Lipid Basis Research Articles

Coronary heart disease is a multifactorial disease

Coronary heart disease (CHD) is the leading cause of death in the Western World. For effective treatment and prevention strategies to be put in place, the major risk factors associated with this disease must be identified. Data show that almost 300 variables are statistically associated with CHD. However, evidence suggests that the vast majority of coronary events can be explained on the basis of blood pressure, lipids, smoking, and diabetes. Laboratory, experimental, and epidemiologic data identify dyslipidemia as a pivotal CHD risk factor, in the absence of which other risk factors cease to produce any important increase in absolute risk of events. For example, in populations with relatively low levels of low-density lipoprotein cholesterol, such as China and Japan, the incidence of CHD remains low even when smoking and hypertension are highly prevalent. Observational data have clearly established that CHD risk factors tend to cluster in individuals. The impact of coexisting risk factors is greater than additive, and indeed is usually multiplicative. The implications of such an interactive effect are that relatively normal levels of two or more risk factors in coexistence may have a profound impact on risk. Despite these findings, in the past most treatment algorithms have viewed risk factors separately and have recommended discrete treatment targets. More recent guidelines have taken a broader view and provide simple, yet accurate, methods of evaluating absolute risk based on the consideration of several risk factors. Coronary heart disease is clearly a multifactorial disease with risk factors that tend to cluster and interact in an individual to determine the level of coronary risk. The current trend towards a more holistic approach in CHD risk evaluation and preventive management appears logical based on evidence from animal-experimental, observational, and clinical trial evidence.

Relation of Lake Ontario Fish Consumption, Lifetime Lactation, and Parity to Breast Milk Polychlorobiphenyl and Pesticide Concentrations

Lactating female members and spouses of male members of the New York State Angler Cohort who agreed to provide breast milk samples were the subjects of this study. Questionnaires were provided to participants focusing on Lake Ontario fish consumption, reproductive history, and lactation history. Milk samples were analyzed for 77 polychlorinated biphenyls (PCB) congeners, 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (DDE), a metabolite of dichlorodiphenyltrichloroethane (DDT), hexachlorobenzene (HCB), and 1,1a,2,2,3,3a, 4,5,5,5a,5b,6-dodecachlorooctahydro-1,3,4-methano-1H-cyclobuta[cd]pentalene (Mirex). The percentage of samples with quantifiable levels, above the limit of detection (LOD), varied among the individual congeners from 10 to 100%. Nine PCB congeners (designated by their IUPAC No.) and DDE were found in all of the 100 samples analyzed. These include the following, in decreasing order of concentration: DDE>153>138>180>118>187>188>177>200. Total PCB concentrations were estimated by taking the sum of the concentrations of all PCB congeners (up to 77 congeners) above their respective LOD in a given sample. PCB concentrations increased with increasing concentration of milk lipid. Lipid adjusted PCB concentrations increased as a function of maternal age. PCB congener profiles in milk favored the higher chlorinated congeners, with the four highest congeners having 5 to 7 chlorine atoms. Fish eaters had a significantly higher level of several major PCB congeners with congeners 153 and 138 being 1.36 and 1.34 times higher, respectively. PCB and DDE concentrations, expressed on a lipid basis, varied inversely with parity. The total number of months of lifetime lactation varied inversely with the total PCB concentration in breast milk. A similar relationship was evident for DDE. These data are of use for risk assessment in estimating the relative exposure to these environmental contaminants in breast fed infants whose mothers consumed contaminated Lake Ontario fish.

Heavy metals and chlorinated hydrocarbon concentrations in the red fox in relation to some biological parameters

Heavy metals and organochlorine contamination were analyzed in tissues of red foxes (Vulpes vulpes) from the Province of Siena (central Italy). Mercury (Hg), cadmium (Cd) and lead (Pb) concentrations were assessed in liver tissues and the data were analyzed for differences in relation to sex and age. Overall Hg, Cd and Pb mean values were 0.16, 0.62 and 0.64 μg g_1 d.w., respectively. HCB, DDT and PCB concentrations were assayed in fatty tissues and muscle. The highest levels of those pollutants were found in muscle (0.47, 1.16 and 20.2 μg g_1 lipid basis of HCB, DDTs and PCBs respectively), rather than in fat (0.23, 0.49 and 7.2 μg g_1 l.b. of HCB, DDTs and PCBs respectively). Pollutant accumulation was analyzed in relation to sex, age and sexual maturity of females.

