Biological effect of PCBs, PCQs and PCDFs present in the oil causing yusho and yu-cheng

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

Background

Over 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.

Methods

From 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.

Results

The 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.

Conclusions

Blood 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.

Electronic supplementary material

The online version of this article (10.1186/s12199-018-0755-7) contains supplementary material, which is available to authorized users.

[A memoir of my researches on xenobiotic metabolism for 48 years--researches on Kanemi Yusho and endocrine disrupting chemicals]

The author started a research on xenobiotic metabolism at Graduate School of Pharmaceutical Sciences, Kyushu University in 1965. In 1968, an epidemic of a "strange disease", called Yusho, occurred in western Japan. The epidemic was soon identified to be a food poisoning caused by the ingestion of commercial Kanemi rice bran oil which had been accidentally contaminated with large amounts of polychlorinated biphenyls (PCBs) and their related compounds such as polychlorinated dibenzofurans (PCDFs.) At first, in this review, our toxicological studies on Yusho during the early thirty years were briefly described. Next, the studies on aldehyde oxidase, a molybdenum hydroxylase, which is involved in the lactam formation reaction such as 1-phenyl-2-(2-oxopyrrolidine)pentane(oxoprolintane) from 1-phenyl-2-pyrrolidinopentane(prolintane) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP) lactam from 1-methyl-4-phenyl-2,3-dihydropyridinium ion (MPDP⁺) were also presented. Finally, we investigated how the xenobiotic metabolism of endocrine disrupting chemicals such as bisphenol A (BPA) and some isoflavones affects their estrogenic activities. In this study, we demonstrated that BPA is converted to 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), an active metabolite as estrogen, by rat liver S9. In the cases of isoflavones, although genistein was inactivated, biochanin A, 4'-methoxy analogue of genistein, was activated to genistein by O-demethylation with rat liver S9.

Long-term effects of polychlorinated biphenyls and dioxins on pregnancy outcomes in women affected by the Yusho incident

BACKGROUND

Maternal exposure to polychlorinated biphenyls (PCBs) is associated with increased proportions of spontaneous abortion and stillbirth in animal studies. In Japan in 1968, accidental human exposure to rice oil contaminated with PCBs and other dioxin-related compounds, such as polychlorinated dibenzofurans (PCDFs), led to the development of what was later referred to as Yusho oil disease.

OBJECTIVE

The aim of this study was to investigate the association of maternal PCB and dioxin exposure with adverse pregnancy outcomes in Yusho women.

METHODS

In 2004, we interviewed 214 Yusho women (512 pregnancies) about their pregnancy outcomes over the past 36 years. Pregnancy outcomes included induced abortion, spontaneous abortion, preterm delivery, and pregnancy loss.

RESULTS

In pregnancy years 1968-1977 (within the first 10 years after exposure), the proportions of induced abortion [odds ratio adjusted for age at delivery (ORadj) = 5.93; 95% confidence interval (CI), 2.21-15.91; two-tailed p < 0.001) and preterm delivery (ORadj = 5.70; 95% CI, 1.17-27.79; p = 0.03) were significantly increased compared with the proportions in pregnancy years 1958-1967 (10 years before the incident). Spontaneous abortion (ORadj = 2.09; 95% CI, 0.84-5.18), and pregnancy loss (ORadj = 2.11; 95% CI, 0.92-4.87) were more frequent (OR = 2.18; 95% CI, 1.02-4.66), but these were not significant (p = 0.11 and p = 0.08, respectively) in pregnancy years 1968-1977. We found no significant increases in the proportions of these adverse pregnancy outcomes in pregnancies occurring during 1978-1987 or 1988-2003 compared with those in pregnancies before 1968.

CONCLUSION

High levels of PCB/PCDF exposure had some adverse effects on pregnancy outcome in Yusho women.

Persistent Organochlorine Chemicals in Plasma and Risk of Non-Hodgkin's Lymphoma

Polychlorinated biphenyls (PCB) have been suspected as possible contributors to increasing non-Hodgkin's lymphoma incidence during the latter half of the 20th century based on their toxicologic properties and provocative epidemiologic reports. We investigated PCBs and other organochlorines and risk of non-Hodgkin's lymphoma in a population-based case-control study in the United States. Congeners of PCBs (including coplanar congeners), dioxins, furans and pesticides or pesticide metabolites were measured in plasma of 100 untreated cases and 100 control subjects. We used a multiple imputation procedure to fill in missing values of levels determined to be below the detection limits. Risks of non-Hodgkin's lymphoma associated with each analyte were estimated using conditional logistic regression for the continuous measure, exposure quartiles, trend across quartile categories, and exposures above the 95th percentile. Certain PCB congeners were associated with increased risk of non-Hodgkin's lymphoma, including coplanar PCBs 156, 180, and 194, with odds ratios for the highest versus lowest quartile ranging from 2.7 to 3.5, and significant trends. Each of the furan congeners was associated with risk of non-Hodgkin's lymphoma, as were total furans, with 3.5-fold increased risk for the highest versus lowest quartile and a significant trend across quartiles (P = 0.006). The toxic equivalency quotient (TEQ), a summed metric that weights congeners by their dioxin-like potency, was associated with non-Hodgkin's lymphoma, with 35% increased risk per 10 TEQ pg/g lipid (95% confidence interval, 1.02-1.79). Our results add to existing literature, which suggests that exposure to organochlorines contributes to non-Hodgkin's lymphoma risk; these risks were most apparent for certain PCBs and furans.

