Dioxins: WHO's tolerable daily intake (TDI) revisited

The Aryl Hydrocarbon Receptor and the Maintenance of Lung Health

Much of what is known about the Aryl Hydrocarbon Receptor (AhR) centers on its ability to mediate the deleterious effects of the environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin). However, the AhR is both ubiquitously-expressed and evolutionarily-conserved, suggesting that it evolved for purposes beyond strictly mediating responses to man-made environmental toxicants. There is growing evidence that the AhR is required for the maintenance of health, as it is implicated in physiological processes such as xenobiotic metabolism, organ development and immunity. Dysregulation of AhR expression and activity is also associated with a variety of disease states, particularly those at barrier organs such as the skin, gut and lungs. The lungs are particularly vulnerable to inhaled toxicants such as cigarette smoke. However, the role of the AhR in diseases such as chronic obstructive pulmonary disease (COPD)-a respiratory illness caused predominately by cigarette smoking-and lung cancer remains largely unexplored. This review will discuss the growing body of literature that provides evidence that the AhR protects the lungs against the damaging effects of cigarette smoke.

Studies on the influence of sampling on the levels of dioxins and PCB in fish

Beaked redfish (Sebastes mentella) and Greenland halibut (Reinhardtius hippoglossoides) were collected in waters around Svalbard (Barents Sea) to study the influence of different muscle separation/filleting techniques at small and medium fishes on the dioxin/PCB content. Sampling of both species included preparation techniques such as fillets with or without belly flaps, commercially trimmed fillets and cutting into anterior and posterior cutlets. In case of Greenland halibut also the whole edible muscle part and middle cutlets were studied. All samples analysed were far below the maximum level of 6.5 pg/g wet weight (ww) WHO-PCDD/F-PCB-TEQ and 75 ng/g ww ndl-PCB. Trimmed fillets of beaked redfish had the lowest fat content and the lowest level of dioxins and PCB (1.70%, WHO-PCDD/F-PCB-TEQ = 0.320 pg/g ww). The respective posterior cutlets showed the highest fat content and highest levels of dioxins and PCB (2.66%, WHO-PCDD/F-PCB-TEQ = 0.729 pg/g ww). Levels of dioxins and PCB in Greenland halibut samples were generally higher and ranged between WHO-PCDD/F-PCB-TEQ = 0.784 pg/g ww (fillets without bells flaps, fat content = 8.83%) and WHO-PCDD/F-PCB-TEQ = 2.022 pg/g ww (edible part whole muscle, fat content = 8.62%). The results show a considerable influence of the different sampling methods on the dioxin and PCB levels of the species analysed.

Aryl Hydrocarbon Receptor Ligands Indoxyl 3-sulfate and Indole-3-carbinol Inhibit FMS-like Tyrosine Kinase 3 Ligand-induced Bone Marrow-derived plasmacytoid Dendritic Cell Differentiation

Aryl hydrocarbon receptor (AhR) regulates both innate and adaptive immune responses by sensing a variety of small synthetic and natural chemicals, which act as its ligands. AhR, which is expressed in dendritic cells (DCs), regulates the differentiation of DCs. However, effects of AhR on the differentiation of DCs are variable due to the heterogeneity of DCs in cell surface marker expression, anatomical location, and functional responses. The plasmacytoid DCs (pDCs), one of DC subsets, not only induce innate as well as adaptive immune responses by secreting type I interferons and pro-inflammatory cytokines, but also induce IL-10 producing regulatory T cell or anergy or deletion of antigen-specific T cells. We showed here that AhR ligands indoxyl 3-sulfate (I3S) and indole-3-carbinol (I3C) inhibited the development of pDCs derived from bone marrow (BM) precursors induced by FMS-like tyrosine kinase 3 ligand (Flt3L). I3S and I3C downregulated the expression of signal transducer and activator of transcription 3 (STAT3) and E2-2 (Tcf4). In mice orally treated with I3S and I3C, oral tolerance to dinitrofluorobenzene was impaired and the proportion of CD11c⁺B220⁺ cells in mesenteric lymph nodes was reduced. These data demonstrate that AhR negatively regulates the development of pDCs from BM precursors induced by Flt3L, probably via repressing the expression of STAT3.

Fatty acids, polychlorinated dibenzo-p-dioxins and dibenzofurans, and dioxin-like polychlorinated biphenyls in paired muscle and skin from fish from the Bohai coast, China: Benefits and risks associated with fish consumption

Fish consumption benefits early cognitive development and cardiovascular health because of the n-3 long-chain polyunsaturated fatty acids in the fish, but toxic pollutants in fish, like dioxin-like polychlorinated biphenyls (dl-PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), may decrease or counteract these benefits. In this study, the fatty acids, dl-PCBs, and PCDD/Fs were analyzed in paired muscle and skin from 13 fish and one squid species from the Bohai coast, which have been influenced by serious dioxin pollution from the Bohai Rim Region. The total fatty acid concentrations in the muscle and skin were 2.6-87 and 3.6-156 mg/g wet weight (ww), respectively. The total polyunsaturated fatty acid concentrations were higher in skin than muscle for almost half of the species. The total PCDD/F and dl-PCB toxic equivalents in the muscle and skin were 0.055-0.68 and 0.0099-0.43 pg/g ww, respectively, and were up to five times higher in the muscle than in the skin for eight species. Few benefit-risk studies for fish consumption with and without skin have been performed, so benefit-risk quotients (BRQs) for eating only muscle, only skin, and eating both were calculated. To achieve the recommended 250 mg of EPA + DHA intake, eating only muscle, only skin, and eating both from seven species with BRQs < 1 would cause no significant risk. Removing skin before eating is not necessary for these species. Three fish species had BRQs < 1 for muscle only but BRQs > 1 for skin only. Removing skin before eating would be better for these species. The other four fish species had BRQs > 1 for eating only muscle, only skin, and eating both, indicating the potential risk caused by PCDD/F and dl-PCB. Amounts of the four fish species consumed should be decreased, and other sources of EPA and DHA should be selected.

Concentrations of PCDD/Fs in the neighborhood of a hazardous waste incinerator: human health risks

In 1996-1998, a wide surveillance program was initiated in the vicinity of a new hazardous waste incinerator (HWI) placed in Constantí (Catalonia, Spain), which started its regular operations in 1999. The program was aimed at assessing the environmental impact of the facility on the surrounding environment, as well as to evaluate the potential risks for the population living in the neighborhood. Since then, among other measurements, the concentrations of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) have been periodically determined in soil and herbage samples. This study shows the results, corresponding to the period 2013-2016. Data were compared with those obtained in the baseline survey (1996-1998), as well as with those of the previous survey (2011-2012). The median PCDD/F concentrations in soils were 0.44 and 0.33 ng toxic equivalent (I-TEQ)/kg in 2015 and 2016, respectively, with a significant decrease in relation to the baseline survey, and a non-significant decrease between 2015 and 2016. In turn, PCDD/F levels in vegetation showed some fluctuations over time, being the concentrations of PCDD/Fs in 2013 very similar to those found in 2012 (1.11 and 1.23 ng I-TEQ/kg, respectively). These concentrations notably decreased along the three last campaigns (0.16, 0.23, and 0.17 ng I-TEQ/kg in 2014, 2015, and 2016, respectively). These changes would be more related to a number of environmental factors rather than to a variation of PCDD/F emissions by the HWI. With respect to human health risks, exposure to PCDD/Fs in the area under potential influence of the HWI is not of concern, as the current environmental concentrations of PCDD/Fs do not mean additional carcinogenic or non-carcinogenic risks for the local population.

