title: Timing of Environmental Exposures as a Critical Element in Breast Cancer Risk.
abstract: OBJECTIVE
  The role of the chemical environment in disease initiation or progression is becoming more evident. Endocrine disruption via environmental chemicals is now well documented in humans, rodent research models, and wildlife. Breast cancer is an endocrine-based disease whose risk may be modified by environmental exposures. Our purpose is to encourage more investigation into early life environmental exposures as they relate to breast cancer risk factors and disease over a lifetime.
  
  
  METHODS
  The 2009 President's Cancer Panel, 2012 Institute of Medicine, 2013 Interagency Breast Cancer and the Environment Research Coordinating Committee reports, and research publications dated ≥2012 in PubMed were used to inform our perspective.
  
  
  METHODS
  Literature was reviewed and evidence gathered on the effects of the environment on risk of breast cancer or mammary tumor development in animal research models as it pertained to the influence of timing of exposure on later-life outcomes.
  
  
  CONCLUSIONS
  Evidence has accumulated for several chemicals that environmental factors have a stronger effect on breast cancer risk when exposure occurred early in life. The insecticide, dichlorodiphenyltrichloroethane, is an excellent example and is just one of several chemicals for which there seems to be both animal and human evidence for the developmental basis of adult disease. The developing breast undergoes many changes in early life, leaving it vulnerable to the effects of epigenetic marks, endocrine disruption, and carcinogens. More research is needed in the area of early beginnings of breast cancer, with prevention of the disease as the ultimate goal.
authors.affiliation: National Toxicology Program (NTP) Laboratory, Division of the NTP (S.E.F.), National Institute of Environmental Health Sciences (L.S.B.), National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709.
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Fenton
authors.affiliation: National Toxicology Program (NTP) Laboratory, Division of the NTP (S.E.F.), National Institute of Environmental Health Sciences (L.S.B.), National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709.
authors.forename: Linda S
authors.initials: LS
authors.lastname: Birnbaum
mesh_terms: D001943:Breast Neoplasms / Q000139:chemically induced* / Q000473:pathology; D052244:Endocrine Disruptors / Q000633:toxicity*; D004781:Environmental Exposure; D006801:Humans; D013997:Time Factors
chemical_list: D052244:Endocrine Disruptors