Background Levels Of Dioxins Research Articles

Effects of Chlorella Supplementation on Decreasing Concentrations of Dioxins in the Blood of Pregnant Japanese Women

Adverse health consequences from prenatal, perinatal and postnatal exposure to background levels of dioxins in the environment, including polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), have been reported. In order to prevent or reduce such health risks, it is important to decrease maternal exposure to dioxins. This study investigated the effect of maternal supplementation with Chlorella on dioxin concentration levels in the blood during pregnancy. Twenty healthy pregnant women participated in the study. Ten received 6 g of Chlorella daily from gestational week 16-20 until the day of delivery (Chlorella group); ten others did not (control group). The blood PCDFs and PCDD/DFs concentrations in the Chlorella group significantly decreased during the supplementation period, from 2.20 ± 1.66 to 1.00 ± 0.61 pg-TEQ/g lipid (p<0.05) and from 5.48 ± 4.01 to 3.38 ± 1.96 pg-TEQ/g lipid ( p<0.05), respectively. The levels of dioxins in the control group did not change significantly. These results suggest that Chlorella supplementation may be effective in reducing dioxin exposure in pregnant woman.

Background concentrations of polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls in the global oceanic atmosphere.

The remote oceans are among the most pristine environments in the world, away from sources of anthropogenic persistent organic pollutants (POP), but nevertheless recipients of atmospheric deposition of POPs that have undergone long-range atmospheric transport (LRAT). In this work, the background occurrence of gas and aerosol phase polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin like polychlorinated biphenyls (dl-PCB) is evaluated for the first time in the atmosphere of the tropical and subtropical Atlantic, Pacific, and Indian oceans. Thirty-nine air samples were collected during the eight-month Malaspina circumnavigation cruise onboard the R/V Hespérides. The background levels of dioxins and dl-PCBs remained very low and in many cases very close to or below the limit of detection. Expectedly, the levels of PCBs were higher than dioxins, PCB#118 being the most abundant compound. In the particular case of dioxins, octachlorodibenzo-p-dioxin (OCDD) was the most abundant PCDD/F congener. Distribution of dl-PCB is dominated by the gas phase, while for PCDD/F the aerosol phase concentrations were higher, particularly for the more hydrophobic congeners. The Atlantic Ocean presented on average the highest PCDD/F and dl-PCB concentrations, being lower in the southern hemisphere. The assessment of air mass back trajectories show a clear influence of continental source regions, and lower concentrations when the air mass has an oceanic origin. In addition, the samples affected by an oceanic air mass are characterized by a lower contribution of the less chlorinated dioxins in comparison with the furans, consistent with the reported higher reaction rate constants of dibenzo-p-dioxins with OH radicals than those of dibenzofurans. The total dry atmospheric deposition of aerosol-bound ∑PCDD/F and ∑dl-PCB to the global oceans was estimated to be 354 and 896 kg/year, respectively.

Signs of enhanced neuromotor maturation in children due to perinatal load with background levels of dioxins: Follow-up until age 2 years and 7 months

We investigated psychomotor development (Bayley-test) and neuromotor functioning (Hempel-test) in a group of children with known perinatal load with background levels of dioxins. Bayley-test (n=32) at 2 years, and additionally investigated growth, medical history, physical condition, TT4, TT4/TBG, TSH, AST and ALT at the age of 2.5 years did not reveal abnormalities, or differences between the high- and the low-exposure group. Although the Hempel-test was normal in all children (n=31), we found in 22 out of 29 items less suboptimal scores in the high-exposure group; in five items this difference reached significance (p<0.05). Total-score and subtotal-score (posture of legs and feet excluded) revealed lower “suboptimality-scores” with a wider range in the high-exposure group in comparison to the low-exposure group (total-score p=0.008 mean 6.7 SD 3.6 and mean 9.3 SD 1.8 respectively and subtotal-score p=0.06 mean 4.5 SD 2.9 and mean 6.1 SD 1.6 respectively (Mann-Whitney or Wilcoxon Two-Sample Test)). Similar signs of enhanced maturation have been described in the tadpole due to low dosis of TCDD. Reflexes were higher (p=0.02), with a wider range of findings in the high-exposure group. Our hypothesis is that these findings may be due to thyroxine agonistic action of dioxins, which is in accordance with the earlier described signs of relatively high thyroid function in the first 11 weeks of life in this high-exposure group.

The use of dioxin isomer group ratios to identify sources and define background levels of dioxins in the environment.

Environmental samples containing a mixture of dioxins of which there are seventy-five isomers, show a characteristic composition indicative of their source and the destruction reactions taking place in the environment. Expressed in terms of isomer group ratios, the study shows that thermochemical reactions rearrange the isomer content to form specific ratios characteristic of the source itself, and upon release to the environment a shift in the ratios to a new and constant set of ratios characteristic of the environment into which thery are released. The observed shift is easily modeled, independent of the source, and presumably caused by oxidation reactions in the atmosphere. The reduction/oxidation reactions needed to account for such an observation is demonstrated in a laboratory unit where a single type of dioxin (octachlorodibenzo-p-dioxin) is transformed into all isomer group species during incineration.