Polychlorinated biphenyls and chlorinated paraffins in home-produced eggs from an e-waste polluted area in South China: Occurrence and human dietary exposure

The levels of polychlorinated biphenyls (PCBs) and short/median-chain chlorinated paraffins (S/MCCPs) in 68 home-produced eggs collected in 2013 and 2016 from an electronic-waste (e-waste) site in South China were measured and the human dietary exposure to these two classes of contaminants via egg consumption was calculated. The levels of PCBs, SCCPs, and MCCPs varied from 236 to 8870 ng/g lipid weight (lw), 477 to 111,000 ng/g lw, and 125 to 91,100 ng/g lw, respectively. There are no significant differences in the levels of PCBs, SCCPs, and MCCPs between 2013 and 2016 (p > 0.05). The congener profiles of PCBs and MCCPs were similar to each other between 2013 and 2016; however, the homologue profiles of SCCPs were different. The Toxic Equivalent Quantities (TEQs) of ∑DL-PCBs and the levels of ∑ICES-6 PCBs strongly exceeded the limits set by EU Regulation 1259/2011 (2.5 pg World Health Organization-TEQ₂₀₀₅ g^-1 lw for DL-∑PCBs and 40 ng/ g lw for ∑ICES-6 PCBs). The estimated daily intakes (EDI) of PCBs, SCCPs, and MCCPs by adults and children ranged between 5.57 and 1100, 11.8 and 11,900, and 3.62 and 11,400 ng/kg bw/d, respectively. PCBs pose serious health risks for local residents, especially for children, due to the high ratios of EDI (68% in 2013 and 70% in 2016 for adults and 100% for children) in excess of the exposure limits.

Investigating the risk-benefit balance of substituting red and processed meat with fish in a Danish diet

Danish dietary guidelines recommend the Danish population to increase the consumption of fish while decreasing the consumption of red and processed meat to prevent nutrition-related diseases. However, the presence of contaminants in these foods may affect the overall risk-benefit balance of such substitution. We performed a quantitative risk-benefit assessment on substituting red and processed meat with fish in a Danish diet. We modeled the substitution among Danish adults based on data from a Danish dietary survey and compared four alternative scenarios based on varying chemical and nutrient exposures to the current consumption. We quantified the overall health impact of the substitutions in terms of Disability-Adjusted Life Years (DALYs). Approximately 150 DALYs/100,000 individuals could be averted each year if Danish adults consumed 350 g of fish/week (fatty or mix of fatty and lean) while decreasing the consumption of red and processed meat. A lower beneficial impact was observed when consumption of fish was restricted to lean fish (80 DALYs/100,000 averted), and a marked health loss (180 DALYs/100,000) was estimated when consumption was restricted to tuna. Our results show an overall beneficial effect of the substitution if the consumption of large predatory fish is low and at least half is fatty fish.

Dietary intake of dioxins in Japan in 2016 with time trends since 1998

Total diet samples collected from seven regions throughout Japan in 2016 were analysed for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls (DL-PCBs), known collectively as dioxins. This led to estimates of the latest dietary intake of these contaminants for the general Japanese population (≥1 year old). The average daily intake of dioxins for a person weighing 50 kg, calculated at non-detected congener concentrations assumed to be equal to zero, was estimated to be 0.54 pg TEQ (toxic equivalents) kg^-1 body weight (bw) day^-1. This value is well below the tolerable daily intake of 4 pg TEQ kg^-1 bw day^-1 for dioxins in Japan. The average intake was highest from fish and shellfish, followed by meat and eggs. The TEQ contribution of the fish and shellfish group to the total dietary TEQs was significant (89%). The DL-PCBs accounted for about 67% of the dioxin intake. The latest dioxin intake level was compared with previous estimates from total diet study results obtained annually since 1998 to determine the time trends in the dietary intake of dioxins in Japan. Overall, the average dioxin intake appeared to be decreasing gradually during the period of study. The previous average intakes of dioxins ranged from 0.58 to 1.9 pg TEQ kg^-1 bw day^-1. The latest average intake was the lowest since 1998 and was about one-third of the average intake in 1998. This decreasing trend in the dietary intake of dioxins was mainly influenced by the decreased dioxin intakes from two food groups, fish and shellfish, and meat and eggs.

Complex toxicity as disruption of adipocyte or osteoblast differentiation in human mesenchymal stem cells under the mixed condition of TBBPA and TCDD

People are frequently and unintentionally exposed to many chemical compounds, such as environmental pollutants and endocrine-disrupting chemicals (EDCs), in food and from the atmosphere. In particular, endocrine-disrupting TBBPA and dioxins are found in human breast milk and in the body. Conventional studies evaluate toxicity by administering a single substance to cells or animals, but evaluation of the toxicity of mixtures of these ingested compounds is essential for “true” toxicological assessment. We evaluated toxic effects in vitro using human mesenchymal stem cells (hMSCs). TBBPA increased the number of lipid droplets, and upregulated the expression of adipocyte-related mRNA, aP2 and LPL, through a PPARγ-dependent mechanism. TCDD suppressed lipid droplets and adipocyte-related mRNA levels. Adipocyte differentiation was stimulated by TBBPA and inhibited by TCDD in a dose-dependent manner. TBBPA did not influence osteoblast differentiation, but TCDD suppressed ALP staining and activity, calcium deposition, and osteoblast-related mRNA levels. In a mixture of TBBPA and TCDD, TBBPA inhibited TCDD suppression of adipocyte and osteoblast differentiation in a dose-dependent manner. Interestingly, we observed lipid droplets in TBBPA-treated cells differentiated into osteoblasts. These results suggest that TBBPA and TCDD disrupted differentiation into adipocytes and osteoblasts and contributes to a more complete toxicological understanding of exposure to these chemical substances.

2,3,7,8-Tetrachlorodibenzo-p-dioxin induces alterations in myogenic differentiation of C2C12 cells

Dioxin-induced toxicities that affect the development of the motor system have been proposed since many years. However, cellular evidence and the molecular basis for the effects are limited. In this study, a cultured mouse myoblast cell line, C2C12, was utilized to examine the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on myogenic differentiation and expression of acetylcholinesterase (AChE), a neuromuscular transmission-related gene. The results showed that TCDD exposure at 10^-10 M repressed the myotube formation of C2C12 cells by disturbing the fusion process and suppressing the expression of myosin heavy chain, a myobute structural protein, and not by induction of cytotoxicity. Furthermore, TCDD dose dependently suppressed the transcriptional expression and enzymatic activity of AChE during the myogenic differentiation, particularly in the middle stage. However, the administration of aryl hydrocarbon receptor antagonists, CH223191 and alpha-naphthoflavone, did not completely reverse the TCDD-induced downregulation of muscular AChE during myogenic differentiation. These findings suggest that low dose exposure to dioxin may result in disturbances of muscle differentiation and neuromuscular transmission.

Occurrence of polybrominated dibenzo-p-dioxins, dibenzofurans (PBDD/Fs) and polybrominated diphenyl ethers (PBDEs) in pilot whales (Globicephala melas) caught around the Faroe Islands

Blubber from Faroese pilot whales (Globicephala melas) was analysed for brominated dioxins PBDD/Fs, with a subset also analysed for chlorinated dioxins, PCDD/Fs. The studied individuals were restricted to juvenile male whales sampled in the Faroe Islands during the period 1997-2013. Among the PBDD/Fs, the furans were predominant, although the relative abundance of various congeners differed between samples. Furans accounted for, on average, 79% of the ∑PBDD/Fs in the samples, with 1,2,3,4,6,7,8-HpBDF the most abundant congener, found in half of the analysed pilot whales. The concentration range for ∑PBDD/Fs among the samples was 0.080-71 pg/g l.w. (lipid weight), and the sum of toxic equivalents ranged from 0.0039 to 4.7 pg TEQ/g l.w. No relationship was found between PBDD/Fs and PCDD/Fs. In addition, 20 pilot whale samples from the period 2010-2013 were analysed for PBDEs. Several PBDE congeners were found in all of the sampled pilot whales, and at noticeably higher levels than PBDD/Fs and PCDD/Fs. The ∑PBDEs ranged from 140 to 1900 ng/g l.w., with BDE #47 the most abundant congener detected in the samples. Results from the present study were then compared with data from previous studies on pilot wales to investigate temporal trends between 1986 and 2013. The comparison indicated that PBDE concentrations in juvenile males have decreased from 1996 to the latest observations in 2013. No relationship between the concentration levels of PBDD/Fs and PBDEs in the sampled pilot whales could be identified, which indicates possible differences in the metabolism of, or exposure to, PBDEs and PBDD/Fs.

An 18-Year Follow-up Survey of Dioxin Levels in Human Milk in Japan

Background

Globally, few published studies have tracked the temporal trend of dioxin levels in the human body since 2000. This study describes the annual trend of dioxin levels in human breast milk in Japanese mothers from 1998 through 2015.

Methods

An observational study was conducted from 1998 through 2015. Participants were 1,194 healthy mothers following their first delivery who were recruited annually in Japan. Breast milk samples obtained from participants were analyzed using gas chromatography and mass spectrometry for dioxins, including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs).

