title: Current status of the epidemiologic evidence linking polychlorinated biphenyls and non-hodgkin lymphoma, and the role of immune dysregulation.
abstract: BACKGROUND
  Although case-control studies conducted to date have largely affirmed the relationship between polychlorinated biphenyls (PCBs) and non-Hodgkin lymphoma (NHL), occupational cohort studies of PCB-exposed workers have been generally interpreted as negative, thereby raising doubts about a potential causal association. A common theme of immune dysregulation unifies many of NHL's strongest risk factors, and several authors have posited that subclinical immune dysregulation may increase NHL risk by decreasing host resistance, reducing control of cellular proliferation and differentiation, and diminishing tumor surveillance mechanisms.
  
  
  OBJECTIVE
  The goals of this review were a) to evaluate the epidemiological research examining the association between PCB exposure and NHL and discuss the contribution to the weight of evidence of case-control studies and occupational cohort studies; and b) to summarize the evidence for immune dysregulation as a means by which PCBs may cause NHL.
  
  
  METHODS
  We performed a literature search using PubMed and seven additional online biomedical and toxicological referencing libraries to identify literature published through August 2011.
  
  
  CONCLUSIONS
  Overall, we conclude that the weight of evidence supports a causal role of PCBs in lymphomagenesis. The strongest epidemiological evidence for the relationship between PCBs and NHL comes from case-control studies conducted among the general population. Epidemiological and toxicological data demonstrating immunosuppressive and inflammatory effects of PCBs further contribute to the weight of evidence by providing a plausible explanation for how PCBs can cause NHL through immune dysregulation.
authors.affiliation: Epidemiology International, Hunt Valley, Maryland, USA. s.kramer@epiinternational.com
authors.forename: Shira
authors.initials: S
authors.lastname: Kramer
authors.forename: Stephanie Moller
authors.initials: SM
authors.lastname: Hikel
authors.forename: Kristen
authors.initials: K
authors.lastname: Adams
authors.forename: David
authors.initials: D
authors.lastname: Hinds
authors.forename: Katherine
authors.initials: K
authors.lastname: Moon
mesh_terms: D015331:Cohort Studies; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000139:chemically induced / Q000453:epidemiology* / Q000276:immunology; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D012307:Risk Factors
chemical_list: D011078:Polychlorinated Biphenyls