcomes. The following research gaps should be addressed in future studies: association of contaminants and health in other Arctic regions (i.e. Inuvialuit Settlement Region, Nunavut, Nunatsiavut, Alaska, European North and Russian North); assessment of contaminants on chronic diseases; inclusion of clinical endpoints in assessments; and assessment of the emerging contaminants of perfluorinated compounds and polybrominated diphenyl ethers.

Biomonitoring and hormone-disrupting effect biomarkers of persistent organic pollutants in vitro and ex vivo

Persistent organic pollutants (POPs) include lipophilic legacy POPs and the amphiphilic perfluorinated alkyl acids (PFAAs). They have long half-lives and bioaccumulate in the environment, animals and human beings. POPs possess toxic, carcinogenic and endocrine-disrupting potentials. Endocrine-disrupting chemicals (EDCs) are compounds that either mimic or block endogenous hormones and thus disrupt the normal hormone homeostasis. Biomonitoring assesses the internal doses of a person to provide information about chemical exposures. Effect biomarkers assess chemicals potential to affect cellular functions in vivo/ex vivo. Human beings are exposed to complex mixtures of chemicals, having individually very different biological potentials and effects. Therefore, the assessment of the combined, integrated biological effect of the actual chemical mixture in human blood is important. In vitro and ex vivo cell systems have been introduced for the assessment of the integrated level of xenobiotic cellular effects in human beings. Ex vivo studies have shown geographical differences in bioaccumulated POP serum levels, being reflected by the combined biomarker effects of the complex mixture extracted from human serum. Xenohormone receptor transactivities can be used as an ex vivo integrated biomarker of POP exposure and effects. Epidemiological and in vitro/ex vivo studies have supported the potential impact of the combined effect of serum POPs on the activity of hormone and/or dioxin receptors as a risk factor for human health. With focus on hormone disruption, this MiniReview will give an update on recent POP-related endocrine-disrupting effects in vitro/ex vivo/in vivo and some related genetic data.

Physiologically based pharmacokinetic modeling of POPs in Greenlanders

Human exposure to persistent organic pollutants (POPs) and the potential health impact in the Arctic far from the emission sources have been highlighted in numerous studies. As a supplement to human POP biomonitoring studies, a physiologically based pharmacokinetic (PBPK) model was set up to estimate the fate of POPs in Greenlandic Inuit's liver, blood, muscle and adipose tissue following long-term exposure to traditional Greenlandic diet. The PBPK model described metabolism, excretion and POP accumulation on the basis of their physicochemical properties and metabolic rates in the organisms. Basic correlations between chemically analyzed blood POP concentrations and calculated daily POP intake from food questionnaire of 118 middle age (18-35years) Greenlandic Inuits from four cities in West Greenland (Qaanaaq: n=40; Qeqertarsuaq: n=36; Nuuk: n=20; Narsaq: n=22) taken during 2003 to 2006 were analyzed. The dietary items included were polar bear, caribou, musk oxen, several marine species such as whales, seals, bird and fish as well as imported food. The contaminant concentrations of the dietary items as well as their chemical properties, uptake, biotransformation and excretion allowed us to estimate the POP concentration in liver, blood, muscle and adipose tissue following long-term exposure to the traditional Greenlandic diet using the PBPK model. Significant correlations were found between chemically analyzed POP blood concentrations and calculated daily intake of POPs for Qeqertarsuaq, Nuuk and Narsaq Inuit but not for the northernmost settlement Qaanaaq, probably because the highest blood POP level was found in this district which might mask the interview-based POP calculations. Despite the large variation in circulating blood POP concentrations, the PBPK model predicted blood concentrations of a factor 2-3 within the actual measured values. Moreover, the PBPK model showed that estimated blood POP concentration increased significantly after consumption of meals. For individuals who had a high internal burden of POPs accumulated over years, the estimated blood levels were less influenced by recent meal intake. The model results also indicated that of the POPs accumulated in the body the concentrations were highest for CB-153 (oxychlordane: 0.6%; DDE and CB-99: 2.9%; HCB: 4.4%; CB-153: 34.5%). Furthermore, the model also estimated a significant internal body POP burden even several years after the mentioned dietetic shift and that contaminant accumulation was 2-6 folds faster than the decay after a shift to a diet low in contaminants. Using the PBPK model approach, we seek to improve the knowledge on contaminant body burden in humans of the Arctic. However, it should be noted that calculations of daily POP intake may be subject to considerable uncertainty due to imprecise information from the dietary interview. Based on these results we suggest that PBPK modeling is implemented as a tool in future human health exposure and effect assessments in Greenland.

Dioxin-like activity in environmental and human samples from Greenland and Denmark

Dioxins and dioxin-like (DL) compounds are some of the most toxic chemicals being highly persistent in the environment. The toxicological effects of dioxins are mediated via the aryl hydrocarbon receptor (AhR). Compounds of diverse structure and lipophility can bind and activate AhR. The AhR transactivation bioassay is utilized in an array of projects to study the AhR-mediated activities of individual chemicals and mixtures and for epidemiological purposes. This review summarizes a series of studies regarding the DL-activity of single compounds and complex compound mixtures in the environment and humans. We found that some pesticides, plasticizers and phytoestrogens can activate the AhR, and the combined effect of compounds with no or weak AhR potency cannot be ignored. The significant DL-activity in the wastewater effluent indicates the treatment is not sufficient to prevent contamination of surface waters with dioxins. Our results from human studies suggest that the serum DL-activity reflect the complex mixture of persistent organic pollutants (POPs). Greenlandic Inuit had lower serum DL-activity level compared to Europeans, probably due to long distance from the dioxin sources and UV degradation of the high potent dioxin and/or the inhibitory effect of the high level of non-DL POPs. Selective bioaccumulation of PCBs in the food chain may contribute to the negative correlation between serum POPs and DL-activity observed in Greenlandic Inuit. Hence the AhR transactivation bioassay provides a cost-effective and integrated screening tool for measurement of the DL-activity in human, environmental and commercial samples.