Results

Mean age was 29.5 years, and 53% of participants were 20–25 years old. A declining trend in total dioxin levels was found, from a peak of 20.8 pg toxic equivalence (TEQ)/g fat in 1998 to 7.2 pg TEQ/g fat in 2014. Data from the last 5 years of the study indicated a plateau at minimal levels. In contrast, an increasing trend was found in the mean age of participants during the last 5 years. Although significantly higher dioxin levels were observed in samples from older participants, an upward trend in dioxin levels was not observed, indicating that dietary and environmental exposure to dioxins had greatly diminished in recent years.

Conclusions

Dioxin levels in human breast milk may be approaching a minimum in recent years in Japan. The findings may contribute to global reference levels for environmental pollution of dioxins, which remains a problem for many developing countries.

Can resveratrol attenuate testicular damage in neonatal and adult rats exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin during gestation?

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is considered one of the most toxic dioxins. The effects of TCDD are exerted via binding to the aryl hydrocarbon receptor (AhR). The aim of the present study was to evaluate the possible protective effects of resveratrol, an AhR antagonist, against testicular damage caused by TCDD exposure during pregnancy. Pregnant female Sprague-Dawley rats were divided into four groups: a control group; a group treated with 1 µg kg−1, p.o., TCDD on Gestational Day (GD) 15; a group treated with 20 µg kg−1, p.o., resveratrol on GD10–21; and a group treated with both TCDD and resveratrol. Rats were weighed and killed, and neonatal testes were collected for histopathological analysis on Postnatal Day (PND) 1. At PND90, adult male rats were killed and the testes collected for histopathological analysis and determination of sperm count. Resveratrol had a protective effect against the effects of TCDD on Sertoli cell number in adult and neonate testes, as well as against the effects of TCDD on abnormal seminiferous tubules in adults. Combined administration of TCDD and resveratrol altered the kinetics of spermatogenesis and the proportion of neonatal testicular compartments compared with the control group In addition, combined TCDD and resveratrol treatment decreased seminiferous tubule diameter in adult male rats compared with the control group. In conclusion, resveratrol may protect against some TCDD-induced testicular damage, but, based on the parameters assessed, the administration of resveratrol and TCDD in combination may result in more severe toxicity than administration of either drug alone.

Evidence for estrogeno-mimetic effects of a mixture of low-dose pollutants in a model of ovariectomized mice

We recently hypothesized that a mixture of low-dosed dioxin, polychlorobiphenyl, phthalate and bisphenol may induce estrogeno-mimetic activities in a model of lifelong-exposed female mice. Herein, we evaluated the impact of this mixture in estrogen deficiency conditions. Based on the protective effects of estrogens against metabolic disorders, we reasoned that exposure to pollutants should attenuate the deleterious metabolic effects induced by ovariectomy. In line with the hypothesis, exposure to pollutants was found to reduce the impact of ovariectomy on glucose intolerance and insulin resistance, to enhance the expression levels of the hepatic estrogen receptor α and to attenuate the ovariectomy-induced enhancement of the chemokine MCP-1/CCL2 considered as an indicator of estrogen signalling. Because of the very low doses of pollutants used in mixture, these findings may have strong implications in terms of understanding the potential role of environmental contaminants in the development of metabolic diseases, specifically in females during menopausal transition.

Occurrence, Loading, and Exposure of Atmospheric Particle-Bound POPs at the African and European Edges of the Western Mediterranean Sea

A comparative study for 62 toxic chemicals based on the simultaneous monthly collection of aerosol samples during 2015-2016 in two coastal cities at both the African (Bizerte, Tunisia) and European (Marseille, France) edges of the Western Mediterranean basin is presented. Legacy polychlorinated biphenyls (∑₁₈PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (∑₁₇PCDD/Fs) show generally higher median levels at the African edge (2.1 and 0.2 pg m^-3, respectively) compared to the European coastal site (1.0 and 0.08 pg m^-3, respectively). Contrarily, the "emerging" polybrominated diphenyl ethers' (∑₂₇PBDEs) median concentrations were higher in Marseille (∼9.0 pg m^-3) compared to Bizerte (∼6.0 pg m^-3). Different past usages and current emission patterns were found at both edges of the Western Mediterranean, most probably linked to the respective different regulatory frameworks for toxic chemicals. Our results indicate that the total organic carbon (TOC) and/or the elemental carbon (EC) contents in the atmospheric aerosol may have a stronger effect than the total suspended particle (TSP) content as a whole on the spatial-temporal variability and the long-range atmospheric transport potential of the studied POPs. A "jumping" of the PBDE local atmospheric stocks from the Northwestern European Mediterranean edge to the Northwestern African coast seems to be possible under favorable conditions at present. While a higher PBDE median loading is estimated for the Marseille area (∼550 ng m^-2 y^-1) compared to Bizerte (∼400 ng m^-2 y^-1), the median PCB and PCDD/F dry deposition fluxes were higher at the African site, resulting in a 3-fold higher toxic equivalent (TEQ) loading of dioxin-like pollutants (400 pg TEQ m^-2 y^-1) compared to Marseille (∼140 pg TEQ m^-2 y^-1), with potential implications for aquatic organisms. However, the inhalation exposure assessment points to a minimum risk for human health at both sites.

Polychlorinated biphenyls (PCBs) residues in commercial pasteurized cows' milk in Tehran, Iran

BACKGROUND

To date, despite the facts that pasteurized milk is the most consumed dairy product in Iran and its consumption has increased almost two fold during the last 10 years, no data are available concerning the concentrations of polychlorinated biphenyls (PCBs) in commercial cow milk in Iran market.

METHODS

This study designed to determine the levels of PCBs in these products and to assess population exposure to PCBs by estimating the daily intakes. Pasteurized cows' milk samples (10 brands) were collected from local markets at two different seasons and analyzed using sensitive and reliable methods.

RESULTS

Based on the results all the indicator PCBs were detected and quantified in all of the samples, the mean ± SD concentration for the sum of the six congeners was 18.92 ± 14.36 ng g^-1 fat. None of the samples surpassed the provisional value established by the EU of 40 ng g^-1 fat. The sum of dioxin-like congeners, expressed as WHO-TEQ was 0.492 pg/g of fat which was considerably lower than the defined limit 3 pg/g fat, set for cow's milk. Furthermore, a similar DL-PCBs profile as other studies was found for analyzed samples. The results indicated that concentrations of DL-PCBs were very low, and all of milk samples were compliant with EC legislation. In addition, seasonal variations were not observed for DL- and NDL-PCBs levels (p values >0.05).

CONCLUSIONS

The estimated dietary intake for target population was 0.06 pg TEQ/kg of body weight/day, much smaller than the amounts declared by the World Health Organization as tolerable daily intake.

Spermatogenesis disruption by dioxins: Epigenetic reprograming and windows of susceptibility

Dioxins are a group of highly persistent chemicals that are generated as by-products of industrial and natural processes. Reduction in sperm counts is among the most sensitive endpoints of dioxin toxicity. The exact mechanism by which dioxins reduce sperm counts is not known. Recent data implicate the role of epididymal factors rather than disruption of spermatogenesis. Studies reviewed here demonstrate that dioxins induce the transfer of environmental conditions to the next generation via male germline following exposures during the window of epigenetic reprogramming of primordial germ cells. Increased incidence of birth defects in offspring of male veterans exposed to dioxin containing, Agent Orange, suggest that dioxins may induce epigenomic changes in male germ cells of adults during spermatogenesis. This is supported by recent animal data that show that environmental conditions can cause epigenetic dysregulation in sperm in the context of specific windows of epigenetic reprogramming during spermatogenesis.

Patterns and dietary intake of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in food products in China

The health risk of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like PCBs (dl-PCBs) to human being should be assessed regularly. To evaluate the contamination levels in various food products in the Chinese market and to assess the dietary exposure of the Chinese population, 11 varieties of food groups totaling 634 samples including beef and mutton, chicken and duck, pork, fish and seafood, milk and dairy products were evaluated. The average concentrations of PCDD/Fs in all groups ranged from 0.291 to 8.468pg/g whole weight (w.w.). The average toxic equivalency concentrations were from 0.012pg TEQ/g w.w. for cereal to 0.367pg TEQ/g fat for marine oil. OCDD and 2,3,7,8-TCDF were the dominant congeners in foodstuffs. The dietary estimated mean intake for the Chinese rural and urban populations were 0.656 and 0.514pg TEQ/kg body weight/day, respectively, however, the cereal group exposure were higher to the estimate daily intake and contributed 81% for rural and 48% for urban population, followed by fish and seafood which contributed 4% and 16% to the estimate daily intake. The estimated dietary intakes were compared with the toxicological reference values and showed that both rural and urban populations were well below those values.

