Polychlorinated Dibenzo-para-dioxins Research Articles

Актуальність проблеми визначення діоксинів і поліхлорованих біфенілів (ПХБ) у продуктах для дитячого харчування

The Aim of the Article. Analysis of the current state of the problem of the dioxins and polychlorinated biphenyls (PCBs) determination in baby food products and the development of sample preparation methods for determining these xenobiotics in food products for infants and young children. Dioxins form a group of structurally and chemically related chlorinated tricyclic oxygen-containing aromatic compounds (congeners), which includes 75 polychlorinated dibenzo-para-dioxins (PCDDs) and 135 polychlorinated dibenzofurans (PCDFs). The most toxic congeners of dioxins, in which chlorine atoms along with other positions are necessarily in 2,3,7,8 positions of benzene rings. Their total number is 17:7 PCDD congeners and 10 PCDF congeners. A group of polychlorinated biphenyls (PCBs) – chlorinated bicyclic aromatic compounds, which consists of 209 different congeners, 12 of which have a spatial and electronic structure and exhibit toxicological properties similar to dioxins, therefore, they are called dioxin-like PCBs (DL-PCBs). In addition, when monitoring food products as a marker, a group of 6 PCBs was selected that did not exhibit dioxin-like toxicity and therefore did not belong to dioxin-like PCBs (NDL-PCBs). Thus, of the total number of 419 PCDDs, PCDFs and PCBs, only 35 are toxicologically significant, therefore, these compounds are subject to control in baby food products. To control the content of the amount of dioxins, the amount of dioxins and DL-PCBs and the amount of NDL-PCBs in foods for infants and children from one to three years in Ukraine, the maximum levels of these compounds on the basis of the order of the Ministry of Health of Ukraine No. 368 of 05/13/2013 were harmonized with the maximum allowable levels in foods for infants and young children in accordance with Commission Regulation (EU) No. 1259/2011. Methods for the analysis of dioxins and PCBs. Two instrumental analysis methods are used to determine dioxins and dioxin-like PCBs in foods for baby food: 1) a combination of high-resolution (capillary) gas chromatography with high-resolution mass spectrometry (GC/MS); 2) a combination of GCHR with tandem mass spectroscopy (GC/MS/MS). High-resolution (capillary) gas chromatography is used to determine non-dioxin-like (marker) PCBs. The stage of sample preparation, including the stages of extraction and purification, is key in determining dioxins and PCBs. Conclusions. The stage of sample preparation using automatic devices (liquid extraction under pressure, an automated extract purification system) and chromatographic columns was developed to further determine the mass concentration of dioxins and PCBs in baby food products. The developed procedures using devices for the automatic extraction and purification of the obtained extracts from baby food samples will make it possible in the future to determine PCDDs/PCDFs, ortho-unsubstituted, mono-ortho-substituted and marker PCBs in one sample. Key Words: dioxins, polychlorinated biphenyls, baby food.

Dioxins levels in human blood after implementation of measures against dioxin exposure in Japan

