Di Carlo A, White N, Guo F, Garrett P, et al. (2002):
The authors had previously shown that exposure of chick embryos to EMFs increased protection against hypoxia. They believed that this was due to increased levels of heat shock proteins. They had also shown that longer-term exposure to ultraviolet radiation decreased protection against hypoxia. The aim of the present study was designed to test whether long-term exposure to EMFs similarly decreased protection against hypoxia. The authors carried out tests using both ELF-EMFs and RF-EMFs. This summary will discuss the RF experiment only.
Chick embryos were exposed to RFR at 915 MHz frequency and an incident power of 3.5 W. The SAR was approximately 1.7 W/kg. The embryos were exposed for 30 minutes once, or 30 minutes daily for 4 days, or 60 minutes daily for 4 days. Temperature increase was less that 0.6 or 1.2 °C respectively with 30 or 60 minute exposure. Hsp 70 levels were assayed. Hypoxic conditions were created by placing the embryos in airtight bags, removing the air by suction, and replacing the air with argon. An observer blinded to their exposure status evaluated the embryos' heart beats through a window. The bags were opened when control embryo hearts were reduced to 15-45% still beating. This range was chosen because < 15% indicated the timing of the hypoxic insult was too long, and >45% suggested that it was not long enough to differentiate between controls and exposed embryos. Final observations were made after recovery for 30 minutes.
The authors report, but do not provide supportive data, that embryos exposed to 30 minutes RFR once on day 4 of the experiment had significantly higher survival after hypoxia than controls. However, the embryos exposed to 30 or 60 minutes RFR daily for 4 days had significantly less survival than controls. The authors do not report HSP 70 levels for the RFR experiment, but state that in the ELF experiment HSP levels increased significantly by 3 hours exposure, but were significantly lower by 4 days than control levels.
The authors conclude that short term RFR exposure increases HSP 70 levels and confers protection against hypoxic stress in chick embryos, while longer term exposure had the opposite effect. It is unfortunate that the authors do not give details of HSP levels in the RFR experiment, nor do they provide the data for the short-term experiment.