A review of the Texas, USA San Jacinto Superfund site and the deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans in the San Jacinto River and Houston Ship Channel

The San Jacinto River (SJR) waste pits that lie just under the 1-10 overpass in eastern Harris County east of Houston, Texas, USA, were created in the 1960s as dumping grounds for paper mill waste. The deposition of this waste led to accumulation of highly toxic polychlorinated dibenzo-p-dioxins and dibenzofurans (PCCDDs/PCDFs) over the course of several decades. After abandonment, the waste material eventually became submerged under the waters of the SJR, resulting in widespread environmental contamination that currently constitutes a significant health concern for eastern Harris County communities. The original waste pits were rediscovered in 2005, and the San Jacinto waste site is now a designated EPA superfund site. The objective of this review then is to discuss the history and current state of containment around the San Jacinto waste pits and analyze spatial and temporal trends in the PCDD/PCDF deposition through the SJR system from the data available. We will discuss the current exposure and health risks represented by the Superfund site and the SJR system itself, as well as the discovery of liver, kidney, brain (glioma), and retinoblastoma cancer clusters in eastern Harris County across multiple census tracts that border the Superfund site. We will also cover the two primary management options, containment versus removal of the waste from the Superfund and provide recommendations for increased monitoring of existing concentrations of polychlorinated waste in the SJR and its nearby associated communities.

Dust levels of polybrominated diphenyl ethers (PBDEs) and polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) in the Taiwanese elementary school classrooms: Assessment of the risk to school-age children

Elementary school classroom dust is an important source of exposure to polybrominated dibenzo-p-dioxins/furans and diphenyl ethers (PBDD/DF/DEs) for school-age children. Our goal is thus to investigate concentrations of PBDD/DF/DEs in elementary school classroom dust to further assess the impact on school-age children via ingestion. The dust from classrooms, including both normal (NR) and computer classrooms (CR), was collected from six urban and four rural schools. Fourteen PBDEs and twelve PBDD/Fs were measured using high-resolution gas-chromatography/high-resolution mass-spectrometry. The mean levels of Σ₁₄PBDEs in NR and CR dust from the urban classrooms were 370 and 2510ng/g and those whose dust from the rural classrooms were 464 and 1780ng/g. The means of ΣPBDD/Fs were 0.0401ng-WHO₂₀₀₅-TEQ/g (concentration: 4.72ng/g) in urban NR dust, 0.0636ng-WHO₂₀₀₅-TEQ/g (7.51ng/g) in urban CR dust, 0.0281ng-WHO₂₀₀₅TEQ/g (3.60ng/g) in rural NR dust, and 0.0474ng-WHO₂₀₀₅TEQ/g (6.28ng/g) in rural CR dust. The PBDEs pattern in NR dust was quite different from that in CR dust, but the PBDD/Fs patterns in NR and CR dust were similar. A linearly significant correlation coefficient (n=20, r=0.862, p<0.001) was found between ΣPBDEs and ΣPBDD/Fs in NR and CR dust, indicating that the PBDEs and PBDD/Fs in the dust may be from the same sources in the elementary school classrooms. This study assessed the risks (daily intake and cancer and non-cancer risks) of PBDEs and PBDD/Fs for the children from the classroom dust, and the calculated risk values did not exceed the related thresholds. With regard to the exposure scenarios for school-age children in an indoor environment, the results suggest that they might ingest more dust PBDD/DF/DEs in their homes than in the schools. In conclusion, the exposure of Taiwanese elementary school children to PBDD/DF/DEs via indoor dust was with a safe range based on our findings.

Polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like PCBs in commercialized food products from Colombia

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) are commonly known as dioxins and are the most toxic members of persistent organic pollutants (POPs) because present a variety of health effects especially as promoting agent of growing and transformation of cancer cells. They are bio-accumulate in humans primarily via the diet, specifically by ingestion of foods that have high lipid content which are generally associated with foods of animal origin such as oils and fats and with fishery and dairy products. In Colombia the Ministry of Health and Social Protection which is the entity responsible for surveillance food conditions, has established maximum levels for dioxins and dl-PCBs in oils from animal and vegetable origins. Oils of vegetable and animal origin represent an appreciable intake in the country thus the presence of dioxins and dl-PCBs in these materials is a matter of concern because they can bioaccumulate in fat. In this contribution the levels of PCDD/Fs and dl-PCBs in olive, soybean, fish oil, butter and shrimp consumed in Colombia were determined using HRGC-HRMS and were compared with the maximum levels permitted in oil samples according to both the Colombian and European regulations. WHO-TEQ concentrations for PCDD/Fs and dioxin like PCBs ranged from 0.24 to 1.710pgWHO-TEQ PCDD/Fg(-1) of fat and from 0.050 to 3.000pgWHO-TEQ PCBg(-1) of fat, respectively. As expected, fish oils and shrimp present the highest WHO-TEQ PCDD/Fs and dl-PCBs values followed by butter and soybean oil sample, while the olive oil shows the lowest levels. In general, the vegetable oils show levels below the limits established by both the Colombian and European regulations. The levels from soybean oil found in this study were slightly higher than the threshold established both by the Commission Regulation European Union (EU) and the Colombian legislation, while fish oils showed concentrations above the European regulations. Furthermore, shrimp exhibited values below the maximum concentration levels established by the EU and Colombian regulation.

The Aryl Hydrocarbon Receptor in Immunity: Tools and Potential

The signaling pathway of the evolutionary old transcription factor AhR is inducible by a number of small molecular weight chemicals, including toxicants such as polycyclic aromatic hydrocarbons, bacterial toxic pigments, and physiological compounds such as tryptophan derivatives or dietary indoles. AhR activation is of immunological importance, but at the same time mediates toxicity of environmental pollutants, such as immunosuppression by dioxins. Measuring AhR activity and identification of ligands is thus of great interest for a variety of research fields. In this chapter, I briefly introduce the AhR signaling pathway, its role in immunology, and the tools and assays needed to analyze AhR signaling. Both are also needed when therapeutic applications are envisioned.

Bioanalytical and instrumental screening of the uptake of sediment-borne, dioxin-like compounds in roach (Rutilus rutilus)

To examine the uptake of dioxin-like compounds (DLCs), common roaches (Rutilus rutilus) were exposed for 28 days to differently contaminated sediments from two major European rivers in a purpose-built facility. Dietary transfer of DLCs was investigated by exposing fish to sediments inoculated or non-inoculated with black worms (Lumbriculus variegatus). Dioxin-like polychlorinated biphenyls (DL-PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), measured via high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) in sediments and whole fish, were used to calculate toxicity equivalent quotients (TEQs). TEQs were compared with biological toxicity equivalent quotients (BEQs) determined via the 7-ethoxyresorufin-O-deethylase (EROD) assay, performed with mammalian (H4IIE) and fish (RTL-W1) liver cell lines. TEQs and BEQs indicated an uptake of sediment-borne DLCs by roach, which was independent of sediment contamination levels, but rather reflected sediment-specific characteristics. For most sediment treatments, DLC uptake did not increase with time. Highest congener-specific uptake (DL-PCB 123) was 10-fold compared to control. Exposure to worm-inoculated sediment of highest overall DLC contamination caused a 2-fold (TEQ and H4IIE BEQ) greater uptake of DLCs by fish compared to the respective non-inoculated treatment. H4IIE cells showed the greatest sensitivity (0.37 ± 0.25 pM TCDD) and the strongest correlation with TEQs (r (2)  = 0.79), hence, they seem to be best suited for DLC screening of sediments and biota, amended by compound-specific instrumental analysis if required.

