Lack of a co-promoting effect of a 60 Hz magnetic field on skin tumorigenesis in SENCAR mice

It has been proposed that extremely low frequency (ELF) magnetic fields mayenhance tumorigenesis through a co-promotional mechanism. This hypothesishas been further tested using the two-stage model of mouse skincarcinogenesis, i.e. 12-O-tetradecanoylphorbol-13-acetate (TPA)- inducedpromotion of skin tumors in mice initiated by a single subcarcinogenic doseof 7,12-dimethylbenz[a]anthracene. Experimentation described hereinutilized the SENCAR mouse and examined the effect of a magnetic field onskin tumor promotion induced by three different doses of TPA within itsdose-response range, i.e. 0.85, 1.70 or 3.40 nmol, administered twice perweek. SENCAR mice (56/treatment group) were exposed to a 60 Hz magneticfield having a flux density of 2 mT for 6 h/day for 5 days/week andcompared with mice exposed to the ambient magnetic field. Tumor incidenceand multiplicity were monitored weekly for 23 weeks of TPA promotion.Statistical evaluation of the effects of the magnetic field on tumorincidence and multiplicity did not reveal any statistically significanteffects; thus, within the sensitivity limits imposed by the animal modeland the exposure parameters employed, no promotional or co-promotionaleffect of a 2 mT magnetic field on skin tumor development in SENCAR micecould be demonstrated.