title: 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.
authors.affiliation: Department of Preventive Medicine, Shantou University Medical College, Shantou, Guangdong, China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Preventive Medicine, Shantou University Medical College, Shantou, Guangdong, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Department of Preventive Medicine, Shantou University Medical College, Shantou, Guangdong, China.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Preventive Medicine, Shantou University Medical College, Shantou, Guangdong, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Lin
authors.affiliation: Department of Preventive Medicine, Shantou University Medical College, Shantou, Guangdong, China.
authors.forename: Kusheng
authors.initials: K
authors.lastname: Wu
mesh_terms: D001943:Breast Neoplasms / Q000139:chemically induced*; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D006801:Humans; D064887:Observational Studies as Topic; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D004785:Environmental Pollutants; D011078:Polychlorinated Biphenyls