Gas and particle size distributions of polychlorinated naphthalenes in the atmosphere of Beijing, China

Polychlorinated naphthalenes (PCNs) were listed as persistent organic pollutants in the Stockholm Convention in 2015. Despite numerous studies on PCNs, little is known about their occurrence in atmospheric particulate matter of different sizes. In this study, 49 PCN congeners were investigated for their concentrations and size-specific distributions in an urban atmosphere, and preliminary exposure assessments were conducted. Ambient air samples were collected using a high-volume cascade impactor for division into a gas fraction and four particle size fractions. Samples were collected from October 2013 to June 2014 at an urban site in Beijing, China. The concentration range for PCNs in the atmosphere (gas + particle fractions) was 6.77-25.90 pg/m(3) (average 16.28 pg/m(3)). The particle-bound concentration range was 0.17-2.78 pg/m(3) (average 1.73 pg/m(3)). Therefore, PCNs were mainly found in the gas phase. The concentrations of PCNs in a fraction increased as the particle size decreased (dae > 10 μm, 10 μm ≥ dae > 2.5 μm, 2.5 μm ≥ dae > 1.0 μm and dae ≤ 1.0 μm). Consequently, PCNs were ubiquitous in inhalable fine particles, and the ΣPCNs associated with PM1.0 and PM2.5 reached 68.4% and 84.3%, respectively. Tetra-CNs and penta-CNs (the lower chlorinated homologues) predominated in the atmosphere. The homologue profiles in different size particles were almost similar, but the particulate profiles were different from those in the gas phase. Among the individual PCNs identified, CN38/40, CN52/60 and CN75 were the dominant compounds in the atmosphere. CN66/67 and CN73 collectively accounted for most of the total dioxin-like TEQ concentrations of the PCNs. Exposure to toxic compounds, such as PCNs present in PM1.0 or PM2.5, may affect human health. This work presents the first data on size-specific distributions of PCNs in the atmosphere.

Levels and profiles of polychlorinated dibenzo-p-dioxin and dibenzofurans in raw and treated water from water treatment plants in Shenzhen, China

Levels and profiles of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) were analyzed for the first time in raw and treated water from five water treatment plants in Shenzhen, South China. The average PCDD/Fs concentrations were 32.93 pg/L (0.057 pg international toxic equivalent quantity (I-TEQ)/L) and 0.64 pg/L (0.021 pg I-TEQ/L) in raw and treated water, respectively. The removal rate of PCDD/Fs in terms of mass concentration varied from 93.4% to 98.8%, whereas a negative removal rate was observed in one plant in terms of TEQ concentration. The PCDD/Fs concentration in raw water was lower than most of the published data from other countries and regions, and the PCDD/Fs concentration in treated water was below the Maximum Contaminants Level (MCL) of 30 pg/L for dioxin in drinking water set by the US EPA. Historical pentachlorophenol usage, local waste incineration and industrial emissions, as well as surface runoff or even soil erosion, might be the main sources for PCDD/F pollution in water. The daily intake of PCDD/Fs for local residents from drinking water was estimated to be 0.69 fg I-TEQ/kg/day, which is negligible compared with that from food consumption (1.23 pg WHO-TEQ/kg/day) in the local area.

Estimated dietary intake and risk assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans and dioxin-like polychlorinated biphenyls from fish consumption in the Korean general population

We analyzed 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and 12 dioxin-like polychlorinated biphenyls (DL-PCBs) in samples from various fish species available at food markets in nine Korean cities. The estimated dietary intake of these chemicals was calculated from the raw concentrations of PCDD/Fs and DL-PCBs in each sample and from the food consumption of the Korean general population, and a comparison was made with the provisional tolerable monthly intake (PTMI). The average daily dietary exposure and the 95th percentile of intake of PCDD/Fs and DL-PCBs were 0.21 and 0.49 pg WHO05-toxic equivalents (TEQ) kg(-1) body weight d(-1) representing 5.27% and 12.26%, respectively, of the Korean tolerable daily intake (TDI). We applied the monthly fish consumption limits to the evaluation of improved risk assessment and concluded that unlimited consumption of most fish species does not contribute to the elevated cancer risk. This investigation was the first such large-scale study in Korea, and incorporated 37 species, including a species of whale, and 480 samples. The major aims of this study were to demonstrate the health risks associated with fish intake and to ensure food safety through total analysis of PCDD/Fs and DL-PCBs using gas chromatography/high-resolution mass spectrometry (GC-HRMS).

Congener profiles of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in sediment, water, and fish at a soil contamination site in Taiwan

The relationship of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in sediment, water, and fish was studied for 55 fish farms near a contaminated site in Tainan, Taiwan. Samples were collected from the farms and analyzed for seventeen 2,3,7,8-substituted PCDD/Fs congeners. High correlations were found between PCDD/Fs in water and sediment in regard to both concentration and toxicity (R(2) = 0.933 for concentration and R(2) = 0.832 for toxicity). The congener profiles of the 17 PCDD/Fs in water were similar to those in the sediment. However, the PCDD/Fs congener composition in the fish and fish belly samples were different from those in the sediment and water samples obtained from the same fish farm and were also different among the fish samples. It is thus suggested that the biotic PCDD/Fs distribution is more complex than the abiotic PCDD/Fs distribution. Among the seven factors analyzed, only the lipid percentage presented a relationship with the PCDD/Fs congener composition in the fish and fish bellies. A multiple linear regression of the concentration of each congener in the fish was conducted using the concentration of each congener in the site-matched sediment and the lipid content of the fish as independent variables. The results showed that only seven PCDD/Fs congeners with a lower degree of chlorination, which were 4-6 chlorine substitutes, in the fish presented a significant correlation with the lipid content in the fish and their concentration in sediment (r > 0.65, P < 0.005 for both independent variables). In addition, the octanol-water partition coefficients were not significantly related to this distribution behavior.

Progressive risk assessment of polychlorinated biphenyls through a Total Diet Study in the Korean population

Human exposure to polychlorinated biphenyls (PCBs) from foods was investigated through a Total Diet Study (TDS) for the first time in Korea. A representative food list was developed from food intake data. Non-selected foods were also included in the TDS through the mapping process to anticipate practical risk assessment. For better representativeness, data (2008-2011) from the Korea National Health and Nutrition Examination Survey (KNHANES) were combined with the TDS data set. And also, we estimated the dietary exposure to PCBs from various food items using a 'best-fit' mapping process and assessed the differences in PCB exposures by sex and age. In this study, we examined total PCBs (62 congeners) including dioxin-like PCBs (DL-PCBs) and indicator PCBs, which are congeners that are mainly detected in various environmental matrices. The average dietary exposure (3.94 ng/kg body weight/day) that was estimated through food intake was 19.7% of the World Health Organization (WHO) recommendation.

Effects of urbanization on gaseous and particulate polycyclic aromatic hydrocarbons and polychlorinated biphenyls in a coastal city, China: levels, sources, and health risks

Gas/particle distributions of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were measured in Xiamen from May 2009 to March 2010 to evaluate the impacts of urbanization on the fate of persistent organic pollutants (POPs) in the atmospheric environment. In a newly developing area (NDA), the concentrations of 16 PAHs (gas + particle) were significantly higher than that a historically urbanized area (HUA) (p value <0.05), while the trend of 28 PCBs was reversed. Diagnostic ratios and principle component analysis (PCA) implied that atmospheric PAHs in the NDA were mainly derived from petrogenic combustion, including mixed sources of vehicle emissions, biomass burning and oil combustion, while pyrogenic combustion (e.g., traffic and coal combustion) was considered the major source of PAHs in the HUA. Atmospheric PCBs in both HUA and NDA were dominated by TriCBs and PeCBs related to the use of commercial mixtures (Aroclors 1242 and 1254). Based on the toxicological equivalent factor (TEF) approach, total benzo[a]pyrene equivalent values in the HUA and NDA were 1.12 and 2.02 ng m(-3), respectively, exceeding the standard threshold values (1.0 ng m(-3)) of China and WHO. Average daily intake of dioxin-like compounds was 0.2 pg kg(-1) day(-1) in the HUA, which are below the WHO tolerable daily intake level. The results showed that the contribution to the toxic equivalency (TEQ) was dominated by PCB169, PCB105, and PCB81.

