Spontaneous and nitrosourea-induced primary tumors of the central nervous system in Fischer 344 rats chronically exposed to 836 MHz modulated microwaves

Radiat Res. 1999 Sep;152(3):293-302.


We have tested an 836.55 MHz field with North American Digital Cellular (NADC) modulation in a 2-year animal bioassay that included fetal exposure. In offspring of pregnant Fischer 344 rats, we tested both spontaneous tumorigenicity and the incidence of induced central nervous system (CNS) tumors after a single dose of the carcinogen ethylnitrosourea (ENU) in utero, followed by intermittent digital-phone field exposure for 24 months. Far-field exposures began on gestational day 19 and continued until weaning at age 21 days. Near-field exposures began at 35 days and continued for the next 22 months, 4 consecutive days weekly, 2 h/day. SAR levels simulated localized peak brain exposures of a cell phone user. Of the 236 original rats, 182 (77%) survived to the termination of the whole experiment and were sacrificed at age 709-712 days. The 54 rats (23%) that died during the study ("preterm rats") formed a separate group for some statistical analyses. There was no evidence of tumorigenic effects in the CNS from exposure to the TDMA field. However, some evidence of tumor-inhibiting effects of TDMA exposure was apparent. Overall, the TDMA field-exposed animals exhibited trends toward a reduced incidence of spontaneous CNS tumors (P < 0. 16, two-tailed) and ENU-induced CNS tumors (P < 0.16, two-tailed). In preterm rats, where primary neural tumors were determined to be the cause of death, fields decreased the incidence of ENU-induced tumors (P < 0.03, two-tailed). We discuss a possible approach to evaluating with greater certainty the possible inhibitory effects of TDMA-field exposure on tumorigenesis in the CNS.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Neoplasms / chemically induced
  • Brain Neoplasms / etiology
  • Brain Neoplasms / pathology
  • Carcinogens*
  • Central Nervous System Neoplasms / chemically induced
  • Central Nervous System Neoplasms / etiology*
  • Central Nervous System Neoplasms / pathology
  • Cocarcinogenesis*
  • Disease Models, Animal
  • Ethylnitrosourea*
  • Female
  • Incidence
  • Male
  • Microwaves / adverse effects*
  • Pregnancy
  • Prenatal Exposure Delayed Effects
  • Rats
  • Rats, Inbred F344
  • Spinal Cord Neoplasms / chemically induced
  • Spinal Cord Neoplasms / etiology
  • Spinal Cord Neoplasms / pathology


  • Carcinogens
  • Ethylnitrosourea