title: Plasma organochlorine levels and the risk of breast cancer.
abstract: BACKGROUND
  Exposure to "environmental estrogens" such as organochlorines in pesticides and industrial chemicals has been proposed as a cause of increasing rates of breast cancer. Several studies have reported higher blood levels of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and polychlorinated biphenyls (PCBs) in patients with breast cancer than in controls.
  
  
  METHODS
  We measured plasma levels of DDE and PCBs prospectively among 240 women who gave a blood sample in 1989 or 1990 and who were subsequently given a diagnosis of breast cancer before June 1, 1992. We compared these levels with those measured in matched control women in whom breast cancer did not develop. Data on DDE were available for 236 pairs, and data on PCBs were available for 230 pairs.
  
  
  RESULTS
  The median level of DDE was lower among case patients than among controls (4.71 vs. 5.35 parts per billion, P=0.14), as was the median level of PCBs (4.49 vs. 4.68 parts per billion, P=0.72). The multivariate relative risk of breast cancer for women in the highest quintile of exposure as compared with women in the lowest quintile was 0.72 for DDE (95 percent confidence interval, 0.37 to 1.40) and 0.66 for PCBs (95 percent confidence interval, 0.32 to 1.37). Exposure to high levels of both DDE and PCBs was associated with a nonsignificantly lower risk of breast cancer (relative risk for women in the highest quintiles of both DDE and PCBs as compared with women in the lowest, 0.43; 95 percent confidence interval, 0.13 to 1.44).
  
  
  CONCLUSIONS
  Our data do not support the hypothesis that exposure to DDT and PCBs increases the risk of breast cancer.
authors.affiliation: Department of Medicine, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Hunter
authors.forename: S E
authors.initials: SE
authors.lastname: Hankinson
authors.forename: F
authors.initials: F
authors.lastname: Laden
authors.forename: G A
authors.initials: GA
authors.lastname: Colditz
authors.forename: J E
authors.initials: JE
authors.lastname: Manson
authors.forename: W C
authors.initials: WC
authors.lastname: Willett
authors.forename: F E
authors.initials: FE
authors.lastname: Speizer
authors.forename: M S
authors.initials: MS
authors.lastname: Wolff
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000097:blood* / Q000139:chemically induced; D016022:Case-Control Studies; D003633:Dichlorodiphenyl Dichloroethylene / Q000009:adverse effects / Q000097:blood*; D005260:Female; D006801:Humans; D007306:Insecticides / Q000009:adverse effects / Q000097:blood*; D008875:Middle Aged; D015999:Multivariate Analysis; D011078:Polychlorinated Biphenyls / Q000009:adverse effects / Q000097:blood*; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D007306:Insecticides; D003633:Dichlorodiphenyl Dichloroethylene; D011078:Polychlorinated Biphenyls