Levels of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in breast milk in Shanghai, China: A temporal upward trend

Human milk samples were collected from 150 mothers in 2011 and 2012 in Shanghai, China and analyzed for 17 polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and 12 dioxin-like polychlorinated biphenyls (DL-PCBs). The up-bound Toxic Equivalent Quantity (TEQ) ranged from 0.27 to 16.8 pg TEQ/g lipid (mean 5.4 pg TEQ/g lipid) for ∑PCDD/Fs and from 0.75 to 10.2 pg TEQ/g lipid (mean 2.9 pg TEQ/g lipid) for ∑DL-PCBs. TEQs in our study were lower than those in most countries worldwide, and displayed a notable uptrend, in contrast with those in China's national survey in 2007. TEQs in mother milks from urban areas were higher than those from rural areas, and an orderly distribution was found in four geographical regions: Eastern China>Central China≈Southwestern China>Northwestern China. Levels of analytes in Shanghai native mothers' milk ranked the first among those from all provinces and cities investigated. Migrant mothers to Shanghai from other inland provinces could potentially represent the population for exposure and risk assessment in their birth and grown-up places. Both the distribution and the uptrend were associated with release of these pollutants due to rapid industrialization and urbanization in China. Fine correlations were observed between TEQs and age of mothers, and weak correlations between TEQs and consumption of meat & meat products. Participants, who preferred both fresh water and marine fish to freshwater fish only, were prone to be exposed to higher level of PCBs. The estimated daily intake (EDI) doses for breastfed neonates entirely exceeded the tolerable intake dose by WHO.

Recent status of organohalogens, heavy metals and PAHs pollution in specific locations in India

Our group of scientists at the Center for Marine Environmental Studies (CMES), Ehime University, Japan has been carrying-out studies in India from the 1980s on chemicals contamination. Due to its agrarian economy, use of fossil fuels, industries, growing population and urbanization, chemicals such as pesticides, dioxins and related chemicals (DRCs), brominated flame retardants (BFRs), heavy metals, and polyaromatic hydrocarbons (PAHs) are widely spread in India. We have published a review (Subramanian and Tanabe, 2007) covering papers published until 2005, on India. A decade had passed and this is the time to provide an update of the spatial and temporal changes during this period and hence this review. At many instances organochlorines such as DDTs and HCHs showed decreasing trends even though they are still at considerable levels. Novel chemicals such as PCDDs/Fs are seen at municipal solid waste dumping sites of India at levels equivalent to similar locations of the developed world. In the e-waste processing sites in India, especially the informal ones, apart from PCDDs/Fs, some brominated flame retardants (BFRs) and heavy metals were present as contaminants. Metro cities of India showed location specific contamination by HCHs, DDTs, PCDDs/Fs, BFRs, PAHs, etc. Coastal regions of India seem to be still unpolluted when compared to the nearby inland locations. This review is concerned mainly with the chemicals that we (CMES) have been evaluating in India in the past three decades. We suggest the importance of further studies, future directions for policy decisions and also for implementing control measures.

Characterization and risk assessment of polychlorinated biphenyls in soils and rice tissues in a suburban paddy field of the Pearl River Delta, South China

We investigated the concentration and composition of polychlorinated biphenyls (PCBs) in paddy soils and rice tissues and the associated potential health risks in the urban agricultural areas of the Pearl River Delta (PRD), South China. The results indicated that highly chlorinated PCBs were more prominent in soil when the concentrations of low-molecular-weight PCBs were relatively high in rice plants. There was a trend of decreasing PCB concentrations with soil depth and a significant correlation between PCBs and the total organic carbon or total nitrogen concentration in section soils. The PCB concentrations followed the order of root > leaf > stem > grain. Although the dioxin toxicity equivalency values and estimated daily intake levels (based direct and indirect consumption) were lower than in other seriously contaminated regions, there is still a need to monitor PCB pollution in urban agriculture because of the PCB emissions from capacitor storage following the rapid urbanization experienced in the PRD.

Metabolic outcome of female mice exposed to a mixture of low-dose pollutants in a diet-induced obesity model

Pollutants are suspected to contribute to the etiology of obesity and related metabolic disorders. Apart from occupational exposure which concerns a subset of chemicals, humans are mostly exposed to a large variety of chemicals, all life-long and at low doses. Food ingestion is a major route of exposure and it is suggested that pollutants have a worsened impact when combined with a high-fat diet. In the experimental studies described herein, we aimed to add further evidence on the metabolic impact of food pollutants using a recently set up model in which mice are life-long fed a high-fat/high-sucrose diet (HFSD) with/without common food pollutants shown to exhibit metabolic disrupting activities. Specifically, this mixture comprised bisphenol A, dioxin, polychlorobiphenyl PCB153, and phthalate and was added in HFSD at doses resulting in mice exposure at the Tolerable Daily Intake dose range for each pollutant. We herein focused on the 7-week-old females which exhibited early signs of obesity upon HFSD feeding. We observed no signs of toxicity and no additional weight gain following exposure to the mixture but alleviated HFSD-induced glucose intolerance in the absence of alteration of gluconeogenesis and steatosis. It suggested that the observed metabolic improvement was more likely due to effects on muscle and/or adipose tissues rather than on the liver. Consistently, female mice exhibited enhanced lean/fat mass ratio and skeletal muscle insulin sensitivity. Moreover, expression levels of inflammatory markers were reduced in adipose tissue at 7 but enhanced at 12 weeks of age in agreement with the inverse alterations of glucose tolerance observed at these ages upon pollutant exposure in the HFSD-fed females. Collectively, these data suggest apparent biphasic effects of pollutants upon HFSD feeding along with obesity development. These effects were not observed in males and may depend on interactions between diet and pollutants.

Human exposure to PCDD/Fs and PCBs through consumption of fish and seafood in Catalonia (Spain): Temporal trend

The concentrations of PCDD/Fs and 18 PCBs (DL- and NDL-) were analyzed in 16 fish and seafood species widely consumed in Catalonia (Spain). The exposure of these pollutants was subsequently estimated according to various groups of population. The concentrations of PCDD/Fs and PCBs showed an important decrease in relation to the baseline study (2000) and our last survey (2008). Sardine and red mullet were the species showing the highest pollutant concentrations, while canned tuna and cuttlefish presented the lowest levels. Sardine was the main contributor to the exposure of PCDD/Fs and PCBs. In contrast, swordfish was the species with the lowest contribution to the exposure of PCDD/Fs, DL-PCBs, and PCDD/Fs+DL-PCBs, while clam was the minor contributor for NDL-PCBs and total PCBs. For all groups of population, the current intakes of PCDD/Fs and PCBs were lower than the TDI (1-4 pg WHO-TEQ/kg body weight/day), being children the group with the highest exposure. However, this exposure should not mean a health risk for this group of population. The current intake of PCDD/Fs and PCBs through fish and seafood consumption was similar or even lower than most values reported in recent studies all over the world.

Estimated dietary dioxin exposure and breast cancer risk among women from the French E3N prospective cohort

Introduction

Dioxins are environmental and persistent pollutants mostly emitted from combustion facilities (e.g. waste incinerators, metal and cement industries). Known to be endocrine disrupting chemicals, dioxins are suspected to increase breast cancer (BC) risk. Although diet is considered the primary source of dioxin exposure, no previous study has been published on dietary dioxin exposure in relation to BC risk. We aimed to assess dietary dioxin exposure among women from the E3N cohort and estimate BC risk associated with this exposure.

Methods

The study included 63,830 women from the E3N cohort who completed a diet history questionnaire (DHQ) in 1993 and were followed until 2008. Dietary dioxin exposure was estimated by combining consumption data from the E3N DHQ and food dioxin contamination data from a French national monitoring program. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated by Cox models adjusted for BC risk factors.

Results

Mean dietary dioxin exposure was estimated at 1.3 ± 0.4 pg/kg body weight (BW)/day. A 0.4 pg/kg BW/d increase in dioxin intake was not associated with overall BC risk (HR = 1.00; 95% CI: 0.96, 1.05). A significant decrease in risk of estrogen receptor negative (ER-)/progesterone receptor negative (PR-) tumors was observed among post-menopausal women in the upper quartile of estimated dioxin intake (HR for Q4 vs. Q1: 0.65; 95% CI: 0.45, 0.96; P for trend across quartiles = 0.0463).

Conclusions

Overall, no association between estimated dietary dioxin exposure and BC risk was found among E3N women. Further studies should include both dietary and environmental exposures to determine whether low-dose dioxin exposure is associated with BC risk.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0536-9) contains supplementary material, which is available to authorized users.

