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National Cancer Institute U.S. National Institutes of Health www.cancer.gov
About DCEG

Martha S. Linet, M.D., M.P.H.

Chief and Senior Investigator, Radiation Epidemiology Branch

Location: Executive Plaza South, Room 7048
Phone: 301-496-6600
Fax: 301-402-0207
E-mail: linetm@mail.nih.gov

 Martha S. Linet, M.D., M.P.H.

Biography

Dr. Linet received an M.D. from Tufts University and an M.P.H. from The John Hopkins School of Hygiene and Public Health. She is board certified in internal medicine and general preventive medicine. Dr. Linet was an Associate Professor at The Johns Hopkins School of Public Health before joining the NCI in 1987, where she is Chief of the Radiation Epidemiology Branch. Dr. Linet received the NIH Director's Award for outstanding research, and was elected to the American Epidemiological Society and the Johns Hopkins University Society of Scholars. She is on the Editorial Board of the American Journal of Epidemiology, and served as President of the American College of Epidemiology during September 2004 to September 2005. Dr. Linet is currently a member of the National Commission on Radiation Protection's Committee on Reproductive and Developmental Effects of Radiation to the Gonads, Embryo, and Fetus and previously served on the Advisory Group on Cancer and the Environment to the American Cancer Society, as NCI liaison to the Committee on Environmental Health of the American Academy of Pediatrics, and the Standing Committee on Epidemiology of the International Commission on non-Ionizing Radiation Protection. Dr. Linet authored The Leukemias: Epidemiologic Aspects, an internationally recognized text in the field.

Research Interests

  • Assess and quantify cancer risks associated with ionizing and non-ionizing radiation
  • Identify etiologies of hematopoietic and lymphoproliferative malignancies and related disorders in adults and children
  • Evaluate and quantify risks of hematopoietic, lymphoproliferative and related disorders associated with occupational exposure to benzene
  • Clarify the relationship of medical conditions, treatments, and other factors that may produce mild immunosuppression, and of familial and genetic factors with risk of malignant lymphoma
  • Identify etiologies of brain cancer in adults and children

Radiation and Cancer; Etiology of Hematopoietic, Lymphoproliferative, and Primary Brain Cancers

My research focuses on assessing and quantifying cancer risks linked with occupational, residential, and medical exposures to ionizing and non-ionizing radiation. A series of investigations have examined a wide range of postulated risk factors for hematopoietic, lymphoproliferative, and primary brain neoplasms in adults and children.

Ionizing Radiation Exposure and Cancer Risks in Radiologic Technologists

In a collaborative investigation with the University of Minnesota, my colleagues and I have investigated mortality and cancer incidence among a nationwide cohort of 146,022 U.S. radiologic technologists certified 2 or more years during 1926-1982. Using work history questionnaire data provided by 90,000 of the technologists (77% women) during 1983-89 and followed up through 1998, we found no increase in total cancer mortality risks, but a 3-fold excess of breast cancer mortality among those first employed before 1940, modest increases in mortality from the combined grouping of acute myeloid, acute lymphoid, and chronic myeloid leukemia among those first employed prior to 1950, and a 40 percent higher circulatory disease mortality risk among those who first worked before 1940 compared with first working in 1960 or later. Mortality and incidence risks according to work history were similar for breast cancer, and for the combined category of leukemias other than chronic lymphocytic leukemia. Basal cell carcinoma incidence risks were more than 2-fold increased and cutaneous melanoma was also significantly elevated, the latter based on small numbers, for those who first worked before 1940 or before 1950, respectively.

Recently, we have reconstructed doses for individual workers and are currently analyzing incidence risks of cancers and other serious diseases according to occupational and personal radiation doses. My colleagues and I are also studying the role of specific molecular and selected genetic factors thought to be directly or indirectly involved in radiation carcinogenesis.

Non-ionizing Radiation, Extremely Low Frequency and Radiofrequency

To address public health concerns about risk of childhood leukemia from exposures to extremely low frequency magnetic fields (50 or 60 Hertz), we conducted a large case control study with the Children's Oncology Group (a NCI funded clinical trials cooperative group) and found that neither high measured residential magnetic field levels (except possibly magnetic field levels greater than 0.4 microtesla) nor high wire code levels (a proxy measure for close distance of residence to power lines) were associated with significantly increased risks of childhood acute lymphoblastic leukemia. Exploratory analyses evaluating various alternative magnetic field exposure metrics, did not alter our conclusions. Childhood acute lymphoblastic leukemia risks were significantly elevated in offspring whose mothers reported use of an electric blanket during pregnancy, and children with postnatal use of electric blankets, hair dryers, video machines in arcades, and video games connected to televisions. However, patterns for duration or frequency of use of these appliances were inconsistent.