Decrease in levels and body burden of dioxins, dibenzofurans, PCBS, DDE, and HCB in blood and milk in a mother nursing twins over a thirty-eight month period

This paper presents measured dioxin, dibenzofuran, PCB, DDE and HCB blood and milk levels and estimated body burdens in a mother who nursed twins for thirty-eight months. A total of thirteen milk samples and three blood samples were collected and analyzed. Measured PCDD and PCDF levels in milk decreased from 309 and 21 ng/kg (ppt) to 173 and 9 ng/kg, respectively, between March 1993 and September 1995. Based on the decrease in breast milk dioxin levels, we estimate that the nursing mother reduced her dioxin body burden from 310 to 96 ng dioxin toxic equivalents (TEQs), or approximately 69%. In two and one half years the level of HCB in the mother's milk decreased from 10.7 to less than 1.8 ng/g (ppb), the level of DDE decreased from 246 to 46 ng/g and the total level of non-coplanar PCBs decreased from 285 to 63 ng/g, on a lipid basis. We estimate that the twin's consumption of dioxins, dibenzofurans, and coplanar PCBs from breast feeding was approximately 115 ng TEQ per twin.

Application of biomarkers for exposure and effect of polyhalogenated aromatic hydrocarbons in naturally exposed European otters ( Lutra lutra)

In the serious decline of European otters ( Lutra lutra) over the last decades, polychlorinated biphenyls (PCBs) are considered to be one of the major factors. As no experiments can be conducted with otters, an eco-epidemiological study was performed to derive no observed effect concentrations (NOECs) for PCBs in the otter. A strong negative correlation was found between hepatic vitamin A and polychlorinated biphenyl (PCB) concentrations expressed as TCDD-equivalents (TEQs), coinciding with a higher incidence of infectious diseases. The no-effect concentration for vitamin A reduction was 2 ng TEQ/g lipid, 10-fold reduction was already found in animals with 5 ng TEQ/g lipid. The TEQ-levels measured with a reporter gene assay based on chemical-activated luciferase expression (the CALUX assay) correlated well with the TEQ levels calculated based on non- and mono- ortho PCB concentrations. The TEQ levels in blood and liver correlated well when expressed on a lipid basis. In living captive otters blood plasma TEQ levels (either measured based on gas chromatography (GC) or CALUX measurement) were lower than in the feral otters, and positively correlated with plasma total and free thyroid hormone but not with plasma retinol levels. Hepatic vitamin A concentration was found to be a physiologically relevant effect parameter. The NOEC for hepatic vitamin A reduction was translated into TEQ levels in fish and sediment. The CALUX response in 50–500 μl blood plasma proved to be a sensitive non-destructive biomarker for quantification of internal TEQ levels.

Pipoprotein Lp(a): Effects of allelic variation at the LPA locus

Concentrations of the lipoprotein Lp(a) vary widely in healthy individuals, but in many studies, high concentrations are strongly associated with cardiovascular disease. On the basis of lipid and protein composition, Lp(a) is a variant of the atherogenic low-density lipoprotein but differs in possessing the unique apolipoprotein(a) [apo(a)]. Lp(a) concentrations are controlled at the level of biosynthesis of the apo(a) protein, which is encoded by the LPA locus, and allelic differences at LPA are responsible for the bulk of variation in Lp(a) phenotype. In this article we describe several aspects of allelic variation at LPA reported in studies of humans and baboons, including (1) polymorphisms for protein size, (2) families of alleles having distinct relationships between apo(a) size and Lp(a) concentration, (3) sequence polymorphisms, (4) a group of alleles whose protein products have a multibanded phenotype, and (5) allelic diversity of null phenotype alleles (whose protein products are not detected in the plasma). The data make clear that no single aspect of allelic variation at LPA is sufficient to fully explain the genetic control of Lp(a). J. Exp. Zool. 282:54–61, 1998. © 1998 Wiley-Liss, Inc.