Mortality after exposure to polychlorinated biphenyls and polychlorinated dibenzofurans: a meta-analysis of two highly exposed cohorts

Both Yucheng and Yusho were events of accidental exposure to highly doses of polychlorinated biphenyls and dibenzofurans in Asian people. Mortality experiences caused by various diseases were reported in both cohorts with similar and dissimilar findings. We thus conducted a meta-analysis of two cohorts to reevaluate the effects of PCBs and PCDFs on major causes of mortalities. Two recently updated Yucheng and Yusho mortality studies were included. For selected diseases, standardized mortality ratios (SMR) and 95% confidence intervals (95% CI) were extracted. Meta-analyses were conducted using a random-effects model only when heterogeneity (I(2)  > 50% and/or p value <0.10 by the Q test) was not found. A total of 1,803 Yucheng subjects (male, N = 830; female, N = 973) with 48,751 person-years of follow-up and 1,664 Yusho subjects (male, N = 860; female, N = 804) with 50,773 person-years are included. An increase in all-cause mortality (pooled SMR=1.2, 95% CI: 1.1-1.3, I(2)  = 0.0%), all cancers (pooled SMR=1.3, 95% CI: 1.1-1.6, I(2)  = 0.0%), lung cancer (pooled SMR=1.7, 95% CI: 1.2-2.3, I(2) =0.0%), heart disease (pooled SMR=1.3, 95% CI: 1.0-1.7, I(2)  = 43.4%) and hepatic disease (pooled SMR=1.9, 95% CI: 1.3-2.8, I(2)  = 0.0%) were found in pooled males. Significant elevation from liver cancer was found in pooled females (pooled SMR=2.0, 95% CI: 1.1-3.6, I(2)  = 0.0%). This meta-analysis of Yucheng and Yusho cohorts showed similar elevation from all cancer, lung cancer, heart disease and hepatic disease mortalities in exposed men. Furthermore, a new finding of elevated liver cancer mortality in exposed women was identified.

Assessment on dioxin-like compounds intake from various marine fish from Zhoushan Fishery, China

Sea fish consuming is an important intake source of dioxin-like compounds, especially for the coastal residents. To assess the intake levels of these contaminants from sea fish and to provide risk-based consumption advice, concentrations of 17 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and 12 dioxin-like polychlorinated biphenyls (dl-PCBs) were measured in 32 commonly consumed fish species from Zhoushan Fishery, China. Due to the different accumulation influenced by fat content, feed habits and living zone in the sea area, the levels of PCDDs, PCDFs and dl-PCBs in different fish species varied significantly ranging from 0.002 to 0.078pg WHO-TEQ/g fresh weight, from 0.002 to 0.553pg WHO-TEQ/g fresh weight and from 0.003 to 2.059pg WHO-TEQ/g fresh weight, respectively. Based on mean fish consuming rate in China, the estimated maximum possible dioxin-like compounds intake through different fish species ranged from 0.26 to 65.61pgTEQkg(-1)bwmonth(-1). Bullet mackerel has the highest monthly intake level which was much higher than other fish species and very close to the provisional tolerable monthly intake (70pgTEQkg(-)(1)bwmonth(-)(1)) proposed by the Joint FAO/WHO Expert Committee on Food Additives. Hence, comparing to other fish species, the consumption of Bullet mackerel from Zhoushan Fishery should be cautious to reduce the potential health risk.

Human dietary intake of organohalogen contaminants at e-waste recycling sites in Eastern China

This study reports concentrations and human dietary intake of hexabromocyclododecanes (HBCDs), polychlorinated biphenyls (PCBs) as well as selected "novel" brominated flame retardants (NBFRs) and organochlorine pesticides, in ten staple food categories. Samples were sourced from areas in Taizhou City, eastern China, where rudimentary recycling and disposal of e-waste is commonplace, as well as from nearby non-e-waste impacted control areas. In most instances, concentrations in foods from e-waste recycling areas exceeded those from control locations. Concentrations of 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB) and bis-(2-ethylhexyl)-3,4,5,6-tetrabromophthalate (BEH-TBP) in samples from e-waste sites were 3.09-62.2ng/g and 0.81-16.3ng/g lipid weight (lw), respectively; exceeding consistently those in foods acquired from control sites by an order of magnitude in many cases. In contrast, while concentrations of HBCD in some foods from e-waste impacted areas exceed those from control locations; concentrations in pork, shrimp, and duck liver are higher in control samples. This highlights the potential significance of non-e-waste sources of HBCD (e.g. building insulation foam) in our study areas. While concentrations of DDT in all foods examined except pork were higher in e-waste impacted samples than controls; our exposure estimates were well below the provisional tolerable daily intake of 0.01mg/kgbw/day derived by the Joint FAO/WHO Meeting on Pesticide Residues. Concentrations of ΣPCBs resulted in exposures (650 and 2340ng/kgbw/day for adults and children respectively) that exceed substantially the Minimal Risk Levels (MRLs) for ΣPCBs of 20ng/kgbw/day derived by the Agency for Toxic Substances & Disease Registry. Moreover, when expressed in terms of dioxin-like toxicity equivalency based on the four dioxin-like PCBs monitored in this study (DL-PCBs) (PCB-105, 118, 156, and 167); concentrations in e-waste impacted foods exceed limits set by the European Union in 6 of the 8 food groups studied and result in dietary exposures for children (10.2pgTEQ/kgbw/day) that exceed the WHO tolerable daily intake of 1-4pgTEQ/kgbw/day.

Mammalian cytochrome P450-dependent metabolism of polychlorinated dibenzo-p-dioxins and coplanar polychlorinated biphenyls

Polychlorinated dibenzo-p-dioxins (PCDDs) and coplanar polychlorinated biphenyls (PCBs) contribute to dioxin toxicity in humans and wildlife after bioaccumulation through the food chain from the environment. The authors examined human and rat cytochrome P450 (CYP)-dependent metabolism of PCDDs and PCBs. A number of human CYP isoforms belonging to the CYP1 and CYP2 families showed remarkable activities toward low-chlorinated PCDDs. In particular, human CYP1A1, CYP1A2, and CYP1B1 showed high activities toward monoCDDs, diCDDs, and triCDDs but no detectable activity toward 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-tetraCDD). Large amino acids located at putative substrate-recognition sites and the F-G loop in rat CYP1A1 contributed to the successful metabolism of 2,3,7,8-tetraCDD. Rat, but not human, CYP1A1 metabolized 3,3',4,4',5-pentachlorobiphenyl (CB126) to two hydroxylated metabolites. These metabolites are probably less toxic than is CB126, due to their higher solubility. Homology models of human and rat CYP1A1s and CB126 docking studies indicated that two amino acid differences in the CB126-binding cavity were important for CB126 metabolism. In this review, the importance of CYPs in the metabolism of dioxins and PCBs in mammals and the species-based differences between humans and rats are described. In addition, the authors reveal the molecular mechanism behind the binding modes of dioxins and PCBs in the heme pocket of CYPs.

Dioxin-related compounds in breast milk of women from Vietnamese e-waste recycling sites: levels, toxic equivalents and relevance of non-dietary exposure

Although informal e-waste recycling sites (EWRSs) are hotspots of both polychlorinated and polybrominated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs and PBDD/Fs), human exposure to the latter has not been studied in details. This study investigated the accumulation levels and profiles of dioxin-related compounds (DRCs) in breast milk samples from women living in two Vietnamese EWRSs and estimated the intake contribution from e-waste-related exposure. Screening results using Dioxin-Responsive Chemically Activated LUciferase gene eXpression assay (DR-CALUX) showed higher dioxin-like (DL) activities in samples from the EWRS Bui Dau than in those from the EWRS Trang Minh and a reference site (2.3-10 vs 1.7-4.8 and 0.60-5.7 pg CALUX-TEQ/g lipid, n=10, 6 and 9, respectively). Chemical analysis results of selected samples show that the WHO-TEQ levels of PCDD/Fs, DL-PCBs and PBDD/Fs in EWRS samples were not significantly higher than in those from the reference site (0.22-7.4 vs 1.1-3.0 pg/g lipid) and within the Vietnamese background range, but women involved in recycling accumulated higher concentrations of PCDFs (13-15 vs 2.3-8.8 pg/g lipid) and PBDFs (1.1-1.5 vs <1.1 pg/g lipid). By comparing the DRC profile in milk of these women with the reported profile in house dust from the same site, dust ingestion was estimated to contribute most of the intake for tetraBDF, 37 per cent to 55 per cent for penta-octaCDFs, but less than twenty per cent for PCDDs and DL-PCBs, and 26 per cent for total WHO-TEQs. The DL activities in some EWRS milk samples were not fully explained by chemical data, suggesting contribution from unidentified compounds. The estimated WHO-TEQ intake doses for breastfed infants (1.3-33 pg/kg/d) mostly exceeded the tolerable value, especially for those living in the EWRSs; and unidentified DRCs might increase further the dioxin-related health risk.

