K. Olie

Mechanisms of Formation and Destruction of Polychlorinated Dibenzo=p=dioxins and Dibenzofurans in Heterogeneous Systems

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans are toxic compounds formed during natural processes and human activities. The basic questions about PCDD/F formation such as (1) what is the influence of process parameters on the formation process, (2) what reaction mechanisms are involved in formation, and (3) what kinetics describes PCDD/F formation are discussed, and recommendations are given.

Chlorinated dibenzo-p-dioxins and related compounds in incinerator effluents: A review of measurements and mechanisms of formation

Incineration of refuse has been an accepted method of solid waste disposal since the end of the nineteenth century and is gaining in popularity in most industrial ized and densely populated countries. In the Netherlands, for instance, where land for disposal is scarce the percentage of refuse which is incinerated has increased steadily from 15% in 1960 to 34% in 1978 as a replacement of l andf i l l (see Table I ) ( I ) .

Presence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in fish-eating birds and fish from The Netherlands

In the period 1980 to 1982, nineteen CormorantsPhalacrocorax carbo, three Grey HeronsArdea cinerea and one Great Crested GrebePodiceps crisatus were collected in The Netherlands. The livers of these fish-eating birdspecies were analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans.Only congeners with a 2,3,7,8-chlorine substitution pattern were found in the livers. Major components were 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin and 1,2,3,7,8-pentachlorodibenzo-p-dioxin were also present. Six pooled samples of the EelAnguilla anguilla, showed the same congeneric pattern of chemicals as found in these bird species. In the Eel, 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin were generally present in the 1 to 5 ng/kg range. Since the Eel is the Cormorants 2 major food, this indicates strong bioaccumulation for both congeners in the liver of the Cormorant.Significant correlations were found between the various congeners retained in the liver of the Cormorant. It is proposed that this is a result of a continous exposure to a relatively stable background mixture, probably originating from fish consumption. Based on the congeneric patterns found in the Cormorant, polychlorinated biphenyls and pentachlorophenol are suggested as major contaminating sources for this species. Based on the results from the Cormorants, an open one compartment model was applied to estimate concentrations of 2,3,4,7,8-PnCDF in the Eel. These calculations were in good agreement with the actual measurements found in the Eels.

Assessment of the toxicity of mixtures of halogenated dibenzo-p-dioxins and dibenzofurans by use of toxicity equivalency factors (TEF)

Abstract In March 1988 the authors completed a report on the risk assessment of mixtures of halogenated dibenzo-p-dioxins and dibenzofurans at the request of the National Institute of Public Health and Environmental Protection in the Netherlands. Based on a study of the current knowledge of these compounds, a set of toxicity equivalency factors was proposed for use in such risk assessments. This paper presents the section of this report that deals with the literature on the effects of these compounds and the choice of toxicity equivalency factors. The uncertanties in the selection and application of toxicity equivalency factors are discussed.

Delayed initiation of breast development in girls with higher prenatal dioxin exposure; a longitudinal cohort study

OBJECTIVES While many studies have assessed the health impacts of PCDD/Fs and PCBs on animals and humans, long-term consequences for especially adolescents, have not (yet) been well documented. This is certainly also true for the effects of PBDE exposure. As part of a longitudinal cohort study, now well into its second decade, effects of perinatal and current PCDD/F exposure, as well as current dl-PCB and PBDE exposures, on puberty, were assessed. STUDY DESIGN Prenatal, lactational and current PCDD/F, dl-PCB and PBDE concentrations were determined using GC-MS. Pubertal development and growth were assessed by means of physical examination and the Tanner scale. 33 Children (born between 1986 and 1991) consented to the current follow-up study. Outcomes were evaluated using linear regression or the non parametric Spearmans correlation coefficient. RESULTS A delay in initiation of breast development was found in girls (n = 18) with higher prenatal (p = 0.023) and lactational PCDD/F exposure (p = 0.048). The males revealed a negative trend with age at first ejaculation. For other endpoints on puberty and growth (pubic hair, axillary hair, genital stage, length, BMI, testicular volume, menarche) no significant relation was found with any of the measured compounds. DISCUSSION AND CONCLUSION A relation between prenatal PCDD/F exposure and later initiation of breast development was seen. A Belgian study found a delay in breast development with higher current serum concentrations of dioxin-like compounds. The initiation of puberty is a complex process and it is yet not clear how dioxin-like compounds precisely affect this process prenatally. Further follow-up into adulthood is warranted, in order to detect the possibility of developing malignancies and fertility problems.

