title: Repeated measurements of organochlorine exposure and breast cancer risk (Denmark).
abstract: OBJECTIVE
  To prospectively evaluate if repeated measurements of organochlorine exposure provide a more precise measure of breast cancer risk.
  
  
  METHODS
  In the Copenhagen City Heart Study (CCHS) participants donated blood twice, in 1976-1978 and 1981 1983. Information on breast cancer risk factors was obtained through standardized questionnaires. A cohort nested case-control study of 155 cases and 274 matched breast cancer-free controls who had participated in both CCHS examinations was conducted. The average serum organochlorine concentration over the course of the two examinations was used, testing a possible association between organochlorine exposure and breast cancer risk.
  
  
  RESULTS
  A high serum concentration of p,p'-DDT over the course of the two examinations was associated with a more than three-fold significantly increased risk of breast cancer, and a dose-response relationship was apparent. Furthermore, the risk of breast cancer increased with increasing serum concentrations of PCB congener 118 and 138 and the total amount of DDT isomers (sigmaDDT), but the trends were not significant.
  
  
  CONCLUSIONS
  This study provides new evidence of the adverse effect of some organochlorines on breast cancer risk. Furthermore, repeated assessment of exposure during a relevant time period may provide a more precise risk estimate than a single measurement.
authors.affiliation: Copenhagen Center for Prospective Populations Studies, Denmark. APH@post8.tele.dk
authors.forename: A P
authors.initials: AP
authors.lastname: Høyer
authors.forename: T
authors.initials: T
authors.lastname: Jørgensen
authors.forename: P
authors.initials: P
authors.lastname: Grandjean
authors.forename: H B
authors.initials: HB
authors.lastname: Hartvig
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000453:epidemiology*; D016022:Case-Control Studies; D015331:Cohort Studies; D016001:Confidence Intervals; D003634:DDT / Q000009:adverse effects* / Q000097:blood; D003718:Denmark / Q000453:epidemiology; D004781:Environmental Exposure / Q000009:adverse effects / Q000032:analysis*; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000009:adverse effects*; D062665:Epidemiological Monitoring; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D010575:Pesticides / Q000009:adverse effects / Q000097:blood; D011336:Probability; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012494:Sampling Studies
chemical_list: D004785:Environmental Pollutants; D010575:Pesticides; D003634:DDT