BackgroundOver the past few decades, the Japanese Ministry of the Environment has been biomonitoring dioxins in the general Japanese population and, in response to public concerns, has taken measures to reduce dioxin exposure. The objectives of this study were to assess the current dioxin dietary intake and corresponding body burden in the Japanese and compare Japanese dioxin data from 2011 to 2016 and 2002–2010 surveys. We also examined the relationship between blood dioxins and health parameters/clinical biomarkers.MethodsFrom 2011 to 2016, cross-sectional dioxin surveys were conducted on 490 Japanese (242 males and 248 females, aged 49.9 ± 7.6 years) from 15 Japanese prefectures. Blood (n = 490) and food samples (n = 90) were measured for 29 dioxin congeners including polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs) using gas chromatography coupled with high-resolution mass spectrometry. Using the 2006 World Health Organization toxic equivalence factors, the toxic equivalents (TEQs) were calculated. Clinical biomarkers and anthropometric parameters were also measured and information on lifestyle behaviours collected. Data imputations were applied to account for blood dioxins below the detection limit.ResultsThe median (95% confidence interval or CI) blood levels and dioxin dietary intake was respectively 9.4 (8.8–9.9) pg TEQ/g lipid and 0.3 (0.2–0.4) pg TEQ/kg body weight/day. The median blood dioxin level in the 2011–2016 survey was found to have decreased by 41.3% compared to the 2002–2010 surveys. Participants who were older were found to be more likely to have higher dioxin levels. Blood dioxins were also significantly associated with body mass index, triglycerides, docosahexaenoic acid, eicosapentaenoic acid, and dihomo-gamma-linoleic acid levels in blood. Furthermore, associations between blood dioxin and dietary dioxin intake were evident in the unadjusted models. However, after adjusting for confounders, blood dioxins were not found to be associated with dietary dioxin intake.ConclusionsBlood dioxin levels declined over the past decade. This study showed that the measures and actions undertaken in Japan have possibly contributed to these reductions in the body burden of dioxins in the Japanese population.

ASSESSMENT OF DIOXINS AND FURANS EMISSIONRESULTING FROM CEMENT INDUSTRY USING UNEP TOOLKIT

Polychlorinated dibenzo-para-dioxins (PCDDs) and Polychlorinated dibenzo- furans (PCDFs) may be released during fuel combustion in several industries including cement production. Estimation of dioxins and furans released from four cement factories in the Red Sea region, Suez Governorate, Egypt, has been calculated. The Standardized Toolkit recommended by the United Nation Environmental Program, UNEP for Identification and Quantification of PCDD’s and PCDF’srelease developed by UNEP was used. Data about incineration of hazardous waste in cement kilns are also collected. Only one plant was found to incinerate according to controlled combustion processes that apply good air pollution control system, APCS, in place. The default emission factors established by UNEP toolkit were used to estimate the PCDD’s and PCDF’s. Only one plant allows the use of hazardous wastes, HW, in its fueling mixture. The calculated dioxins and furans for this plant (A) was 0.77 g TEQ/year into air with dioxins residue of 12.135 g TEQ/year. However, emission rate of other plants(B,C and D) were, 0.1165, 0.1 and0.07 g TEQ/year, respectively, compared with the permissible limit set by the European Union as is 0.1 ng TEQ /Nm³ TEQ for concentration of dioxin-like compounds in the discharged flue gas is 0.1 ng TEQ/Nm³ TEQ.( EU limit value. europa.eu)

Effect of Feeding Milk Replacers on the Tissue Burden of Polychlorinated Dibenzo-para-dioxins, Dibenzofurans, and Dioxin-like Polychlorinated Biphenyls in Suckling Beef Calves

To reduce the intake and accumulation of dioxins and dioxin-like compounds in nursing beef calves, the concentrations of seven polychlorinated dibenzo-para-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), and 12 dioxin-like polychlorinated biphenyls (PCBs) were analyzed and compared in the natural milk of grazing beef cows and bovine milk replacers, and in the blood, testis, and adipose tissue of mother-fed and bottle-fed calves at two months of age. The total toxic equivalent quantities (TEQs) of these compounds were approximately tenfold less (P < 0.001) in synthetic milk substitute and starter feed for calves than in natural milk (1.0 and 0.88 vs. 9.28 pg/g-lipid, respectively). The TEQ in the blood of mother-fed calves increased (P < 0.01) two months after birth (1.35 vs. 8.44 pg/g-lipid), whereas no difference in TEQ was found in bottle-fed calves between birth and two months of age (0.94 and 0.93 pg/g-lipid, respectively). Consequently, TEQs in the blood, testis, and adipose tissue were less (P < 0.05) in bottle-fed calves as compared with mother-fed calves at two months of age (0.93 vs. 8.44, 4.97 vs. 21.7, and 5.17 vs. 18.1 pg/g-lipid, respectively). Regarding individual congeners, the concentrations of dioxins with four or five chlorine substitutions were lower (P < 0.05) in synthetic milk substitute and starter feed than in natural milk, whereas the concentrations of hepta- and octa- chlorinated congeners were conversely higher in synthetic milk substitute and starter feed. Similarly, the accumulation of tetra- and penta- chlorinated congeners in adipose tissue of bottle-fed calves was lower (P < 0.01) than that in mother-fed calves. In contrast, congener specific accumulation characteristics like PCDDs were not observed in PCDFs and dioxin-like PCBs, and none of these congeners detected in bottle-fed calves were greater than that found in mother-fed calves. These results suggest that the feeding of milk replacers can markedly reduce the intake and accumulation of dioxins and dioxin-like compounds in nursing beef calves as compared with natural feeding, because the milk replacers contain preferably lower concentrations of these compounds than in natural milk.

