A HEMATOLOGICAL STUDY IN MICE FOR EVALUATION OF LEUKEMOGENESIS BY EXTREMELY LOW FREQUENCY MAGNETIC FIELDS

Abstract

OF1 mice were chronically exposed to a 50-Hz sinusoidal East–West magnetic field of 15 μT (rms), in order to make a peripheral blood study for a leukemogenic evaluation of this non-ionizing radiation. Mating and pregnancy of ancestors (first generation), and birth, lactation, and development of second-generation female mice until adulthood occurred in the experimental field. A hematological study of both control and exposed 14- to 15-week-old and 50- to 52-week-old, second-generation females was realized. Individual diagnosis of specimens and statistical analysis of results revealed a high incidence of blood leukoproliferative disorders in 14- to 15-week-old exposed females (relative risk [RR] = 3.00, p = 0.0033), despite the resistance of this strain of mice to developing malignancies under normal environmental conditions before they are 26 weeks old. Especially elevated incidences of lymphocytic (RR = 6.50, p = 0.0021) and chronic (RR = 4.00, p = 0.0153) leukemias were associated with medium-term (14–15 weeks) exposure. After 50–52 weeks of exposure, the mortality of exposed mice was 30% versus 0% of control mice. From dead exposed females, 67% revealed some type of malignancy. Corresponding RR for blood leukoproliferative disorders of those exposed which survived was 2.57 (p = 0.0351). Especially important was the proportion of chronic leukemias after long-term (50–52 weeks) exposure (RR = 8.57, p = 0.0118). Moreover, a statistically nonsignificant increase of lymphoblastic–myeloblastic leukemias pointed to a relation between age of specimen and type of alteration. We suggest that the increase in blood leukemias in OF1 mice agrees with the results of numerous epidemiological studies.

• Extremely low frequency magnetic fields
• Leukemogenic effects
• Medium-term and long-term exposures
• OF1 mice