Dataset Information

Environmental Polychlorinated Biphenyl Exposure and Breast Cancer Risk: A Meta-Analysis of Observational Studies.

ABSTRACT:

Background

Association between polychlorinated biphenyl (PCB) exposure and breast cancer risk has been widely studied, but the results remain controversial. We performed a meta-analysis to evaluate the evidences from observational studies on PCB exposure and breast cancer risk.

Methods

Relevant studies with data on internal PCB dose were identified from PubMed, EMBASE, CBM and CNKI databases through November 2014. Multivariable-adjusted odds ratio (OR) with 95% confidence intervals (CIs) were applied to assess the association between PCB exposure and breast cancer risk. Heterogeneity test, sensitivity analysis, subgroup analysis and publication bias test were also performed. To further explore the association between specific groups of PCB congeners and breast cancer, we examined the PCB congeners classified, according to their structural, biological and pharmacokinetics properties, as group I (potentially estrogenic), group II (potentially anti-estrogenic and immunotoxic, dioxin-like), and group III (phenobarbital, CYP1A and CYP2B inducers, biologically persistent).

Results

Of 660 studies screened, 25 studies which met criteria were selected, involving a total of 12866 participants (6088 cases and 6778 controls) from eight countries. The results showed that the risk of breast cancer was associated with group II (OR = 1.23, 95% CI: 1.08-1.40) and group III (OR = 1.25, 95% CI: 1.09-1.43) PCBs, but not with group I (OR = 1.10, 95%CI: 0.97-1.24) PCBs or total PCB exposure (OR = 1.09, 95%CI: 0.97-1.22).

Conclusions

Our meta-analysis based on the selected studies found group II and group III PCB exposure might contribute to the risk of breast cancer. More studies in developing countries with higher PCB levels are needed, as well as studies to explore the relationships between mixtures of organochlorine compounds and breast cancer risk.

SUBMITTER: Zhang J

PROVIDER: S-EPMC4640539 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Publications

Environmental Polychlorinated Biphenyl Exposure and Breast Cancer Risk: A Meta-Analysis of Observational Studies.

Zhang Jingwen J Huang Yue Y Wang Xiaoling X Lin Kun K Wu Kusheng K

PloS one 20151110 11

<h4>Background</h4>Association between polychlorinated biphenyl (PCB) exposure and breast cancer risk has been widely studied, but the results remain controversial. We performed a meta-analysis to evaluate the evidences from observational studies on PCB exposure and breast cancer risk.<h4>Methods</h4>Relevant studies with data on internal PCB dose were identified from PubMed, EMBASE, CBM and CNKI databases through November 2014. Multivariable-adjusted odds ratio (OR) with 95% confidence interval ...[more]

PMID: 26555153

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Project description:In 1973-74, a polybrominated biphenyl (PBB) flame retardant mixture was shipped to Michigan livestock feed mills in place of a nutritional supplement and contaminated the food supply. Following the accident, the Michigan PBB Registry was established to study the long-term health effects of halogenated compounds and is now led by a community-academic partnership. PBB exposure is associated with altered DNA methylation in sperm, which may lead to adverse birth outcomes in children whose fathers have increased levels of serum PBB or polychlorinated biphenyl (PCB). Paternal PBB and PCB levels of men enrolled in the Michigan PBB Registry (n = 155) were analyzed against matched offspring birthweight and gestational age (n = 336). Birthweight and gestational age were dichotomized at the 25th percentile and 37 weeks, respectively, and paternal PBB and PCB levels were examined as continuous measures and divided into tertiles. Associations of offspring birthweight and gestational age with paternal PBB and PCB serum concentrations were modeled using multivariable linear spline and log-risk regression, adjusting for family clustering, paternal health and lifestyle factors, maternal PBB, and PCB serum concentrations, sex, and offspring gestational age (for birthweight). Fathers in the middle and upper PBB and PCB tertiles had increased risks for lowest quartile birthweight compared to the first tertile, with adjusted risk ratios (aRR) = 1.67 (95% CI: 0.93, 2.99) and aRR = 2.06 (95% CI: 1.12, 3.79) for PBB, and aRR = 1.47 (95% CI: 0.79, 2.75) and aRR = 1.34 (95% CI: 0.70, 2.54) for PCB, respectively. Elevated paternal PBB levels were not associated with an increased risk for preterm birth, while PCB levels were associated with a small, but not significant, decrease in gestational age, β = -0.37 (95% CI: -0.76, 0.03) weeks per log unit increase PCB. The findings suggest that increased paternal PBB and PCB levels negatively impact offspring birthweight, and paternal PCB levels may negatively impact gestational age.

Project description:Polychlorinated biphenyls (PCBs) are environmental pollutants and endocrine disruptors, harmfully affecting reproductive, endocrine, neurological and immunological systems. This broad influence has implications for processes such as wound healing, which is modulated by the immunological response of the body. Conversely, while PCBs can be linked to diminished wound healing, outside of PCB pollution systems, exercise has been shown to accelerate wound healing. However, the potential for moderate intensity exercise to modulate or offset the harmful effects of a toxin like PCB are yet unknown. A key aim of the present study was to examine how PCB exposure at different doses (0, 100, 500, 1000 ppm i.p.) altered wound healing in exercised versus non-exercised subgroups of mice. We examined PCB effects on immune function in more depth by analyzing the concentrations of cytokines, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), Interleukin-6 (IL-6) and granulocyte macrophage colony stimulating factor (GM-CSF) in these wounds inflicted by punch biopsy. Mice were euthanized at Day 3 or Day 5 after PCB injection (n = 3-6) and skin excised from the wound area was homogenized and analyzed for cytokine content. Results revealed that wound healing was not signficantly impacted by either PCB exposure or exercise, but there were patterns of delays in healing that depended on PCB dose. Changes in cytokines were also observed and depended on PCB dose and exercise experience. For example, IL-1β concentrations in Day 5 mice without PCB administration were 33% less in exercised mice than mice not exercised. However, IL-1β concentrations in Day 3 mice administered 100 ppm were 130% greater in exercised mice than not exercisedmice. Changes in the other measured cytokines varied with mainly depressions at lesser PCB doses and elevations at higher doses. Exercise had diverse effects on cytokine levels, but increased cytokine levels in the two greater doses. Explanations for these diverse effects include the use of young animals with more rapid wound healing rates less affected by toxin exposure, as well as PCB-mediated compensatory effects at specific doses which could actually enhance immune function. Future work should examine these interactions in more detail across a developmental time span. Understanding how manipulating the effects of exposure to environemntal contaminants using behavioral modification could be very useful in certain high risk populations or exposed individuals.

Dataset Information

Environmental Polychlorinated Biphenyl Exposure and Breast Cancer Risk: A Meta-Analysis of Observational Studies.

Background

Methods

Results

Conclusions

Publications

Environmental Polychlorinated Biphenyl Exposure and Breast Cancer Risk: A Meta-Analysis of Observational Studies.

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