My colleagues and I conducted a large hospital-based case-central study and found that risks of gliomas, meningiomas, and acoustic neurons were not associated with cumulative use, duration or minutes per day of use of hand-held cellular telephones. In a multi-center population-based study of non-hodgkin lymphoma, we found that risks of lymphoma were not significantly associated with minutes per week, duration, cumulative lifetime or year of first use of cellular telephones.

Nonionizing Radiation, Ultraviolet or Sunlight Exposures

My colleagues and I conducted a methodological study to improve the effectiveness of questionnaires in assessing individual UV or sunlight exposures. We enrolled 124 U.S. radiologic technologists (half men, half women, evenly divided between residence in northern and southern latitudes) in a study in which each participant completed a daily activity diary for one week in September 2004 while wearing dosimetry badges to record UV exposure. Participants subsequently completed brief questionnaires about their time and activities outdoors during the week monitored to evaluate the reproducibility and validity of questionnaire responses. Comparing assessment of time spent outdoors with an activity-based approach we found higher relativity for the activity-based approach during adult ages and over subjects' lifetimes then the time-based approach particularly for women.

Benzene Related Hematopoietic Disorders

A cohort study of mortality and hematopoietic malignancy incidence risks was carried out among 75,000 benzene exposed workers employed between 1949 and 1987 in 12 cities in China. We found a three fold excess risk for non Hodgkin lymphoma (NHL), with risks rising with increasing duration of benzene exposure and associated with benzene exposure more than 10 years prior to diagnosis of NHL. In contrast, a three-fold excess of acute nonlymphocytic leukemia (ANLL) was linked with recent exposures; risk did not vary according to exposure duration. Significantly elevated risks were also seen for myelodysplastic syndromes and aplastic anemia, and there were non-significant excesses of acute lymphoid leukemia and chronic myeloid leukemia, but the numbers of cases were small.

We are currently conducting a case-control cohort study to quantify benzene dose-response risk of hematopoietic malignancies, benzene hematotoxicity, and lung cancer during 1972-1999, and also conducting a molecular and genetic case investigation of benzene hematotoxiticity.

Keywords

benzene; childhood cancers; genetics; hematopoietic cancers; leukemia; lymphoma; myelodysplastic syndromes; radiation, ionizing; radiation, non-ionizing

Selected Publications

Collaborators

DCEG Collaborators

  • Amy Berrington, Ph.D.
  • Susan Devesa, Ph.D.
  • Michele Doody, M.S.
  • Lynn Goldin, Ph.D.
  • Gloria Gridley, M.S.
  • Thomas Fears, Ph.D.
  • Michal Freedman, Ph.D.
  • Lynn Goldin, Ph.D.
  • Patricia Hartge, Sc.D.
  • Peter Inskip, Sc.D.
  • Bu Tian Ji, M.D., Dr.P.H.
  • Ruth Kleinerman, M.P.H.
  • Qing Lan, M.D., Ph.D.
  • Ola Landgren, M.D., Ph.D.
  • Kiyohiko Mabuchi, M.D., Dr. P.H.
  • Lindsay Morton, Ph.D.
  • Preetha Rajaraman, Ph.D.
  • Elaine Ron, Ph.D.
  • Nathaniel Rothman, M.D.
  • Alice Sigurdson, Ph.D.
  • Sholom Wacholder, Ph.D.

Other Scientific Collaborators

  • Jim Cerhan, M.D., Ph.D., Mayo Clinic
  • Wendy Cozen, D.O., University of Southern California, School of Medicine, Los Angeles, CA
  • Richard Hayes, D.D.S., Ph. D., New York University, New York, NY.
  • Kari Hemminki, M.D., Ph.D., Karolinska Institute, Stockholm, Sweden
  • Gui Lan Li, Ph.D., China Centers for Disease Controls, Beijing, China
  • Dale Preston, Ph.D., Hirosoft International
  • Leslie Robison, Ph.D., St. Jude's Hospital, Memphis, TN
  • Eve Roman, Ph.D., University of York, U.K.
  • Joachim Schuez, Ph.D., Mainz University, Mainz, Germany
  • Roel Vermeulen, Ph.D., University of Utrecht, Holland
  • Song Nian Yin, M.D., China Centers for Disease Controls, Beijing, China