Pipoprotein Lp(a): Effects of allelic variation at theLPA locus

Concentrations of the lipoprotein Lp(a) vary widely in healthy individuals, but in many studies, high concentrations are strongly associated with cardiovascular disease. On the basis of lipid and protein composition, Lp(a) is a variant of the atherogenic low-density lipoprotein but differs in possessing the unique apolipoprotein(a) [apo(a)]. Lp(a) concentrations are controlled at the level of biosynthesis of the apo(a) protein, which is encoded by the LPA locus, and allelic differences at LPA are responsible for the bulk of variation in Lp(a) phenotype. In this article we describe several aspects of allelic variation at LPA reported in studies of human and baboons, including (1) polymorphisms for protein size, (2) families of alleles having distinct relationships between apo(a) size and Lp(a) concentration, (3) sequence polymorphisms, (4) a group of alleles whose protein products have a multibanded phenotype, and (5) allelic diversity of null phenotype alleles (whose protein products are not detected in the plasma). The data make clear that no single aspect of allelic variation at LPA is sufficient to fully explain the genetic control of Lp(a).

Temporal variation of organochlorine contaminants in the zebra mussel Dreissena polymorpha in Lake Erie

Zebra mussels ( Dreissena polymorpha) are commonly employed as contaminant biomonitors in Europe and North America. Accumulation of hydrophobic, organochlorine contaminants into an organism depends, in part, on the organism's lipid content. In this study, we assess the influence of temporal variation in lipid content and reproductive activity on contaminant dynamics in zebra mussels collected from the western basin of Lake Erie. Mussels spawned twice during 1995, first in June and again in August. Lipid content of mussels was highest following the first spawning event and declined thereafter. Lipid-adjusted concentrations of moderately hydrophobic (mid- K ow) compounds were much higher than those of either low or high hydrophobicity. Principal component analysis (PCA) of seasonal variation of concentrations of nine compounds revealed two primary axes, the first determined by mid- and high- K ow compounds (PCBs 52, 101, 118, 153, 138 and 180), the latter by a low K ow compound (hexachlorobenzene). A second principal component model separated physiological, environmental and temporal factors. Variation in mid- and high- K ow compounds corresponded with precipitation and reproductive status of mussels. By contrast, variation in hexachlorobenzene concentration was associated with lipid content and reproductive cycle. Concentrations of all nine compounds did not differ significantly between gravid and laboratory-spawned mussels, indicating that the effect of reproduction may be decoupled from the actual spawning event. Concentrations did not differ between spent male and female mussels. Examination of lipid composition revealed that neutral lipids comprise only 39% of total lipids in zebra mussels. Concentrations of PCBs with log K ow>5.71 were more highly correlated with neutral than with total lipid content, indicating that concentration normalization on a neutral lipid basis may be more appropriate than adjustment based on total lipid. Results from this study indicate that reproductive status and lipid content affect contaminant dynamics in zebra mussels and that these factors require consideration when mussels are deployed as biomonitors.

Comment on “Accumulation of Organochlorine Pesticides and PCBs by Semipermeable Membrane Devices and Mytilus edulis in New Bedford Harbor”

We deployed semipermeable membrane devices (SPMDs) and transplanted blue mussels (Mytilus edulis) side-by-side at five sites in New Bedford Harbor, MA. A good correlation was obtained between accumulation in the SPMDs and the caged mussels, with r 2 values ranging from 0.57 to 0.85 for individual pesticides (n = 16) and from 0.81 to 0.96 for individual PCB congeners (n = 20). An excellent correlation also was found between the log K ow and the log BAF (bioaccumulation factor in mussels) and between the log K ow and log AF (accumulation factor in SPMDs). Accumulation in the mussels was approximately 2-fold higher than in the SPMDs when concentrations were expressed on a lipid basis. These correlations are significantly better than any reported previously and probably result from modifications that we made to the original design of the SPMD. A close examination of accumulation into SPMDs demonstrates that the uptake rate and equilibrium status of an SPMD can be easily manipulated by modifying membrane thickness, surface area, and lipid substrate volume. Knowledge of these parameters and their effect on SPMD uptake rates is critical to the interpretation of SPMD data and can be used to optimize the design of SPMDs for specific applications.

Critical considerations on the analysis and bioaccumulation of musk xylene and other synthetic nitro musks in fish

Several analytical methods for the residue analysis of musk xylene (MX), musk ketone (MK), and other nitro musks in fish are presented and discussed. In particular because of a publication about a fast and simple analysis without any clean-up procedure, the necessity of a thorough clean-up of fatcontaining samples is emphasized. In addition, the present knowledge about the high bioconcentration of these lipophilic pollutants in fish is summarized. In a long-term bioconcentration study we found in rainbow trouts bioconcentration factors (BCF) on a wet weight basis (BCF w) of MX from 4,200 to 5,100 while the BCF values on a lipid basis (BCF L) ranged from 115,000 to 122,000. These BCF values of MX are in good agreement with the BCF values calculated from the noctanol/water partition coefficient (log K OW = 4.90) using the Quantitative Structure-Activity Relationship (QSAR). A published study with extremely low bioconcentration factors of MX is critically discussed.

