Prenatal exposure to 900 MHz, cell-phone electromagnetic fields had no effect on operant-behavior performances of adult rats

To clarify potential health risks of radio‐frequency electromagnetic fields (EMFs) used in cellular telephone technology to the developing brain, Wistar rats were continuously exposed during pregnancy to a low‐level (0.1 mW/cm2) 900 MHz, 217 Hz pulse modulated EMF that approximated the highest legal exposure of normal populations to the radiation of base antennas of the GSM digital cell‐phone technology. Whole body average specific absorption rate (SAR) values for the freely roaming, pregnant animals were measured in models; they ranged between 17.5 and 75 mW/kg. The offspring of exposed and of sham‐exposed dams were coded and tested later as adults in a battery of ten simultaneously operated test chambers (Skinner boxes) during night time. Eight groups of ten coded animals in each group were tested for learning deficits in a sequence of nine, computer‐controlled, 15 h sessions of the food‐reinforced contingency Differential Reinforcement of Rate with increasing performance requirements. Two different sets of events were recorded: The food‐reinforced lever‐pressing activity of the animals and the inter‐response intervals (IRIs) between consecutive lever presses. IRI‐occurence patterns discriminated consistently between “learners” and “non‐learners”. Analyses of performance scores and of IRI‐patterns both showed that exposure in‐utero to the GSM field did not induce any measurable cognitive deficits. Bioelectromagnetics 21:566–574, 2000. © 2000 Wiley‐Liss, Inc.