Metals as Catalysts during the Formation and Decomposition of Chlorinated Dioxins and Furans in Incineration Processes

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are found on fly ash and in flue gas of municipal waste incinerators. Municipal waste incinerators seem to be the most important source for PCDDs and PCDFs emitted into the air during the last decades. PCDD/F formation takes place in the cooler zones (250 °C-450 °C) of a municipal waste incinerator, at the electrostatic precipitator. Copper is an important component of the fly ash that can catalyse the formation of PCDDs and PCDFs. Inhibition of the formation can be done by complexation of the metals (Cu) with EDTA or NTA.

Thyroid hormone metabolism and environmental chemical exposure

BackgroundPolychlorinated dioxins and –furans (PCDD/Fs) and polychlorinated-biphenyls (PCBs) are environmental toxicants that have been proven to influence thyroid metabolism both in animal studies and in human beings. In recent years polybrominated diphenyl ethers (PBDEs) also have been found to have a negative influence on thyroid hormone metabolism. The lower brominated flame retardants are now banned in the EU, however higher brominated decabromo-diphenyl ether (DBDE) and the brominated flame retardant hexabromocyclododecane (HBCD) are not yet banned. They too can negatively influence thyroid hormone metabolism. An additional brominated flame retardant that is still in use is tetrabromobisphenol-A (TBBPA), which has also been shown to influence thyroid hormone metabolism.Influences of brominated flame retardants, PCDD/F’s and dioxin like-PCBs (dl-PCB’s) on thyroid hormone metabolism in adolescence in the Netherlands will be presented in this study and determined if there are reasons for concern to human health for these toxins. In the period 1987-1991, a cohort of mother-baby pairs was formed in order to detect abnormalities in relation to dioxin levels in the perinatal period. The study demonstrated that PCDD/Fs were found around the time of birth, suggesting a modulation of the setpoint of thyroid hormone metabolism with a higher 3,3’, 5,5’tetrathyroxine (T4) levels and an increased thyroid stimulating hormone (TSH). While the same serum thyroid hormone tests (- TSH and T4) were again normal by 2 years of age and were still normal at 8-12 years, adolescence is a period with extra stress on thyroid hormone metabolism. Therefore we measured serum levels of TSH, T4, 3,3’,5- triiodothyronine (T3), free T4 (FT4), antibodies and thyroxine-binding globulin (TBG) in our adolescent cohort.MethodsVena puncture was performed to obtain samples for the measurement of thyroid hormone metabolism related parameters and the current serum dioxin (PCDD/Fs), PCB and PBDE levels.ResultsThe current levels of T3 were positively correlated to BDE-99. A positive trend with FT4 and BDE-99 was also seen, while a positive correlation with T3 and dl-PCB was also seen. No correlation with TBG was seen for any of the contaminants. Neither the prenatal nor the current PCDD/F levels showed a relationship with the thyroid parameters in this relatively small group.ConclusionOnce again the thyroid hormone metabolism (an increase in T3) seems to have been influenced by current background levels of common environmental contaminants: dl-PCBs and BDE-99. T3 is a product of target organs and abnormalities might indicate effects on hormone transporters and could cause pathology. While the influence on T3 levels may have been compensated, because the adolescents functioned normal at the time of the study period, it is questionable if this compensation is enough for all organs depending on thyroid hormones.