Half-lives and bioconcentration of lindane (γ-HCH) in different fish species and relationship with their lipid content

In this investigation it is demonstrated that the half-lives of the insecticide lindane (γ-HCH) in mussels and different fish species are dependent on their lipid content. It is found that the bioconcentration factors on a wet weight basis (BCF w) of γ-HCH in different aquatic organisms such as mussels, Daphnia, and fishes range from 43 to 4240. It is further demonstrated that the bioconcentration factors on a wet weight basis are positively correlated with the lipid content (%). The mean bioconcentration factor on a lipid basis (BCF L) of γ-HCH is 11,000. This BCF L value is in satisfactory agreement with the log K ow value of lindane (4.10).

ELIMINATION OF β-HEXACHLOROCYCLOHEXANE IN OCCUPATIONALLY EXPOSED PERSONS

The elimination offi-hexachlorocyclohexane ($-HCH) in humans was investigated in a group of 40 former workers of a lindane-producing plant by analyzing at least 2 blood specimens (3 specimens in 3 workers) from different time points. Assuming a first-order kinetic model for excretion, the median half-life of$-HCH is 7.2 yr calculated by concentrations in whole blood and 7.6 yr calculated by concentrations in extractable lipids. In univariate analyses an influence of age, percent body fat, and liver disease (additionally in whole blood an influence of contents of extractable lipids) on clearance was observed. All factors show a positive correlation with half-life. According to a multiple regression model, influence of percent body fat calculated according to Deurenberg et al. (1991) is an important covariate in the description of the variations of the clearance rate (calculated on the basis of extractable lipids) of$-HCH. The data support the assumption of first-order kinetics.

Bioaccumulation of polychlorinated biphenyls (PCBs) in the marine pelagic food web, based on a seasonal study in the southern Gulf of St. Lawrence, 1976–1977

Polychlorinated biphenyls (PCBs) were quantified in bulk seawater (3.1 ± 1.0 ngl−1, N = 3) in 1976, in plankton (2.9 ± 3.3 ng g−1 wet weight, N = 176) in 1976 and 1977 and in fish (155 ± 194 ng g−1 wet weight, N = 135) in 1977 collected from St. Georges Bay in the southern Gulf of St. Lawrence. PCB concentrations in the plankton of the entire water column varied seasonally by ten times, with the highest values occurring in spring, lowest during summer and variable levels in late fall. The lower PCB levels in the total summer community coincide with a reduced biomass in certain size fractions in the Bay rather than a decrease in PCB concentration of the plankton. PCBs were concentrated in the middle-sized fractions of the planktonic community and this is attributed to the greater biomass present in these categories. PCB concentrations in plankton were most highly correlated with their lipid content at the time of sampling. Seasonal reductions of lipid in the plankton per m3 resulted in a higher concentration of PCB per unit lipid in the remaining community. Planktonic PCB concentrations, expressed on a lipid basis, are found to be correlated with cumulative rainfall 21 d before sampling for both years combined. Adult fish were more contaminated by PCBs than either their egg or juvenile stages. Mature gaspereau, herring and smelt had higher concentrations of PCB contamination than mackerel, capelin, white hake and silversides. No difference was found between PCB contamination of the sexes of fish species analyzed. PCBs were transferred from mother to offspring in fish, but at lower levels than the level present in the parent; and the maximum accumulation from the environment occurred between immature and adult fish. The best predictors of PCB contamination in fish in St. Georges Bay are lipid content followed by size and age. PCB concentrations in plankton, normalized to lipid content, did not increase with size or trophic level. PCB concentrations in fish increased with size and on average were ten times the levels found in plankton. Marine mammals collected by other researchers in the region during the 1970s had accumulated up to several orders-of-magnitude higher concentrations than those found in fish, with a more gradual increase with size of organism. Lipid content and age or exposure period appear to be the main factors which determine PCB concentrations in the marine food chain in the southern Gulf of St. Lawrence.