PCNs (polychlorinated napthalenes): dietary exposure via cereal crops, distribution and screening-level risk assessment in wheat, rice, soil and air along two tributaries of the River Chenab, Pakistan

There is a lack of scientific literature regarding the bioaccumulation, dietary and toxicity exposure of PCN via food crops. The current study presents the information of dietary intake, distribution pattern and screening level risk assessment of PCN in wheat, rice, soil and air along upstream feeding tributaries of the River Chenab, Punjab Province, Pakistan. A total six air and twenty eight of soil, wheat and rice samples were collected during Jan, 2013 to June, 2013 to analyze the thirty nine PCN congeners. ∑39PCN concentrations were ranged between 0.02 and 0.21 ng g(-1) dw, 0.02-1.21 ng g(-1) dw, 24.6-233 ng g(-1) dw and 1,222-5,052 pg m(-3) in wheat, rice, soil and air samples, respectively. In this study soil exhibited higher TEQ values while in case of air, wheat and rice TEQ concentrations were in accordance with the previously reported pattern from other parts of the world. Estimated daily intake (EDI) of ∑39PCN through consumption of wheat and rice was estimated as 0.21 ng kg(-1) (body weight)day(-1) and 0.03 ng kg(-1) (body weight)day(-1), respectively. This is the first report of PCN dietary intake and screening-level risk assessment by consumption of cereal crops from Pakistan. The results of dietary and toxicity exposure of PCN warrant auxiliary devotion in future, to this group of contaminant.

Gas-particle distributions, sources and health effects of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in Venice aerosols

Air samples were collected in Venice during summer 2009 and 2012 to measure gas and particulate concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs). PCB-11, considered a marker for non-Aroclor contamination of the environment, was found for the first time in the Venetian lagoon and in Europe. An investigation on sources has been conducted, evidencing traffic as the major source of PAHs, whereas PCBs have a similar composition to Aroclor 1248 and 1254; in 2009 a release of PCN-42 has been hypothesized. Toxicological evaluation by TCA and TEQ methods, conducted for the first time in Venice air samples, identified BaP, PCB-126 and PCB-169 as the most important contributors to the total carcinogenic activity of PAHs and the total dioxin-like activity of PCBs and PCNs.

Atmospheric polychlorinated naphthalenes (PCNs) in India and Pakistan

Polychlorinated naphthalenes (PCNs) are now under review by the Stockholm Convention as candidates for persistent organic pollutants (POPs) due to their persistence, toxicity, bioaccumulation, and long-range atmospheric transport. Data on PCN levels are sparse in South Asia. Atmospheric PCNs in India and Pakistan were monitored during the winter by polyurethane foam disk passive air samplers (PUF-PAS). The average concentrations were 29 pg/m(3) and 7.7 pg/m(3) in the Indian and Pakistani samples, respectively. Those concentration levels were relatively lower than the previously reported values in other Asian countries, but still considerably higher than in other sites in the world. Tri-CNs and tetra-CNs were the dominant homologues in the air, especially in India. Spatially, the PCNs were ubiquitous in the target areas, and local distribution was generally impacted by the proximity to potential sources. Major sources of PCNs in this study were the re-emission of Halowax and industrial thermal processes. Biomass burning influenced some sites in Pakistan. However, the enrichment of tri-CNs in Indian cities cannot be ascribed to either the signature of a specific source or the preferential volatilization and/or photodegradation in tropical areas. Despite this unclear issue in South Asia, the present study indicates that the potential health impact was generally comparable to that in non-urban sites worldwide.

Levels of PCDD/Fs, PCBs and PBDEs in breast milk of women living in the vicinity of a hazardous waste incinerator: assessment of the temporal trend

The concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were determined in breast milk from women living in the vicinity of a hazardous waste incinerator (HWI) in Catalonia, Spain. The results were compared with the levels obtained in previous surveys carried out in the same area in 1998 (baseline study), 2002 and 2007. The current total concentrations of 2,3,7,8-chlorinated PCDD/Fs in breast milk ranged from 18 to 126 pg g(-1)fat (1.1-12. 3 pg WHO2005-TEQPCDD/F), while the total levels of PCBs ranged from 27 to 405 pg g(-1)fat(0.7-5.3 pg WHO2005-TEQPCB). In turn, PBDE concentrations (sum of 15 congeners) ranged 0.3-5.1 g g(-1)fat, with a mean value of 1.3 ng g(-1)fat. A general decrease in the concentrations for PCDD/Fs, both planar and total PCBs, and PBDEs in breast milk was observed. The levels of PCDD/Fs, PCBs, and PBDEs in milk of women living in urban zones were higher than those corresponding to industrial zones (41%, 26%, and 8%, respectively). For PCDD/Fs and PCBs, the current decreases are in accordance with the reduction in the dietary intake of these pollutants that we have also observed in recent studies carried out in the same area of study.

Global deposition of airborne dioxin

We present a global dioxin model that simulates one year of atmospheric emissions, transport processes, and depositions to the earth's terrestrial and marine habitats. We map starting emission levels for each land area, and we also map the resulting deposits to terrestrial and marine environments. This model confirms that 'hot spots' of deposition are likely to be in northern Europe, eastern North America, and in parts of Asia with the highest marine dioxin depositions being the northeast and northwest Atlantic, western Pacific, northern Indian Ocean and the Mediterranean. It also reveals that approximately 40% of airborne dioxin emissions are deposited to marine environments and that many countries in Africa receive more dioxin than they produce, which results in these countries being disproportionately impacted. Since human exposure to dioxin is largely through diet, this work highlights food producing areas that receive higher atmospheric deposits of dioxin than others.

Dioxin-related compounds in house dust from New York State: occurrence, in vitro toxic evaluation and implications for indoor exposure

This study analysed sulphuric-acid-treated extracts of house dust from New York State with DR-CALUX assay and HRGC-HRMS to elucidate the total dioxin-like (DL) activities, the occurrence of various dioxin-related compounds (DRCs), including PBDD/Fs, and their toxic contribution. The DL activities were 30-8000, median 210 pg CALUX-TEQ/g. PCDD/Fs, PBDD/Fs and DL-PCBs were detected with a large variation in concentrations (0.12-80, 0.33-150, 0.46-35, medians 1.7, 2.1 and 5.6 ng/g, respectively) and profiles, indicating the existence of multiple contamination sources in homes. PCDD/Fs, PBDD/Fs and DL-PCBs with known potency theoretically contributed <1%-130%, <1%-21% and <1%-6.8%, respectively, of the measured CALUX-TEQs. These results and those from DR-CALUX assays with fractionated dust extracts indicated that a substantial portion of the CALUX-TEQs could be caused by unknown dust contaminants. Considering that the DRC intake from indoor dust ingestion can be significant, identification of unknown DL contaminants in indoor dust is necessary.

Biological monitoring of PCDD/Fs and PCBs in the City of Mataró. A population-based cohort study (1995-2012)

There is great concern about the exposure to PCDD/Fs in areas near solid waste incineration (SWI) plants as, in the past, thermal waste treatment was a major source of PCDD/Fs, affecting negatively the environment and the population living nearby the area of influence. The aim of the present study was to monitor PCDD/Fs and PCBs levels in blood samples in general population living nearby a modern SWI. Up to 7 different campaigns were performed between 1995 and 2012. Overall, 104 exposed subjects (living <1000 m from the incinerator plant) and 97 non-exposed subjects (living >3000 m from the incinerator plant) were randomly selected from the municipal census of the City of Mataró in 1995. In addition, workers of the SWI plant were included in the study. Moreover, in 1999, 100 non-exposed subjects living in the nearby City of Arenys de Mar were added to the project. Overall, this study represents the longest consecutive human biomonitoring study of dioxins, furans and PCBs ever conducted in Spain. Concentrations of PCDD/Fs and PCBs were determined according to age, sex and distance to the SWI exposure in whole blood sample pools. No relevant differences in PCDD/Fs and PCBs levels were observed between SWI exposure groups. It could be noted that since 1999 all groups experienced a slight decrease in the levels of PCDD/Fs and marker PCBs. Moreover, concentrations of PCDD/Fs and marker PCBs were higher in women than in men, and in older age group in comparison to the younger ones.