Dietary exposure to, and internal organ transfer of, selected halogenated organic compounds in birds eating fish from the Southern Baltic

The aim of this study was to assess the effect of a marine diet on the accumulation, magnification, maternal transfer and detoxification of chlorinated organic pollutants on the highest trophic level in the Baltic Sea. Results showed that birds eating whole herring received the highest doses of herbicides > pesticides > fungicides > polychlorinated dibenzofurans (PCDFs) > polychlorinated dibenzo-para-dioxins (PCDDs). The toxicity of PCDD/Fs in a penguin's 24-h alimentary exposure was estimated at 7.77 ng TEQ-WHO2005. Among pesticides, the highest concentrations—both in fish and penguin tissue—were those of the pp-DDE isomer. In terms of herbicides, simazine and terbutrine were predominant. The majority of Persistent Organic Pollutants (POPs) underwent accumulation and magnification, and these factors were observed to increase with the birds' age. Guano was found to be an effective means of elimination for all of the studied xenobiotics. Maternal transfer of PCDD/Fs into eggs from internal tissues was most prominent for highly chlorinated dioxins and low chlorinated furans.

Biomedical Pollutants in the Urban Environment and Implications for Public Health: A Case Study

This study investigated the management of biomedical pollutants in the Accra Metropolitan Area in Ghana, using a qualitative case study approach involving interviews, focus-group discussions, and observation techniques. A state of precariousness was found to characterize the management of biomedical pollutants in the study area, culminating in the magnification of risks to the environment and public health. There is neither a single sanitary landfill nor a properly functioning incineration system in the entire metropolis, and most of the healthcare facilities surveyed lack access to suitable treatment technologies. As a result, crude burning and indiscriminate dumping of infectious and toxic biomedical residues were found to be widespread. The crude burning of toxic biomedical pollutants was found to provide environmental pathways for carcinogenic substances. These include polynuclear aromatic hydrocarbons (PAHs), polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated biphenyls (PCBs), hydrogen, lead, mercury, cadmium, chlorobenzenes, particulate matter, and chlorophenols. The improper disposal of biomedical pollutants in open dumps and unsanitary landfills also carries a risk of providing environmental entry points for volatile organic compounds (VOCs), inorganic macrocomponents, heavy metals, and xenobiotic organic compounds.

An assessment of dioxin contamination from the intermittent operation of a municipal waste incinerator in Japan and associated remediation