Immunotoxicity of PCBs (Aroclors) in relation to Great Lakes

Polychlorinated biphenyls (PCBs) are among the most widespread environmental pollutants and a prominent contaminant of the Great Lakes basin. Due to their resistance to biodegradation and lipophilic properties, PCBs bioaccumulate in fish tissues and in fish-eating humans. PCBs are also known to cross the placenta and to be excreted into the mother's milk, thus predisposing the infant to potentially adverse health effects. For example, a higher incidence of bacterial infections was reported for breast-fed infants born to mothers who consumed large amounts of Great Lakes fish compared to the incidence in control infants whose mothers ingested low amounts of fish. While data regarding the PCB-induced immunotoxic effects in humans are scarce, data derived from the use of experimental animals, including nonhuman primates, indicate that the immune system is a potential target for the immunotoxic effects of PCBs. Such studies have used the commercially available PCB mixtures alone. However, PCBs have the potential of partially antagonizing the effects of other structurally related compounds including the highly toxic dioxins, which are also present in small amounts in the Great Lakes. Thus, to fully evaluate the magnitude of the immunotoxic risk PCBs pose to humans, consideration should be given to investigations in which the interactive effects of PCBs are combined with other contaminants present in the Great Lakes.

Association between blood polychlorinated biphenyl concentration and serum triglyceride level in chronic "Yusho" (polychlorinated biphenyl poisoning) patients

The association between blood polychlorinated biphenyl (PCB) concentration and serum triglyceride level was investigated in 259 "Yusho" patients (PCB poisoning) who underwent health examinations for Yusho in 1988. Geometric means of PCB and triglyceride were 3.84 ppb (95% confidence interval: 3.54-4.17) and 114.3 mg/dl (106.6-122.6), respectively. Both correlation and multiple regression analyses showed a weak but statistically significant correlation between these two variables. The mean triglyceride level adjusted for age and sex was then calculated for comparison among four PCB levels, using analysis of covariance. This indicated a progressive increase with increasing PCB: 98.36, 117.78, 117.84, and 127.65 mg/dl at < 2.7, 2.7+, 4.1+, and 6.1+ ppb, respectively (F = 2.01, P = 0.113). Comparing PCB levels, the difference in adjusted mean triglyceride levels was marginally significant between the first and second (P = 0.088), and the first and third quartiles (P = 0.066), and reached significance between the first and fourth quartiles (P = 0.021). Thus, a weak but significant association between blood PCB and serum triglyceride was observed in the patients 20 years after exposure, although their blood PCB and serum triglyceride were relatively close to the normal levels.

Environmental teratogens

By far the largest category of malformations, 65% falls into the group of those with an unknown cause(s). Purely genetic causes of malformations (autosomal and cytogenetic), estimated to produce 20 to 25% of all human malformations, comprise the largest group of congenital malformations with known etiology. Although environmental causes of human malformations account for 10% or fewer of malformations, most of these environmentally induced malformations are related to maternal disease states. Fewer than 1% of all human malformations are related to drug exposure, chemicals, or radiation, but studies of environmentally induced malformations are important because they may teach us how to predict and test for teratogenicity, understand the mechanisms of teratogenesis from all etiologies, and provide a means by which human malformations can be prevented.

Respiratory involvement and immune status in yusho patients

Clinical and experimental studies on respiratory involvement and alterations in immune status were carried out. Respiratory distress occurring in these patients has improved gradually for 14 years but still remains. Copious expectoration at an early stage of the disease may be related to the fact that a number of discrete polychlorinated biphenyls (PCBs) are distributed throughout the lung parenchyma. For accumulation in the bronchial mucosa, structural requirements and specific dose dependence of PCBs have been clearly shown; however, pathological and physiological studies have indicated that respiratory involvement in yusho is mainly small airway disease that may be caused by involvement of cellular component (Clara cells) in bronchioles and/or associated infection. Respiratory distress is often exacerbated by viral or bacterial infection. Changes in the immune status in PCB and polychlorinated dibenzofuran (PCDF) poisoning are as follows: IgA and IgM in the serum are decreased at an early stage of the disease and then return to normal; suppression of cellular immunity was reported in Taiwanese patients and some may remain in the later stages of the disease, as shown in our patients. PCDFs now appear to be the main causal agents in yusho. Rats given PCDFs showed necrosis of the Clara cells in bronchioles and marked thymus atrophy, while few such changes were noted in rats given PCBs. Therefore, further examination is needed for the difference of the toxic effects between two compounds.