Assessing the potential leukemogenic effects of 50 Hz magnetic fields and their harmonics using an animal leukemia model.

To answer the still unresolved question of the possible leukemogenic effects of extremely low frequency magnetic fields (ELF-MFs) and of their harmonics on the incidence of B acute lymphoblastic leukemia in children, we used an animal model to explore the possible co-initiating or co-promoting effects of ELF-MFs on the development of leukemia. We used a rat model in which B acute lymphoblastic leukemia is chemically induced by a nitrosurea derivative. From the onset of the chemical treatment, the animals were also exposed to ELF-MFs (100 microT, sinusoidal 50 Hz MFs), with or without harmonics. The experiment was conducted on 280 rats. We compared body weight and survival time, percentage of bone marrow blast cells, cumulative incidence of leukemia and type of leukemia in the unexposed groups and in the groups exposed to 50 Hz MFs, with and without harmonics. The results showed no significant differences between exposed and unexposed rats for any of these parameters (p > 0.05). Significant changes in the leukemia type obtained after gamma-irradiation of the leukemia model, showed its sensitivity to a physical agent. Our results do not support the hypothesis that ELF-MFs, with or without harmonics, affect the development of B acute lymphoblastic leukemia in children.

[Update on transmissible spongiform subacute encephalopathies (TSSE)]. / Actualités sur les encéphalopathies spongiformes subaiguës transmissibles (ESST).

This update concerns human and ruminant transmissible spongiform subacute encephalopathies (TSSE). The latest data on variant Creutzfeldt-Jakob disease confirm that new cases are less frequent than feared some years ago, but subclinical carriers could be a source of iatrogenic infection. The macaque is a good model of human oral transmission of bovine spongiform encephalopathy (BSE). The latest data on BSE in Europe confirm the effectiveness of precautionary measures taken in 1996 and 2000. Concerns in other ruminants include a chronic wasting disease of Cervidae in North America, the discovery of a BSE-like agent associated with natural scrapie in a French goat, maternal transmission of natural scrapie in sheep, with an exceptionally short incubation period (6.5 months), and doubts over the efficacy of genetic selection for combating ovine scrapie (atypical cases in " resistant " sheep, especially with the scrapie strain Nor 98 in Europe). These data demonstrate the value of active European surveillance of scrapie in small ruminants.