Significant dioxin (polychlorinated dibenzo-para-dioxins (PCDDs)/polychlorinated dibenzo-furans (PCDFs)) pollution from a municipal solid waste incinerator was discovered in 1997 in Osaka prefecture/Japan. The cause and mechanism of pollution was identified by a detailed assessment of the environment and incinerator plant. The primary sources of PCDD/PCDF pollution were high dioxin releases from an intermittently operated waste incinerator with PCDD/PCDF emissions of 150 ng-TEQ/Nm(3). PCDD/PCDF also accumulated in the wet scrubber system (3,000 μg TEQ/L) by adsorption and water recirculation in the incinerator. Scrubber water was air-cooled with a cooling tower located on the roof of the incinerator. High concentrations of dioxins in the cooling water were released as aerosols into the surrounding and caused heavy soil pollution in the area near the plant. These emissions were considered as the major contamination pathway from the plant. Decontamination and soil remediation in and around the incinerator plant were conducted using a variety of destruction technologies (including incineration, photochemical degradation and GeoMelt technology). Although the soil remediation process was successfully finished in December 2006 about 3% of the waste still remains. The case demonstrates that releases from incinerators which do not use best available technology or which are not operated according to best environmental practices can contaminate their operators and surrounding land. This significant pollution had a large impact on the Japanese government's approach toward controlling dioxin pollution. Since this incident, a ministerial conference on dioxins has successfully strengthened control measures.

Spatial distribution of PCDDs, PCDFs and dl-PCBs along the cascade of urban reservoirs

The river environment is a highly complex system with a variety of processes continuously changing along its continuum (River Continuum Concept). Therefore identification of the threats that result from different elements of the river ecosystem is an intricate task, mainly because of the transportation and biological, geological and chemical processes occurring in such a system. The overall objective of the presented study was to examine the concentration and pattern of polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in the five urban, cascade reservoirs. The obtained data demonstrated an increasing total concentration of toxic PCDDs/PCDFs and dl-PCBs along the studied reservoirs starting from 266 ng/kg d.w. in the first pond up to 11,400 ng/kg d.w. in the last pond, wherein the highest World Health Organization – Toxic Equivalent (WHO-TEQ) concentration (18.9 ng TEQ/kg d.w.) was also recorded. The exception from this rule, with the lowest total and WHO-TEQ concentrations (182 ng/kg d.w. and 1.31 ng TEQ/kg d.w., respectively) was the middle newly constructed III reservoir, equipped with the sediment traps and sand separators at the stormwater outlets and ecotone zones around its catchment for enhancing the purification of inflowing stormwater. This situation may indicate the importance of such solutions for the reduction of PCDDs, PCDFs and dl-PCBs in the urban water ecosystems.

Effect of Coal Drying on the Behavior of Inorganic Species during Victorian Brown Coal Pyrolysis and Combustion

The purpose of this work was to determine whether coal pre-drying will affect the behavior of the low concentrations of inorganic species present in coal during combustion. A drop tube furnace was used to generate chars and ashes from both wet and dry coal. Raw coal, char, and ash were then analyzed for the presence of inorganic species (i.e., Na, Mg, Ca, K, S, Si, Al, Fe, and Ca) using X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDX). There were no major differences observed between the ash formation during combustion of dry and wet coal within the temperature ranges investigated. However, there may be other implications, such as higher furnace temperature and heat flux and slagging in the furnace. This may change the ashing behavior, which warrants further investigation. Chars contained Na, Mg, and Cl bound to the char matrix and an array of excluded minerals present in low concentrations. At 800 °C, more metals were lost from wet coal than dry coal during pyrolysis. This was possibly due to the inability of the metals to migrate back into the char matrix during rapid drying prior to pyrolysis. Char formed at 1000 °C seemed to be unaffected by the coal moisture content, likely because the rate of decomposition reactions at that temperature become significant, leading to the loss of inorganics from the char matrix as well as the coal moisture. An increase in the ratio of C–Cl to inorganic chlorine was observed with an increasing temperature. This may mean that the propensity for the formation of polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) is increased in the dry coal case, given that that the particle temperature during coal pyrolysis is increased with a decreased moisture content. The pyrolysis rate was found to be similar for both dry and wet coal, meaning that the assumptions used in computational fluid dynamic (CFD) modeling for predicting the outcomes of changes to operating conditions in industrial boilers will still stand with pre-dried coal as the input.