Effects of Dioxins, PCBs, and PBDEs on Immunology and Hematology in Adolescents

Dioxins and PCBs are environmental pollutants, proven to be immunotoxic. In the period 1987-1991 a cohort of mother-baby pairs was initiated to detect abnormalities in relation to dioxin levels in the mothers milk. At birth and at follow-up at 8-12 years, immunological and hematological effects were seen, prompting us to perform a new follow-up during adolescence. In addition, we assessed the immunological and hematological parameters in relation to current levels of PBDEs and PCBs. In the Netherlands, the pre- and postnatal exposure to dioxins have been studied prospectively since 1987. Venapuncture was performed to assess hematological (Hemoglobin, thrombocytes, thrombopoietin) and immunological (leukocytes, leukocyte differentiation) parameters and the current serum levels of dioxin, dioxinlike (dl)-PCBs and PBDEs. A decrease in the number of polymorphic neutrophils was found in adolescents with higher dl-PCBs in their serum (p = 0.021). No relation with total leukocytes, thrombocytes, hemoglobin, or thrombopoietin levels was seen. Similarly, we found no relation between prenatal, nor current dioxin levels and the hematological and the immunological parameters determined. The SigmaPBDEs were negatively associated with the number of lymphocytes (p = 0.01) and positively associated with the hemoglobin concentration (p = 0.003). These effects on the innate immunity by current levels of dl-PCBs and on the adaptive immunity by PBDEs are disconcerting, especially as the dl-PCB (0.04-7.8 WHOTEQ pg/g lipid, mean: 2.2 WHOTEQ pg/g lipid) and SigmaPBDE levels (mean 14.0 ng/g lipid, including one outlier with a sum of 73.6 ng/g lipid) were not high.

Role of oxygen in formation of polychlorinated dibenzo-p-dioxins/dibenzofurans from carbon and fly ash.

Under an oxygen-deficient flow, no PCDD/F is formed from a carbon/fly ash mixture, but with a mixture of 1% O 2 in N 2 de novo synthesis of PCDD/F sets in. The O 2 concentration was varied 0-10%, formation was highest at 5-10% O 2 . The [PCDD] :[PCDF] ratio rises with increasing [O 2 ], but the average degree of chlorination of PCDD and PCDF does not depend on the O 2 concentration. Especially 3,4,6,7-substituted PCDD/F congeners are formed. Without a gas flow, carbon/fly ash mixtures can give PCDD/F formation too : the O 2 now enters the mixture by diffusion. This formation process can continue for several hours. Isomer distributions do not change with increased reaction times. Formation rates under conditions without a gas flow are higher than with a gas flow present, suggesting that O 2 diffusion into the fly ash bed is more efficient than the supply of O 2 through a gas flow.

The presence of PCDDs and PCDFs in human breast milk from the Netherlands

Abstract Sixteen individual and two pooled human milk samples were analyzed for PCDDs and PCDFs. All detected PCDD and PCDF congeners had a 2,3,7,8-chlorine substitution pattern. The PCDDs and PCDFs were associated with the lipid fraction of the milk. Major components were 2,3,4,7,8-PnCDF (0.2 – 2.6 ppt), 1,2,3,6,7,8-HxCDD (0.2 – 5.7 ppt), 1,2,3,4,6,7,8-HpCDD (1.3 – 19.1) and OCDD (1.7 – 37.8 ppt), with concentrations on total milk basis. Minor components were 1,2,3,7,8-PnCDD, 1,2,3,7,8,9- and 1,2,3,4,7,8- HxCDD (⩽ 1 ppt). Qualitatively and quantitatively the milk samples from the Netherlands strongly resemble those from Sweden and West-Germany. A linear relationship was found between some congeners. This correlation was highest for congeners having an equal number of chlorine atoms or those with a difference of one chlorine atom. By using a one compartment open model for multiple doses, a maximum liver concentration of approximately 200 ppt 2,3,4,7,8-PnCDF in the neonate was calculated after six months.