Lipid extraction from blood and biological samples and concentrations of dioxin-like compounds

The extraction of lipid from human blood and other biological materials in the determination of dioxin-like and organochlorine compounds has been studied using different amounts of extracting solvent. When large volumes of ethanol-hexane are used to extract small blood samples, the total lipid extracted is incomplete as the polar phospholipids do not partition into the organic phase. This failure to extract all the blood lipid results in an inaccurately high concentration expressed on a lipid basis and, by corollary, a high biased body burden. This solvent dependence of lipid extraction does not appear to be a problem for most other biological and food samples since over 90% of the lipid is in the form of readily extractable neutral glycerides.

Polychlorinated dibenzo- p-dioxins and polychlorinated dibenzofurans (P)CDD/PCDF) in food samples collected in Southern Mississippi, USA

In 1994, we analyzed 43 foodstuff samples from local supermarkets in southern Mississippi, USA, for PCDD/PCDF. 2,3,7,8-Cl 4DD could be quantified in 31 of these samples. On a lipid basis, levels in meat (0.53–1.10 pg I-TEQ/g) and dairy products (0.42–1.10 pg I-TEQ/g) were slightly lower than those reported from other industrialized countries. While levels in dairy samples from the United States and Europe are comparable, there is a difference in the contribution of individual congeners to the I-TEQ: for example, in milk samples from Germany approximately 40% of the I-TEQ is due to the presence of 2,3,4,7,8-Cl 5DF while in the Mississippi samples this congener only contributes 16%. The highest concentrations of PCDD/PCDF in our study were detected in the farm-raised catfish (10.2–27.8 pg I-TEQ/g). A unique finding was that in addition to the 2,3,7,8-substituted PCDD/PCDF the catfish samples contained many non-2,3,7,8-substituted congeners. This is unusual because vertebrate animals selectively eliminate or metabolize the non-2,3,7,8-substituted congeners.

Accumulation of Organochlorine Pesticides and PCBs by Semipermeable Membrane Devices and Mytilus edulis in New Bedford Harbor

We deployed semipermeable membrane devices (SPMDs) and transplanted blue mussels (Mytilus edulis) side-by-side at five sites in New Bedford Harbor, MA. A good correlation was obtained between accumulation in the SPMDs and the caged mussels, with r2 values ranging from 0.57 to 0.85 for individual pesticides (n = 16) and from 0.81 to 0.96 for individual PCB congeners (n = 20). An excellent correlation also was found between the log Kow and the log BAF (bioaccumulation factor in mussels) and between the log Kow and log AF (accumulation factor in SPMDs). Accumulation in the mussels was approximately 2-fold higher than in the SPMDs when concentrations were expressed on a lipid basis. These correlations are significantly better than any reported previously and probably result from modifications that we made to the original design of the SPMD. A close examination of accumulation into SPMDs demonstrates that the uptake rate and equilibrium status of an SPMD can be easily manipulated by modifying membrane thickness, surface area, and lipid substrate volume. Knowledge of these parameters and their effect on SPMD uptake rates is critical to the interpretation of SPMD data and can be used to optimize the design of SPMDs for specific applications.

Dioxins and dioxin‐like chemicals in blood and semen of American Vietnam veterans from the state of Michigan

This exposure assessment pilot study tested the hypothesis that elevated blood levels of the dioxin congener 2,3,7,8-TCDD (“TCDD”), due to Agent Orange exposure, in American Vietnam veterans could be demonstrated two to three decades after Vietnam service. A second objective was to determine if dioxins, including TCDD, are present in the semen of adult males. In the early 1990s, blood samples from 50 Vietnam veterans and three pooled semen samples from 17 of them were analyzed by high-resolution gas chromatography-mass spectroscopy for dioxins, dibenzofurans, and the dioxin-like PCBs. Fifty volunteers from the Michigan Vietnam veteran bonus list, which documented Vietnam service, were invited to participate based on their self-reported exposure to Agent Orange in Vietnam. Screening of military and medical records was performed by an epidemiologist and a physician to assure that Agent Orange exposure was possible based on job description, location of service in Vietnam, and military Agent Orange spray records. Elevated 2,3,7,8-TCDD levels, over 20 ppt on a lipid basis, could still be detected in six of the 50 veterans in this nonrandomly selected group. The dioxin and dibenzofuran congeners commonly found in the U.S. population, including TCDD, were also detected in the three pooled semen samples. Quantification and comparison on a lipid basis were not possible due to low lipid concentrations where levels were below the detection limit. Therefore, semen samples were measured and reported on a wet-weight basis. Elevated blood TCDD levels, probably related to Agent Orange exposure, can be detected between two and three decades after potential exposure in some American veterans. Original levels were estimated to be 35–1,500-fold greater than that of the general population (4 ppt, lipid) at the time of exposure. In addition, the detection of dioxins in semen suggests a possible mechanism for male-mediated adverse reproductive outcomes following Agent Orange or other dioxin exposure. © 1996 Wiley-Liss, Inc.