Comparison of the levels of dioxins and dioxin‐like compounds in blood and milk in grazing beef cows

AbstractTo characterize the transfer profiles of dioxins and dioxin‐like compounds from the blood to milk in grazing beef cows, seven polychlorinated dibenzo‐para‐dioxins (PCDD), 10 polychlorinated dibenzofurans (PCDF) and 12 coplanar polychlorinated biphenyls (Co‐PCB) were analyzed in blood and milk samples collected from four Japanese Black cows at parturition, 1 and 2 months postpartum. The mean toxic equivalent quantities (TEQ) of all three stages normalized by lipid content were 2.94 ± 0.35 and 7.83 ± 0.33 pg TEQ g−1 in the blood and milk, respectively. The total TEQ levels were highly correlated with each other in blood and milk samples (r = 0.58, P &lt; 0.05). Temporal TEQ profiles of PCDD, PCDF (PCDD/F) and Co‐PCB were similar to those of the total TEQ. Regarding individual congeners, blood levels remained almost stable during the first 2 months after parturition irrespective of lactation length. Concentrations of highly chlorinated PCDD/F were significantly higher in colostrum than in mature milk, whereas no differences were found in their concentrations between milk samples collected 1 and 2 months after freshening. In contrast, concentrations of several Co‐PCB congeners were higher in milk collected at 2 months postpartum than in colostrum on a lipid weight basis. Furthermore, concentrations of octachlorodibenzo‐para‐dioxin and 2,3′,4,4′,5,5′‐hexachloro‐biphenyl in milk samples were significantly lower than those in blood samples, whereas milk concentrations of the other congeners were equivalent to or higher than blood concentrations of themselves. These results suggest that milk levels of dioxins and dioxin‐like compounds reflect the blood concentrations in beef cows, and that highly chlorinated PCDD/F congeners are hard to transfer from blood circulation to mature milk compared with colostrum, whereas most of Co‐PCB are readily excreted in both colostrum and mature milk.

Concentration of polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans and dioxin-like PCBs in human adipose tissue from Turkish men

There is no previous report from Turkey on chemically determined polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (PCBs) in human tissues expressed as World Health Organization (WHO) toxic equivalents (TEQs). The objective of this study was to determine the occurrence of PCDDs/Fs, and dioxin-like PCBs in the general adult Turkish population. For this reason we measured adipose tissue concentrations of PCDDs/Fs and dioxin-like PCBs in 23 Turkish men living in Ankara,Turkey in 2004. PCDD/F concentrations ranged between 3.2 and 19.7 pg WHO-TEQ/g fat (5.34 and 42.7 WHO-TEQ/g fat, respectively, including dioxin-like PCBs). The mean concentrations of WHO PCDD/F-TEQ and WHO PCB-TEQ were 9.2 and 6.67 pg/g on a lipid basis , respectively. Samples were analyzed for PCDD/F and twelve dioxin-like PCB congeners using high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). This study is very important since it is the first report on PCDDs/Fs and dioxin-like PCB contamination in human adipose tissue from Turkey.

