John Jake Ryan

Polybrominated Diphenyl Ethers: Human Tissue Levels and Toxicology

PBDEs are being released to the environment in wastes from their production facilities, degradation, or leaching and volatilization from products that contain PBDEs during the products useful life. Brominated diphenyl ether congeners BDE-47, -99, and -153 are ubiquitous in the environment and are regarded as the most dominant congeners present in wildlife and humans. The tetra- to hexa-BDE are most likely the congeners to which humans are exposed through food consumption. Knowledge of PBDE uptake, metabolism, elimination, and enzyme induction is restricted largely to rodents (rats and mice) in vitro and in vivo. Feeding studies have shown that excretion of higher brominated BDEs is much greater than lower brominated BDEs. Penta-BDE is more toxic than octa- and deca-BDE following oral administration (oral LD50 in rats, 0.5-5 g/kg). In rodents, repeated exposure to PBDEs results in thyroid hormone disruption, developmental neurotoxicity, some changes of fetal development, and hepatotoxic effects. The observed chronic NOELs depend upon the technical mixture type (i.e., deca-, octa-, or penta- and their congener composition), animal species, and study protocol. Values range from 0.6 to 100 mg/kg in rats and from I to 100 mg/kg in mice. PBDEs are neither mutagenic nor genotoxic. Immunotoxicity in mice is observed following exposure to BDE-47 at 18 mg/kg/d, where splenocyte number decreased. Mice exposed neonatally to a single oral dose of BDE-47(10.5 mg/kg) or BDE-99 (12 mg/kg) on Pnd10 (period of rapid brain growth and development) show permanent impairment of spontaneous motor behavior when reaching adulthood. BDE-99 also induced adverse effects on learning and memory functions of mice. The estimated daily intake based on food consumption for PBDEs ranges from 44 to 51 ng/d, with fish contributing almost one-half. The BDE-99 body burden from a human milk survey can be estimated at 0.64 microg/kg, well below the experimental body burden of 0.4 mg/kg BDE-99 associated with behavioral alterations in neonatal mice. When considering the outlier value for PBDE-99 at 229 ng/g, this would result in an estimated PBDE-99 body burden of 46 microg/kg, or a MOS of only 9. However, no toxicokinetics data are available for humans, and the actual margin of safety may be much smaller if based on levels in critical target organs or tissues.

Survey of Canadian human blood plasma for ochratoxin A.

Blood plasma samples collected from 144 healthy volunteers in 16 locations across Canada in 1994 were analysed for ochratoxin A (OTA). The method of analysis included cleanup by C18 solid phase extraction and immunoaffinity columns followed by liquid chromatography (LC) with fluorescence detection, which gave 86.5% (s.d. = 9.7) recovery (n = 31) of OTA (added at 2 ng/ml) with a detection limit of 0.15 ng/ml. The arithmetic mean concentration found in the plasma samples, corrected for volume of anticoagulant added, was 0.88 ng/ml with a standard deviation of 0.35 ng/ml and a range of 0.29-2.37 ng/ml. Confirmation of identity of OTA was by methyl ester formation for 65 samples and by LC-tandem mass spectrometry for 17 samples (some of which were included in pooled samples). Statistical analysis, by ANOVA of the log OTA plasma concentrations, showed a highly significant effect due to location in Canada (p = < 0.0001) but no effect due to age, sex or blood group of donors. The highest mean concentration was found in Winnipeg, significantly different (p = 0.05) by the Student-Newman-Keuls multiple range test from the lowest levels found in Toronto, Vancouver and Saint John.

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 mothers 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 twins consumption of dioxins, dibenzofurans, and coplanar PCBs from breast feeding was approximately 115 ng TEQ per twin.

Musculoskeletal changes in children prenatally exposed to polychlorinated biphenyls and related compounds (Yu-Cheng children)

Fifty-five Yu-Cheng (oil-disease) children born between 1978 and 1985 to mothers who ate PCB-contaminated rice oil in 1978-1979 were studied and compared to age- and sex-matched control subjects in 1991. The childrens growth profiles, bone mineral density and soft tissue composition, joint laxity, and serum parathyroid hormone, vitamin D, calcium, alkaline phosphatase, and phosphate were compared. The Yu-Cheng children were 3.1 cm (p < .05) smaller and had less total lean mass and soft tissue mass as compared to the matched control subjects. All other parameters studied were similar in both groups. The shorter height and decreased total lean mass and soft tissue content were only seen in the Yu-Cheng children who were the first born after the ingestion, but not in subsequent children. This was most likely due to decreased body burdens of the PCBs and related contaminants over time in the mothers.

