title: DDT and breast cancer in young women: new data on the significance of age at exposure.
abstract: BACKGROUND
  Previous studies of DDT and breast cancer assessed exposure later in life when the breast may not have been vulnerable, after most DDT had been eliminated, and after DDT had been banned.
  
  
  OBJECTIVE
  We investigated whether DDT exposure in young women during the period of peak DDT use predicts breast cancer.
  
  
  METHODS
  We conducted a prospective, nested case-control study with a median time to diagnosis of 17 years using blood samples obtained from young women during 1959-1967. Subjects were members of the Child Health and Development Studies, Oakland, California, who provided blood samples 1-3 days after giving birth (mean age, 26 years). Cases (n = 129) developed breast cancer before the age of 50 years. Controls (n = 129) were matched to cases on birth year. Serum was assayed for p,p'-DDT, the active ingredient of DDT; o,p'-DDT, a low concentration contaminant; and p,p'-DDE, the most abundant p,p'-DDT metabolite.
  
  
  RESULTS
  High levels of serum p,p'-DDT predicted a statistically significant 5-fold increased risk of breast cancer among women who were born after 1931. These women were under 14 years of age in 1945, when DDT came into widespread use, and mostly under 20 years as DDT use peaked. Women who were not exposed to p,p'-DDT before 14 years of age showed no association between p,p'-DDT and breast cancer (p = 0.02 for difference by age).
  
  
  CONCLUSIONS
  Exposure to p,p'-DDT early in life may increase breast cancer risk. Many U.S. women heavily exposed to DDT in childhood have not yet reached 50 years of age. The public health significance of DDT exposure in early life may be large.
authors.affiliation: Child Health and Development Studies, Center for Research on Women's and Children's Health, Public Health Institute, Berkeley, California 94709, USA. bcohn@chdstudies.org
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Cohn
authors.forename: Mary S
authors.initials: MS
authors.lastname: Wolff
authors.forename: Piera M
authors.initials: PM
authors.lastname: Cirillo
authors.forename: Robert I
authors.initials: RI
authors.lastname: Sholtz
mesh_terms: D000328:Adult; D000367:Age Factors; D001943:Breast Neoplasms / Q000453:epidemiology*; D002140:California / Q000453:epidemiology; D002274:Carcinogens, Environmental / Q000009:adverse effects* / Q000032:analysis; D016022:Case-Control Studies; D003634:DDT / Q000009:adverse effects* / Q000097:blood; D003633:Dichlorodiphenyl Dichloroethylene / Q000097:blood*; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D014481:United States / Q000453:epidemiology
chemical_list: D002274:Carcinogens, Environmental; D003633:Dichlorodiphenyl Dichloroethylene; D003634:DDT