Breast Milk Dioxins in Hong Kong and Pearl River Delta

There are no previous reports from South China on chemically determined polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like poly-chlorinated biphenyls (PCBs) in human breast milk expressed as World Health Organization (WHO) toxic equivalents (TEQs). In a 2002–2003 WHO exposure study, 13 pools of breast milk comprising samples from 316 primiparous women in Hong Kong in 2002 were analyzed by gas chromatography/mass spectrometry for 29 PCDD/F and dioxin-like PCB congeners. Total WHO-TEQs ranged from 8.97 to 16.7 pg/g fat (weighted mean, 12.9 pg; weighted median, 13.4 pg). Variations in TEQs included positive associations with age (R2 = 0.73, p < 0.0005), higher consumption of dairy products and seafood, and lower TEQs in overseas mothers and ever-smokers. Congener profiles indicated geographic specificity of exposure in Hong Kong, mainland China, and overseas Asian countries, including higher proportions of PCB-TEQs (overseas) and PCDF-TEQs (mainland China). The median TEQs of PCDD/Fs (8.69 pg/g fat) and PCBs (4.73 pg/g fat) in Hong Kong were highest among the five Asian Pacific countries but lower than the levels for at least half of the European countries that participated in the WHO study. However, future international studies should incorporate mother’s age in the design of the pooling strategy to allow standardization by other exposure factors and valid comparisons among different countries. The findings allow support for the WHO breast-feeding advisory. Trends in human dioxin levels in the region cannot yet be determined, and rigorous controls are needed to reduce emissions of dioxins and human exposure in mainland China.

Characterization of dioxin exposure in residents of Chapaevsk, Russia.

Since 1967, a chemical plant in the town of Chapaevsk (Samara province, Russia) has produced large amounts of chlorinated compounds and is suspected to be a major source of local environmental dioxin contamination. Dioxins have been detected in the local air, soil, drinking water, vegetables, and cow's milk. Human exposure to dioxins is suspected as a factor in the deteriorating local public health. In an effort to characterize nonoccupational dioxin exposure among local residents, during the summer of 1998, 24 volunteers were recruited to donate blood and to provide information about their residence, employment, demographics, medical history, and dietary habits. Selected polychlorinated dibenzodioxins, dibenzofurans, and coplanar biphenyls were measured in blood serum samples. The mean concentration of total dioxin World Health Organization toxic equivalents (WHO-TEQ(98)) based on polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) was 61.2 (range 16.4-168.1) pg/g lipid. Subjects living in close proximity to the plant (less than 5 km) had significantly higher dioxin levels (mean WHO-TEQ(98), 75.7 pg/g lipid), as compared to subjects living more than 5 km from the plant (mean WHO-TEQ(98), 44.1 pg/g lipid) (P<0.04). Comparisons of the study results with available published data indicate that average blood dioxin levels were substantially higher in Chapaevsk residents than in nonoccupationally exposed populations of other parts of Russia, Europe, and North America. Chronic exposures of such magnitude may have appreciable adverse effects on public health.

Electrostatic Potentials and CoMFA Analysis of Toxicity of Dioxins

The structures of dioxins were optimized by the ab initio molecular orbital method at the HF/6-31G* level with the Gaussian 98 program package, and then electrostatic potentials were mapped out to explore the pharmacophore image of the receptor complementary to that. The maps were additive on the constitutional atoms, showing similarly the negative values around the oxygen and chlorine atoms and the positive values around the carbon and hydrogen atoms; and with the similarity of the molecular shapes, the applicability of the Comparative Molecular Field Analysis (CoMFA) was anticipated. Total 18 compounds, to which the toxic equivalency factors (WHO-TEF) are given, were used for CoMFA. These compounds consist of three congeners: polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar poly-chlorinated biphenyls (Coplanar PCBs). CoMFA was executed by using the receptor binding avidities (EC50) as the activity. The receptor was rat hepatic cytosol aryl hydrocarbon receptor (AhR). The structures were superimposed by fitting pairs of atoms so as to minimize RMS of the distances. As the template molecule 1, 2, 3, 7, 8-PeCDD was selected. PCDFs were superimposed to PCDDs in planar position, but twisted PCBs went through from one side of PCDD to the other side. Electrostatic potential derived charges of CHelpG by ab initio HF/6-31G* calculations were given to the structures. Partial least squares gave a cross-validated correlation coefficient q² = 0.955 at the number of components 3. From the correlation, extrapolation to the higher value of bromine derivatives as 2, 3, 7, 8-TBrDD and interpolation to the lower value as 1, 3, 7, 8-TCDD were done.