Patterns of PCBs and PCDD/PCDFs in chicken and pork fat following a Belgian food contamination incident

A food contamination incident involving polychlorobiphenyls (PCBs) and PCDD/Fs occurred in 1999 in Belgium. On heavily affected farms, concentrations of PCBs in chicken or pork fat exceeded the Belgium tolerance limit of 200 ng/g lipid weight for the sum of seven marker PCBs. Analysis of contaminated samples showed that the patterns for PCB and PCDD/F congeners differed among feed, chicken fat and pork fat. Lower chlorinated PCBs and polychlorodibenzofurans (PCDFs) including those with high TEFs (PCBs 105, 118, 126 and 2,3,4,7,8-PeCDF) were shown to either bioaccumulate more in chicken fat or to be eliminated more readily in pork. This leads to the possibility that consumption of chicken would result in a higher TEQ human body burden than that from the same consumption of pork. In addition, PCDF congeners with non-2,3,7,8-substitution (e.g., 1,2,4,7,8-PeCDF) were present in chicken fat but absent in pork fat. Since the residue pattern in this commercial episode changes less in the avian species, these results reinforce the value of birds rather than mammals as markers of the source of contamination with persistent organochlorine pollutants.

Correlations among Human Plasma Levels of Dioxin-Like Compounds and Polychlorinated Biphenyls (PCBs) and Implications for Epidemiologic Studies

Abstract In studies of the potential health effects of background-level exposure to organochlorine compounds (e.g., polychlorinated biphenyls, polychlorinated dibenzodioxins, and polychlorinated dibenzofurans), investigators have often measured either polychlorinated biphenyls or polychlorinated dibenzodioxins/polychlorinated dibenzofurans—but not both. We measured polychlorinated biphenyls (including specific non-, mono-, and di-ortho congeners) and specific polychlorinated dibenzodioxins/dibenzofurans among 63 Canadian blood donors. Levels of these compounds were, in general, fairly correlated. For example, Pearsons correlation coefficient between log total polychlorinated biphenyl and log total polychlorinated dibenzodioxins was .52. These results suggest that in epidemiologic studies of health effects of background-level exposures to these compounds, the quantitative dose-response relation observed for a given compound (or class of compounds acting through a similar mechanism) may easily be miscalibrated or confounded.

The brominated flame retardants, PBDEs and HBCD, in Canadian human milk samples collected from 1992 to 2005; concentrations and trends.

Human milk samples were collected from individuals residing in various regions across Canada mostly in the years 1992 to 2005. These included five large cities in southern Canada as well as samples from Nunavik in northern Quebec. Comparative samples were also collected from residents of Austin, Texas, USA in 2002 and 2004. More than 300 milk samples were analysed for the brominated flame retardants (BFRs), PBDEs and HBCD, by extraction, purification and quantification using either isotope dilution gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-MS. The Canadian total PBDE values in the years 2002-2005 show median levels of about 20μg/kg on a lipid basis; a value significantly higher than in the 1980s and 1990s. Milk samples from Inuit donors in the northern region of Nunavik were slightly lower in PBDE concentrations than those from populated regions in the south of Quebec. Milk samples from Ontario contained slightly lower amounts of PBDEs in two time periods than those from Texas. HBCD levels in most milk samples were usually less than 1ppb milk lipid and dominated by the α-isomer. This large data set of BFRs in Canadian human milk demonstrates an increase in the last few decades in human exposure to BFRs which now appears to have stabilized.

Neonatal and childhood teeth in relation to perinatal exposure to polychlorinated biphenyls and dibenzofurans: observations of the Yucheng children in Taiwan.

In order to determine the effect of perinatal polychlorinated biphenyls and dibenzofurans (PCBs/PCDFs) exposure on neonatal and childhood teeth in Yucheng children, we carried out complete dental examinations on 73 Yucheng children born to mothers who ingested high levels of PCBs/PCDFs and 75 matched controls, aged 7-11 years, in 1992. Ten of 73 (10%) exposed children were reported to have borne teeth during the neonatal period, while none of the controls did. The exposed group also had a significantly higher percentage of teeth with congenitally missing tooth germ compared to the controls (29 vs 2.7%) or rotation (19 vs 2.7%). The percentages of developmental defects increased significantly with increasing maternal serum PCB levels, childhood PCB and PCDF levels, and the duration of breast feeding. The maternal PCB level clearly played a more important role in an increased risk of neonatal teeth and developmental defects. The defects were apparent from the lowest tertile, with a total PCB level of <10 ppb in maternal serum measured nearest to childbirth. The number of permanent teeth tended to be less in exposed children than in the control group from the age of 11 years onwards. Our present study has demonstrated for the first time a dose-response relationship between perinatal PCBs/PCDFs exposure and dental defects.

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 studies 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.

GUIDELINES FOR ANALYSIS OF HUMAN MILK FOR ENVIRONMENTAL CHEMICALS

When analyzing human milk for environmental chemicals, in either a monitoring or research project, researchers must ensure that the technique used for measuring the target analytes complies with certain analytical criteria and that a quality control/quality assurance program is in place. In this report, these analytical criteria and the accompanying quality assurance program are elaborated in more detail. Examples of representative methods are also given for the determination of a number of classes of chemicals of environmental concern, such as polychlorinated dibenzo- p -dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, volatile organics, and halogenated flame retardants. Most of these techniques are physical/chemical in nature, but the possibility of the use of bioassays for screening of analytes in human milk is noted. The described methods are not exclusive, but any laboratory undertaking the analysis of human milk should demonstrate proficiency in their execution. This is usually accomplished by producing reliable data in interlaboratory studies. Human milk is an ideal matrix for estimating exposure to certain environmental chemicals, and researchers must ensure that the techniques used to determine these compounds adhere to known and accepted analytical requirements.