Multivariate modeling of pcb bioaccumulation in three-spined stickleback (Gasterosteus aculeatus)

Three-spined sticklebacks were exposed to 20 polychlorinated biphenyls (PCBs) through gastrointestinal intake. The PCBs, viz. 2,2{prime},3,4-TeCB, 2,2{prime},4,6{prime}-TeCB, 2,3,3{prime},5{prime}-TeCB, 2,3,4,4{prime}-TeCB, 2,3{prime},4,5{prime}-TeCB, 3,3{prime},4,5-TeCB, 2,2{prime},3,4{prime},6-PeCB, 2,2{prime},4,4{prime},5-PeCB, 2,2{prime},4,6,6{prime}-PeCB, 2,3,3{prime},5,6-PeCB, 2,3,4,4{prime},6-PeCB, 3,3{prime}4,4{prime}5-PeCB, 2,2{prime},3,4,5,6{prime}-HxCB, 2,2{prime},4,4{prime},5,5{prime}-HxCB, 3,3{prime},4,4{prime},5,5{prime}-HxCB, 2,2{prime},3,3{prime},4,5,6-HpCB, 2,2{prime},3,4,4{prime},6,6{prime}-HpCB, 2,2{prime},3,4{prime},5,6,6{prime}-HpCB, 2,3,3{prime},4,4{prime},5,6-HpCB, and 2,3,3{prime},4{prime},5,5{prime},6-HpCB, were selected by means of a full factorial design in combination with principal component analyses based on several physicochemical properties of tetra- through hepta-PCBs. After exposure to the training set, pooled samples of the sticklebacks were analyzed by GC-MS after lipid determination and cleanup using Florisil open-column chromatography. Bioaccumulation factors (BAFs) were calculated on a lipid basis by dividing the PCB concentrations in the fish by the respective concentrations in the feed. Higher chlorinated PCBs showed, in general, higher bioaccumulation than the lower chlorinated congeners. Polychlorinated biphenyls with vicinal hydrogens in the meta- and para-positions exhibited low bioaccumulation. Finally, 18 of the 20 measured BAFs were used to calculate a multivariate quantitative structure-activity relationship (QSAR) by means of partial least squares fitting to latent structures. By applying this QSAR, the bioaccumulation potentials of 136 nontested tetra- through hepta-PCB congeners were predicted.

Seasonal Fluctuation of Organochlorines in Mytilus Edulis L. from the South West Baltic Sea

Seasonal and spatial variations in organochlorine concentrations in mussels Mytilus Edulis from the Baltic Sea were assessed The mussels from highly contaminated harbour areas showed a strong short term fluctuation in comparison to mussels from less contaminated beach areas. In all observed stations, PCB concentrations increased during autumn and decreased during early and late summer. Their change correlated positively with their lipid content. The reduction of the residue level during summer could be related with spawning activity. During winter the change in PCB concentration in observed stations were not uniform. The strongly elevated accumulation during winter, which was found at most harbour stations, may be caused by diminished Filtration activity due to increased stress. The pattern of seasonal change expressed on a dry weight and lipid weight basis was different. The change of PCB concentration on a lipid basis resulted from a dilution effect during seasonal lipid accumulation and a concentration effect during utilisation and release of body lipids. On a lipid weight basis therefore the actual exchange of organochlorines in mussel tissue can not be observed.

Concentrations of polychlorinated dibenzo- p-dioxins and dibenzofurans in human placental and fetal tissues from the U.S. and in placentas from Yu-Cheng exposed mothers

We report the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) found in human placentas and fetal tissue from the U.S. and in placentas from Yu-Cheng mothers. In placental material from sources in the U.S. we found concentrations, expressed as dioxin toxic equivalence (TEQ) values and on a lipid basis, between 8.4 and 17.6 ng/kg. In a pooled sample of fetal tissue (8–14 week) the concentration, 5.3 ng/kg, was somewhat smaller. In placental material from Taiwanese Yu-Cheng subjects much higher concentrations were found, in the range 610 to 9010 TEQ ng/kg, again on a lipid basis.