Contaminant‐related disruption of vitamin a dynamics in free‐ranging harbor seal (Phoca vitulina) pups from british columbia, canada, and washington state, usa

AbstractMarine mammals can bioaccumulate high concentrations of lipophilic environmental contaminants, such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo‐para‐dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs), through the diet. Both laboratory and wildlife studies have shown that these persistent chemicals can disrupt the regulation of vitamin A (retinol), a dietary hormone required for immune function, reproduction, growth, and development. To determine whether environmental contaminants affect the circulatory vitamin A dynamics of free‐ranging harbor seals (Phoca vitulina), we live‐captured 61 pups from British Columbia, Canada, and Washington State, USA, and obtained blood and blubber biopsy samples. Harbor seal pups from Washington State were six times more contaminated with total PCBs than pups from British Columbia and had significantly lower circulatory retinol levels. However, when data were corrected for differences in nursing status and analyzed as ungrouped sets of data, circulatory retinol levels were positively correlated with contaminant levels in the blubber of nonnursing pups. This increase in retinol may have resulted from a mobilization of liver vitamin A stores into circulation following exposure to milk‐derived contaminants; this has been observed in laboratory animals exposed experimentally. The contaminant‐related disruption of vitamin A dynamics observed in our study occurs at a time when vitamin A is required for growth and development.

Vitamin A physiology and its application as a biomarker of contaminant-related toxicity in marine mammals: a review.

In recent decades, marine mammal populations living in highly polluted areas have experienced incidences of low reproductive success, developmental abnormalities and disease outbreaks. In many of these cases, environmental contaminants were suspected as causal or contributing factors. However, demonstrating a mechanistic link between contaminant exposure and effect in marine mammal populations has proven challenging. Consequently, the development and application of relatively noninvasive biomarkers represents a potentially valuable means of monitoring wildlife populations exposed to elevated levels of contaminants. One touted biomarker is vitamin A (retinol), a "dietary hormone" whose metabolites are required for reproduction, growth, development, immune function, vision and epithelial maintenance. Laboratory studies have shown that many contaminants, including polychlorinated biphenyls (PCBs), polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), can disrupt vitamin A physiology and alter the distribution of its essential metabolites. Field studies suggest that complex environmental mixtures of these chemicals can also interfere with vitamin A dynamics in free-ranging marine mammals and other fish-eating wildlife. However, circulatory retinol, which is the least invasive measurement of vitamin A status, appears to have variable responses to contaminant exposure. In addition, "normal" circulatory retinol levels have not yet been described for most wildlife species, and not enough is known about the natural physiological events that can alter these concentrations. Confounding factors must therefore be characterized before retinoids can be used as an effective indicator of adverse health effects in marine mammals exposed to elevated levels of environmental contaminants.

Assessment of dioxins in foods from animal origins.

Dioxin is the common name for 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) but is also used for the structurally and chemically related polychlorinated dibenzo-para-dioxins (PCDD), dibenzofurans (PCDF), and the coplanar polychlorinated biphenyls (PCB). There are 75 PCDD congeners, 135 PCDF, and 209 PCB. Seven PCDD and 10 PCDF with substitutions at the 2,3,7, and 8 positions are considered toxic, and 11 PCB have dioxin-like toxicity. The majority of toxic dioxin is and(or) has been derived from industrial chlorination processes, incineration of municipal waste, and production of certain herbicides. The potential for health risks due to the cancer-promoting, immunomodulating, and teratogenic activities of dioxins in rodents has raised concerns over their presence in the human food chain. The lipophilic nature of dioxins results in higher concentrations in the fat of animal and fish products, and their excretion via milk secretion in dairy cattle may result in relatively high concentrations of dioxin contamination in high-fat dairy products. Surface contamination of plant foods and soil due to deposition of atmospheric emissions may also be a significant direct source of dioxin ingestion for livestock and thereby an indirect source of dioxin for humans. Despite numerous epidemiological studies, dioxin has not been conclusively determined to be problematic for humans. Certain management practices such as trimming fat from meat, consuming low-fat dairy products, and simply cooking food can substantially decrease exposure to dioxin compounds.

Distribution and partitioning of polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls in the Humber Estuary, UK

The distribution and concentration of polychlorinated dibenzo-para-dioxins (PCDDs), polychlorinated dibenzo-furans (PCDFs) and polychlorinated biphenyls (PCBs) in Humber Estuary bed sediment and in suspended particulate matter were extensively studied. Dioxin concentrations in sediments ranged from below detection to 3830 pg g −1 and PCB concentrations were from nondetectable to 84 ng g −1. These concentrations were low in comparison to other estuaries. The concentrations of chlorinated organics were found to be correlated with sediment lipid content, which is a significant factor in determining the contaminant distribution in the Humber Estuary. Laboratory experiments were carried out using 14C-radiolabelled compounds to determine partition coefficients ( K D). A K D of 2.5 × 10 5 was determined for 2,3,7,8-TCDD and that of 6.4 × 10 4 for 2,2′,5,5′-TCB; these did not vary significantly with salinity. There was no evidence in either the concentration data or the homolog profiles that contamination from tributaries to the Humber Estuary had penetrated the estuary in significant quantities.

The Estuarine Clam Rangia cuneata as a Biomonitor of Dioxins and Furans in the Neches River, Taylor Bayou, and Fence Lake, Texas

Polychlorinated dibenzo-para-dioxins (PCDDs) and dibenzofurans (PCDFs) were measured in the tissues of the estuarine clamRangia cuneata at four sites in the Neches River that had been subjected to paper mill effluent and at two remote sites. One of the river samplings was taken before dioxin control measures and another 2 yr after the control measures began. Measurable concentrations of PCDD/Fs were present at all sites, but higher concentrations were present at the Neches River sites. Whole tissue concentrations of 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) and all PCDD congeners for the two collections were not significantly different (p>0.05), but lipid-normalized concentrations for the two collections were significantly different (p<0.05). Highest concentrations of PCDDs at sites located 8 km and 16 km upriver from the paper mill effluent outfall indicated that the materials were transported upriver by saltwater intrusion and/or that nonpoint sources existed upriver. The presences of PCDD/Fs in clam tissues from the remote sites also indicated that other sources of these materials existed. Even under extreme physiological conditions (spent reproductive phase, low lipid contents, water temperature 10°C; ripe reproductive phase, high lipids, water temperature 32°C)Rangia cuneata was an effective biomonitor to determine the distribution of PCDD/Fs at specific sites. *** DIRECT SUPPORT *** A01BY069 00021

Polychlorinated Dibenzo-para-dioxins and Polychlorinated Dibenzofurans in Sediments from U.K. Estuaries

Concentrations of polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) have been determined in sediments from U.K. coastal locations adjacent to the estuaries of the Dee, Humber, Mersey, Tees, Tweed and Tyne and from an offshore site in Morecambe Bay. The sediments had total PCDD/DF concentrations of <100 pg g -1, except for the Dee and Morecambe Bay which had total PCDD (total PCDF) concentrations of 750 (390) and 207 pg g -1 (116 pg g -1), respectively. However, estuarine sediments collected during axial transects of Dee, Humber and Clyde Estuaries had total PCDD (total PCDF) concentrations in the range 530-1880 (340-710), 300-1890 (260-1240) and 290-4670 pg g -1 (100-1540 pg g -1), respectively. Examination of the homologue groups showed that about 70% of PCDDs were in the octa-chlorinated form in the Dee and Clyde, whereas for PCDFs the hepta- and hexa-chlorinated forms were relatively more important. The association of PCDD/DFs with particle surfaces was interpreted using data on sediment characteristics and a two-stage adsorption model. The conclusions from this study have implications for the estuarine transport of PCDD and PCDF and their uptake by benthic organisms.